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1. Assessing the water quality of the Seine land-to-sea continuum for three agro-food system scenarios

Author

Estela Romero, Josette Garnier, Gilles Billen, Antsiva Ramarson, Philippe Riou, and Romain Le Gendre

Subjects
scenarios, biogeochemical processes, estuary, eutrophication, agro-food system, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract

Three scenarios for the future of the French agro-food system were specified for the territory draining into the Seine Bight, comprising Paris megacity and the Seine watershed. The first scenario assumes the pursuit of the current trend of opening and specialization of agriculture, as well as of concentration of population within the Paris agglomeration. The second scenario assesses the generalization of agro-ecological practices and a healthier human diet. A third, hybrid, scenario was elaborated assuming that agro-ecological practices were implemented in some protected areas (namely Regional Natural Parks and drinking water protection areas, making up about one-third of the total watershed area), while the rest of the territory will follow the trends of the first scenario. We use a unique modelling chain (GRAFS-Riverstrahler-ECOMARS3D) that couples the biogeochemical functioning of the river basin, the estuary and the adjacent bay. It allows exploring the implications of changes in terrestrial activities throughout the aquatic continuum in a consistent way and assessing to what extent changes in population, agricultural practices, food consumption, and sanitation may sustain the current trend of recovery in the Seine River or either increase stress on the system. Results show that only the full agro-ecological scenario would be able to restore good water quality everywhere in the river network, as well as decrease significantly the risks of toxic algal blooms in the coastal zone. Intermediate situations, such as the protection of specific areas, however attractive as a solution, are not enough to offset the impacts of intensive human activities unless the protected areas dedicated to compensating for damage are sufficiently large.

Published
2022
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2. Shallow Water Bathymetry Retrieval Using a Band-Optimization Iterative Approach: Application to New Caledonia Coral Reef Lagoons Using Sentinel-2 Data

Author

Sélim Amrari, Emmanuel Bourassin, Serge Andréfouët, Benoit Soulard, Hugues Lemonnier, and Romain Le Gendre

Subjects
satellite derived bathymetry, rugose lagoon, adaptive iterative model, band ratio, UNESCO World Heritage Area, multispectral image, Science
Abstract

To achieve high accuracy bathymetry retrieval using remote sensing images with robust performance in a 0 to 25 m-deep lagoon with sharp bottom depth variations, a new Iterative Multiple Band Ratio (IMBR) algorithm is tested against known Multiple Band Ratio (MBR) and Single Band Ratio (SBR) algorithms. The test was conducted using the five multispectral bands, at 10 to 60 m resolution, of a Sentinel-2 image of the 25 km2 Poe lagoon, a UNESCO World Heritage Area. The IMBR approach requires training datasets for the definitions of depth threshold at which optimal band ratios vary. IMBR achieved accuracy, quantified with an original block cross-validation procedure across the entire depth range reached a mean absolute error of 46.0 cm. It compares very favorably against MBR (78.3 cm) and the various SBR results (188–254 cm). The method is suitable for generalization to other sites pending a minimal ground-truth dataset crossing all the depth range being available. We stress that different users may need different precisions and can use MBR or SBR algorithms for their applications. For the hydrodynamic modelling applications that are developing in New Caledonia, the IMBR solutions applied to Sentinel imagery are optimal.

Published
2021
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3. Carbon Dynamics Along the Seine River Network: Insight From a Coupled Estuarine/River Modeling Approach

Author

Goulven G. Laruelle, Audrey Marescaux, Romain Le Gendre, Josette Garnier, Christophe Rabouille, and Vincent Thieu

Subjects
dissolved inorganic and organic carbon, carbon dioxide, reactive-transport model, Seine river and estuary, biogeochemical budget, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract

The Seine river discharges over 700 Gg of carbon (C) every year into the sea mostly under the form of dissolved inorganic carbon (DIC) and emits 445 Gg under the form of carbon dioxide (CO2) to the atmosphere over its entire river network. The watershed, which drains 76,000 km2, is heavily populated with 18 106 inhabitants and is thus submitted to large anthropic pressure. The offline coupling of two Reactive Transport Models is used to understand the complex spatial and temporal dynamics of carbon, oxygen and nutrients and quantify the CO2 exchange at the air-water interface along the main axis of the river. The estuarine section of the Seine is simulated by the generic estuarine model C-GEM (for Carbon Generic Estuarine Model), while the upstream part of the network, devoid of tidal influence is simulated by the pyNuts-Riverstrahler modeling platform which also includes an explicit representation of the drainage network ecological functioning. Our simulations provide a process-based representation of nutrients, oxygen, total organic carbon (TOC) and the carbonate system (DIC and alkalinity) over the entire year 2010. Our coupled modeling chain allows quantifying the respective contributions of the estuarine and freshwater sections of the system in the removal of carbon as well as following the fate of TOC and DIC along the river network. Our results also allow calculating an integrated carbon budget of the Seine river network for year 2010.

Published
2019
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4. Hindcast and Near Real-Time Monitoring of Green Macroalgae Blooms in Shallow Coral Reef Lagoons Using Sentinel-2: A New-Caledonia Case Study

Author

Maële Brisset, Simon Van Wynsberge, Serge Andréfouët, Claude Payri, Benoît Soulard, Emmanuel Bourassin, Romain Le Gendre, and Emmanuel Coutures

Subjects
Ulva, Sentinel-2, satellite, remote sensing, algal bloom, coral reefs, Science
Abstract

Despite the necessary trade-offs between spatial and temporal resolution, remote sensing is an effective approach to monitor macroalgae blooms, understand their origins and anticipate their developments. Monitoring of small tropical lagoons is challenging because they require high resolutions. Since 2017, the Sentinel-2 satellites has provided new perspectives, and the feasibility of monitoring green algae blooms was investigated in this study. In the Poé-Gouaro-Déva lagoon, New Caledonia, recent Ulva blooms are the cause of significant nuisances when beaching. Spectral indices using the blue and green spectral bands were confronted with field observations of algal abundances using images concurrent with fieldwork. Depending on seabed compositions and types of correction applied to reflectance data, the spectral indices explained between 1 and 64.9% of variance. The models providing the best statistical fit were used to revisit the algal dynamics using Sentinel-2 data from January 2017 to December 2019, through two image segmentation approaches: unsupervised and supervised. The latter accurately reproduced the two algal blooms that occurred in the area in 2018. This paper demonstrates that Sentinel-2 data can be an effective source to hindcast and monitor the dynamics of green algae in shallow lagoons.

Published
2021
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5. Managing the Agri-Food System of Watersheds to Combat Coastal Eutrophication: A Land-to-Sea Modelling Approach to the French Coastal English Channel

Author

Josette Garnier, Philippe Riou, Romain Le Gendre, Antsiva Ramarson, Gilles Billen, Philippe Cugier, Mathilde Schapira, Sylvain Théry, Vincent Thieu, and Alain Ménesguen

Subjects
toxic microalgae, pseudo-nitzschia spp., river basins, nutrient flows, scenarios, coastal zone ecosystem, modelling, Geology, QE1-996.5
Abstract

The continental coastal waters of the Eastern Channel, from Normandy to Hauts-de-France, are subject to the major influence of unbalanced nutrient inputs from inflowing rivers. Several episodes of harmful algal blooms (HABs) compromising fishing and shellfish farming activities have been observed at the coast. For a better understanding of how the land-to-sea aquatic continuum functions, the GRAFS-RIVERSTRAHLER river biogeochemical model was implemented to cover the watersheds of 11 rivers flowing into this area (including the Seine) and chained with the ecological marine ECO-MARS3D model, applied to the French Northern coastal zone. Human activities strongly impact on the functioning of coastal ecosystems. Specifically, for these fertile soils of Northern France, intensive agricultural nitrogen (N) deliveries in excess over silica (Si) and phosphorus (P), essentially of diffuse origin, are potentially responsible for coastal eutrophication. Phosphorous is today equally supplied by diffuse and point sources, after a drastic reduction of inputs from wastewater treatment plants since the 2000s, and is better balanced regarding Si, as shown by the indicators of coastal eutrophication potential (P-ICEP versus N-ICEP). However, despite this drastic P reduction, HABs still appear repeatedly. Exploration of several scenarios of agro-food chain reorganization shows that (i) further progress in urban wastewater treatment to fully comply with current European regulations will not result in a significant reduction of nutrient fluxes to the sea, hence including HABs, and (ii) radical structural changes in agriculture, based on generalization of long and diversified organic crop rotations, reconnection of crop and livestock farming and changes in the human diet have the capacity to significantly reduce nutrient flows, coastal eutrophication and HABs.

Published
2019
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6. Towards the determination of Mytilus edulis food preferences using the dynamic energy budget (DEB) theory.

Author

Coralie Picoche, Romain Le Gendre, Jonathan Flye-Sainte-Marie, Sylvaine Françoise, Frank Maheux, Benjamin Simon, and Aline Gangnery

Subjects
Medicine, Science
Abstract

The blue mussel, Mytilus edulis, is a commercially important species, with production based on both fisheries and aquaculture. Dynamic Energy Budget (DEB) models have been extensively applied to study its energetics but such applications require a deep understanding of its nutrition, from filtration to assimilation. Being filter feeders, mussels show multiple responses to temporal fluctuations in their food and environment, raising questions that can be investigated by modeling. To provide a better insight into mussel-environment interactions, an experiment was conducted in one of the main French growing zones (Utah Beach, Normandy). Mussel growth was monitored monthly for 18 months, with a large number of environmental descriptors measured in parallel. Food proxies such as chlorophyll a, particulate organic carbon and phytoplankton were also sampled, in addition to non-nutritious particles. High-frequency physical data recording (e.g., water temperature, immersion duration) completed the habitat description. Measures revealed an increase in dry flesh mass during the first year, followed by a high mass loss, which could not be completely explained by the DEB model using raw external signals. We propose two methods that reconstruct food from shell length and dry flesh mass variations. The former depends on the inversion of the growth equation while the latter is based on iterative simulations. Assemblages of food proxies are then related to reconstructed food input, with a special focus on plankton species. A characteristic contribution is attributed to these sources to estimate nutritional values for mussels. M. edulis shows no preference between most plankton life history traits. Selection is based on the size of the ingested particles, which is modified by the volume and social behavior of plankton species. This finding reveals the importance of diet diversity and both passive and active selections, and confirms the need to adjust DEB models to different populations and sites.

Published
2014
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7. Spatial variability of benthic-pelagic coupling in an estuary ecosystem: consequences for microphytobenthos resuspension phenomenon.

Author

Martin Ubertini, Sébastien Lefebvre, Aline Gangnery, Karine Grangeré, Romain Le Gendre, and Francis Orvain

Subjects
Medicine, Science
Abstract

The high degree of physical factors in intertidal estuarine ecosystem increases material processing between benthic and pelagic compartments. In these ecosystems, microphytobenthos resuspension is a major phenomenon since its contribution to higher trophic levels can be highly significant. Understanding the sediment and associated microphytobenthos resuspension and its fate in the water column is indispensable for measuring the food available to benthic and pelagic food webs. To identify and hierarchize the physical/biological factors potentially involved in MPB resuspension, the entire intertidal area and surrounding water column of an estuarine ecosystem, the Bay des Veys, was sampled during ebb tide. A wide range of physical parameters (hydrodynamic regime, grain size of the sediment, and suspended matter) and biological parameters (flora and fauna assemblages, chlorophyll) were analyzed to characterize benthic-pelagic coupling at the bay scale. Samples were collected in two contrasted periods, spring and late summer, to assess the impact of forcing variables on benthic-pelagic coupling. A mapping approach using kriging interpolation enabled us to overlay benthic and pelagic maps of physical and biological variables, for both hydrological conditions and trophic indicators. Pelagic Chl a concentration was the best predictor explaining the suspension-feeders spatial distribution. Our results also suggest a perennial spatio-temporal structure of both benthic and pelagic compartments in the ecosystem, at least when the system is not imposed to intense wind, with MPB distribution controlled by both grain size and bathymetry. The benthic component appeared to control the pelagic one via resuspension phenomena at the scale of the bay. Co-inertia analysis showed closer benthic-pelagic coupling between the variables in spring. The higher MPB biomass observed in summer suggests a higher contribution to filter-feeders diets, indicating a higher resuspension effect in summer than in spring, in turn suggesting an important role of macrofauna bioturbation and filter feeding (Cerastoderma edule).

Published
2012
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8. Nutrient transport and transformation in macrotidal estuaries of the French Atlantic coast: a modeling approach using the Carbon-Generic Estuarine Model

Author

Xi Wei, Josette Garnier, Vincent Thieu, Paul Passy, Romain Le Gendre, Gilles Billen, Maia Akopian, Goulven Gildas Laruelle, Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-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), Pôle de recherche pour l'organisation et la diffusion de l'information géographique (PRODIG (UMR_8586 / UMR_D_215 / UM_115)), Université Paris 1 Panthéon-Sorbonne (UP1)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Ifremer - Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Office français de la biodiversité (OFB), Service Biogéochimie et Modélisation du Système Terre (BGEOSYS), and Université Libre de Bruxelles

Subjects
[SDV.EE]Life Sciences [q-bio]/Ecology, environment, QE1-996.5, Ecology, Life, QH501-531, Geology, Ecology, Evolution, Behavior and Systematics, QH540-549.5, Earth-Surface Processes
Abstract

Estuaries are key reactive ecosystems along the land–ocean aquatic continuum, with significant ecological and economic value. However, they have been facing strong morphological management changes and increased nutrient and contaminant inputs, possibly leading to ecological problems such as coastal eutrophication. Therefore, it is necessary to quantify the import and export fluxes of the estuaries, their retention capacity, and estuarine eutrophication potential. The 1-D Carbon-Generic Estuary Model (C-GEM) was used to simulate the transient hydrodynamics, transport, and biogeochemistry for estuaries with different sizes and morphologies along the French Atlantic coast during the period 2014–2016 using readily available geometric, hydraulic, and biogeochemical data. These simulations allowed us to evaluate the budgets of the main nutrients (phosphorus – P; nitrogen – N; silica – Si) and total organic carbon (TOC), and their imbalance, providing insights into their eutrophication potential. Cumulated average annual fluxes to the Atlantic coast from the seven estuaries studied were 9.6 kt P yr−1, 259 kt N yr−1, 304 kt Si yr−1, and 145 kt C yr−1. Retention rates varied depending on the estuarine residence times, ranging from 0 %–27 % and 0 %–34 % to 2 %–39 % and 8 %–96 % for total phosphorus (TP), total nitrogen (TN), dissolved silica (DSi), and TOC, respectively. Large-scale estuaries had higher retention rates than medium and small estuaries, which we interpreted in terms of estuarine residence times. As shown by the indicator of eutrophication potential (ICEP), there might be a risk of coastal eutrophication, i.e., the development of non-siliceous algae that is potentially harmful to the systems studied due to the excess TN over DSi. This study also demonstrates the ability of our model to be applied with a similar setup to several estuarine systems characterized by different sizes, geometries, and riverine loads.

Published
2022
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9. Hydrodynamic and hydrological processes within a variety of coral reef lagoons: field observations during six cyclonic seasons in New Caledonia

Author

Oriane Bruyère, Benoit Soulard, Hugues Lemonnier, Thierry Laugier, Morgane Hubert, Sébastien Petton, Térence Desclaux, Simon Van Wynsberge, Eric Le Tesson, Jérôme Lefèvre, Franck Dumas, Jean-François Kayara, Emmanuel Bourassin, Noémie Lalau, Florence Antypas, Romain Le Gendre, Ecologie marine tropicale dans les Océans Pacifique et Indien (ENTROPIE [Réunion]), Institut de Recherche pour le Développement (IRD)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 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), Institut de Recherche pour le Développement (IRD), Service Hydrographique et Océanographique de la Marine (SHOM), Ministère de la Défense, Direction du Développement Economique et de l’Environnement (DDEE), Koohnê (Koné), Province Nord, New Caledonia, France, and Gouvernement, provinces sud et nord de Nouvelle Calédonie

Subjects
PACIFIC, OCEAN, IMPACT, CIRCULATION, General Earth and Planetary Sciences, REEF-LAGOON, SOUTH-WEST LAGOON, WIND, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, RAINFALL, SUSPENDED-SEDIMENT TRANSPORT, SYSTEM
Abstract

From 2014 to 2021 during the cyclone seasons, extensive monitoring of the hydrodynamics within a variety of lagoons of New Caledonia was conducted as a part of the PRESENCE project (PRESsures on coral Ecosystems of New CalEdonia). The PRESENCE project is aimed at building an efficient representation of the land–lagoon–ocean continuum at Grande Terre, New Caledonia's main island. Overall, coastal physical observations encompassed five different lagoons (four of which were never before monitored) and at least eight major atmospheric events ranging from tropical depressions to category 4 cyclones. The main objectives of this study were to characterize the processes controlling the hydrodynamics and hydrology of these lagoons (e.g., ocean–lagoon exchanges, circulation, level dynamics, temperature, and salinity variability), and to capture the magnitude of change during extreme events. An additional objective was to compile an adequate data set for future use in high-resolution hydrodynamic models. Autonomous oceanographic instruments were moored at strategic locations to collect time series of temperature, salinity, pressure, and Eulerian currents. Additionally, Lagrangian surface currents were observed through deploying drifter buoys, and cross-shore hydrological profile radials were carried out using CTDs (conductivity, temperature, depth). In total, five survey campaigns were conducted, beginning with the SPHYNX campaign which lasted 15 months (December 2014 to February 2016) in the Hienghène–Touho lagoon and ended with the 9 months NEMO campaign (September 2020 to April 2021) in Moindou lagoon. Between these were the 5 months NOUMEA campaign (December 2016 to April 2017) in Noumea lagoon, the 6 months ELADE campaign (February to August 2018) in the Poe lagoon, and the 5 months CADHYAK campaign (December 2019 to May 2020) in Koumac lagoon. In addition to characterizing these lagoons, the data set identifies important features and processes, such as the presence of internal waves on forereefs, wave-driven fluxes over reef barriers, and exchanges through passes. Signatures from strong events were also identified, including surges, thermal drops inside lagoons, and massive flash flood plume dispersion. Raw data sets were processed, controlled for quality, validated, and analyzed. Processed files are made publicly available in dedicated repositories on the SEANOE marine data platform in NetCDF format. Links (DOI) of individual data sets are provided herein.

Published
2022
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10. Nutrient transport and transformation in macrotidal estuaries of the French Atlantic coast: a modelling approach using C-GEM

Author

Goulven Gildas Laruelle, Paul Passy, Vincent Thieu, Maia Akopian, Gilles Billen, Xi Wei, Romain Le Gendre, and Josette Garnier

Subjects
Total organic carbon, Biogeochemical cycle, geography, geography.geographical_feature_category, Phosphorus, chemistry.chemical_element, Biogeochemistry, Estuary, Nutrient, Oceanography, chemistry, 13. Climate action, Environmental science, Ecosystem, 14. Life underwater, Eutrophication
Abstract

Estuaries are key reactive ecosystems along the land–ocean aquatic continuum, with significant ecological and economic value. However, they have been facing strong morphological management changes as well as increased nutrient and contaminant inputs, possibly leading to ecological problems such as coastal eutrophication. Therefore, it is necessary to quantify the ingoing and outgoing fluxes of the estuaries, their retention capacity, and estuarine eutrophication potential. A 1-D Carbon–Generic Estuary Model (C-GEM) was used to simulate the transient hydrodynamics, transport, and biogeochemistry for estuaries with different sizes and morphologies along the French Atlantic coast during the period 2014–2016 using readily available geometric, hydraulic, and biogeochemical data. These simulations allowed us to evaluate the budgets of the main nutrients (phosphorus [P], nitrogen [N], silica [Si]) and total organic carbon (TOC), and their imbalance with respect to estuarine eutrophication potential. Cumulated average annual fluxes to the Atlantic coast from the seven estuaries studied were 9.6 kt P yr−1, 259 kt N yr−1, 304 kt Si yr−1, and 145 kt C yr−1. Retention rates varied depending on the estuarine residence times, ranging from 0–27 %, 0–34 %, 2–39 %, and 8–96 % for TP, TN, DSi, and TOC, respectively. Large-scale estuaries had higher retention rates than medium and small estuaries, which we interpreted in terms of estuarine residence times. As shown by the indicator of eutrophication potential (ICEP), there might be a risk of coastal eutrophication, i.e., the development of nonsiliceous algae that is potentially harmful to the systems studied due to the excess TN over DSi.

Published
2021

11. Understanding connectivity of pearl oyster populations within Tuamotu atoll semi-closed lagoons: Cumulative insight from genetics and biophysical modelling approaches

Author

Céline M. O. Reisser, Romain Le Gendre, Serge Andréfouët, Alain Lo-Yat, Yoann Thomas, Institut de Recherche pour le Développement (IRD), Ifremer - Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), and ANR-16-CE32-0004,MANA,Gestion des Atolls(2016)

Subjects
0106 biological sciences, Connectivity matrix, Biogeography, Population, Population Dynamics, Atoll, Aquaculture, 010501 environmental sciences, Aquatic Science, engineering.material, Oceanography, 01 natural sciences, Pinctada margaritifera, Population genomics, Dispersal modelling, Animals, 14. Life underwater, Pinctada, education, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Genetics, geography, education.field_of_study, geography.geographical_feature_category, Pacific Ocean, biology, 010604 marine biology & hydrobiology, Sampling (statistics), Agriculture, biology.organism_classification, Pollution, Lagoon hydrodynamics, engineering, Biological dispersal, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Pearl
Abstract

Connectivity affects species demography, (meta)population dynamics, evolution, phylogeny and biogeography. Various methodological approaches are applied to measure connectivity. Biophysical modelling can explore systematically the influence of atmospheric, oceanic and ecological forcing, while genetics measures connectivity patterns within the sampling strategy limit. In the Pacific Ocean pearl farming lagoons, the activity relies on spat collecting of the black lipped pearl oyster Pinctada margaritifera occurring after the larval dispersal phase, which follows spawning from wild or farmed populations. Biophysical 3D modelling and genomic studies have both separately brought insights on within-lagoon connectivity and on the origin of spats. Here, we combined previous genetics results with new realistic biophysical modelling scenarios to elucidate connectivity in Ahe Atoll lagoon. When combined, we identified the weather sequence likely explaining the realized connectivity observations. We discuss the strengths, weaknesses, opportunities and threats of combining these two approaches considering specific pearl farming demographic connectivity questions.

Published
2021
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12. Correction: Reisser, C.M.O. et al. Population Connectivity and Genetic Assessment of Exploited and Natural Populations of Pearl Oysters within a French Polynesian Atoll Lagoon. Genes 2020, 11, 426

Author

Céline M. O. Reisser, Romain Le Gendre, Alain Lo-Yat, Serge Planes, Serge Andréfouët, Cassandre Chupeau, and PSL Research University, EPHE-UPVD-CNRS, USR 3278 CRIOBE, Université de Perpignan, 58 Avenue Paul Alduy, 66860 Perpignan Cedex, France

Subjects
0303 health sciences, education.field_of_study, geography, geography.geographical_feature_category, lcsh:QH426-470, Ecology, Population, Atoll, engineering.material, Biology, Natural (archaeology), 03 medical and health sciences, lcsh:Genetics, 0302 clinical medicine, n/a, 030220 oncology & carcinogenesis, [SDE]Environmental Sciences, Genetics, engineering, 14. Life underwater, education, Pearl, Genetics (clinical), ComputingMilieux_MISCELLANEOUS, 030304 developmental biology
Abstract

International audience; The authors wish to make the following corrections to this paper [...]

Published
2020
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13. Population Connectivity and Genetic Assessment of Exploited and Natural Populations of Pearl Oysters within a French Polynesian Atoll Lagoon

Author

Serge Andréfouët, Cassandre Chupeau, Romain Le Gendre, Alain Lo-Yat, Serge Planes, Céline M. O. Reisser, Ecosystèmes Insulaires Océaniens (UMR 241) (EIO), Université de la Polynésie Française (UPF)-Institut Louis Malardé [Papeete] (ILM), Institut de Recherche pour le Développement (IRD)-Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE [Nouvelle-Calédonie]), Ifremer - Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Université de la Nouvelle-Calédonie (UNC), Centre de recherches insulaires et observatoire de l'environnement (CRIOBE), Université de Perpignan Via Domitia (UPVD)-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), Ecologie marine tropicale dans les Océans Pacifique et Indien (ENTROPIE [Réunion]), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Institut de Recherche pour le Développement (IRD), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de la Polynésie Française (UPF)-Institut Louis Malardé [Papeete] (ILM), Institut de Recherche pour le Développement (IRD), Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Ifremer - Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de la Nouvelle-Calédonie (UNC), Université de Perpignan Via Domitia (UPVD)-École Pratique des Hautes Études (EPHE), Institut de Recherche pour le Développement (IRD)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), and ANR-16-CE32-0004,MANA,Gestion des Atolls(2016)

Subjects
0106 biological sciences, 0301 basic medicine, Population Dynamics, Atoll, Aquaculture, 01 natural sciences, Population genomics, Pinctada margaritifera, MARS3D, Genetics (clinical), education.field_of_study, geography.geographical_feature_category, Geography, biology, Agriculture, Biodiversity, pearl farming, connectivity, Seasons, Pearl, Conservation of Natural Resources, population genomics, lcsh:QH426-470, Population, engineering.material, Polynesia, Article, farming, Life history theory, 03 medical and health sciences, Genetics, Animals, Pinctada, 14. Life underwater, pearl, education, geography, [SDV.GEN.GPO]Life Sciences [q-bio]/Genetics/Populations and Evolution [q-bio.PE], business.industry, 010604 marine biology & hydrobiology, larval dispersal modelling, Correction, biology.organism_classification, Fishery, [SDV.GEN.GA]Life Sciences [q-bio]/Genetics/Animal genetics, lcsh:Genetics, Genetics, Population, 030104 developmental biology, Hydrodynamics, engineering, Biological dispersal, business
Abstract

International audience; In French Polynesia, the production and exportation of black pearls through the aquaculture of the black-lip pearl oyster Pinctada margaritifera provide the second largest economic income for the country after tourism. This industry entirely relies on the collection of natural spats from few highly recruiting lagoons. In recent years, pearl oyster producers have experienced variable success rates in spat collection, with significant spatial and temporal variability in spat supply, driving uncertainty in the future of pearl production. This study combines, for the first time in a farmed lagoon, genetic (SNPs), demographic (sex ratio, age), and biophysical data (larval dispersal modelling) to shed new light on population dynamics, connectivity, and spat recruitment in Ahe Atoll, a well-studied pearl farming site. Our results indicate that the geographical structuring of the natural populations and the contribution of both natural and exploited stocks to the production of spats result from the interaction of hydrodynamic features, life history traits and demographic parameters: the northeastern natural populations are older, not well connected to the southwestern natural populations and are not replenished by larvae produced by adjacent exploited populations. Moreover, we observe that the exploited populations did not contribute to larval production during our experiment, despite a sampling period set during the most productive season for spat collection. This is likely the result of a strong male bias in the exploited populations, coupled with a sweepstakes reproductive strategy of the species. Our results warrant further investigations over the future of the northeastern older natural populations and a reflection on the current perliculture techniques

Published
2020
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14. Managing the Agri-Food System of Watersheds to Combat Coastal Eutrophication: A Land-to-Sea Modelling Approach to the French Coastal English Channel

Author

Romain Le Gendre, Gilles Billen, Sylvain Théry, Philippe Riou, Vincent Thieu, Josette Garnier, Mathilde Schapira, Antsiva Ramarson, Alain Menesguen, Philippe Cugier, Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), 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), ODE/LITTORAL/LERN, laboratoire d'Ecologie Benthique (IFREMER), Institut Français de Recherche pour l'Exploitation de la Mer - Atlantique (IFREMER Atlantique), Fédération Île-de-France de Recherche sur l'Environnement (FIRE ), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-AgroParisTech-Université Paris Diderot - Paris 7 (UPD7)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Lagons, Ecosystèmes et Aquaculture Durable de Nouvelle Calédonie (LEADNC), 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), Laboratoire Environnement Ressources Morbihan Pays de Loire (LERMPL), LITTORAL (LITTORAL), École Pratique des Hautes Études (EPHE), Ifremer - Nouvelle-Calédonie, Fédération Île-de-France de Recherche sur l'Environnement (FIRE), and Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)

Subjects
0106 biological sciences, Pseudo-nitzschia spp, Fishing, Drainage basin, 010501 environmental sciences, Riparian wetlands, 01 natural sciences, Algal bloom, modelling, Ecosystem, 14. Life underwater, Greenhouse gas indirect emissions, river basins, 0105 earth and related environmental sciences, Seine river, 2. Zero hunger, nutrient flows, geography, geography.geographical_feature_category, business.industry, 010604 marine biology & hydrobiology, lcsh:QE1-996.5, scenarios, Loir river, 15. Life on land, Crop rotation, 6. Clean water, pseudo-nitzschia spp, lcsh:Geology, 13. Climate action, Agriculture, [SDE]Environmental Sciences, Denitrification, General Earth and Planetary Sciences, Food systems, Environmental science, coastal zone ecosystem, toxic microalgae, Water resource management, business, Eutrophication
Abstract

International audience; The continental coastal waters of the Eastern Channel, from Normandy to Hauts-de-France, are subject to the major influence of unbalanced nutrient inputs from inflowing rivers. Several episodes of harmful algal blooms (HABs) compromising fishing and shellfish farming activities have been observed at the coast. For a better understanding of how the land-to-sea aquatic continuum functions, the GRAFS-RIVERSTRAHLER river biogeochemical model was implemented to cover the watersheds of 11 rivers flowing into this area (including the Seine) and chained with the ecological marine ECO-MARS3D model, applied to the French Northern coastal zone. Human activities strongly impact on the functioning of coastal ecosystems. Specifically, for these fertile soils of Northern France, intensive agricultural nitrogen (N) deliveries in excess over silica (Si) and phosphorus (P), essentially of diffuse origin, are potentially responsible for coastal eutrophication. Phosphorous is today equally supplied by diffuse and point sources, after a drastic reduction of inputs from wastewater treatment plants since the 2000s, and is better balanced regarding Si, as shown by the indicators of coastal eutrophication potential (P-ICEP versus N-ICEP). However, despite this drastic P reduction, HABs still appear repeatedly. Exploration of several scenarios of agro-food chain reorganization shows that (i) further progress in urban wastewater treatment to fully comply with current European regulations will not result in a significant reduction of nutrient fluxes to the sea, hence including HABs, and (ii) radical structural changes in agriculture, based on generalization of long and diversified organic crop rotations, reconnection of crop and livestock farming and changes in the human diet have the capacity to significantly reduce nutrient flows, coastal eutrophication and HABs.

Published
2019
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15. Are Sea Surface Temperature satellite measurements reliable proxies of lagoon temperature in the South Pacific?

Author

Teuru Passfield, Serge Andréfouët, Simon Van Wynsberge, Romain Le Gendre, Christophe E. Menkès, Ecologie marine tropicale des océans Pacifique et Indien (ENTROPIE [Nouvelle-Calédonie]), Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Ifremer - Nouvelle-Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de la Nouvelle-Calédonie (UNC), Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs (PEPS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-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 Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Lagons, Ecosystèmes et Aquaculture Durable de Nouvelle Calédonie (LEADNC), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Ministry of Marine Resources, GOPS (www.observatoire-gops.org) and by the Direction des Ressources Marines et Minières in French Polynesia., ANR-16-CE32-0004,MANA,Gestion des Atolls(2016), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-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 Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Unité de recherche Lagons, Ecosystèmes et Aquaculture Durable en Nouvelle Calédonie, Ifremer - Nouvelle-Calédonie, and Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD [Nouvelle-Calédonie])-Université de la Nouvelle-Calédonie (UNC)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Coral bleaching, Atoll, Climate change, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Aquatic Science, Oceanography, 01 natural sciences, Pacific ocean, Sea Surface Temperature, 14. Life underwater, Reef, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, 010604 marine biology & hydrobiology, Pacific islands, Reef aperture, Coral reef, Sea surface temperature, 13. Climate action, Climatology, Atoll lagoon, Linear correlation, Geology
Abstract

International audience; In remote coral reef environments, lagoon and reef in situ measurements of temperature are scarce. Sea Surface Temperature (SST) measured by satellite has been frequently used as a proxy of the lagoon temperature experienced by coral reef organisms (TL) especially during coral bleaching events. However, the link between SST and TL is poorly characterized. First, we compared the correlation between various SST series and TL from 2012 to 2016 in three atolls and one island in the Central South Pacific Ocean. Simple linear correlation between SST and TLranged between 0.44 and 0.97 depending on lagoons, localities of sensors, and type of SST data. High-resolution-satellite-measurements of SST inside the lagoons did not outperform oceanic SST series, suggesting that SST products are not adapted for small lagoons. Second, we modelled the difference between oceanic SST and TL as a function of the drivers of lagoon water renewal and mixing, namely waves, tide, wind, and season. The multivariate models reduced significantly the bias between oceanic SST and T. In atoll lagoons, and probably in other hydrodynamically semi-open systems, a correction taking into account these factors is necessary when SST are used to characterize organisms’ thermal stress thresholds.

Published
2017
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16. Nutrient ratios influence variability in Pseudo-nitzschia species diversity and particulate domoic acid production in the Bay of Seine (France)

Author

Pauline Bazin, Bertrand Le Roy, Juliette Fauchot, Romain Le Gendre, Didier Goux, Philippe Riou, Pascal Claquin, Mathilde Schapira, Maxine Thorel, Anne-Flore Deton-Cabanillas, Virginie Raimbault, Valérie Kientz-Bouchart, Biologie des mollusques marins et des écosystèmes associés (BioMEA), Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Sorbonne Université (SU)-Université des Antilles (UA)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut de Recherche pour le Développement (IRD), IFREMER LEAD-NC, Laboratoire Environnement et Ressources de Normandie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Interactions Cellules Organismes Environnement (ICORE), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-CHU Caen, Normandie Université (NU)-Tumorothèque de Caen Basse-Normandie (TCBN)-Tumorothèque de Caen Basse-Normandie (TCBN), Chirurgie digestive et hépatobiliaire, Centre Hospitalier Universitaire Estaing, Institut Pascal - Clermont Auvergne (IP), Sigma CLERMONT (Sigma CLERMONT)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA), Normandie Université (NU)-Normandie Université (NU)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Centre de Microscopie Appliquée à la Biologie [Caen] (CMABio3), Normandie Université (NU)-Tumorothèque de Caen Basse-Normandie (TCBN)-Tumorothèque de Caen Basse-Normandie (TCBN)-Université de Caen Normandie (UNICAEN), LABÉO, Pôle d’analyses et de recherche de Normandie (LABÉO), Institut méditerranéen de biodiversité et d'écologie marine et continentale (IMBE), Avignon Université (AU)-Aix Marseille Université (AMU)-Institut de recherche pour le développement [IRD] : UMR237-Centre National de la Recherche Scientifique (CNRS), ODE/LITTORAL/LERN, Institut Français de Recherche pour l'Exploitation de la Mer - Brest (IFREMER), CHU Estaing [Clermont-Ferrand], Institut de biologie de l'ENS Paris (UMR 8197/1024) (IBENS), Département de Biologie - ENS Paris, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 - Faculté des sciences pharmaceutiques et biologiques (UR1 Pharmacie), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES), Normandie Université (NU), and Centre National de la Recherche Scientifique (CNRS)

Subjects
0106 biological sciences, Time Factors, 010504 meteorology & atmospheric sciences, Plant Science, 01 natural sciences, chemistry.chemical_compound, Nutrient, English channel, ComputingMilieux_MISCELLANEOUS, Species diversity, education.field_of_study, Principal Component Analysis, Kainic Acid, Geography, Ecology, Domoic acid, Biodiversity, Bloom dynamics, Spring bloom, Bays, Environmental chemistry, [SDE]Environmental Sciences, France, Seasons, Bloom, [SDE.MCG]Environmental Sciences/Global Changes, Population, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Aquatic Science, Biology, Phosphates, Species Specificity, 14. Life underwater, education, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 0105 earth and related environmental sciences, Diatoms, Nitrates, 010604 marine biology & hydrobiology, biology.organism_classification, Nutrient ratios, chemistry, Phytoplankton, Pseudo-nitzschia, Particulate Matter, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bay
Abstract

International audience; The population dynamics of different Pseudo-nitzschia species, along with particulate domoic acid (pDA) concentrations, were studied from May 2012 to December 2013 in the Bay of Seine (English Channel, Normandy). While Pseudo-nitzschia spp. blooms occurred during the two years of study, Pseudo-nitzschia species diversity and particulate domoic acid concentrations varied greatly. In 2012, three different species were identified during the spring bloom (P. australis, P. pungens and P. fraudulenta) with high pDA concentrations (similar to 1400 ngl(-1)) resulting in shellfish harvesting closures. In contrast, the 2013 spring was characterised by a P. delicatissima bloom without any toxic event. Above all, the results show that high pDA concentrations coincided with the presence of P. australis and with potential silicate limitation (Si: N < 1), while nitrate concentrations were still replete. The contrasting environmental conditions between 2012 and 2013 highlight different environmental controls that might favour the development of either P. delicatissima or P. australis. This study points to the key role of Pseudo-nitzschia diversity and cellular toxicity in the control of particulate domoic acid variations and highlights the fact that diversity and toxicity are influenced by nutrients, especially nutrient ratios. (C) 2017 Elsevier B.V. All rights reserved.

Published
2017
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17. Long-term water quality in the lower Seine: Lessons learned over 4 decades of monitoring

Author

Marie Silvestre, Estela Romero, Gilles Billen, Philippe Riou, Romain Le Gendre, Josette Garnier, Cédric Fisson, Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), Unité de recherche Lagons, Ecosystèmes et Aquaculture Durable en Nouvelle Calédonie, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Groupement d’Intérêt Public Seine-Aval (GIP-Seine-Aval), Pôle Régional des Savoirs, Fédération Île-de-France de Recherche sur l'Environnement (FIRE), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-AgroParisTech-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Environnement et Ressources de Normandie, Université Pierre et Marie Curie - Paris 6 (UPMC)-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), Lagons, Ecosystèmes et Aquaculture Durable de Nouvelle Calédonie (LEADNC), Laboratoire Environnement Ressources de Normandie (LERN), LITTORAL (LITTORAL), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), 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)-Université Pierre et Marie Curie - Paris 6 (UPMC), and Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Recherche Agronomique (INRA)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-AgroParisTech

Subjects
Pollution, 010504 meteorology & atmospheric sciences, media_common.quotation_subject, Geography, Planning and Development, Drainage basin, WFD, 010501 environmental sciences, Management, Monitoring, Policy and Law, 01 natural sciences, water quality, nutrients, 14. Life underwater, Environmental quality, 0105 earth and related environmental sciences, media_common, Seine River, Hydrology, geography, geography.geographical_feature_category, business.industry, Estuary, Nutrients, Long-term trends, Anoxic waters, 6. Clean water, Water quality, Policy, Water Framework Directive, 13. Climate action, Agriculture, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Water resource management, business, long - ­‐term trends, policy
Abstract

International audience; The Seine River is a highly artificialised catchment in Europe, comprising both productive agricultural areas and intense industrial and commercial activity. Due to its strategic importance, monitoring programs in the river started as early as the 1970s. The present study compiles and analyses this valuable data set (1970–2014), thoroughly describing the riverine section downstream of Paris and the estuary. We identify long-term trends and shifting patterns in nutrients and oxygen, and pay special attention to the river’s evolution after the year 2000, when the European Water Framework Directive came into force. The study has a manifest management perspective, and the results are discussed on the basis of the environmental quality standards proposed in current environmental regulations. The data show that water quality has improved remarkably over the past two decades, with sharp reductions of ammonium and phosphate and a progressive increase of dissolved oxygen levels. The amelioration is prominent in the estuary, where summer anoxic episodes have nearly disappeared. As a result, these three parameters are nowadays in good or very good condition throughout the year. The successful abatement of point sources contrasts, however, with the low effectiveness of the measures provided for the control of nutrients from diffuse sources. Nitrate concentration has increased by 150% since the early 1980s, and only very recently has the upward trend been reversed. Bold agri-environmental management measures are required if we are to prevent chronic pollution problems and truly restore the good ecological status of rivers.

Published
2016
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18. Eutrophication modelling chain for improved management strategies to prevent algal blooms in the Bay of Seine

Author

Francois Paris, Josette Garnier, Philippe Riou, Paul Passy, Philippe Cugier, Gilles Billen, Estella Romero, Romain Le Gendre, Julie Callens, Department of Geography, National University of Singapore (NUS), Fédération Île-de-France de Recherche sur l'Environnement (FIRE), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-AgroParisTech-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Environnement Ressources de Normandie (LERN), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Université Pierre et Marie Curie - Paris 6 (UPMC), Dynamiques de l'Environnement Côtier (DYNECO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Université Pierre et Marie Curie - Paris 6 (UPMC)-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 Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE)-Centre National de la Recherche Scientifique (CNRS), LITTORAL (LITTORAL), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Laboratoire d'Ecologie Benthique Côtière (LEBCO), and Dynamiques des Écosystèmes Côtiers (DYNECO)

Subjects
010504 meteorology & atmospheric sciences, 010501 environmental sciences, Aquatic Science, 01 natural sciences, Algal bloom, Modelling, Harmful algal blooms, Nutrient load, Ecosystem, 14. Life underwater, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Ecology, Primary producers, biology, Estuary, Seine, Plankton, Eutrophication, biology.organism_classification, 6. Clean water, Fishery, Water quality, 13. Climate action, Environmental science, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bay, Dinophysis
Abstract

International audience; Eutrophication of the Seine estuary and the Bay of Seine is a crucial environmental issue for the management of ecosystems and economic activities related to fisheries and tourism in the region. A large quantity of nutrients, especially nitrogen, is brought to the coastal zone by the Seine River, the main input into that area, but also by smaller rivers along the Normandy coast. This large delivery of nitrogen leads to an imbalance between nitrogen (N), phosphorus (P) and silica (Si), which affects the growth of planktonic organisms and can exacerbate the occurrence of harmful algal blooms (HABs). These events can be damaging for shellfish fisheries, an important economic resource for the region. The study describes a new modelling chain coupling a riverine and a marine model (the Seneque/Riverstrahler and the ECO-MARS3D, respectively), which allows us to explore the effects on the coast of 2 scenarios of watershed management. The first one, focused on an upgrade of wastewater treatment plants, decreases the P fluxes by 5 to 35 kg P km–2 yr–1 on average over the 2000 to 2006 period, depending on the watershed, and would reduce about 3-fold the concentration of dinoflagellates in the adjacent coastal zone. The second one explores a hypothetical scenario of generalisation of organic farming in all agricultural areas of the basin. Although this is not realistic, it shows the best theoretical results we can achieve. With this scenario, the N fluxes decrease by almost 50%, and the dinoflagellate blooms and thus possibly the Dinophysis spp. blooms are drastically reduced by a factor of 20 to 40. Nevertheless, diatoms, which are the main primary producers in the bay and sustain the marine food web, are not significantly affected by this drastic scenario.

Published
2016
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19. Large-scale patterns of river inputs in southwestern Europe: seasonal and interannual variations and potential eutrophication effects at the coastal zone

Author

Estela Romero, Philippe Riou, Josette Garnier, Gilles Billen, Romain Le Gendre, Luis Lassaletta, Philippe Cugier, Structure et fonctionnement des systèmes hydriques continentaux (SISYPHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Mines Paris - PSL (École nationale supérieure des mines de Paris), Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Environnement Ressources de Normandie (LERN), LITTORAL (LITTORAL), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Laboratoire d'Ecologie Benthique Côtière (LEBCO), Dynamiques des Écosystèmes Côtiers (DYNECO), Federation Ile-de-France for Research on the Environment (FIRE FR3020 CNRS UPMC), European Science Foundation, Paris City Council (Research in Paris), French project NEREIS, FP7 European AWARE project, French project PASTEK (GIS-Climat), Agence de l'Eau Seine Normandie, Region Basse Normandie, Université Pierre et Marie Curie - Paris 6 (UPMC)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-MINES ParisTech - École nationale supérieure des mines de Paris, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), and Laboratoire Écologie Benthique (LEB)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Context (language use), Coastal zone, 01 natural sciences, Algal bloom, Nutrient, [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry, Phytoplankton, medicine, Environmental Chemistry, Ecosystem, 14. Life underwater, P:Si stoichiometry [N], 0105 earth and related environmental sciences, Earth-Surface Processes, Water Science and Technology, 010604 marine biology & hydrobiology, N:P:Si stoichiometry, Seasonality, 15. Life on land, Eutrophication, medicine.disease, 6. Clean water, Europe, Oceanography, 13. Climate action, Environmental science, River inputs, Bay
Abstract

International audience; We provide data on nutrient export for 28 rivers in southwestern Europe and analyze long-term changes in the context of anthropogenic pressures and regulation policies. Special attention is given to seasonal variations, because the integrated annual values that are usually provided do not allow us to establish comparisons with seasonal phytoplankton dynamics. The eutrophication risk associated with river inputs is addressed by means of an indicator (Index of Coastal Eutrophication Potential, ICEP, Billen and Garnier, Mar Chem 106:148-160, 2007). An overview of the temporal evolution and the intra-annual variability of the ICEP is discussed for specific rivers and integrated coastal regions. The annual dynamics of the eutrophication indicator is analyzed to delimit those periods when the risk of eutrophication is particularly high. The trends in nutrient fluxes and coastal phytoplankton are compared by means of a case study (Seine Bay). The decrease in phosphorus matches a general decrease in phytoplankton biomass in the summer. However, sustained high values of nitrogen still foster the emergence of harmful algal blooms, and we found an increase in the summer abundance of dinoflagellates. The abatement of phosphorus alone is not enough to shortcut harmful blooms and toxic outbreaks in the Seine Bay. A reduction in nitrogen inputs may be necessary to effectively minimize eutrophication problems.

Published
2013
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20. Spatial Variability of Benthic-Pelagic Coupling in an Estuary Ecosystem: Consequences for Microphytobenthos Resuspension Phenomenon

Author

Karine Grangeré, Martin Ubertini, Romain Le Gendre, Aline Gangnery, Sébastien Lefebvre, Francis Orvain, 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), and 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])

Subjects
0106 biological sciences, Geologic Sediments, Time Factors, 010504 meteorology & atmospheric sciences, Marine and Aquatic Sciences, lcsh:Medicine, Oceanography, 01 natural sciences, Water column, Microalgae, Spatial and Landscape Ecology, Biomass, lcsh:Science, Trophic level, Biomass (ecology), Principal Component Analysis, Multidisciplinary, geography.geographical_feature_category, Geography, Ecology, Marine Ecology, Malacology, Biota, Benthic zone, Phycology, Seasons, Estuaries, Marine Geology, Coastal Ecology, Research Article, Marine Biology, Ecosystems, Animals, Ecosystem, 14. Life underwater, Biology, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, Spatial Analysis, 010604 marine biology & hydrobiology, Plant Ecology, lcsh:R, Reproducibility of Results, Pelagic zone, Estuary, 15. Life on land, 13. Climate action, Mollusca, Earth Sciences, lcsh:Q, Bay, Zoology, Environmental Sciences, Ecological Environments
Abstract

International audience; The high degree of physical factors in intertidal estuarine ecosystem increases material processing between benthic and pelagic compartments. In these ecosystems, microphytobenthos resuspension is a major phenomenon since its contribution to higher trophic levels can be highly significant. Understanding the sediment and associated microphytobenthos resuspension and its fate in the water column is indispensable for measuring the food available to benthic and pelagic food webs. To identify and hierarchize the physical/biological factors potentially involved in MPB resuspension, the entire intertidal area and surrounding water column of an estuarine ecosystem, the Bay des Veys, was sampled during ebb tide. A wide range of physical parameters (hydrodynamic regime, grain size of the sediment, and suspended matter) and biological parameters (flora and fauna assemblages, chlorophyll) were analyzed to characterize benthic-pelagic coupling at the bay scale. Samples were collected in two contrasted periods, spring and late summer, to assess the impact of forcing variables on benthic-pelagic coupling. A mapping approach using kriging interpolation enabled us to overlay benthic and pelagic maps of physical and biological variables, for both hydrological conditions and trophic indicators. Pelagic Chl a concentration was the best predictor explaining the suspension-feeders spatial distribution. Our results also suggest a perennial spatio-temporal structure of both benthic and pelagic compartments in the ecosystem, at least when the system is not imposed to intense wind, with MPB distribution controlled by both grain size and bathymetry. The benthic component appeared to control the pelagic one via resuspension phenomena at the scale of the bay. Co-inertia analysis showed closer benthic-pelagic coupling between the variables in spring. The higher MPB biomass observed in summer suggests a higher contribution to filter-feeders diets, indicating a higher resuspension effect in summer than in spring, in turn suggesting an important role of macrofauna bioturbation and filter feeding (Cerastoderma edule).

Published
2012
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21. Island shadow effects and the wave climate of the western Tuamotu archipelago (French Polynesia) inferred from altimetry and numerical model data

Author

Serge Andréfouët, Fabrice Ardhuin, Romain Le Gendre, Pierre Queffeulou, Andréfouët, Serge (ed.), and Charpy, Loïc (ed.)

Subjects
0106 biological sciences, 010504 meteorology & atmospheric sciences, Climate, Atoll, Aquatic Science, Oceanography, 01 natural sciences, CLIMATOLOGIE, Polynesia, ALTIMETRIE, Wave model, LAGON, Shadow, Water Movements, Seawater, 14. Life underwater, Altimeter, Spacecraft, Weather, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, Atmosphere, Altitude, 010604 marine biology & hydrobiology, IMPACT DE L'ENVIRONNEMENT, Storm, Models, Theoretical, Pollution, Swell, CIRCULATION OCEANIQUE, Climatology, Remote Sensing Technology, Archipelago, MODELE NUMERIQUE DE TERRAIN, Seasons, Significant wave height, Geology, Environmental Monitoring
Abstract

To implement a numerical model of atoll lagoon circulation, we characterized first the significant wave height (Hs) regime of the Western Tuamotu Archipelago and the local attenuation due to the protection offered by large atolls in the south Tuamotu. Altimetry satellite data and a WAVEWATCH III two-way nested wave model at 5 km resolution from 2000 to 2010 were used. Correlation between altimetry and model was high (0.88) over the period. According to the wave model, the archipelago inner seas experienced attenuated Hs year-long with a yearly average Hs around 1.3 m vs a minimum of 1.6 m elsewhere. The island shadow effect is especially significant in the austral winter. In contrast with southern atolls, Western Tuamotu experienced only few days per year of Hs larger than 2.5 m generated by very high Hs southern swell, transient western local storms, strong easterly winds, and during the passage of distant hurricanes.

Published
2012

22. Coastal cliff falls and triggering factors in Upper Normandy: spatial, temporal, and statistical approaches

Author

Pauline Letortu, Stéphane Costa, Jean-Michel Cador, Olivier Cantat, Olivier Maquaire, Robert Davidson, Sébastien Caillault, Romain Le Gendre, Hervé Quénol, Littoral, Environnement, Télédétection, Géomatique (LETG - Caen), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), Laboratoire Environnement Ressources de Normandie (LERN), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Littoral, Environnement, Télédétection, Géomatique (LETG - Rennes), and Letortu, Pauline

Subjects
Processus, Effondrements, [SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology, [SHS.GEO] Humanities and Social Sciences/Geography, Upper Normandy, Statistics, Erosion côtière, Geomorphology, [SHS.GEO]Humanities and Social Sciences/Geography, Falaises crayeuses, Haute-Normandie, Coastal Chalk Cliff, Processes, Coastal Erosion, Statistiques, Cliff Fall, [SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology, Géomorphologie
Abstract

6 pages; National audience; The coastline of Upper Normandy (France) is made up of a 130 km long chalk cliff in the central part of the English Channel shoreline. For the last 30 years the average chalk cliff retreat rate is about 0.21 m/y. This cliff retreat changes from location to location, and its rate can reach a metric value. Due to cliff falls threatening settlements close to the coastline, better understanding of this rocky coast erosion is greatly needed. The primary aim of this study is to determine the triggering factors of coastal chalk cliff retreat. This study is carried out in collaboration with the ESTRAN non-profit corporation that has made a weekly inventory of cliff falls (location, volume and dating) from Saint-Valéry-en-Caux to Le Tréport. Based on this unique and considerable database of 332 cliff fall events from 2002 to 2009, many analyses were made: spatial and temporal distributions of coastal cliff falls and statistical analyses of the relationship between processes and cliff falls. Coastal cliff falls occur predominantly in winter but can also occur in summer and are mainly located at the Ailly Cape. Annual return periods according to cliff fall volume were calculated. The statistical analyses point the difficulty to identify the key-processes that trigger coastal chalk cliff falls. Indeed, numerous combinations of factors and the phenomena of process shifts or even hysteresis effects make the connection between triggering agents and cliff falls more complex.

Published
2011

23. On the Determination of Triggering Factors of Coastal Chalk Cliff Collapses in Upper Normandy

Author

Letortu, Pauline, Cador, Jean-Michel, Romain Le Gendre, quenol Hervé, Costa, Stéphane, Littoral, Environnement, Télédétection, Géomatique (LETG - Brest), Littoral, Environnement, Télédétection, Géomatique UMR 6554 (LETG), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Université d'Angers (UA)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Brest (UBO)-Université de Rennes 2 (UR2), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Géographie et d'Aménagement Régional de l'Université de Nantes (IGARUN), Université de Nantes (UN)-Université de Nantes (UN)-Université de Caen Normandie (UNICAEN), Université de Nantes (UN)-Université de Nantes (UN), Littoral, Environnement, Télédétection, Géomatique (LETG - Caen), ODE/LITTORAL/LERN, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Littoral, Environnement, Télédétection, Géomatique (LETG - Rennes), and Letortu, Pauline

Subjects
genetic structures, [SHS.GEO] Humanities and Social Sciences/Geography, parasitic diseases, education, [SHS.GEO]Humanities and Social Sciences/Geography, ComputingMilieux_MISCELLANEOUS, geographic locations, humanities
Abstract

Objectives : The primary aim of this study is to determine the triggering factors of coastal cliff retreat. (...)

Published
2011

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