Author: "Gérard Thouzeau" / Topic: 01 natural sciences - Searchworks@Jio Institute Digital Library Search Results

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1. Predicting the energy budget of the scallop Argopecten purpuratus in an oxygen–limiting environment

Author: Frédéric Jean, Gérard Thouzeau, Laure Pecquerie, Jonathan Flye-Sainte-Marie, Arturo Aguirre-Velarde, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto del Mar del Peru (IMARPE), Institut de Recherche pour le Développement (IRD), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Argopecten purpuratus, growth, [SDE.MCG]Environmental Sciences/Global Changes, Dynamic energy budget, hydrogen sulfide, Growth, Bioenergetics, Aquatic Science, bioenergetics, Oceanography, 010603 evolutionary biology, 01 natural sciences, reproduction, DEB theory, Water column, Aquaculture, Peru, 14. Life underwater, Hypoxia, Ecology, Evolution, Behavior and Systematics, Hydrogen sulfide, biology, hypoxia, business.industry, Reproduction, ACL, 010604 marine biology & hydrobiology, Hypoxia (environmental), biology.organism_classification, Energy budget, [SDE]Environmental Sciences, Scallop, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, business, Bay
Abstract: International audience; Low concentrations of oxygen determine marine species distribution and abundance along the Peruvian 1 coast with consequences for human activity such as fishing and aquaculture. In order to assess bioener-2 getic consequences of oxygen limitation on the Peruvian scallop Argopecten purpuratus, we first devel-3 oped a Dynamic Energy Budget (DEB) model of growth and reproduction calibrated on field experimen-4 tal datasets. Then, we included oxygen availability as an additional forcing variable using a simple rule 5 based on the ability of the scallop to regulate oxygen consumption. The resulting model was tested using 6 growth/reproduction monitoring and simultaneous high frequency environmental records in Paracas Bay 7 (Peru) at two different depths: suspended in the water column and on the sea bottom. Simulations indicated 8 that scallops growth and reproduction was not food-limited. The negative observed effects of hypoxia on 9 growth and reproduction could be explained by a decrease in both assimilation and reserve mobilization. 10 However, hypoxic conditions in summer were not sufficient to explain the observed losses in somatic tissue 11 weights and the disruption of reproduction. The latter two patterns were better simulated when assuming in-12 creased somatic maintenance costs due to the presence of H 2 S during milky turquoise water discolouration 13 events observed during summer. 14
Published: 2019
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2. Comparison of benthic oxygen exchange measured by aquatic Eddy Covariance and Benthic Chambers in two contrasting coastal biotopes (Bay of Brest, France)

Author: Gérard Thouzeau, E. Amice, Sylvain Rigaud, Tom Cox, Thierry Le Bec, Bruno Deflandre, Pierre Polsenaere, Isabelle Bihannic, Olivier Maire, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Détection, évaluation, gestion des risques CHROniques et éMErgents (CHROME) / Université de Nîmes (CHROME), Université de Nîmes (UNIMES), Royal Netherlands Institute for Sea Research (NIOZ), The EDDYCO project (INSU EC2CO/DRIL program) provided financial support for this study. The Région Aquitaine (FEBBA project) and the IZOFLUX project from the French National Research Agency (white program) funded the EC system. The Région Aquitaine (FEBBA project) and the Vrije Universiteit Brussel supported the two-year postdoctoral fellowships awarded to P.P. The development of the new EC system, EC2, was realized in collaboration with Unisense A/S and the NIOZ-Yerseke. We would like to express our thanks to the INSU team from L’Albert Lucas and Henry Bouillard and Christian Portier from EPOC. This work has been carried out within the framework of the Cluster of Excellence COTE, ANR-10-BLAN-0612,IZOFLUX,Étude intégrée de l'Impact des herbiers de ZOstères sur les processus et FLUX benthiques en milieu côtier(2010), ANR-10-LABX-0045,COTE,COntinental To coastal Ecosystems: evolution, adaptability and governance(2010), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Benthic Chambers, 010504 meteorology & atmospheric sciences, Fauna, Eddy covariance, Aquatic Science, 01 natural sciences, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Benthic O-2 fluxes, Aquatic Eddy Covariance, Maerl bed, 14. Life underwater, Maerl, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, Ecology, Benthic oxygen fluxes, 010604 marine biology & hydrobiology, Bay of Brest, Sediment, 15. Life on land, Spatial heterogeneity, Bare mudflat, Oceanography, 13. Climate action, Benthic zone, Environmental science, Animal Science and Zoology, Bay, Bioturbation
Abstract: To the best of our knowledge, the understanding of benthic metabolism of coastal sedimentary areas is still limited due to the complexity of determining their true in situ dynamics over large spatial and temporal scales. Multidisciplinary methodological approaches are then necessary to increase our comprehension of factors controlling benthic processes and fluxes. An aquatic Eddy Covariance (EC) system and Benthic Chambers (BC) were simultaneously deployed during the winter of 2013 in the Bay of Brest within a Maerl bed and a bare mudflat to quantify and compare O2 exchange at the sediment–water interface. Environmental abiotic parameters (i.e., light, temperature, salinity, current velocity and water depth) were additionally monitored to better understand the mechanisms driving benthic O2 exchange. At both sites, EC measurements showed short-term variations (i.e. 15 min) in benthic O2 fluxes according to environmental conditions. At the Maerl station, EC fluxes ranged from-21.0 mmol m−2 d−1 to 71.3 mmol m−2 d −1 and averaged 22.0 ± 32.7 mmol m−2 d−1 (mean ± SD), whilst at the bare muddy station, EC fluxes ranged from -43.1mmol m−2 d−1 to 12.1 mmol m−2 d −1 and averaged -15.9 ± 14.0 mmol m−2 d−1 (mean ± SD) during the total deployment. Eddy Covariance and Benthic Chambers measurements showed similar patterns of temporal O2 flux changes at both sites. However, at the Maerl station, BC may have underestimated community respiration. This may be due to the relative large size of the EC footprint (compared to BC), which takes into account the mesoscale spatial heterogeneity (e.g. may have included contributions from bare sediment patches). Also, we hypothesize that the influence of bioturbation induced by large-sized mobile benthic fauna on sediment oxygen consumption was not fully captured by BC compared to EC. Overall, the results of the present study highlight the importance of taking into account specific methodology limitations with respect to sediment spatial macro-heterogeneity and short-term variations of environmental parameters to accurately assess benthic O2 exchange in the various benthic ecosystems of the coastal zone.
Published: 2021
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3. Easily Implemented Methods of Radiometric Corrections for Hyperspectral-UAV-Application to Guianese Equatorial Mudbanks Colonized by Pioneer Mangroves

Author: Emma Michaud, Nicolas Le Dantec, Marion Jaud, Guillaume Sicot, Jérôme Ammann, Christophe Delacourt, Philippe Grandjean, Gérard Thouzeau, Patrick Launeau, Jules Fleury, Guillaume Brunier, Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Géosciences Océan (LGO), Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER Centre de Bretagne), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Equipe Marine Mapping & Metrology (Lab-STICC_M3), Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT), École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement [Lyon] (LGL-TPE), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), ANR-17-EURE-0015,ISBlue,Interdisciplinary Graduate School for the Blue planet(2017), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), ANR-11-EQPX-0011,CRITEX,Parc national d'équipements innovants pour l'étude spatiale et temporelle de la Zone Critique des Bassins Versants(2011), Université de Bretagne Sud (UBS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 010504 meteorology & atmospheric sciences, reflectance, hyperspectral imaging, Science, 0211 other engineering and technologies, 02 engineering and technology, drone, 01 natural sciences, [SPI.AUTO]Engineering Sciences [physics]/Automatic, Littoral zone, intertidal sediments, 14. Life underwater, Radiometric calibration, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing, Vignetting, Spectrometer, Orientation (computer vision), [SDE.IE]Environmental Sciences/Environmental Engineering, radiometric calibration, pioneer mangroves, Hyperspectral imaging, Benthic zone, General Earth and Planetary Sciences, Environmental science, Mangrove, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing
Abstract: International audience; Hyper-DRELIO (Hyperspectral DRone for Environmental and LIttoral Observations) is a custom, mini-UAV (Unmanned Aerial Vehicle) platform (< 20 kg) equipped with a light push broom hyperspectral sensor combined with a navigation module measuring position and orientation. Because of the particularities of UAV surveys (low flight altitude, small spatial scale and high resolution), dedicated pre-processing methods have to be developed when reconstructing hy-perspectral imagery.This article presents light easy-implementation in-situ methods, using only two Spectralon® and a field spectrometer, allowing to perform an initial calibration of the sensor in order to correct “vignetting effects” and a field standardization to convert Digital Numbers (DN) collected by the hyperspectral camera to reflectance, taking into account the time-varying illumination con-ditions. Radiometric corrections are applied to a subset of a dataset collected above mudflats colonized by pioneer mangroves in French Guiana. The efficiency of the radiometric corrections is assessed by comparing spectra from Hyper-DRELIO imagery to in-situ spectrometer meas-urements above the intertidal benthic biofilm and mangroves. The shapes of the spectra are con-sistent and the Spectral Angle Mapper (SAM) distance is of 0.039 above the benthic biofilm and of 0.159 above the mangroves. These preliminary results provide new perspectives for quanti-fying and mapping the benthic biofilm and mangroves at the scale of the Guianese intertidal mudbanks system, given their importance in the coastal food webs, biogeochemical cycles and the sediment stabilization.
Published: 2021
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4. Size‐based survival of cultured Argopecten purpuratus (L, 1819) under severe hypoxia

Author: Fred Jean, Arturo Aguirre-Velarde, Jonathan Flye-Sainte-Marie, Rosa Cueto-Vega, Patricia Gil-Kodaka, Gérard Thouzeau, Universidad Nacional Agraria La Molina (UNALM), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto del Mar del Peru (IMARPE), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, severe hypoxia, Argopecten purpuratus, 010504 meteorology & atmospheric sciences, biology, 010604 marine biology & hydrobiology, [SDV.SA.ZOO]Life Sciences [q-bio]/Agricultural sciences/Zootechny, Lt(50), Severe hypoxia, Aquatic Science, biology.organism_classification, 01 natural sciences, Mass mortality, Andrology, size effect, mass mortality, 14. Life underwater, Lt50, [SDV.EE.BIO]Life Sciences [q-bio]/Ecology, environment/Bioclimatology, Agronomy and Crop Science, 0105 earth and related environmental sciences
Abstract: International audience; During recent years, mass mortalities of cultured scallops became more frequent in Peruvian bays. One of the main drivers related to these mortalities was hypoxic events. This study was designed to understand the hypoxia phenomenon in these bays and to assess how the Peruvian scallop, Argopecten purpuratus, can cope with reduced oxygen levels in seawater based on individual size. First, we analyzed the relationships between dissolved oxygen saturation and other environmental parameters (the Coastal El Niño Index, temperature, salinity and pH) in bottom seawater, the frequency and intensity of hypoxic events in two main culture areas (Sechura and Paracas Bays), and their relationship with scallop mass mortalities. Then, we performed experiments with two size groups of A. purpuratus (31 and 80 mm shell height; seed and commercial size, respectively) to assess their respective survival time under severe hypoxia (1% oxygen saturation) at 16°C and a salinity of 35. Finally, the results of the field records and the experimental data are used to suggest ways to improve scallop cultivation along the Peruvian coast.
Published: 2021
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5. Mangrove‐Derived Organic and Inorganic Carbon Exchanges Between the Sinnamary Estuarine System (French Guiana, South America) and Atlantic Ocean

Author: Romain Walcker, Raghab Ray, Emma Michaud, Sylvain Morvan, Jérémy Devesa, Vincent Vantrepotte, Gerd Gleixner, Gérard Thouzeau, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Laboratoire Ecologie, Evolution, Interactions des Systèmes amazoniens (LEEISA), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Biogeochemistry (MPI-BGC), Max-Planck-Gesellschaft, ANR-10-LABX-0025,CEBA,CEnter of the study of Biodiversity in Amazonia(2010), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), ANR-12-JSV7-0012,BIOMANGO,BIOdiversité et fonctionnement des écosystèmes dans les MANgroves de Guyane française : perspectives pour une gestion de l'écOsystème dans son contexte amazonien(2012), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS), Centre National de la Recherche Scientifique (CNRS)-Université de Guyane (UG)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Atmospheric Science, 010504 meteorology & atmospheric sciences, Soil Science, Aquatic Science, 01 natural sciences, Tidal cycle, Total inorganic carbon, Organic matter, 14. Life underwater, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Water Science and Technology, Carbon flux, organic matter, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, chemistry.chemical_classification, geography, geography.geographical_feature_category, Ecology, 010604 marine biology & hydrobiology, ACL, mangroves, Paleontology, Forestry, Estuary, 15. Life on land, French Guiana, carbon flux, Oceanography, chemistry, 13. Climate action, [SDE]Environmental Sciences, Environmental science, Mangrove, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, tidal cycle
Abstract: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JG005739; International audience; There is growing evidence that a substantial fraction of the dissolved organic and inorganic carbon (DOC and DIC) and particulate organic carbon (POC) can be exported from mangroves to the ocean. Yet our understanding of C fluxes in mangrove forests is limited to only few regional studies that exclude the world's longest sediment dispersal system connected to the Amazon River. The present study aims at (1) examining tidal fluctuations of DOC, POC, and DIC; their isotopes; and optical properties such as chromophoric dissolved organic matter (CDOM) and (2) estimating their exchange fluxes between the mangroves and adjacent coastal water in the Sinnamary estuary, French Guiana. Time series observation highlighted that physical processes coupled to tides controlled diel dynamics and sources of DOC (e.g., litter leaching and pore water seepage) and POC (microphytobenthos, sediment resuspension, and bioturbation activities). Intense benthic remineralization could account for high water column pCO2 and DIC exchange flux during the low tide. Mangrove-derived DOC export to inner shelf (8.14 g C m−2 day−1) was exceeding import of POC and DIC from the mud bank and marine sources to the mangroves (1.35 and 0.90 g C m−2 day−1, respectively). Because of specific dynamics of the Amazon mobile muds, local geomorphology, water column stratification, and environmental forcing, Guianese mangroves cannot be seen as simple C exporters to the Atlantic waters. These first data setting on C fluxes for the region should be included along with other studies to improve global mangrove C budget estimate.
Published: 2020
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6. The sources and distribution of carbon (DOC, POC, DIC) in a mangrove dominated estuary (French Guiana, South America)

Author: Jérémy Devesa, Sylvain Morvan, V. Vantrepotte, Gerd Gleixner, Raghab Ray, Romain Walcker, Gérard Thouzeau, M. Le Goff, Robert C. Aller, Emma Michaud, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), School of Marine and Atmospheric Sciences [Stony Brook] (SoMAS), Stony Brook University [SUNY] (SBU), State University of New York (SUNY)-State University of New York (SUNY), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS), Max Planck Institute for Biogeochemistry (MPI-BGC), Max-Planck-Gesellschaft, Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie, Evolution, Interactions des Systèmes amazoniens (LEEISA), Centre National de la Recherche Scientifique (CNRS)-Université de Guyane (UG)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), ANR-12-JSV7-0012,BIOMANGO,BIOdiversité et fonctionnement des écosystèmes dans les MANgroves de Guyane française : perspectives pour une gestion de l'écOsystème dans son contexte amazonien(2012), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), ANR-10-LABX-0025,CEBA,CEnter of the study of Biodiversity in Amazonia(2010), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, 01 natural sciences, Carbon cycle, Dissolved organic carbon, Phytoplankton, Mangroves, Environmental Chemistry, Methanotrophy, Ecosystem, 14. Life underwater, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Stable isotopes, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Total organic carbon, geography, Amazonian system, geography.geographical_feature_category, ACL, 010604 marine biology & hydrobiology, Microphytobenthos, Estuary, 15. Life on land, Oceanography, 13. Climate action, Benthic zone, [SDE]Environmental Sciences, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Mangrove, Remineralization
Abstract: International audience; Mangrove forests are highly productive coastal ecosystems that significantly influence global carbon cycling. This study characterized the sources of dissolved organic carbon (DOC), particulate organic carbon (POC) and dissolved inorganic carbon (DIC) and the processes affecting their distributions in a mangrove-influenced estuary located in French Guiana (FG), a region representative of these dynamic systems down drift of the Amazon River. Four sampling cruises were carried out between 2013 and 2015 in surface waters of the estuary during dry and wet seasons. Stable isotopes (δ13DOC, δ13POC, δ13DIC), elemental ratios and optical properties (absorption) were used as proxies to identify different C sources. Property–salinity relationships revealed regions of approximately linear mixing (e.g., alkalinity) or net sources or sinks (e.g., DOC). DIC speciation and isotopic distributions demonstrated dynamic source–sink reaction processes within the estuary. DOC was the major form of organic carbon representing mixtures of terrestrial sources (e.g., pore water, litter leaching) and very high concentration (400–800 µM) compared to other mangrove settings (e.g. Brazilian, Sundarbans, African). Highly negative δ13POC (− 40‰) in the riverine part presumably suggests the role of freshwater phytoplankton in the dry season and methanotrophic sources derived from senescent mangrove deposits or upstream hydrothermal dam during the wet season. Microphytobenthos and marine phytoplankton were the primary sources of POC inshore and DOC offshore, respectively. Mangrove products and benthic microalgae dominated estuarine sources of C in FG coastal waters (~ 10 km, inner shelf region), and there was extensive exchange of C between forest and tidal flat and the estuarine reservoirs.
Published: 2018
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7. Evidence of clandestine harvest and failure of conservation policies for Argopecten purpuratus in the Rinconada Marine Reserve (Chile)

Author: Marcela Cantillánez, Gérard Thouzeau, and Miguel Avendaño
Subjects: 0106 biological sciences, Argopecten purpuratus, Stock assessment, Ecology, biology, Overfishing, 010604 marine biology & hydrobiology, Population size, Fishing, Marine reserve, 04 agricultural and veterinary sciences, Aquatic Science, biology.organism_classification, 01 natural sciences, Fishery, Scallop, 040102 fisheries, 0401 agriculture, forestry, and fisheries, 14. Life underwater, Bay, Nature and Landscape Conservation
Abstract: The study of Argopecten purpuratus reproduction, post-larval settlement, stock size, and population size structure and shell growth was undertaken in the 2000s in the Rinconada marine reserve (Chile) to evaluate the effectiveness of scallop recruitment and self-sustainability. The results highlight strong seasonal and inter-annual variations of environmental conditions and scallop gonadosomatic index, spat collection, benthic distribution, total abundance and population size structure. The Von Bertalanffy growth parameters were L∞ = 120.12 mm and K = 0.9681; commercial size would be reached in about 17.2 months in the bay. Substrate availability, meteorological conditions, hydrodynamics and illegal harvesting explain spatial and temporal variations in scallop distribution and abundance. Recruitment strength depends on one main cohort from year to year. While recruitment made up 81% and 94% of total abundances in May 2002 and May 2003, respectively, there were no overall density-dependent relationships between stock size and recruitment. Spawning asynchrony in the bay supports the hypothesis that multiple gamete releases form part of a reproductive strategy in response to environmental variability. The massive disappearance of large-sized scallops during the study periods was direct evidence of overfishing owing to clandestine harvesting within the marine reserve. The failure of current legislation, strategies and policies for scallop conservation requires new regulations to restore scallop stock size, maintain its reproductive performance and limit illegal harvesting in the Rinconada. A scenario allowing harvesting regulated by stock-dependent fishing quotas would more efficiently ensure stock recovery and self-sustainability. The modalities of this new policy are discussed.
Published: 2017
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8. Feeding behaviour and growth of the Peruvian scallop ( Argopecten purpuratus ) under daily cyclic hypoxia conditions

Author: Jonathan Flye-Sainte-Marie, Fred Jean, Gérard Thouzeau, Arturo Aguirre-Velarde, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto del Mar del Peru (IMARPE), and ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010)
Subjects: 0106 biological sciences, Argopecten purpuratus, 010504 meteorology & atmospheric sciences, Bioenergetics, Dynamic energy budget, [SDE.MCG]Environmental Sciences/Global Changes, Growth, Aquatic Science, Biology, Oceanography, 01 natural sciences, Animal science, Dry weight, 14. Life underwater, Hypoxia, Ecology, Evolution, Behavior and Systematics, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, 010604 marine biology & hydrobiology, ACL, Hypoxia (environmental), Aquatic animal, biology.organism_classification, Clearance rate, Fishery, Pectinidae, Scallop, Feeding behaviour, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: International audience; As a secondary consequence of the high productivity of the upwelling system, organisms inhabiting Peruvian coastal bays are frequently exposed to hypoxic conditions. The aim of the present paper was to investigate the effects of daily-cyclic-severe hypoxia on energetics of a species presenting little escape ability when facing hypoxia. For this purpose, juvenile Peruvian scallops (Argopecten purpuratus) were exposed to four experimental conditions: fed and starved, combined or not to nightly severe hypoxia (5% oxygen saturation) for ≈ 12 h over a 21-day experiment. In both fed conditions, clearance rate was measured by the mean of an open-flow system. Our results indicate that the Peruvian scallop is able to maintain an active filtration even at low oxygen saturation, at least during expositions up to 12 h. During the first phase of exposure to hypoxia, clearance rate decreased abruptly when oxygen saturation dropped below 10%, but rapidly recovered to values close to those found under normoxia. As a consequence of this ability to feed during hypoxia, no difference in soft tissue dry weight (digestive gland not included) was observed at the end of the experimental period between oxic conditions among fed scallops. However, shell growth was negatively affected by hypoxic condition. Starved individuals exhibited similar weight loss between hypoxic and normoxic conditions indicating no or little effect of oxic condition on maintenance costs. Considering the observed responses for feeding, growth and maintenance, we can hypothesize that this species presents metabolic/bioenergetic efficient adaptations to deal with hypoxic conditions that are recurrent in Peruvian coastal bays. We hypothesize that the small observed effects might be modelled in the context of the Dynamic Energy Budget theory as a restriction of reserve mobilization under hypoxic conditions.
Published: 2018
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9. A review of potential impacts of submarine power cables on the marine environment: Knowledge gaps, recommendations and future directions

Author: Morgane Lejart, Andrew Want, Nicolas Desroy, Gérard Thouzeau, Bastien Taormina, Antoine Carlier, Juan Bald, France Energies Marines [Brest], Laboratoire d'Ecologie Benthique Côtière (LEBCO), Dynamiques des Écosystèmes Côtiers (DYNECO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), AZTI - Tecnalia, Heriot-Watt University [Edinburgh] (HWU), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Environnement Ressource Bretagne Nord (LERBN), LITTORAL (LITTORAL), Dynamiques de l'Environnement Côtier (DYNECO), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Sociology of scientific knowledge, Project commissioning, 010603 evolutionary biology, 01 natural sciences, Nuclear decommissioning, Submarine power cables, Marine energy, 14. Life underwater, Environmental planning, Marine renewable energy, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Renewable Energy, Sustainability and the Environment, business.industry, [SDE.IE]Environmental Sciences/Environmental Engineering, 010604 marine biology & hydrobiology, ACL, Submarine, Chemical pollution, Environmental impacts, Renewable energy, Habitat, 13. Climate action, Benthic habitats, Ecosystem functioning, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, business
Abstract: International audience; Submarine power cables (SPC) have been in use since the mid-19th century, but environmental concerns about them are much more recent. With the development of marine renewable energy technologies, it is vital to understand their potential impacts. The commissioning of SPC may temporarily or permanently impact the marine environment through habitat damage or loss, noise, chemical pollution, heat and electromagnetic field emissions, risk of entanglement, introduction of artificial substrates, and the creation of reserve effects. While growing numbers of scientific publications focus on impacts of the marine energy harnessing devices, data on impacts of associated power connections such as SPC are scarce and knowledge gaps persist. The present study (1) examines the different categories of potential ecological effects of SPC during installation, operation and decommissioning phases and hierarchizes these types of interactions according to their ecological relevance and existing scientific knowledge, (2) identifies the main knowledge gaps and needs for research, and (3) sets recommendations for better monitoring and mitigation of the most significant impacts. Overall, ecological impacts associated with SPC can be considered weak or moderate, although many uncertainties remain, particularly concerning electromagnetic effects.
Published: 2018
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10. Marine Species Introduced on the French Channel-Atlantic Coasts: A Review of Main Biological Invasions and Impacts

Author: Gérard Thouzeau, Valérie Stiger-Pouvreau, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Codium fragile, [SDE.MCG]Environmental Sciences/Global Changes, Halophyte, Biodiversity, Invasive Species, Remediation, Introduced species, Spartina alterniflora, 01 natural sciences, Invasive species, Macroalgae, 0502 economics and business, 14. Life underwater, Sargassum muticum, ACLN, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Mollusks, biology, Ecology, 010604 marine biology & hydrobiology, 05 social sciences, 15. Life on land, biology.organism_classification, Fishery, French Channel-Atlantic Coasts, 13. Climate action, Benthic zone, Impacts, Biological dispersal, 050202 agricultural economics & policy, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: International audience; The impacts of anthropogenisation modify permanently the distribution patterns of brackish and marine species. Globalization leads to a rapid increase of the numbers of introduced species anywhere in the world. Biological invasions often result in significant losses in the economic value, biological diversity and function of invaded ecosystems. This review presents the main pathways of introduction of non-indigenous species and the main benthic taxonomic groups being established and/or invasive along the French Channel-Atlantic coasts. A focus is put on main invasive marine species in the intertidal and subtidal zones of Brittany (France), among macroalgae (Sargassum muticum, Grateloupia turuturu, Undaria pinnatifida, Codium fragile and Gracilaria vermiculophylla), halophytes (Spartina alterniflora) and benthic invertebrates (Mollusks: Crepidula fornicata, Crassostrea gigas and Venerupis philippinarum). The species biology, introduction vectors, reproductive and dispersal capacities are considered, together with proliferation patterns along the Channel-Atlantic coasts. The ecological impacts of these species on the environment are also described, as well as the European regulations existing to limit alien species introduction and some examples of struggle against the invaders including eradication trials and biomass valorization. Last, the on-going impacts of global changes on alien species invasiveness along the Channel- Atlantic coasts are discussed.
Published: 2015
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11. Bioturbation functional roles associated with mangrove development in French Guiana, South America

Author: Arthur Alt, Gérard Thouzeau, François Fromard, Franck Gilbert, Emma Michaud, Arnaud De Coninck, Vincent Le Garrec, Adélaïde Aschenbroich, Isabelle Bihannic, Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut Français de Recherche pour l'Exploitation de la MER - IFREMER (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Institut National de la Recherche Scientifique - INRS (CANADA), Institut de Recherche pour le Développement - IRD (FRANCE), Université de Bretagne Occidentale - UBO (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université de Lorraine (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Université Toulouse III - Paul Sabatier - UPS (FRANCE), Laboratoire des Sciences de l'Environnement Marin - LEMAR (Plouzané, France), Laboratoire Ecologie fonctionnelle et Environnement - EcoLab (Toulouse, France), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Scientifique [Québec] (INRS), ANR-12-JSV7-0012,BIOMANGO,BIOdiversité et fonctionnement des écosystèmes dans les MANgroves de Guyane française : perspectives pour une gestion de l'écOsystème dans son contexte amazonien(2012), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Biodiversité et Ecologie, Aquatic Science, 01 natural sciences, Mesofauna, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Benthic community, Dry season, Dominance (ecology), Organic matter, 14. Life underwater, Sediment reworking, Soil mesofauna, 0105 earth and related environmental sciences, chemistry.chemical_classification, Amazonian system, Ecology, 010604 marine biology & hydrobiology, ACL, Community structure, 15. Life on land, Dynamic system, chemistry, Ecosystèmes, Mud bank, Environmental science, Species richness, Macrofauna, Mangrove, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bioturbation
Abstract: International audience; This study aims to qualify, quantify, and compare the sediment reworking rates induced by the meso- (0.25–1 mm) and macro-infauna ([1 mm) along a mangrove growth gradient in the sedimentary dynamics of the French Guiana coast. The characterization of the role of small-infauna bioturbation in mangroves is new despite their known numerical dominance in tropical environments. Bare sediment, pioneer mangroves, and young mangroves were investigated during the dry season and spring tide to characterize their environment, infaunal functional community structure and sediment reworking rates. The biodiffusion differed significantly between mangrove stages, co-varying mainly with density and functional richness. On the contrary, the non-local transport remained similar, despite the mangrove-agespecificity of infauna functional compositions, which responded to modifications in the nature and content of organic matter. The first mangrove infaunal functional sequence is described: organisms that first colonize deposited mud generate the maximum biodiffusive mixing and induce a total downward particle flux (BDF) as high as in the young mangroves; in the pioneer mangroves, the infauna variables and BDF are stressed to minimum values. Our study sheds light on the functional contribution of the small infauna in a mangrove coastal area and quantifies its role in particle transport during mangrove development.
Published: 2017
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12. Brachyuran crab community structure and associated sediment reworking activities in pioneer and young mangroves of French Guiana, South America

Author: Gérard Thouzeau, Emma Michaud, Marcos Tavares, Antoine Gardel, Adélaïde Aschenbroich, Thomas Stieglitz, François Fromard, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre for TropicalWater and Aquatic Ecosystem Research (TropWATER), School of Earth and Environmental Sciences [Australia], James Cook University (JCU)-James Cook University (JCU), Laboratoire Ecologie Fonctionnelle et Environnement (ECOLAB), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie, Evolution, Interactions des Systèmes amazoniens (LEEISA), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Guyane (UG)-Centre National de la Recherche Scientifique (CNRS), University of São Paulo (USP), ANR-12-JSV7-0012,BIOMANGO,BIOdiversité et fonctionnement des écosystèmes dans les MANgroves de Guyane française : perspectives pour une gestion de l'écOsystème dans son contexte amazonien(2012), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut Ecologie et Environnement (INEE), Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT), Institut national des sciences de l'Univers (INSU - CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Nord]), and Universidade de São Paulo = University of São Paulo (USP)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, habitat, Crabs, Aquatic Science, Oceanography, 01 natural sciences, chasmagnathus-granulata, Mangroves, Community composition, 14. Life underwater, Amazon, organic-matter, 0105 earth and related environmental sciences, biodiversity, ecosystem, geography, geography.geographical_feature_category, Ecology, burrowing crabs, 010604 marine biology & hydrobiology, ACL, Sediment, Estuary, dynamics, 15. Life on land, Burrow, Spatial heterogeneity, French Guiana, Benthic zone, genus uca, salt-marsh, Salt marsh, DISCOVERY, ecological role, Mangrove, Bioturbation, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Geology
Abstract: 00001 ăWOS:000390627700006; International audience; This study in French Guiana evaluates the changes of crab assemblages and their bioturbation activities between mangrove early stages (pioneer and young mangrove) and within stages by taking their spatial heterogeneity (tidal channels, flat areas, pools) into account. The results show differences in crab assemblage structure between and within the early stages of mangrove in relation to microhabitat and sediment characteristics. The sediment reworking rates are a function of the biomass or density of particular species (Ucides cordatus, Uca cumulanta) and burrower functional groups. Crab species or functional interactions mediate changes in sediment reworking rates suggesting the need to consider entire benthic communities rather than single species. This study suggests that the role of the micro habitat in determining the biologically -induced sediment reworking rates depends on the age of the mangrove. Feeding activity results in a sediment turnover of 11.7 +/- 9.7 g(dw) m(-2) day(-1) and 6.8 +/- 3.0 g(dw) m(-2) day(-1) in the pioneer and young mangroves, respectively. Burrow maintenance excavates 40.5 +/- 7.4 g(dw) m(-2) day(-1) and 251.3 +/- 419.7 g(dw) m(-2) day(-1) in the pioneer and young mangroves, respectively. Upscaling to the studied area (Sinnamary estuary: 6 km(2)), shows that 500 tons.day(-1) and 20 tons.day(-1) of sediments could be excavated and pelletized, respectively, during the spring tides of the dry season. Thus, biological sediment reworking would greatly contribute to the sedimentary dynamics of the Guianese mangroves under Amazonian influence.
Published: 2016
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13. Effects of progressive hypoxia on oxygen uptake in juveniles of the Peruvian scallop, Argopecten purpuratus (Lamarck, 1819)

Author: Gérard Thouzeau, Arturo Aguirre-Velarde, Fred Jean, Jonathan Flye-Sainte-Marie, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Instituto del Mar del Peru (IMARPE), ANR-10-LABX-0019,LabexMER,LabexMER Marine Excellence Research: a changing ocean(2010), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Argopecten purpuratus, Q10, chemistry.chemical_element, Aquaculture, Aquatic Science, 01 natural sciences, Oxygen, Animal science, Respiration, Peru, 14. Life underwater, Oxygen saturation, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, Argopecten, biology, 010604 marine biology & hydrobiology, ACL, Hypoxia (environmental), 04 agricultural and veterinary sciences, Oxygen critical point, biology.organism_classification, Oceanography, chemistry, 13. Climate action, Scallop, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Oxyregulation, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, circulatory and respiratory physiology
Abstract: International audience; A field survey performed in Paracas Bay (Peru), a major scallop culture area, showed that the Peruvian scallop, Argopecten purpu-ratus, periodically faces severe hypoxic events. Oxygen uptake rate (VO2) of A. purpuratus juveniles facing progressive decrease of environmental oxygen saturation (from 100% to 5%) was measured at two contrasting temperatures ("normal condition" = 16°C and "warm condition" = 25°C). In normoxia, (oxygen saturation >70%) average VO2 was significantly (p < 0.001) higher in warm condition (0.20 ±0.004 mgO 2 ind −1 h −1) than in normal condition (0.12 ±0.007 mgO 2 ind −1 h −1). The shape of the VO2 response curve during increasing hypoxic conditions was evaluated using a segmented linear regression. The break points between linear segments allowed estimating the oxygen critical points (PcO2 , oxygen saturation units), while the slopes of the various segments was used to assess the VO2 regulatory capacity. In both temperature conditions at oxygen saturation lower than PcO2 , VO2 was a fourth of the values recorded in normoxic condition. This trend was more pronounced in the warm condition. Paradoxically, the estimated PcO2 was lower in warm condition (21.4% ±0.7) compared to the normal condition (24.4% ±1.9). However, the study of the slopes at oxygen saturations higher than PcO2 revealed that A. purpuratus can regulate its respiratory rate similarly and efficiently at both 16 and 25°C. Moreover, for VO2 above PcO2 , the estimated Q10 between normal and warm conditions was 1.78 (Arrhenius temperature = 4983 K), highlighting a moderate effect of temperature on VO2. These results reflect the adaptive capacity of this species to the changing environment along the Peruvian-Chilean coasts influenced by upwelling system and ENSO events. However, results from this study indicate that, at least during some periods, A. purpuratus spend more than 70% of its time exposed to hypoxic conditions below the estimated PcO2. Such conditions could have negative consequences on the species metabolism and harm the performance of A. purpuratus culture.
Published: 2016
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14. Diurnal heterogeneity in silicic acid fluxes in shallow coastal sites: Causes and implications

Author: Sorcha Ní Longphuirt, Aude Leynaert, Laurent Chauvaud, Olivier Ragueneau, Sophie Martin, Gérard Thouzeau, Frédéric Jean, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Marine Environment Laboratories, and International Atomic Energy Agency [Vienna] (IAEA)
Subjects: 0106 biological sciences, silicic acid, diurnal variations, microphytobenthos, 010504 meteorology & atmospheric sciences, Aquatic Science, Oceanography, 01 natural sciences, chemistry.chemical_compound, Benthos, Diurnal cycle, Phytoplankton, 14. Life underwater, Silicic acid, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, subtidal, migrations, 010604 marine biology & hydrobiology, Diurnal temperature variation, Bay of Brest, Pelagic zone, Plankton, chemistry, 13. Climate action, Benthic zone, Environmental science, France
Abstract: International audience; In shallow coastal areas the amplitude and range of benthic silicic acid fluxes can have a significant influence on benthic–pelagic coupling and the functioning of the pelagic system. To explore the oscillation in fluxes over the diurnal cycle and in particular the influence of microphytobenthos (MPB), an experiment was carried out in a shallow subtidal site in the Bay of Brest (France). Benthic chambers were employed over a 48 h period to measure the variability in silicic acid and oxygen fluxes; MPB migration was investigated using a diving Pulse Amplitude Modulated (PAM) fluorometer and uptake rhythms of silicic acid by natural MPB populations were measured using the 32Si isotope. It was discovered that silicic acid fluxes fluctuated greatly throughout the diurnal period resulting in an oscillation in the availability of this nutrient for phytoplankton communities. The uptake of silicic acid by the MPB was quantified for the first time and highlighted a 2-fold increase in the demand from night to afternoon periods. The combined silicic acid uptake and the concentration of cells at the sediment–water interface, forming a dense biofilm of MPB, were postulated to be the main processes reducing effluxes at midday. Our work highlighted the many processes which influence silicic acid effluxes in shallow coastal areas and the possible interaction between uptake and dissolution processes. The variations in benthic fluxes over the diurnal period were comparable to observations reported at the seasonal scale. Therefore, up-scaling hourly flux observations to daily and annual estimates should be undertaken with caution. Further we suggest that the main processes influencing flux oscillations over the diurnal period should be considered when planning sampling strategies and extrapolating to larger time scales.
Published: 2009
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15. Response of a phytoplankton community to increased nutrient inputs: A mesocosm experiment in the Bay of Brest (France)

Author: Pascal Claquin, Stéphane L'Helguen, Philippe Pondaven, Aude Leynaert, Annick Masson, Pierre Fouillaron, Véronique Martin-Jézéquel, Gérard Thouzeau, Pierre Huonnic, Sorcha Ní Longphuirt, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), Physiologie et Ecophysiologie des Mollusques Marins (PE2M), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS), Adaptation et diversité en milieu marin (AD2M), Station biologique de Roscoff [Roscoff] (SBR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Mer, molécules et santé EA 2160 (MMS), Université de Nantes - UFR des Sciences Pharmaceutiques et Biologiques, Université de Nantes (UN)-Université de Nantes (UN)-Le Mans Université (UM)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN), Région Bretagne and is part of an INVABIO 2 project that was funded by the Ministère de l'Ecologie et du Développement Durable, Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Le Mans Université (UM)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Université de Nantes - UFR des Sciences Pharmaceutiques et Biologiques, and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, biology, Ecology, 010604 marine biology & hydrobiology, Chaetoceros, Aquatic Science, biology.organism_classification, 01 natural sciences, Algal bloom, Mesocosm, Diatom, Benthic zone, Phytoplankton, Dominance (ecology), 14. Life underwater, Bay, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences
Abstract: International audience; In the Bay of Brest (France), benthic fluxes of silicic acid (DSi) are thought to be strongly involved in diatom dominance and their intensity depends on the density of an invasive gastropod, Crepidula fornicata. While the proliferation of this gastropod is likely to support diatom dominance, local fishermen have proposed its removal as it perturbs the development of the native Great Scallop, Pecten maximus. However, such a removal may be associated with potentially harmful algal blooms. The response of the phytoplankton community to modifications of the benthic fluxes of DSi, resulting from a further proliferation or the removal of C fornicata, was examined in a mesocosm nutrient enrichment experiment over a period of 16 days in the spring of 2004. Six mesocosms (5.4 m(3)) were filled using a natural planktonic assemblage from the Bay and received N, P and Si additions at the stoichiometric ratio of the in situ benthic fluxes (Si:N:P=16:16:1), with a gradient of enrichment ranging from 0 to almost 4 times the maximal benthic flux measured in the Bay. The diatom Chaetoceros (mainly C. debilis) rapidly outgrew non-siliceous species of microphytoplankton in all enclosures although kinetic experiments provided direct evidence of Si limitation. This dominance of diatoms at DSi concentrations
Published: 2007
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16. Biological control of trace metal and organometal benthic fluxes in a eutrophic lagoon (Thau Lagoon, Mediterranean Sea, France)

Author: Jacques Grall, Frédéric Jean, David Point, David Amouroux, Gérard Thouzeau, Olivier F. X. Donard, Erwan Amice, Emmanuel Tessier, Mathilde Monperrus, Aude Leynaert, Jacques Clavier, Laurent Chauvaud, Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université européenne de Bretagne - European University of Brittany (UEB)
Subjects: Biogeochemical cycle, mercury, 010504 meteorology & atmospheric sciences, trace metals, sediment–water exchanges, biota, 010501 environmental sciences, Aquatic Science, Oceanography, 01 natural sciences, Mediterranean Sea, Trace metal, 14. Life underwater, 0105 earth and related environmental sciences, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, geography, geography.geographical_feature_category, Thau Lagoon, Trace element, Sediment, Estuary, Redox gradient, speciation, 13. Climate action, Benthic zone, Environmental science, Spatial variability, France, organotin
Abstract: International audience; In situ benthic chamber experiments were conducted in the Thau Lagoon that allowed the simultaneous determination of the benthic exchanges of trace metals (Cd, Co, Cu, Mn, Pb and U) and mercury species (iHg and MMHg). Fluxes of organotin compounds (MBT, DBT and TBT) were also investigated for the first time. The benthic incubations were performed during two campaigns at four stations that presented different macrobenthic and macrophytic species distribution and abundance (see [Thouzeau, G., Grall, J., Clavier, J., Chauvaud, L., Jean, F., Leynaert, A., Longpuirt, S., Amice, E., Amouroux, D., 2007. Spatial and temporal variability of benthic biogeochemical fluxes associated with macrophytic and macrofaunal distributions in the Thau lagoon (France). Estuarine, Coastal and Shelf Science 72 (3), 432–446.]). The results indicate that most of the flux intensity as well as the temporal and spatial variability can be explained by the combined influence of microscale and macroscale processes. Microscale changes were identified using Mn flux as a good indicator of the redox conditions at the sediment–water interface, and by extension, as an accurate proxy of benthic fluxes for most trace metals and mercury species. We also observed that the redox gradient at the interface is promoted by both microbial and macrobenthic species activity that governs O2 budgets. Macroscale processes have been investigated considering macrobenthic organisms activity (macrofauna and macroalgal cover). The density of such macroorganisms is able to explain most of the spatial and temporal variability of the benthic metal fluxes within a specific site. A tentative estimation of the flux of metals and organometals associated with deposit feeder and suspension feeder activity was found to be in the range of the flux determined within the chambers for most considered elements. Furthermore, a light/dark incubation investigating a dense macroalgal cover present at the sediment surface illustrates the role of photosynthetic activity in controlling benthic exchanges. Significant changes in benthic flux intensity and/or direction were reported for all redox sensitive elements (Cd, Co, Cu, Mn, Pb, U, and iHg). For MMHg and organotin species, other complimentary processes such as photodegradation/uptake and hydrophobic absorption/desorption need to be considered. This work demonstrates that the processes governing benthic exchanges are complex and that benthic organisms play a major role in the significant seasonal, diurnal and spatial variability of trace metals and organometals benthic fluxes in the lagoon.
Published: 2007
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17. Benthic O2 distribution and dynamics in a Mediterranean lagoon (Thau, France): An in situ microelectrode study

Author: Jacques Clavier, Christophe Rabouille, Karine Dedieu, S. Ogier, Gérard Thouzeau, Laurent Chauvaud, Frédéric Jean, Valérie Mesnage, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Océan et Interfaces (OCEANIS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO)
Subjects: 0106 biological sciences, Oyster, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, coastal ocean, Oyster farming, Aquatic Science, Oceanography, 01 natural sciences, Bottom water, biology.animal, sedimentewater exchange, medicine, benthic recycling, Organic matter, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, 14. Life underwater, 0105 earth and related environmental sciences, Total organic carbon, chemistry.chemical_classification, biology, 010604 marine biology & hydrobiology, 15. Life on land, Seasonality, biology.organism_classification, medicine.disease, microelectrode, chemistry, 13. Climate action, Benthic zone, organic carbon mineralization, Environmental science, oxygen
Abstract: Benthic oxygen profiles were acquired using microsensors over two seasonal cycles (December 2001, April and August 2002, January and May 2003) at two stations differently affected by shellfish farming activity in the Thau lagoon (French Mediterranean coast). This study was part of the Microbent-PNEC Program on the study of biogeochemical processes at the sedimentewater interface in an eutrophicated environment. We explored seasonal and spatial heterogeneity as well as the biogeochemical drivers of oxygen uptake, such as in situ temperature, bottom water oxygenation and organic matter deposition. O2 consumption rates were determined by using a transport-reaction model. Maximum rates were reached in August and May and minimum rates in December, April or January. The effect of oyster farming on oxygen fluxes was clearly identified with higher diffusive oxygen uptake in the station inside the oyster parks (C5; 36.8 18.5e87.7 40.8 mmol m2 d1), compared with the station lying outside the oyster parks (C4; 8.6 2.1e30.7 8.3 mmol m2 d1). At C5, the large spatial heterogeneity was statistically concealing temporal variation, whereas a clear statistical difference between cold and warm periods appeared at C4. In these lagoon sediments, the seasonal dynamics of diffusive oxygen demand and consumption rates were mainly driven by seasonal temperature variation at both stations, as well as by seasonal organic matter delivery to the sediment at the station located outside the oyster parks. In the station located below the oyster parks, seasonal variation of organic matter deposition was dampened by oyster filtering activity. Seasonal temperature variation thus appeared as the major driver of oxygen dynamics in this station. Measurements of total O2 uptake rates indicated a significant fraction of microbial recycling and diffusive transport in oxygen uptake at the station located close to the oyster parks. In the open water site, fauna-mediated O2 transport prevailed in April 2002 (cold conditions), whereas the microbial recycling seemed to dominate in May 2003 (warm conditions). 2006 Elsevier Ltd. All rights reserved.
Published: 2007
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18. Gregariousness and protandry promote reproductive insurance in the invasive gastropod Crepidula fornicata: evidence from assignment of larval paternity

Author: Lise Dupont, Joëlle Richard, Frédérique Viard, Gérard Thouzeau, and Yves-Marie Paulet
Subjects: 0106 biological sciences, biology, Sequential hermaphroditism, Reproductive success, Ecology, 010604 marine biology & hydrobiology, Zoology, Sex reversal, biology.organism_classification, 010603 evolutionary biology, 01 natural sciences, Intraspecific competition, Hermaphrodite, Genetics, Crepidula, Mating, Sperm competition, reproductive and urinary physiology, Ecology, Evolution, Behavior and Systematics
Abstract: According to the size-advantage hypothesis, protandric sequential hermaphroditism is expected when the increase in reproductive success with age or size is small for males but large for females. Interestingly, some protandrous molluscs have developed gregarious strategies that might enhance male reproductive success but at the cost of intraspecific competition. The gastropod Crepidula fornicata, a European invading species, is ideal for investigating mating patterns in a sequential hermaphrodite in relation to grouping behaviour because individuals of different size (age) live in perennial stacks, fertilization is internal and embryos are brooded. Paternity analyses were undertaken in stacks sampled in three close and recently invaded sites in Brittany, France. Paternity assignment of 239 larvae, sampled from a set of 18 brooding females and carried out using five microsatellite loci, revealed that 92% of the crosses occurred between individuals located in the same stack. These stacks thus function as independent mating groups in which individuals may reproduce consecutively as male and female over a short time period, a pattern explained by sperm storage capacity. Gregariousness and sex reversal are promoting reproductive insurance in this species. In addition, females are usually fertilized by several males (78% of the broods were multiply sired) occupying any position within the stack, a result reinforcing the hypothesis of sperm competition. Our study pointed out that mating behaviours and patterns of gender allocation varied in concert across sites suggesting that multiple paternities might enhance sex reversal depending on sperm competition intensity.
Published: 2006
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19. Comparison of Zostera marina and maerl community metabolism

Author: Jean-Marc Guarini, Laurent Chauvaud, Jacques Grall, Joëlle Richard, Sophie Martin, Frédéric Jean, Gérard Thouzeau, Christian Hily, Jacques Clavier, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche sur les Ecosystèmes Marins et Aquacoles (CREMA), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS), and Sanz, Frédérique
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 0106 biological sciences, biology, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, Ecology, 010604 marine biology & hydrobiology, Plant Science, Aquatic Science, biology.organism_classification, 010603 evolutionary biology, 01 natural sciences, Seagrass, Benthic zone, Temperate climate, Zostera marina, Ecosystem, 14. Life underwater, Autotroph, Maerl, Bay
Abstract: The photosynthetic and repiratory metabolism of Zostera marina and maerl communities was compared, in the same area of the Bay of Brest in March–April, using benthic chambers. P–E curves for both oxygen and carbon were established for bottom irradiances between 0 and 525 μmol m−2 s−1. An exponential function was fitted to calculate daily production. Community metabolic quotients did not differ for maerl and seagrass beds. Community photosynthetic quotients were significantly higher (1.19) whereas community respiratory quotients were lower (0.70) than 1. Maerl and seagrass bed P–E curves mainly differed by the minimum saturating irradiance (Ek). Net community production was estimated to 26.8 mmol C m−2 d−1 for Z. marina meadows and 8.6 mmol C m−2 d−1 for maerl beds. The two communities can, therefore, be considered as autotrophic during the March–April period. Community respiration did not differ between Z. marina meadows and maerl beds, with an average value of 53.8 mmol C m−2 d−1 during a day. In similar environmental conditions, the production of maerl beds corresponds to approximately one third that of seagrass meadows. The maerl communities, therefore, form productive ecosystems, relevant to temperate coastal ecosystems functioning.
Published: 2005
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20. MMHg production and export from intertidal sediments to the water column of a tidal lagoon (Arcachon Bay, France)

Author: Jacques Clavier, Pablo Rodríguez-González, Jonathan Deborde, Jacques Grall, Stéphane Bujan, David Amouroux, Pierre Anschutz, Emmanuel Tessier, Erwan Amice, Gérard Thouzeau, Sylvain Bouchet, Mathilde Monperrus, Laboratoire de Chimie Analytique Bio-Inorganique et Environnement (LCABIE), Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and Université de Brest (UBO)
Subjects: 010504 meteorology & atmospheric sciences, Benthic reactivity, Tidal cycling, Sediment, Intertidal zone, 010501 environmental sciences, 01 natural sciences, 6. Clean water, Water column, Oceanography, 13. Climate action, Benthic zone, Bioaccumulation, [SDE]Environmental Sciences, Erosion, Environmental Chemistry, Environmental science, Ecosystem, 14. Life underwater, Mercury species, Coastal ecosystem, Bay, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology
Abstract: International audience; Hg cycling in biologically productive coastal areas is of special importance given the potential for bioaccumulation of monomethylmercury (MMHg) into aquatic organisms. Field experiments were performed during three different seasons in Arcachon Bay, a mesotidal lagoon (SW France), to assess the variability of the water column concentrations, sediment-water exchanges and potential formation and degradation of MMHg. The objectives were to evaluate the contribution of intertidal mudflats to MMHg production and the various pathways of Hg species export. Dissolved and bulk concentrations of Hg species in the water column downstream of tidal flats were measured throughout several tidal cycles. The Hg benthic fluxes at the sediment-water interface were determined by means of benthic chambers for three different stations. Hg methylation and demethylation potentials were determined in surficial sediments and the water column using isotopic tracers. The tidal surveys demonstrated that benthic remobilization of Hg occurs primarily in association with sediment erosion and advection during ebb tide. However, elevated dissolved Hg concentrations observed at low tide were found to be caused by a combination of pore-waters seeping, benthic fluxes and methylation in the water column. Benthic fluxes were more intense during late winter conditions (median MMHg and inorganic Hg (IHg) fluxes: 64 and 179 pmol m-2 h-1, respectively) and subsequently decreased in spring (median 0.7 and -5 pmol m-2 h-1, respectively) and fall (median -0.4 and -1.3 pmol m-2 h-1, respectively). The trends in methylation and demethylation potentials were at the opposite of the fluxes, two times lower during winter than for spring or fall conditions. In this tidal environment, MMHg production in surface sediments and its subsequent release is estimated to be the major source of MMHg to the water column during winter and spring time. However, during the more productive summer period, the Hg methylation extent in the water column may be very significant and equivalent to the sediment contribution.
Published: 2013
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21. Measurements of gaseous mercury exchanges at the sediment-water, water-atmosphere and sediment-atmosphere interfaces of a tidal environment (Arcachon Bay, France)

Author: Gérard Thouzeau, Jacques Clavier, Romain Bridou, Emmanuel Tessier, Mathilde Monperrus, Sylvain Bouchet, David Amouroux, Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and ANR-06-BLAN-0040,PROTIDAL,Les processus biogéochimiques transitoires de la zone intertidale(2006)
Subjects: Geologic Sediments, 010504 meteorology & atmospheric sciences, Intertidal zone, 010501 environmental sciences, Management, Monitoring, Policy and Law, Atmospheric sciences, 01 natural sciences, Phase Transition, Wind speed, Flux (metallurgy), Water column, Seawater, 0105 earth and related environmental sciences, Hydrology, Air Pollutants, Gaseous mercury, Atmosphere, Public Health, Environmental and Occupational Health, Mercury, General Medicine, Contamination, 13. Climate action, [SDE]Environmental Sciences, Environmental science, France, Bay, Exchange model, Water Pollutants, Chemical, Environmental Monitoring
Abstract: International audience; The elemental mercury evasion from non-impacted natural areas is of significant importance in the global Hg cycle due to their large spatial coverage. Intertidal areas represent a dynamic environment promoting the transformations of Hg species and their subsequent redistribution. A major challenge remains in providing reliable data on Hg species variability and fluxes under typical transient tidal conditions found in such environment. Field experiments were thus carried out to allow the assessment and comparison of the magnitude of the gaseous Hg fluxes at the three interfaces, sediment-water, sediment-atmosphere and water-atmosphere of a mesotidal temperate lagoon (Arcachon Bay, Aquitaine, France) over three distinct seasonal conditions. The fluxes between the sediment-water and the sediment-atmosphere interfaces were directly evaluated with field flux chambers, respectively static or dynamic. Water-atmosphere fluxes were evaluated from ambient concentrations using a gas exchange model. The fluxes at the sediment-water interface ranged from −5.0 to 5.1 ng m−2 h−1 and appeared mainly controlled by diffusion. The occurrence of macrophytic covers (i.e.Zostera noltii sp.) enhanced the fluxes under light radiations. The first direct measurements of sediment-atmosphere fluxes are reported here. The exchanges were more intense and variable than the two other interfaces, ranging between −78 and 40 ng m−2 h−1 and were mostly driven by the overlying atmospheric Hg concentrations and superficial sediment temperature. The exchanges between the water column and the atmosphere, computed as a function of wind speed and gaseous mercury saturation ranged from 0.4 to 14.5 ng m−2 h−1. The flux intensities recorded over the intertidal sediments periodically exposed to the atmosphere were roughly 2 to 3 times higher than the fluxes of the other interfaces. The evasion of elemental mercury from emerged intertidal sediments is probably a significant pathway for Hg evasion in such tidal environments exhibiting background contamination level.
Published: 2011
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22. Methane sources, sinks and fluxes in a temperate tidal lagoon: The Arcachon Lagoon (SW France)

Author: Guy Boucher, Mathieu Canton, Jonathan Deborde, Frédéric Guérin, Gwenaël Abril, Dominique Poirier, Gérard Thouzeau, Danielle Marty, Pierre Anschutz, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Mécanismes et Transfert en Géologie (LMTG), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Centre d'océanologie de Marseille (COM), Université de la Méditerranée - Aix-Marseille 2-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Biologie des organismes marins et écosystèmes (BOME), Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), French National Programme on Coastal Environment (PNEC 'Chantier Littoral Atlantique') and the ANR project PROTIDAL, ANR-06-BLAN-0040,PROTIDAL,Les processus biogéochimiques transitoires de la zone intertidale(2006), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Wetland, Aquatic Science, Oceanography, 01 natural sciences, Methane, Atmosphere, chemistry.chemical_compound, Pore water pressure, Water column, Arcachon Lagoon, 14. Life underwater, Water pollution, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, methane, Sediment, 6. Clean water, coastal environment, chemistry, chamber flux measurements, 13. Climate action, Environmental science, Water quality, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: The Arcachon lagoon is a 156 km 2 temperate mesotidal lagoon dominated by tidal flats (66% of the surface area). The methane (CH 4 ) sources, sinks and fluxes were estimated from water and pore water concentrations, from chamber flux measurements at the sediment–air (low tide), sediment–water and water–air (high tide) interfaces, and from potential oxidation and production rate measurements in sediments. CH 4 concentrations in waters were maximal (500–1000 nmol l −1 ) in river waters and in tidal creeks at low tide, and minimal in the lagoon at high tide ( −1 ). The major CH 4 sources are continental waters and the tidal pumping of sediment pore waters at low tide. Methanogenesis occurred in the tidal flat sediments, in which pore water concentrations were relatively high (2.5–8.0 μmol l −1 ). Nevertheless, the sediment was a minor CH 4 source for the water column and the atmosphere because of a high degree of anaerobic and aerobic CH 4 oxidation in sediments. Atmospheric CH 4 fluxes at high and low tide were low compared to freshwater wetlands. Temperate tidal lagoons appear to be very minor contributor of CH 4 to global atmosphere and to open ocean.
Published: 2010
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23. Benthic-pelagic coupling and the seasonal silica cycle in the Bay of Brest (France): new insights from a coupled physical-biological model

Author: Olivier Ragueneau, Goulven Gildas Laruelle, M. Kempa, Gérard Thouzeau, Brivaëla Moriceau, Pierre Regnier, Ni S.N. Longphuirt, Aude Leynaert, Laurent Chauvaud, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Mass distribution, 0106 biological sciences, 010504 meteorology & atmospheric sciences, Dissolved silica, Numerical models, Population, Aquatic Science, Biology, Coastal zone, 01 natural sciences, Algal bloom, 14. Life underwater, education, Crepidula fornicata, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, education.field_of_study, geography, geography.geographical_feature_category, Ecology, Harmful algal bloom, 010604 marine biology & hydrobiology, Silica, Pelagic zone, Estuary, ANE, France, Brittany, Brest Bay, Benthic-pelagic coupling, Plankton, Estuarine environment, Oceanography, 13. Climate action, Benthic zone, Nutrient cycles, [SDE]Environmental Sciences, Algal blooms, Heterogeneity, Crepidula fornicata (Linnaeus, 1758), Bay
Abstract: International audience; A fully transient, 2-dimensional physical and biological model has been developed to quantify the seasonal cycle of silica in the estuaries-coastal zone continuum of the Bay of Brest (France). The numerical model includes an explicit representation of the benthic-pelagic coupling, which is stimulated by the increasing density of an invasive megabenthic filter feeder, the slipper limpet Crepidula fornicata. The selected spatial resolution allows resolution of the heterogeneous density distribution of these organisms in the bay. Results show that the benthic nutrient dynamics are highly variable and strongly depend on the local conditions. This heterogeneity is not reflected in the pelagic phytoplankton Population dynamics because transport and mixing homogenize the distribution of nutrients and biomass. A seasonally resolved silica budget over the entire bay and estuaries emphasizes the important contribution of the benthic recycling fluxes to the supply of dissolved silica (dSi) during the productive period (similar to 50%, from 1 April to 1 September). In a prognostic scenario which forecasts the impact of removing the invasive benthic filter feeders, the dSi efflux is reduced by 63% and a pronounced harmful algal bloom of dinoflagellates develops in late summer.
Published: 2009
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24. Diel variation of benthic respiration in a coral reef sediment (Reunion Island, Indian Ocean)

Author: Clémentine Esbelin, Jacques Clavier, Gérard Thouzeau, Laurent Chauvaud, Patrick Frouin, Pascale Cuet, Dorothée Taddei, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Ecologie Marine (ECOMAR), and Université de La Réunion (UR)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Aquatic Science, Oceanography, 01 natural sciences, chemistry.chemical_compound, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Respiration, Dissolved organic carbon, 14. Life underwater, Reef, Diel vertical migration, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, fungi, sediments, carbon dioxide, Coral reef, chemistry, Benthic zone, Carbon dioxide, coral reef, Limiting oxygen concentration, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, metabolism, oxygen, Geology, geographic locations, respiration
Abstract: International audience; Oxygen and total dissolved inorganic carbon (DIC) fluxes at the water–sediment interface were measured using benthic chambers to assess the short-term variations of community respiration (CR) in the back reef sediments of Reunion Island (Indian Ocean). Benthic CR had a daily cycle of minimal (6:00 AM) and maximal values (6:00 PM), showing increases of oxygen and DIC fluxes of 2.8- and 3.8-fold, respectively. Average CR values were observed at midday and midnight. The evolution of fluxes was positively related to oxygen concentration in ambient water, but not to temperature changes. In the study area, high daytime primary production augments the amount of energy available for community metabolism and increases benthic respiration. The benthic communities are therefore subjected to short-term variable environmental conditions with oxygen supersaturation during the day, and moderately hypoxic conditions at the end of the night.
Published: 2008
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25. Effects of seasonal dynamics in a Zostera noltiimeadow on phosphorus and iron cycles in a tidalmudflat (Arcachon Bay, France)

Author: Gérard Thouzeau, Jonathan Deborde, Guy Bachelet, Aurélia Mouret, Pierre Anschutz, Gwenaël Abril, Didier Jézéquel, Jacques Clavier, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Institut de Physique du Globe de Paris (IPGP (UMR_7154)), Institut national des sciences de l'Univers (INSU - CNRS)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, eelgrass growth, Intertidal zone, Aquatic Science, 01 natural sciences, Pore water pressure, Water column, Nutrient, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Organic matter, Zostera, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Early diagenesis, Ecology, Evolution, Behavior and Systematics, Eelgrass growth, 0105 earth and related environmental sciences, intertidal zone, chemistry.chemical_classification, Ecology, biology, 010604 marine biology & hydrobiology, nutrient, Sediment, Lagoon, 15. Life on land, biology.organism_classification, 6. Clean water, lagoon, Oceanography, chemistry, Environmental chemistry, early diagenesis, Bay
Abstract: International audience; A study was conducted in Arcachon Bay, France, to determine the effect of seasonal dynamics in a Zostera noltii meadow on P and Fe cycles in the superficial sediments of a tidal mudflat. The redox-sensitive Fe particulate pool and associated P in the root zone showed a seasonal variation following the growth and decay of Z. noltii biomass, with a maximum content during the growth period. In comparison, the bare sediments did not show significant seasonal changes. A dissolved inorganic phosphorus (DIP) uptake was measured from the water column to the sediment in vegetated sediments, whereas a net DIP efflux was observed in the unvegetated sediments. During the growth period, the formation of an iron oxihydroxide-rich zone occurred and acted as a trap for dissolved phosphorus, constituting a reserve of available P for eelgrass growth. At the periphery of the rhizosphere, a strong reduction of the sediment occurred during the growth phase, probably due to increasing organic matter inputs via the roots. The iron oxihydroxide dissolution releases Fe(II) and the recently bound phosphorus to the pore water, making it available for assimilation by the eelgrass roots for growth metabolism. Fe(II) is re-oxidized to solid Fe(III) forms depleted in P into the root zone, or re-precipitated below as sulphur forms. The highest P uptake occurs by this process, and the seasonal variations in redox-sensitive P stock are sufficient to support the annual Z. noltii P requirement. During the decline period, as the P plant demand and the oxic layer thickness drop, the unused released DIP pool supplies large amounts of DIP to the pore water and water column.
Published: 2008
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26. Growth of Argopecten purpuratus (Mollusca: Bivalvia) on a natural bank in Northern Chile: sclerochronological record and environmental controls

Author: Laurent Chauvaud, Miguel Avendaño, Marcela Cantillánez, Julien Thébault, Gérard Thouzeau, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Universidad de Antofagasta, Facultad de Recursos del Mar, Universidad de Antofagasta, This work was supported by international programs of cooperation between France and Chile (CNRS-CONICYT and ECOS-Sud C98B02 and C06B04) undertaken by the University of Antofagasta (Departamento de Acuicultura) and the University of Western Brittany (UMR 6539 CNRS)., and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Argopecten purpuratus, Population, Aquatic Science, 01 natural sciences, Scallop aquaculture, 14. Life underwater, education, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, education.field_of_study, biology, Ecology, 010604 marine biology & hydrobiology, Marine reserve, 04 agricultural and veterinary sciences, Bivalvia, biology.organism_classification, [SDV.BA.ZI]Life Sciences [q-bio]/Animal biology/Invertebrate Zoology, Oceanography, Scallop, [SDE]Environmental Sciences, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Upwelling, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bay
Abstract: The copyright to this article was transferred to EDP Sciences, IFREMER and IRD. The original publication is available at www.edpsciences.org/alr.; International audience; Daily striae on the shell of the scallop, Argopecten purpuratus, were used to investigate its growth in a protected population within La Rinconada Bay, near Antofagasta (2nd Region, Northern Chile), and to determine how environmental forcings control shell growth. This sclerochronological approach was useful to describe daily shell growth a posteriori. Mean shell growth rates were calculated daily between February and October 1999 from shells of six specimens harvested on 15 October 1999. A multiple regression analysis performed on shell growth and environmental data shows that a temperature increase stimulates shell growth whereas particulate organic carbon concentration might be stressful above 2.5 mg L-1. The lunar cycle might also have an effect on growth, most potent around New Moons, by synchronizing an endogenous oscillator. The age at commercial size (90 mm) was only 10–11 months in La Rinconada Marine Reserve and the von Bertalanffy growth parameters were K = 2.24 y-1 and Hoo = 117 mm. Differences in shell growth performances between this study and previous ones dealing with A. purpuratus growth may be explained by the different methods used for shell growth modelling, higher growth rate on the seabed compared to suspended cultures, and particular environmental forcings (e.g. El Niño Southern Oscillation-ENSO events). Growth performance seems better during La Niña than during El Niño events, probably because of the large temperature increase (above the highest temperatures recorded in “normal” conditions) and the decline in coastal upwelling (which affects food availability) during El Niño. La Rinconada Marine Reserve appears as a very favourable site for A. purpuratus growth, probably because of the active upwelling zone off Antofagasta. These new insights on A. purpuratus shell growth confirm the importance of La Rinconada Marine Reserve as an area supporting repopulation of endangered wild stocks and scallop aquaculture in Chile.
Published: 2008
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27. Effects of water depth on survival and growth of Argopecten purpuratus (Lamarck, 1819) spat in Northern Chile

Author: Gérard Thouzeau, Marcela Cantillánez, Miguel Avendaño, Thouzeau, Gérard, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Argopecten purpuratus, biology, 010604 marine biology & hydrobiology, Marine reserve, 04 agricultural and veterinary sciences, Aquatic Science, biology.organism_classification, 01 natural sciences, Water depth, Fishery, [SDE.BE] Environmental Sciences/Biodiversity and Ecology, stomatognathic diseases, [SDV.AEN] Life Sciences [q-bio]/Food and Nutrition, Scallop, otorhinolaryngologic diseases, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Environmental science, 14. Life underwater, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Agronomy and Crop Science, Bay, [SDV.AEN]Life Sciences [q-bio]/Food and Nutrition, ComputingMilieux_MISCELLANEOUS
Abstract: Collection and suspended culture of Argopecten purpuratus spat in Japanese-type collectors was undertaken in the Rinconada Marine Reserve (Antofagasta, Chile) to determine growth variations between surface and bottom waters. Scallop spat was collected at 16-m depth and grown at 1- and 16-m depths. An initial settlement of ca. 13,000 post-larvae per bottom collector (2 cohorts) was observed on 3 February 2001. Two new cohorts settled in bottom collectors on 3 March, while no spat settlement occurred in surface collectors. The four cohorts exhibited substantial and different mortality rates over the study period, depending on the cohort and on-growing depth. The first and second cohorts exhibited mortality rates of 80.3 and 53.1% in bottom collectors, respectively, versus 29 and 43.6% in surface structures. The third and fourth cohorts exhibited mortality rates of 21.4 and 59.7% in bottom collectors, respectively. Mean shell height of scallop spat after 88 days of culture was 6.46 mm for the first cohort and 4.37 mm for the second cohort in bottom collectors, versus 10.33 and 7.31 mm in surface collectors, respectively. Mean post-larval growth rate in bottom collectors (86 μm day−1) was significantly lower than growth rate in surface collectors (146 μm day−1). Factors explaining the depth-related mortality and growth rates are discussed to improve scallop culture in the Reserve. It was concluded from the results that culture improvement in Antofagasta Bay would require collecting spat in bottom waters and raising it near the surface during initial cultivation stages.
Published: 2008

28. Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay

Author: Gérald Duchemin, Gérard Thouzeau, Christian Hily, Françoise Andrieux-Loyer, Frans Jorissen, François Le Loc'h, and Thouzeau, Gérard
Subjects: 010506 paleontology, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Aquatic Science, Oceanography, 01 natural sciences, Algal bloom, Foraminifera, Phytoplankton, 14. Life underwater, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, biology, Continental shelf, Benthic foraminifera, Phytodetritus, Pelagic-benthic coupling, Bay of biscay, Seasonality, biology.organism_classification, [SDE.BE] Environmental Sciences/Biodiversity and Ecology, Cassidulina, [SDE.MCG] Environmental Sciences/Global Changes, Benthic zone, France, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bay, Geology
Abstract: Living benthic foraminiferal faunas of six stations from the continental shelf of the Bay of Biscay have been investigated during three successive seasons (spring, summer and autumn 2002). For the three investigated stations, bottom water oxygen concentration, oxygen penetration into the sediment and sediment organic carbon contents are all relatively similar. Therefore, we think that the density and the composition of the foraminiferal faunas is mainly controlled by the quantity and quality of organic input resulting from a succession of phytoplankton bloom events, occurring from late February to early September. The earliest blooms are positioned at the shelf break, late spring and early summer blooms occur off Brittany, whereas in late summer and early autumn, only coastal blooms appear, often in the vicinity of river outlets. In spring, the benthic foraminiferal faunas of central (B, C and D) and outer (E) continental shelf stations are characterised by strong dominance in the first area and strong presence in the second area of Nonionella iridea. In fact, station E does not serve as a major depocenter for the remains of phytoplankton blooms. If station E is not considered, the densities of this taxon show a clear gradient from the shelf-break, where the species dominates the assemblages, to the coast, where it attains very low densities. We explain this gradient as a response to the presence, in early spring, of an important phytoplankton bloom, mainly composed of coccolithophorids, over the shelf break. This observation is supported by the maximum particles flux values at stations close to the shelf break (18.5 g m− 2 h− 1) and lower values in a station closer to the coast (6.8 g m− 2 h− 1). In summer, the faunal density is maximum at station A, relatively close to more varied phytoplancton blooms that occur off Brittany until early June. We suggest that the dominant species, Nonion fabum, Cassidulina carinata and Bolivina ex. gr. dilatata respond to phytodetritus input from these blooms. In autumn, the rich faunas of inner shelf station G are dominated by N. fabum, B. ex. gr. dilatata, Hyalinea balthica and Nonionella turgida. These taxa seem to be correlated with the presence of coastal blooms phenomena, in front of river outlets. They may be favoured by an organic input with a significant contribution of terrestrial, rather low quality organic matter.
Published: 2008

29. Capacitación artificial y crecimiento temprano de la 'semilla' de Argopecten purpuratus (Lamarck, 1819) en la reserva marina La Rinconada, Antofagasta, Chile

Author: Gérard Thouzeau, D Miguel Avendaño, S Marcela Cantillánez, Juan B. Peña, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: 0106 biological sciences, Argopecten purpuratus, Survival, captación de semilla, crecimiento, SH1-691, Growth, Aquatic Science, Oceanography, 01 natural sciences, lcsh:Aquaculture. Fisheries. Angling, Intraspecific competition, Larvae, Aquaculture. Fisheries. Angling, 14. Life underwater, larvas, Chile, [SDV.BDLR] Life Sciences [q-bio]/Reproductive Biology, ComputingMilieux_MISCELLANEOUS, lcsh:SH1-691, Larva, supervivencia, biology, 010604 marine biology & hydrobiology, Marine reserve, [SDV.BDLR]Life Sciences [q-bio]/Reproductive Biology, Spat collection, 04 agricultural and veterinary sciences, biology.organism_classification, [SDE.BE] Environmental Sciences/Biodiversity and Ecology, Fishery, Scallop, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Scallop larvae, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bay
Abstract: Artificial collection of early juveniles ("spat") of the scallop Argopecten purpuratus in Japanese-type collectors was evaluated between January 2001 and July 2002 in the La Rinconada Marine Reserve, Antofagasta, Chile. This area of Antofagasta Bay has in the past been noted for the retention of scallop larvae by local gyres, in which their numbers can vary between 89 and 34175 larvae m-3, producing larval sets of 400 to 15340 post-larvae (spat) per collector. The results showed no quantitative relationship between larval abundance in the water and the spat density collected per day in the collectors, although high settlement rates were associated with high numbers of umboned larvae in the water. Allowing collectors to remain in situ for extended periods of 88 and 159 days resulted in a severe loss of seed which had settled in the collectors during the first 28 to 40 days of immersion. These losses varied between 50.9 and 99.6% of the spat collected, and were more prejudicial for the smaller cohorts that had settled in the collectors at the end of the first immersion period. The growth rates measured among different cohorts for each immersion period varied between 81.3 and 235.2 mm/day for the first cohort (C1) and between 64.0 and 167.4 mm/day for the second cohort (C2). The highest growth rates occurred in collectors containing the lowest numbers of spat after the occurrence of spat losses during the long periods of immersion. Occurrence of intraspecific competition within the collectors is discussed as potentially responsible for the decreases in spat numbers and the variations observed in their growth rates., Un programa mensual de captación de A. purpuratus, implementado en la reserva marina de La Rinconada, entre enero de 2001 y julio de 2002, la caracterizó como zona de retención larvaria, con densidades variando entre 89 y 34175 larvas m-3, y de fijaciones entre 400 y 15340 post-larvas por colector. No se encontró una relación directa entre abundancia larvaria y asentamiento, sin embargo, las mayores captaciones estuvieron asociadas a la presencia de un elevado número de estados umbonados. La mantenimiento prolongado de colectores in situ, por periodos que variaron entre 88 y 159 días, provocó una fuerte reducción en el número de semillas que se asentaron en ellos durante los primeros 28 a 40 días de inmersión. Estas reducciones variaron entre el 99.6 y el 50.9% de la semilla fijada, siendo las más perjudicadas las cohortes más pequeñas, asentadas al final del primer periodo de inmersión. Las tasas de crecimiento registradas en estas cohortes, para cada periodo de inmersión, variaron entre 81.3 y 235.2 μm/día para las cohortes C1 y entre 64.0 y 167.4 μm/día para las cohortes C2. Las mayores tasas están directamente relacionadas con un menor número de semilla recuperada. Se discuten las competencias intraespecíficas ocurridas en los colectores, como responsables de la disminución del número de semilla y de las variaciones registradas en sus tasas de crecimiento., The present study was carried out within the framework of the FNDR project, Code BIP N°20127869-0.
Published: 2007
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30. Summer influence of 1 and 2 yr old mussel cultures on benthic fluxes in Grande-Entrée lagoon, Iles-de-la-Madeleine (Québec, Canada)

Author: Marion Richard, Philippe Archambault, Gérard Thouzeau, Gaston Desrosiers, Thouzeau, Gérard, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, [SDE.MCG]Environmental Sciences/Global Changes, Aquatic Science, 01 natural sciences, Bottom water, Nutrient, Water column, Organic matter, 14. Life underwater, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, chemistry.chemical_classification, Biomass (ecology), Ecology, 010604 marine biology & hydrobiology, Sediment, 04 agricultural and veterinary sciences, Mussel, 6. Clean water, [SDE.MCG] Environmental Sciences/Global Changes, Oceanography, chemistry, Benthic zone, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Environmental science
Abstract: The summer influence of 1 and 2 yr old suspended mussel lines on benthic fluxes (oxy- gen, silicates, ammonium, phosphates, nitrates and nitrites) was studied in Grande-Entree lagoon (GEL), Iles-de-la-Madeleine, Quebec, Canada. This influence and its temporal variation were exam- ined in relation to bottom water, sediment and macrofauna characteristics. In situ mensurative exper- iments using benthic chambers and sediment cores were carried out at 2 mussel sites (M1 and M2) and 2 control sites (C1 and C2) in July, August and September 2003. In contrast to 1 yr old mussel lines (M1), 2 yr old lines (M2) enriched the sediment in organic matter and increased silicate, ammo- nium, phosphate and nitrite fluxes at the water-sediment interface. Silicate, ammonium and phos- phate fluxes were highest in August, when temperature was highest. The main nutrient releases observed at the water-sediment interface in M2 could reduce nitrogen and silica limitation in the water column. Mussel lines did not influence benthic macrofauna biomass, but favoured the recruit- ment of many small-sized organisms. No influence of mussel lines was observed on oxygen consump- tion at the water-sediment interface. Macrofauna biomass and oxygen consumption increased in parallel during the summer, but the respiration of the low biomass alone cannot explain the greater overall benthic oxygen demand. The latter was probably also driven by the oxidation of reduced compounds such as sulfides. The reduced nature of the sediment could be natural in GEL, but the continuous accumulation of mussel biodeposits since 1985 has probably contributed to the degrada- tion of the benthic environment in the mussel farm.
Published: 2007

31. Influence of suspended scallop cages and mussel lines on pelagic and benthic biogeochemical fluxes in Havre-aux-Maisons lagoon, Iles-de-la-Madeleine (Quebec, Canada)

Author: Marion Richard, Gérard Thouzeau, Gaston Desrosiers, Philippe Archambault, Christopher W. McKindsey, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: 0106 biological sciences, Biogeochemical cycle, 010604 marine biology & hydrobiology, [SDE.MCG]Environmental Sciences/Global Changes, Placopecten, Pelagic zone, Mussel, Aquatic Science, Biology, Test (biology), biology.organism_classification, 010603 evolutionary biology, 01 natural sciences, Mytilus, Fishery, [SDE.MCG] Environmental Sciences/Global Changes, Benthic zone, Scallop, 14. Life underwater, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS
Abstract: An in situ experiment was done in July 2004 to test and compare the influence of suspended bivalve cultures (1- and 2-year-old blue mussels (Mytilus edulis) and sea scallops (Placopecten magellanicus)) on biogeochemical fluxes in the water column and at the benthic interface in Havre-aux-Maisons Lagoon (Quebec, Canada). Aquaculture structures increased the pelagic macrofaunal biomass (PMB) and acted as an oxygen sink and nutrient source in the water column under dark conditions. Although PMB was lower in scallop culture, the influence of scallop cages on pelagic fluxes was similar to or greater (nitrate and nitrite) than that of mussel lines. Sediments were organically enriched, and benthic macrofaunal abundances were decreased in mussel culture zones relative to the control zone, but such an effect was not observed in the scallop zone. Nevertheless, benthic oxygen demand did not vary among culture types and control zones. Benthic nutrient fluxes were greatest beneath aquaculture structures. Both pelagic and benthic interfaces may modify oxygen and nutrient pools in culture zones in Havre-aux-Maisons Lagoon. The contribution of aquaculture structures to oxygen, ammonium, and phosphate pools may be a function of PMB and type. While aquaculture structures had an important role on nitrate and nitrite cycling, silicate turnover was mainly driven by benthic mineralization of biodeposits.
Published: 2007

32. Vernal sedimentation trends in north Norwegian fjords: temporary anomaly in 234Th particulate fluxes related to Phaeocystis pouchetii proliferation

Author: Sabine Schmidt, Sauveur Belviso, Paul Wassmann, Gérard Thouzeau, Jacqueline Stefels, Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), ICOS-RAMCES (ICOS-RAMCES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Norwegian College of Fishery Science, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS)-Université de Brest (UBO), University of Groningen [Groningen], Stefels lab, Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Phaeocystis, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 0106 biological sciences, 010604 marine biology & hydrobiology, Particle flux, fjord, 010402 general chemistry, 01 natural sciences, 0104 chemical sciences, 13. Climate action, Sediment trap, Th, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, Northern Norwegian shelf waters, ComputingMilieux_MISCELLANEOUS
Abstract: We report data of a naturally occurring radionuclide, 234Th, an in situ tracer, to investigate vertical export of biogenic matter during a vernal bloom of Phaeocystis pouchetii in the fjords of northern Norway. To optimise sampling of different stages of the bloom, three fjords with increasing oceanic influence (Balsfjord, Malangen fjord and Ullsfjord, respectively) were investigated in April 1997. Contrasting situations were encountered between the three fjords: the proliferation of P. pouchetii in Ullsfjord surface waters coincided with a drastic reduction of particulate 234Th fluxes in traps, although particulate organic carbon (POC) and dimethylsulphoniopropionate (DMSP) were exported and 234Th was available in surface waters. When large colonies make up a significant fraction of the vertical flux, as observed in Ullsfjord in April 1997, there may be a large and rapid change in the POC/234Th ratio, further complicating the use of 234Th as a tracer for POC export. The results suggest that the proliferation of Phaeocystis pouchetii during vernal bloom could temporary increase OC/ 234Th ratio of particles and delay the particulate export of 234Th, and probably of other particle-reactive species, from surface waters.
Published: 2007
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33. Vernal sedimentation trends in north Norwegian fjords: temporary anomaly in 234Th particulate fluxes related to Phaeocystis pouchetii proliferation

Author: Jacqueline Stefels, Paul Wassmann, Gérard Thouzeau, Sabine Schmidt, Sauveur Belviso, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), and Elzenga lab
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, fjord, particle flux, Fjord, 01 natural sciences, VERTICAL FLUX, ORGANIC-CARBON, OCEAN, Environmental Chemistry, SPRING BLOOM, 14. Life underwater, Th-234, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, Phaeocystis, MEDITERRANEAN SURFACE WATERS, Total organic carbon, geography, SEA, geography.geographical_feature_category, 010604 marine biology & hydrobiology, DISEQUILIBRIA, PARTICLE DYNAMICS, Particulates, Spring bloom, Sedimentation, EXPORT, Oceanography, 13. Climate action, sediment trap, Sediment trap, Bloom, Northern Norwegian shelf waters, MATTER, Surface water, Geology
Abstract: We report data of a naturally occurring radionuclide, Th-234, an in situ tracer, to investigate vertical export of biogenic matter during a vernal bloom of Phaeocystis pouchetii in the fjords of northern Norway. To optimise sampling of different stages of the bloom, three fjords with increasing oceanic influence (Balsfjord, Malangen fjord and Ullsfjord, respectively) were investigated in April 1997. Contrasting situations were encountered between the three fjords: the proliferation of P. pouchetii in Ullsfjord surface waters coincided with a drastic reduction of particulate Th-234 fluxes in traps, although particulate organic carbon (POC) and dimethylsulphoniopropionate (DMSP) were exported and Th-234 was available in surface waters. When large colonies make up a significant fraction of the vertical flux, as observed in Ullsfjord in April 1997, there may be a large and rapid change in the POC/Th-234 ratio, further complicating the use of Th-234 as a tracer for POC export. The results suggest that the proliferation of Phaeocystis pouchetii during vernal bloom could temporary increase OC/Th-234 ratio of particles and delay the particulate export of Th-234, and probably of other particle-reactive species, from surface waters.
Published: 2007

34. The biogeochemistry of mercury at the sediment-water interface in the Thau lagoon. 2. Evaluation of mercury methylation potential in both surface sediment and the water column

Author: David Amouroux, Emmanuel Tessier, Aude Leynaert, Gérard Thouzeau, Rémy Guyoneaud, K. Vidimova, Laurent Chauvaud, David Point, Mathilde Monperrus, Jacques Grall, Olivier F. X. Donard, Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux (IPREM), Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Hydrology, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, chemistry.chemical_element, Sediment, 010501 environmental sciences, Aquatic Science, Plankton, Oceanography, 01 natural sciences, 6. Clean water, Mercury (element), chemistry.chemical_compound, Water column, chemistry, 13. Climate action, Sediment–water interface, Benthic zone, Environmental chemistry, 14. Life underwater, Methylmercury, Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: Methylation rates of mercury have been determined in both surface sediments and the water column of a shallow coastal lagoon (Thau, France) using in situ incubation experiments. The experiments were conducted in order to evidence and evaluate the significance of such pathways on the fate of methylmercury (MeHg) as influenced by both benthic and pelagic dynamics. Isotopically labelled Hg species have been used as chemical tracers allowing the direct determination of specific methylation and demethylation yields. Each experimental method (cores experiments and water experiments) has been carefully evaluated in terms of sensitivity and reproducibility of the transformation rates and has been demonstrated as a powerful method to investigate transformation processes. Although mercury methylation in surface sediments is a major process, significant MeHg formation in the water column has been measured for the first time in a coastal environment. In spring conditions, methylation yields are found to be higher in the water column (6.3%) than in sediments (0.8–1.3%). Area integrated rates for the experimental site demonstrate, however, that MeHg is mostly produced in surface sediments with a formation rate of 12 nmol m−2 d−1 compared to 1.8 nmol m−2 d−1 in the water column. Biological characteristics of the incubated samples indicate that sediment and plankton microorganisms are involved in Hg methylation which is thus directly associated to the pelagic–benthic turnover occurring in the lagoon.
Published: 2007

35. Community metabolism in temperate maerl beds: I. carbon and carbonate fluxes

Author: Sophie Martin, Gérard Thouzeau, Jacques Clavier, Laurent Chauvaud, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: 0106 biological sciences, [SDE.MCG]Environmental Sciences/Global Changes, Heterotroph, Aquatic Science, Biology, Photosynthesis, 010603 evolutionary biology, 01 natural sciences, chemistry.chemical_compound, Animal science, Respiration, Botany, Temperate climate, 14. Life underwater, Maerl, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, Ecology, 010604 marine biology & hydrobiology, 6. Clean water, [SDE.MCG] Environmental Sciences/Global Changes, chemistry, 13. Climate action, Benthic zone, Carbonate, Bay
Abstract: Maerl community respiration, photosynthesis and calcification were measured season- ally in the Bay of Brest (France). The dynamics of oxygen, carbon and carbonate fluxes at the water-sediment interface were assessed using benthic chambers. Community respiration (CR) fluc- tuated in accordance with the seasonal changes in water temperature, from 1.5 mmol C m -2 h -1 in winter to 8.7 mmol C m -2 h -1 in summer. Mean gross community production (GCP) varied signifi- cantly among seasons, according to incident irradiance and temperature, from 3.4 mmol C m -2 h -1 in winter to 12.7 mmol C m -2 h -1 in summer. Mean annual Pmax for the P-E curve was estimated to 13.3 mmol C m -2 h -1 . Carbonate precipitation only occurred during light incubations and varied sea- sonally from 0.7 mmol CaCO3 m -2 h -1 in winter to 4.2 mmol CaCO3 m -2 h -1 in summer. Mean annual Pmax was 3.2 mmol CaCO3 m -2 h -1 . Annual CR was estimated to 407.4 g C m -2 yr -1 , and GCP, to 240.9 g C m -2 yr -1 . Maerl communities are, therefore, heterotrophic systems (GCP:CR = 0.6), and are a source of CO2 for surrounding environments. In addition, CO2 released by calcification averaged 39.2 g C m -2 yr -1 . Maerl community annual carbonate production was estimated to 486.7 g CaCO3 m -2 yr -1 ; they are therefore one of the most important carbonate producers in shallow coastal waters.
Published: 2007

36. Community metabolism in temperate maerl beds: II. Nutrient fluxes

Author: Jacques Clavier, Laurent Chauvaud, Gérard Thouzeau, Sophie Martin, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, chemistry.chemical_element, Aquatic Science, 01 natural sciences, chemistry.chemical_compound, Nutrient, Water column, Nitrate, Ammonium, 14. Life underwater, Maerl, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Ecology, Chemistry, 010604 marine biology & hydrobiology, Phosphorus, Nitrogen, 6. Clean water, [SDE.MCG] Environmental Sciences/Global Changes, Oceanography, 13. Climate action, Benthic zone, Environmental chemistry
Abstract: Maerl community ammonium (NH4 + ), nitrate + nitrite (NO3 - + NO2 - ), dissolved silicic acid (DSi) and phosphate (PO4 3- ) fluxes were measured seasonally in the Bay of Brest (France). Nutri- ent exchanges at the sediment-water interface were assessed using benthic chambers. Nutrient fluxes differed between light and dark conditions, and fluctuated seasonally, with minimum values in winter and spring and maximum values in summer and autumn. In the dark, net community fluxes of NH4 + , NO3 - + NO2 - , DSi and PO4 3- varied from 53 to 226 μmol N m -2 h -1 , -107 to 70 μmol N m -2 h -1 , 18 to 180 μmol Si m -2 h -1 and 5 to 19 μmol P m -2 h -1 , respectively. In the light, NH4 + , NO3 - + NO2 - , DSi and PO4 3- fluxes ranged from 17 to 110 μmol N m -2 h -1 , -223 to -10 μmol N m -2 h -1 , -34 to 112 μmol Si m -2 h -1 and 1 to 12 μmol P m -2 h -1 , respectively. Temperature, community respiration, gross com- munity production and bottom water dissolved oxygen and nutrient concentrations mainly controlled seasonal fluctuations of benthic nutrient fluxes. Annual net community fluxes of dissolved inorganic nitrogen (DIN), DSi and PO4 3- were 6 g N m -2 yr -1 , 10 g Si m -2 yr -1 and 2 g P m -2 yr -1 , respectively. Annual gross community uptakes of DIN, DSi and PO4 3- were 12 g N m -2 yr -1 , 9 g Si m -2 yr -1 and 1 g P m -2 yr -1 , respectively. Nutrient supply from the maerl community to the water column contributed potentially to between 18 and 55% of the annual phytoplanktonic production in the Bay of Brest.
Published: 2007

37. Reproduction of the invasive slipper limpet, Crepidula fornicata, in the Bay of Brest, France

Author: Gérard Thouzeau, Joëlle Richard, Martial Huet, Yves-Marie Paulet, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Programme National d'Environnement Coˆ tier (PNEC), and the University of Geneva
Subjects: 0106 biological sciences, media_common.quotation_subject, Population, Zoology, Aquatic Science, Biology, 010603 evolutionary biology, 01 natural sciences, ddc:590, 14. Life underwater, Crepidula, education, Ecology, Evolution, Behavior and Systematics, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, media_common, education.field_of_study, Ecology, Hatching, 010604 marine biology & hydrobiology, Fecundity, biology.organism_classification, Calyptraeidae, Reproduction, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bay, Sex ratio
Abstract: International audience; The reproduction of Crepidula fornicata was studied in the Bay of Brest in order to characterise the first step of the reproductive cycle of this invasive species. The survey was carried out from 2000 to 2003 and different parameters were measured, namely, the percentage of the different sexual stages, the straight length of the shell and the percentage of brooding females using a survey of the embryonic development and the fecundity. The juvenile frequency increases generally from mid-June or mid-August, depending on the year. In 2001 and 2003, a first peak was observed as early as May, but it was followed by a rapid disappearance of the individuals. The sex-ratio female/male increased from 0.22 to 0.46 between 2001 and 2003. The sex change between intermediates and females took place mainly in summer and was well marked in 2001 and 2003. The survey of the embryonic development in the egg capsules brooded by the females provided an annual phenology of the laying and hatching processes. The laying period extends from February to September with three to four major periods of egg-laying per year and corresponding hatching periods about 1 month later. Each female lays two to four times per year on average. The first egg-laying concerned fewer females than subsequent ones, except in 2003, and exhibited a higher fecundity. The annual mean of the number of eggs for each stage was not significantly different, thus indicating no significant mortality rate during embryonic development. For the C. fornicata population in the Bay of Brest, several reproductive characteristics tend to highlight its invasive capacity: (1) a long reproductive period, (2) reproduction in a ‘multi-trials' process equivalent to a spreading out of the risks and (3) a relatively high fecundity.
Published: 2006
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38. Significance of vertical flux as a sink for surface water DMSP and as a source for the sediment surface in coastal zones of northern Europe

Author: Jacqueline Stefels, Gérard Thouzeau, Sauveur Belviso, Sabine Schmidt, Marit Reigstad, Elena Arashkevich, Paul Wassmann, Thouzeau, Gérard, Elzenga lab, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), ICOS-RAMCES (ICOS-RAMCES), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE)
Subjects: 0106 biological sciences, DYNAMICS, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Fjord, Aquatic Science, Oceanography, 01 natural sciences, MICROZOOPLANKTON, Sink (geography), fjords, Benthos, OCEAN, North sea, 14. Life underwater, TRAP EFFICIENCY, PHAEOCYSTIS, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, SEA, 010604 marine biology & hydrobiology, dimethylsulphoniopropionate, dimethylsulphide, Sediment, PATHWAYS, Pelagic zone, [SDE.MCG] Environmental Sciences/Global Changes, DIMETHYL SULFIDE, sediment, PARTICULATE DMSP, Seawater, TIDAL FLAT, sedimentation, Bloom, Surface water, Geology
Abstract: In April 1997 and 1998 the significance of sedimentation as a sink for epipelagic dimethylsulphoniopropionate (DMSP) production and as a source for marine sediments was reassessed using a newly designed sediment trap. The behaviour of the traps in immersion was monitored continuously and the collection efficiency was evaluated with Th-234 measurements. Net DMS(P) fluxes were corrected for some physical and biological losses during the whole sedimentation process providing reliable estimates of gross DMSP fluxes. It is shown that daily losses by sedimentation account for between 0.1% and 16% of seawater particulate DMSP (DMSPp) standing stocks, and between 3% and 75% of daily DMSPp production. In the Malangen fjord we observed temporal increases of DMSP production and standing stocks which resulted also in increases of DMSP vertical fluxes and DMS(P) concentrations at the sediment surface. This result illustrates how tight the coupling can be between pelagos and benthos, and confirms that DMS(P) concentration in the sediment was a reliable diagnostic indicator of vertical export from overlying waters in Malangen fjord. In Ullsfjord, however, DMS(P) concentrations in the sediment were poorly indicators of Phaeocystis pouchetii export during the early stage of growth of a bloom. The high load of DMS(P) in Balsfjord's sediments could neither be attributed to local vertical sedimentation nor to short-term lateral advection of fresh DMSP-containing phytoplanktonic, material, and provides indication that this tracer sometimes also can be misleading. The highest loads of DMS(P) in sediments and the fastest rates of sedimentation occurred in the Southern Bight of the North Sea. (c) 2006 Elsevier Ltd. All rights reserved.
Published: 2006

39. Shell of the Great ScallopPecten maximusas a high-frequency archive of paleoenvironmental changes

Author: Laurent Chauvaud, Jean-Marc Guarini, Yves-Marie Paulet, Frédéric Jean, Gérard Thouzeau, Robert B. Dunbar, Anne Lorrain, and David A. Mucciarone
Subjects: Calcite, 010504 meteorology & atmospheric sciences, biology, δ18O, Temperature salinity diagrams, 010502 geochemistry & geophysics, biology.organism_classification, 01 natural sciences, Isotopes of oxygen, Bottom water, chemistry.chemical_compound, Geophysics, Oceanography, chemistry, 13. Climate action, Geochemistry and Petrology, Scallop, Pecten maximus, Seawater, 14. Life underwater, Geology, 0105 earth and related environmental sciences
Abstract: [1] We investigate the environmental and biological controls on oxygen isotope ratios in the shells of modern Pecten maximus bivalves collected alive in the Bay of Brest (France). Seasonal δ18O profiles, obtained by drilling the daily calcite ridges deposited at the surface of the left valve, were compared with in situ measurements of temperature and salinity. We show that P. maximus δ18O values accurately track seasonal variations in bottom water temperature. Shell growth rate has no significant effect on shell δ18O values. Our study demonstrates that daily variations in water temperature can be reconstructed within about 0.5°C. Temperatures estimated with the paleotemperature equation established in this study were compared with temperatures derived from previously published equations. The comparison indicates that the most commonly used paleotemperature equation for biogenic calcite (Epstein et al., 1953) provides inaccurate temperature estimates, but the Kim and O'Neil (1997) equation, established from abiogenic calcite precipitation, provides results very similar to ours and should therefore be used for scallop individuals coming from populations where proper empirical calibration cannot be done. Pecten maximus bivalves precipitate calcite in isotopic equilibrium with seawater, produce large daily growth striae, are stenohaline, and are well preserved in archeological and geological deposits, making them an excellent high-frequency archive of paleoenvironmental change.
Published: 2005
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40. Biodeposition by an invasive suspension feeder impacts the biogeochemical cycle of Si in a coastal ecosystem (Bay of Brest, France)

Author: Olivier Ragueneau, Frédéric Jean, Gérard Thouzeau, F. Le Loc’h, Brivaëla Moriceau, Laurent Chauvaud, Aude Leynaert, Anne Donval, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: 0106 biological sciences, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Ecology, 010604 marine biology & hydrobiology, [SDE.MCG]Environmental Sciences/Global Changes, Plankton, Biogenic silica, 01 natural sciences, Geochemical cycle, [SDE.MCG] Environmental Sciences/Global Changes, Oceanography, 13. Climate action, Benthic zone, Sediment–water interface, Phytoplankton, Environmental Chemistry, Environmental science, 14. Life underwater, Bay, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology
Abstract: Biodeposition is a process that strongly affects physical, chemical and biological properties near the sediment–water interface, and mollusks have been shown to influence the cycling of many biogenic elements. In the Bay of Brest ecosystem, the invasive benthic suspension feeder Crepidula fornicata has been proliferating for 50 years, and its influence on phytoplankton dynamics at a seasonal scale, via its role on a coastal silicate pump, has been suggested by Chauvaud et al. (2000) [Chauvaud L., Jean F., Ragueneau O. and Thouzeau G. 2000. Mar. Ecol. Prog. Ser. 200: 35–48] and tested by Ragueneau et al. (2002a) [Ragueneau O., Chauvaud L., Leynaert A., Thouzeau G., Paulet Y.-M., Bonnet S., Lorrain A., Grall J., Corvaisier R., Le Hir M., Jean F. and Clavier J. (2002a). Limnol. Oceanogr. 47(6): 1849–1854]. In the present manuscript, we explore further, at an annual scale, the role of biodeposition in the Si cycle of the Bay of Brest. We show that annual biodeposition Si can represent up to 84% of river silicic acid inputs. We also show that preservation of biogenic silica in C. fornicata mats is very good (27%), leading to an annual retention of Si of 23% of river inputs. We suggest that this high retention is essentially controlled by the biodeposition mechanism, which is directly under the control of the proliferation of the exotic suspension feeder. We conclude that this mechanism might be very important in controlling the Si retention along the land–ocean continuum and should be tested in the many areas of the coastal ocean submitted to the proliferation of such exotic species that modify sedimentation of biogenic matter.
Published: 2005

41. Reproductive cycle of Argopecten purpuratus (Bivalvia: Pectinidae) in La Rinconada marine reserve (Antofagasta, Chile): response to environmental effects of El Niño and La Niña

Author: Gérard Thouzeau, Miguel Avendaño, Marcela Cantillánez, Marcel Le Pennec, Thouzeau, Gérard, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, Gonad, Argopecten purpuratus, media_common.quotation_subject, Population, Aquatic Science, 010603 evolutionary biology, 01 natural sciences, [SDV.BDLR.RS]Life Sciences [q-bio]/Reproductive Biology/Sexual reproduction, medicine, 14. Life underwater, education, ComputingMilieux_MISCELLANEOUS, media_common, education.field_of_study, Argopecten, [SDV.BDLR.RS] Life Sciences [q-bio]/Reproductive Biology/Sexual reproduction, biology, Ecology, 010604 marine biology & hydrobiology, Marine reserve, biology.organism_classification, Gonadosomatic Index, La Niña, medicine.anatomical_structure, Reproduction
Abstract: Gonadosomatic index (GSI) and ovarian histology were used to determine the seasonality, amplitude, and magnitude of spawnings of the Argopecten purpuratus population within the marine reserve at La Rinconada, Chile, between December 1995 and February 2000. In general, spawnings occurred most of the year without prolonged periods of reproductive inactivity. Studies of this population throughout warm and cold oceanographic phenomena such as the El Nino-Southern Oscillation (ENSO) event of 1997-1998 and the La Nina event of 1998-2000 showed that the reproduction of this population occurred mainly between September and April, declining in the winter months from June through August, during which a period of sexual quiescence was observed in some individuals. An intense reproductive activity in the population, following the 1997-1998 warmer period, extended over the whole year. Histological analysis of the female portion of the gonad confirmed the GSI results and demonstrated the presence both of acini which appeared to be mature and other acini with various degrees of atresia and/or oocyte lysis. The study also revealed spawning asynchrony in this species and the presence of various stages of maturity within the same individual. Periods of high reproductive activity were correlated with strong diurnal temperature fluctuations and rises in phaeopigment concentration and phytoplankton cell counts, suggesting that these factors could be triggers for Argopecten spawning. These new insights on the reproductive cycle and conditioning of A. purpuratus would facilitate future management practices on the timing of artificial collectors and spat collection.
Published: 2005

42. Variations in food intake of Pecten maximus (L.) from the Bay of Brest (France): influence of environmental factors and phytoplankton species composition

Author: Anne Donval, Elisabeth Nézan, Yves-Marie Paulet, Gérard Thouzeau, Laurent Chauvaud, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Thouzeau, Gérard
Subjects: 0106 biological sciences, [SDE.MCG]Environmental Sciences/Global Changes, Environment, 010603 evolutionary biology, 01 natural sciences, Algal bloom, General Biochemistry, Genetics and Molecular Biology, Eating, Species Specificity, Phytoplankton, Pecten maximus, Animals, 14. Life underwater, Gymnodinium, ComputingMilieux_MISCELLANEOUS, Ecology, biology, 010604 marine biology & hydrobiology, fungi, Dinoflagellate, musculoskeletal system, Bivalvia, biology.organism_classification, [SDE.MCG] Environmental Sciences/Global Changes, Diatom, Mollusca, France, Bay
Abstract: Previous studies carried out in the bay of Brest on daily shell growth of Pecten maximus have demonstrated that temperature is a major control on daily shell growth in contrast to food supply. However, repeated events of slow growth have been observed during diatom and dinoflagellate blooms. The aim of this study was to determine how fluctuations in environmental parameters influence P. maximus food intake and daily shell growth rate. In 1995, P. maximus food intake and growth were highest when Cerataulina pelagica (diatom) blooms occurred and lowest during Gymnodinium cf. nagasakiense (dinoflagellate) blooms. During blooms of other diatom species, P. maximus food intake and growth were high when the algal concentration did not exceed a critical threshold, dependent upon the dominant species and sedimentation rate of diatoms. These results demonstrate that the morphological and physiological features of phytoplankton bloom species strongly affect benthic microphytophagy, a component of benthic-pelagic coupling.
Published: 2001

43. Variabilité spatio-temporelle de la biomasse microphytobenthique en Rade de Brest et en Manche occidentale

Author: Gérard Thouzeau, Gaëlle Sagan, Thouzeau, Gérard, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, microphytobenthos, [SDE.MCG]Environmental Sciences/Global Changes, Population, Aquatic Science, Oceanography, 010603 evolutionary biology, 01 natural sciences, physical forcing, Phytoplankton, biomasse, 14. Life underwater, education, ComputingMilieux_MISCELLANEOUS, education.field_of_study, Biomass (ecology), geography, geography.geographical_feature_category, biomass, 010604 marine biology & hydrobiology, Estuary, forçage physique, coastal ecosystems, écosystèmes côtiers, Light intensity, [SDE.MCG] Environmental Sciences/Global Changes, 13. Climate action, Benthic zone, Environmental science, Eutrophication, Bay
Abstract: Microphytobenthic biomass was estimated in the Bay of Brest (1994) and the western English Channel (Trezen Vraz, 1993) using spectrophotometry. Best results (42 % difference) were obtained with an instantaneous extraction procedure at room temperature, compared with the cold extraction procedure. Chlorophyll biomass in sediment was higher in the western English Channel (65-215 mg Chl a m(-2)) than in the Bay of Brest (10-113 mg Chl a m(-2)), in contrast to total pigment biomass (Chl a + pheo a : 88-254 mg m(-2) at Trezen Vraz vs. 131-934 mg m(-2) in the Bay of Brest). This study emphasized decreasing pigment biomass from the estuary to the open sea. Low benthic pigment biomass in the Bay, compared to eutrophic ecosystems, agrees with previous studies on the pelagic system, suggesting that there is no eutrophication in the Bay of Brest. Microphytobenthic blooms were strongly correlated with environmental factors, such as river floods, light intensity, water temperature and the spring/neap tidal cycle. Turbidity and light could be limiting factors at Roscanvel, i.e. the deepest site facing gyre circulation. The latter would favour sedimentation of silt particles at the sediment-water interface. Microphytobenthos population dynamics would be also dependent on the spring/neap tidal cycle, since maximum chlorophyll biomass occurred at neap tides at all three sites in the Bay of Brest, in contrast to the western English Channel. Lower temporal variations of pigment biomass in sediment were observed in the Channel, compared with the Bay of Brest; maximum chlorophyll biomass in sediment was found to occur three to four weeks after the phytoplankton blooms., La biomasse microphytobenthique a été estimée par spectrophotométrie en rade de Brest (1994) et en Manche occidentale (1993). La comparaison de deux protocoles d'extraction pigmentaire montre que l'extraction instantanée à température ambiante est supérieure de 42 %, à l'extraction conventionnelle à froid. La biomasse chlorophyllienne en Manche (65–215 mg Chl a m−2) est supérieure à celle de la rade de Brest (10–113 mg Chl a m−2), mais la biomasse pigmentaire totale (Chl a + phéo a) est deux à quatre fois plus élevée dans les sédiments de la rade (131–934 mg m−2) que dans les sédiments du Trezen Vraz (88–254 mg m−2). Un gradient de biomasse décroissant de l'estuaire vers la mer ouverte est observé. Les biomasses pigmentaires en rade de Brest sont inférieures à celles observées dans les systèmes marins eutrophisés, confortant ainsi plusieurs études du système pélagique selon lesquelles la rade de Brest constitue un milieu eutrophe mais non eutrophisé. Les floraisons microphytobenthiques en rade de Brest sont fortement dépendantes de l'évolution des facteurs physico-chimiques du milieu (crues des rivières, lumière, température, cycles de marée). En particulier, l'impact des variations de l'intensité du mélange turbulent (et de la lumière) est montré lors de l'alternance vive-eau/morteeau, les maxima de biomasse chlorophyllienne dans le sédiment étant observés en périodes de morte-eau. En Manche en revanche, les variations temporelles de la biomasse pigmentaire dans les sédiments sont de faible amplitude, avec des pics de biomasse en vive-eau; la biomasse pigmentaire dans le sédiment augmente en moyenne trois à quatre semaines après les blooms planctoniques.
Published: 1998

44. Experimental collection of postlarvae of Pecten maximus (L.) and other benthic macrofaunal species in the Bay of Saint-Brieuc, France. I. Settlement patterns and biotic interactions among the species collected

Author: Gérard Thouzeau, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, biology, Ecology, 010604 marine biology & hydrobiology, Species diversity, 04 agricultural and veterinary sciences, Aquatic Science, biology.organism_classification, 01 natural sciences, Fishery, Benthic zone, Scallop, [SDE]Environmental Sciences, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Pecten maximus, 14. Life underwater, Chlamys varia, Crepidula, Bay, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, Trophic level
Abstract: Settlement patterns of Pecten maximus (L.) postlarvae and 105 other species of benthic macrofauna in the Bay of Saint-Brieuc were studied from spat collectors in order to clarify biotic interactions at the postlarval stage. Between-sites differences in taxonomic group abundances reflected the bottom sediment type beneath the collectors and were partly explained by hydrographic mechanisms; larval retention occurred in the collection areas. Other factors regulating settlement process were the water turbulence and trophic resources. Temporal variability in collection occurred between and within the taxonomic groups. Optimal collection for all the species was within 2 m above the seabed for an immersion period of
Published: 1991
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45. Experimental collection of postlarvae of Pecten maximus (L.) and other benthic macrofaunal species in the Bay of Saint-Brieuc, France. II. Reproduction patterns and postlarval growth of five mollusc species

Author: Gérard Thouzeau, Laboratoire d'Océanographie biologique, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, biology, Ecology, 010604 marine biology & hydrobiology, 04 agricultural and veterinary sciences, Aquatic Science, biology.organism_classification, Bivalvia, 01 natural sciences, Benthic zone, [SDE]Environmental Sciences, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Pecten maximus, Chlamys, 14. Life underwater, Chlamys varia, Crepidula, Mollusca, Bay, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS
Abstract: Spawning seasonality and postlarval (spat) growth of five mollusc species taken in spat collectors in the Bay of St-Brieuc in 1985 were analysed from size-frequency distributions. There is evidence for a short spawning period and a major spawning for all species. The respective abundance peaks of the three pectinid species in the collectors were shifted with time; the settlement of Pecten maximus occurred 15–30 days before those of Chlamys sp. A spatial intracohort growth variability was found in P. maximus, depending on the collector height from the seabed. This variability appeared as early as the first benthic stages (mean height < 500 μm), with growth being lower by 25–30% in the collectors located nearest to the bottom. Postlarval growth of P. maximus, Anomia ephippium and Crepidula fornicata also varied seasonally between cohorts, with growth rates decreasing during the reproductive season. Temperature and trophic resources were the main factors determining these variations. In P. maximus, another source of growth variation, the gamete quality, is suggested. These results, added to those obtained in a study of biotic interactions within the collectors (Thouzeau, 1991), help define ways to improve collection of pectinid spat in the Bay of St-Brieuc.
Published: 1991
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46. Déterminisme du pré-recrutement de Pecten maximus (L.), en baie de Saint-Brieuc: processus régulateurs de l'abondance, de la survie et de la croissance des post-larves et juvéniles

Author: Gérard Thouzeau, Thouzeau, Gérard, Laboratoire d'Océanographie biologique, Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, Forestry, 04 agricultural and veterinary sciences, Aquatic Science, Biology, biology.organism_classification, 010603 evolutionary biology, 01 natural sciences, [SDE.BE] Environmental Sciences/Biodiversity and Ecology, [SDE]Environmental Sciences, 040102 fisheries, 0401 agriculture, forestry, and fisheries, Pecten maximus, Population management, 14. Life underwater, Post larvae, ComputingMilieux_MISCELLANEOUS
Abstract: L'etude du determinisme du pre-recrutement de Pecten maximus (L.) en baie de Saint-Brieuc a ete realisee par captage de post-larves sur des collecteurs artificiels, et par echantillonnage benthique des juveniles de coquille Saint-Jacques et de la macrofaune epigee et endogee superficielle. Les techniques mises en œuvres fournissent des estimations fiables de l'abondance des pre-recrues et de la force d'une classe d'âge, des les quatre premiers mois de vie benthique. L'abondance d'une classe d'âge pre-recrutee est determinee par la fecondite des adultes, l'hydrodynamisme (courants; turbulence a l'interface eau-sediment), la nature sedimentaire des fonds (degre d'envasement; substrats disponibles), la temperature hivernale des eaux, l'intensite des interactions biotiques (competition; predation), et par les facteurs regulant la croissance du groupe d'âge 0 (la survie lors du 1er hiver est fonction de la taille des juveniles). Les trois annees d'etude montrent l'existence d'une forte variabilite spatio-temporelle intra- et interannuelle des mecanismes regulant l'abondance du pre-recrutement de Pecten maximus.
Published: 1991
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