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1. Seasonal survey of the composition and degradation state of particulate organic matter in the Rhône River using lipid tracers

Author

M.-A. Galeron, R. Amiraux, B. Charriere, O. Radakovitch, P. Raimbault, N. Garcia, V. Lagadec, F. Vaultier, and J.-F. Rontani

Subjects
Ecology, QH540-549.5, Life, QH501-531, Geology, QE1-996.5
Abstract

Lipid tracers including fatty acids, hydroxyacids, n-alkanols, sterols and triterpenoids were used to determine the origin and fate of suspended particulate organic matter (POM) collected in the Rhône River (France). This seasonal survey (April 2011 to May 2013) revealed a year-round strong terrestrial higher-plant contribution to the particulate organic matter (POM), with significant algal inputs observed in March and attributed to phytoplanktonic blooms likely dominated by diatoms. Major terrigenous contributors to our samples are gymnosperms, and more precisely their roots and stems, as evidenced by the presence of high proportions of ω-hydroxydocosanoic acid (a suberin biomarker). The high amounts of coprostanol detected clearly show that the Rhône River is significantly affected by sewage waters. Specific sterol degradation products were quantified and used to assess the part of biotic and abiotic degradation of POM within the river. Higher-plant-derived organic matter appears to be mainly affected by photo-oxidation and autoxidation (free radical oxidation), while organic matter of mammal or human origin, evidenced by the presence of coprostanol, is clearly more prone to bacterial degradation. Despite the involvement of an intense autoxidation-inducing homolytic cleavage of peroxy bonds, a significant proportion of hydroperoxides is still intact in higher plant debris. These compounds could affect the degradation of terrestrial material by inducing an intense autoxidation upon its arrival at sea.

Published
2015
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2. Bi-decadal variability in physico-biogeochemical characteristics of temperate coastal ecosystems: from large-scale to local drivers

Author

A Lheureux, N Savoye, Y Del Amo, E Goberville, Y Bozec, E Breton, P Conan, S L’Helguen, L Mousseau, P Raimbault, P Rimelin-Maury, L Seuront, R Vuillemin, J Caparros, T Cariou, MA Cordier, AM Corre, L Costes, O Crispi, M Crouvoisier, H Derriennic, J Devesa, M Durozier, S Ferreira, N Garcia, E Grossteffan, A Gueux, M Lafont, V Lagadec, E Lecuyer, C Leroux, E Macé, E Maria, L Mornet, A Nowaczyk, M Parra, F Petit, V David, 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), Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Université de Caen Normandie (UNICAEN), 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), Adaptation et diversité en milieu marin (ADMM), Institut national des sciences de l'Univers (INSU - CNRS)-Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Station biologique de Roscoff (SBR), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Océanographie Microbienne (LOMIC), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Observatoire océanologique de Banyuls (OOB), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-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), Laboratoire d'océanographie de Villefranche (LOV), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut de la Mer de Villefranche (IMEV), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), 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 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]), Observatoire océanologique de Banyuls (OOB), Laboratoire GéoSciences Réunion (LGSR), Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris), 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), Fédération de recherche de Roscoff (FR2424), UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), 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), Adaptation et diversité en milieu marin (AD2M), Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff (SBR), Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire océanologique de Banyuls (OOB), Observatoire océanologique de Villefranche-sur-mer (OOVM), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Analytical, Environmental and Geo- Chemistry, Vrije Universiteit Brussel (VUB), Ecosystèmes forestiers (UR EFNO), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-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), 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), 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, Biogeochemical cycle, 010504 meteorology & atmospheric sciences, Temperature salinity diagrams, Climate change, Aquatic Science, Coastal ecosystems, 01 natural sciences, Temperate climate, Marine ecosystem, Ecosystem, 14. Life underwater, Temporal scales, Long-term changes, Ecology, Evolution, Behavior and Systematics, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Ecology, 010604 marine biology & hydrobiology, Monitoring programme, Biogeochemistry, 15. Life on land, Oceanography, Multivariate analysis, 13. Climate action, [SDE]Environmental Sciences, Environmental science
Abstract

Coastal marine ecosystems, which play a crucial role in the biogeochemical and ecological functioning of the Earth, are highly sensitive to the combined effects of climate and human activities. Because of their location, coastal ecosystems are directly influenced by human activities, but it remains challenging to assess the spatial and temporal scales at which climate influences coastal ecosystems. We monitored 12 sampling stations, distributed in 8 ecosystems in France, over 2 decades for physico-biogeochemical parameters (temperature, salinity, concentrations of dissolved oxygen, nutrients and particulate material). The study encompasses a large diversity of temperate coastal ecosystems with respect to e.g. geomorphology, trophic status, tidal regime, river influence and turbidity. Time-series analysis coupled with standardised 3-mode principal component analyses, partial triadic analyses and correlations were used to assess bi-decadal variability and ecosystem trajectories, and to identify large-scale, regional and local drivers. Our results highlighted 2 abrupt changes in 2001 and 2005. The bi-decadal changes were related to changes in large-scale and regional climate, detected through proxies of temperature and atmospheric circulation, as well as through river discharge. Ecosystem trajectories tended to move towards an increase in temperature and salinity, and/or a decrease in chlorophyll a, nutrients and particulate matter. However, the magnitude of change, the year-to-year variability and the sensitivity to the 2001 and 2005 changes varied among the ecosystems. This study highlights the need for establishing long-term time series and combining data sets as well as undertaking multi-ecosystem and local studies to better understand the long-term variability of coastal ecosystems and its associated drivers.

Published
2021
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3. Catch-Up Saccades in Vestibulo-Ocular Reflex Deficit: Contribution of Visual Information?

Author

Hermann R, Ramat S, Colnaghi S, Lagadec V, Desoche C, Pelisson D, and Froment Tilikete C

Abstract

Objectives: Catch-up saccades help to compensate for loss of gaze stabilization during rapid head rotation in case of vestibular deficit. While overt saccades observed after head rotation are obviously visually guided, some of these catch-up saccades occur with shorter latency while the head is still moving, anticipating the needed final eye position. These covert saccades seem to be generated based on the integration of multisensory inputs. Vision could be one of these inputs, but the known delay for triggering visually guided saccades questions this possibility. The main objective of this study is to evaluate the potential role of visual information for controlling (triggering and guiding) the first catch-up saccades in patients suffering from bilateral vestibulopathy. To investigate this, we used head impulse test in a virtual reality setting allowing to create different visuo-vestibular mismatch conditions., Design: Twelve patients with bilateral vestibulopathy were recruited. We assessed in our patient group the validity of our virtual reality head impulse testing approach by comparing recorded eye and head movement to classical video head impulse test. Then, using the virtual reality system, we tested head impulse test under both normal and three visuo-vestibular mismatch conditions. In these mismatch conditions, the movement of the visual scene relative to the head movement was altered: decreased in amplitude by 50% (half), nullified (freeze), or inverted in direction (inverse). Recorded eye and head movements during these different conditions were then analyzed, more specifically the characteristics of the first catch-up saccade., Results: Impaired vestibulo-ocular reflex required subjects to systematically perform catch-up saccades, which could be covert or overt. The latency of the first catch-up saccade increased along with the amount of visuo-vestibular mismatch between the four conditions (i.e., from normal to half to freeze to inverse) and, consequently, the mean percentage of covert saccades decreased with increasing visual feedback error. However, the freeze and inverse conditions allowed us to reveal the existence of many saccades performed in the wrong direction relative to visual feedback. These visually discordant saccades were present in over half of the trials, they were mainly covert and their percentage was inversely correlated with residual vestibulo-ocular reflex gain., Conclusions: Visual information significantly impacts catch-up saccade latency and the relative number of covert saccades during head impulse testing in vestibular deficit. However, in more than 50% of trials involving a visuo-vestibular mismatch, catch-up saccades remained directed in the compensatory direction relative to head movement, that is, they were visually discordant. Therefore, contrary to previously published proposals, visual information does not appear to be the primary component of the multisensory inputs required for the production of catch-up covert saccades in vestibular deficit. Finally, we discuss a new nomenclature of catch-up saccades in case of vestibular deficit introducing the terms of open and closed loop saccades., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2024 The American Auditory Society.)

Published
2024
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5. Catch-Up Saccades in Vestibular Hypofunction: A Contribution of the Cerebellum?

Author

Hermann R, Robert C, Lagadec V, Dupre M, Pelisson D, and Froment Tilikete C

Subjects
Humans, Reflex, Vestibulo-Ocular physiology, Head Impulse Test methods, Cerebellum, Saccades, Cerebellar Diseases
Abstract

Long-term deficits of the vestibulo-ocular reflex (VOR) elicited by head rotation can be partially compensated by catch-up saccades (CuS). These saccades are initially visually guided, but their latency can greatly decrease resulting in short latency CuS (SL-CuS). It is still unclear what triggers these CuS and what are the underlying neural circuits. In this study, we aimed at evaluating the impact of cerebellar pathology on CuS by comparing their characteristics between two groups of patients with bilateral vestibular hypofunction, with or without additional cerebellar dysfunction. We recruited 12 patients with both bilateral vestibular hypofunction and cerebellar dysfunction (BVH-CD group) and 12 patients with isolated bilateral vestibular hypofunction (BVH group). Both groups were matched for age and residual VOR gain. Subjects underwent video head impulse test recording of the horizontal semicircular canals responses as well as recording of visually guided saccades in the step, gap, and overlap paradigms. Latency and gain of the different saccades were calculated. The mean age for BVH-CD and BVH was, respectively, 67.8 and 67.2 years, and the mean residual VOR gain was, respectively, 0.24 and 0.26. The mean latency of the first catch-up saccade was significantly longer for the BVH-CD group than that for the BVH group (204 ms vs 145 ms, p < 0.05). There was no significant difference in the latency of visually guided saccades between the two groups, for none of the three paradigms. The gain of covert saccades tended to be lower in the BVH-CD group than in BVH group (t test; p = 0.06). The mean gain of the 12° or 20° visually guided saccades were not different in both groups. Our results suggest that the cerebellum plays a role in the generation of compensatory SL-CuS observed in BVH patients., (© 2023. The Author(s).)

Published
2024
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