Role of suspended particulate material on growth and metal bioaccumulation in oysters (Crassostrea gigas) from a French coastal semi-enclosed production area, Arcachon Bay
Arcachon Bay is a prominent oyster production area on the coast of Western Europe, and is subject to chemical contamination including by trace metals. Recently, the national "mussel-watch" monitoring network - using local bivalves as semi-quantitative bioindicators of coastal chemical contamination - highlighted a significant increase in copper (Cu) concentrations in oysters from this bay. Here, we conducted a one-year multi-compartment and multi-parameter field study to investigate some aspects of the surrounding environment of oysters that could explain their metal bioaccumulation. Sediment, seawater (through punctual and passive sampling), particles (suspended particulate material of selected sizes, including trophic resources for oysters) and transplanted oysters were regularly collected at two contrasted sites of the bay (i.e. under continental versus more oceanic influence). These matrices were characterised for their total Cu, zinc (Zn), nickel (Ni), cadmium (Cd) and lead (Pb) concentrations. Several physico-chemical and biological parameters (e.g. salinity, particle loads, oyster growth rate and condition indices, carbon and nitrogen stable isotope compositions, etc.) were also analysed. Overall, sediment, particles and oysters from the outermost site had slightly lower δ13C values, confirming the more oceanic influence in this part of the bay. Among organic particles, although dinoflagellates tended to be more abundant at the outermost site while ciliates were more abundant at the innermost site of the bay, the two sites did not differ in mean total microphytoplankton and diatom densities. However, the variations observed for most of the other parameters studied show that oysters located near the continental shore are exposed to higher loads of particles in general, and to higher metal contents in the dissolved phase and "bulk" seawater (dissolved plus particulate phases) during the year. While fluvial inputs and continental/urban run-offs are suspected sources of anthropogenic metal inputs into the bay, (fine) sediment particle resuspension appears to be a likely major contributor to metal release and hence to the contamination of the bay including oysters. The decline of seagrass beds in the last two decades in the bay could also have decreased the potential of fine particle retention in the sedimentary stratum. Concomitantly, oysters presenting the highest metal concentrations were those with the lower growth rates and condition indices, which may be induced by physical constraints, high amounts of pseudo-faeces produced and/or reduced food and energy acquisition by oysters due to high particle loads in the water column. The findings of this study imply that using raw metal concentrations in bivalves to monitor marine coastal contamination can lead to misleading interpretations if potentially great spatial variations in bivalve growth rates or condition indices are not considered. Finally, peculiar trends were observed for Cu compared to other metals, highlighting the need of further studies to fully address the Cu contamination in this marine system (e.g. specific sources of contamination for this metal in the bay). This study more broadly raises the issue of potentially man-induced ecological changes (e.g. modification of natural habitats) and their consequences on metal transfer and physiological performance of marine biota.
(Journal of Marine Systems. vol. 234, n° 0924-7963, 13/04/2026)
IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Video-Based Nearshore Bathymetric Inversion on a Geologically Constrained Mesotidal Beach during Storm Events
Although geologically constrained sandy beaches are ubiquitous along wave-exposed coasts, there is still a limited understanding of their morphological response, particularly under storm conditions, which is mainly due to a critical lack of nearshore bathymetry observations. This paper examines the potential to derive bathymetries from video imagery under challenging wave conditions in order to investigate headland control on morphological beach response. For this purpose, a video-based linear depth inversion algorithm is applied to three consecutive weeks of frames collected during daylight hours from a single fixed camera located at La Petite Chambre d’Amour beach (Anglet, SW France). Video-derived bathymetries are compared against in situ topo-bathymetric surveys carried out at the beginning and end of the field experiment in order to assess the performance of the bathymetric estimates. The results show that the rates of accretion/erosion within the surf zone are strongly influenced by the headland, whereas the beach morphological response can be classified into three main regimes depending on the angle of wave incidence θp: (1) under deflection configuration (θp>0°), the alongshore sediment transport was trapped at the updrift side of the headland, promoting sand accretion. (2) Under shadowed configuration (θp<0°), the interruption of the longshore current drove a deficit of sand supply at the downdrift side of the headland, leading to an overall erosion in the surf zone. (3) Under shore-normal configuration (θp=0°), rip channels developed, and up-state beach transition was observed. A comparison between video-derived bathymetries and surveys shows an overall root mean square error (RMSE) around 0.49 to 0.57 m with a bias ranging between −0.36 and −0.29 m. The results show that video-derived bathymetries can provide new insight into the morphological change driven by storm events. The combination of such inferred bathymetry with video-derived surface current data is discussed, showing great potential to address the coupled morphodynamics system under time-varying wave conditions.
(Remote Sensing. vol. 14, n° 2072-4292, pp. 3850, 13/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SIAME, UPPA
Évolutions paysagères et occupations humaines passées du Marais poitevin occidental durant la fin de l’Holocène
Dans le contexte actuel du changement climatique, l’analyse croisée de l’évolution paléoenvironnementale et paléosociétale d’un secteur littoral vulnérable illustre différentes formes d’occupations humaines liées à leur environnement durant les derniers millénaires. Une analyse sédimentologique couplée avec des cartographies historiques permet de reconstruire et de dater finement l’évolution des principaux paléopaysages de la bordure ouest du Marais poitevin. Cette analyse confirme que cet espace a profondément évolué, notamment durant l’Antiquité et le début du Moyen Âge, périodes durant lesquelles l’ancien golfe maritime s’est transformé en un marais aujourd’hui colmaté. En parallèle, l’évolution de l’occupation humaine historique est qualifiée par des données géoarchéologiques. Des vestiges d’anciennes pêcheries et empierrements ont été identifiés à proximité des points rocheux. Ils témoignent d’une occupation humaine historique dans les anciennes îles, au sein desquelles les Hommes se trouvaient en sécurité face aux aléas météo-marins.
(Géomorphologie : relief, processus, environnement. vol. 27, n° 1266-5304, pp. 263-278, 30/12/2021)
IGARUN, UN, LETG - Nantes, UNICAEN, NU, EPHE, PSL, UBO EPE, UR2, CNRS, IGARUN, UN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UB, UFR HHAA, UN, CReAAH, UM, UR, UR2, CNRS, UFR HHAA, UN, MC
Les Auzières (Méthamis, Vaucluse)
(15/12/2021)
LAMPEA, AMU, CNRS, MC, IRAMAT-CRP2A, IRAMAT, UTBM, UO, UBM, CNRS, HNHP, MNHN, UPVD, CNRS, TRACES, EHESS, UT2J, Comue de Toulouse, MCC, Inrap, CNRS, CEPAM, UNS, CNRS, UniCA, PACEA, UB, CNRS, ADES, AMU, CNRS, EFS Alpes-Méditerranée, EFS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The “Spaghetti Project”: the final identification guide to European Terebellidae (sensu lato) (Annelida, Terebelliformia)
This paper is the conclusion of the “Spaghetti Project” aiming to revise French species of Terebellidae sensu lato (s.l.) belonging to the five families: Polycirridae, Telothelepodidae, Terebellidae sensu stricto (s.s.), Thelepodidae and Trichobranchidae. During this project, 41 species were observed, 31 of them new for science: eight species of Polycirridae, eleven species of Terebellidae s.s., three species of Thelepodidae and nine species of Trichobranchidae. We provide a comprehensive key for all European species of terebellids with a focus on the important diagnostic characters for each family. Finally, we discuss issues on taxonomy, biodiversity and cryptic and pseudo-cryptic species of polychaetes in European waters, based on results obtained during this project.
(European Journal of Taxonomy. vol. 782, pp. 108-156, 14/12/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIFESP, UMS POREA, INSU - CNRS, CNRS, INRAE, GU, SBR, SU, CNRS, FR2424, SBR, SU, CNRS, M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, DYNECO, IFREMER, IUEM, IRD, INSU - CNRS, UBO EPE, CNRS, PatriNat, MNHN, CNRS, OFB, LIENSs, INSU - CNRS, ULR, CNRS, LECOB, SU, CNRS, OOB, SU, CNRS
Multidisciplinary assessment of nearshore nursery habitat restoration for an exploited population of marine fish
Nearshore habitats are essential for many marine fish species but are subject to anthropogenic stressors. Assessing the consequences of essential fish habitat degradation on population dynamics and productivity is challenging. We address this by focusing on a metapopulation of the common sole Solea solea , a high-value, exploited flatfish in the Eastern English Channel (EEC). Multidisciplinary data and expert knowledge were compiled to build feasible restoration scenarios for the availability of suitable habitat (measured in habitat surface extent) and chemical quality of juvenile habitats in the highly anthropized Seine estuary, the largest estuary and potentially a sole nursery area of primary interest in the EEC. Scenarios were simulated with a spatially structured life-cycle model to investigate the consequences of local restoration on restricted nursery habitats in the estuary. Restoring surface extent and habitat quality in the Seine estuary dramatically enhances spawning stock biomass (+18%) and fishery catches (+13%) in the EEC. Restoring habitat quality has a greater effect than restoring habitat surface. Because of the low connectivity between subpopulations of sole in the EEC, most of the local restoration benefits remain regional and affect the subpopulation that directly depends on the Seine nursery, with only moderate spread to the entire EEC. Our study emphasizes the utility of spatial simulation models for integrating multidisciplinary knowledge and assessing the consequences of local anthropogenic pressures at wider metapopulation scales. We provide a means of building robust methods to assess the benefits of nearshore habitat restoration for enhancing fish populations and fisheries and integrate habitat value into the sustainable management of exploited species.
(Marine Ecology Progress Series. vol. 680, n° 0171-8630, pp. 97-109, 09/12/2021)
ESE, INRAE, Institut Agro, Institut Agro, DYNECO, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, GIP-Seine-Aval
Are complementarity effects of species richness on productivity the strongest in species-rich communities?
How the relationship between species richness and productivity changes along environmental gradients remains poorly understood. We examined the context dependency of complementarity processes underpinning this relationship (biotic feedbacks, resource partitioning and facilitation) using the framework of Grime's (1973) humped-back model. We considered several scenarios of variation in competition and facilitation along environmental gradients, either monotonic with the most common or intense facilitation at the most abiotically severe end of gradients or nonlinear with the strongest facilitation at intermediate positions along gradients. How competition shifts to facilitation along environmental gradients is a key for determining where the effect of species richness on productivity occurs. Based on the literature, the original Stress Gradient Hypothesis would likely predict that complementarity effects should be the greatest, or the most important, in the most abiotically stressful environments. Alternatively, both the ‘collapse of facilitation’ and the ‘shift back to competition’ scenarios predict that the highest overall complementary effects on productivity, not biomass, would most likely occur at intermediate positions along environmental stress gradients, but this might vary depending on the source of stress. This latter prediction is consistent with a great deal of literature on natural gradients of productivity and species richness. Synthesis. Our predictions illustrate the importance of better understanding the context dependency of complementarity processes and the key role of facilitation along environmental gradients to better focus conservation efforts where ecosystem functioning is more likely to be negatively affected by species loss, in particular in species-rich communities. © 2021 British Ecological Society
(Journal of Ecology. vol. 109, n° 0022-0477, pp. 2038-2046, 01/12/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Live (stained) benthic foraminifera from the West-Gironde Mud Patch (Bay of Biscay, NE Atlantic): Assessing the reliability of bio-indicators in a complex shelf sedimentary unit.
(Continental Shelf Research, n° 0278-4343, pp. 104616, 01/12/2021)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CHROME, UNIMES, OIST, LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France]
Early life neonicotinoid exposure results in proximal benefits and ultimate carryover effects
Neonicotinoids are insecticides widely used as seed treatments that appear to have multiple negative effects on birds at a diversity of biological scales. Adult birds exposed to a low dose of imidacloprid, one of the most commonly used neonicotinoids, presented reduced fat stores, delayed migration and potentially altered orientation. However, little is known on the effect of imidacloprid on birds growth rate despite studies that have documented disruptive effects of low imidacloprid doses on thyroid gland communication. We performed a 2×2 factorial design experiment in Zebra finches, in which nestling birds were exposed to a very low dose (0.205 mg kg body mass−1) of imidacloprid combined with food restriction during posthatch development. During the early developmental period, imidacloprid exposure resulted in an improvement of body condition index in treated nestlings relative to controls. Imidacloprid also led to compensatory growth in food restricted nestlings. This early life neonicotinoid exposure also carried over to adult age, with exposed birds showing higher lean mass and basal metabolic rate than controls at ages of 90–800 days. This study presents the first evidence that very low-dose neonicotinoid exposure during early life can permanently alter adult phenotype in birds.
(Scientific Reports. vol. 11, n° 2045-2322, 01/12/2021)
CEBC, ULR, CNRS, INRAE, CEN, ULaval, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Vulnerability of the North Water ecosystem to climate change
Abstract High Arctic ecosystems and Indigenous livelihoods are tightly linked and exposed to climate change, yet assessing their sensitivity requires a long-term perspective. Here, we assess the vulnerability of the North Water polynya, a unique seaice ecosystem that sustains the world’s northernmost Inuit communities and several keystone Arctic species. We reconstruct mid-to-late Holocene changes in sea ice, marine primary production, and little auk colony dynamics through multi-proxy analysis of marine and lake sediment cores. Our results suggest a productive ecosystem by 4400–4200 cal yrs b2k coincident with the arrival of the first humans in Greenland. Climate forcing during the late Holocene, leading to periods of polynya instability and marine productivity decline, is strikingly coeval with the human abandonment of Greenland from c. 2200–1200 cal yrs b2k. Our long-term perspective highlights the future decline of the North Water ecosystem, due to climate warming and changing sea-ice conditions, as an important climate change risk.
(Nature Communications. vol. 12, n° 2041-1723, 01/12/2021)
GEUS, LOCEAN-VOG, LOCEAN, MNHN, IRD, INSU - CNRS, SU, CNRS, IPSL (FR_636), ENS-PSL, UVSQ, CEA, INSU - CNRS, X, CNES, SU, CNRS, UPCité, DGD.REVE, MNHN, HELSUS, ULaval, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DMI, IGN, UCPH, AWI, UEF, UNIVERSITé DE DURHAM, JYU, JYU, METU, IRSTEA, UCPH, GINR