Mercury toxicity to terrestrial snails in a partial life cycle experiment.
Despite growing concerns about the potential adverse effects of elevated mercury (Hg) concentrations in the terrestrial environment, only a few toxicity data are available for soil invertebrates. The chronic toxicity of inorganic Hg-Hg(II)-through food or soil contaminations was therefore assessed for the snail Cantareus aspersus, a well-recognized soil quality bioindicator. The 28-day EC50s (the concentrations causing 50 % effect) for the snail growth were 600 and 5048 mg Hg kg(-1) for food and soil, respectively. A survey of growth over its entire duration (91 days) allowed to show that the effects took place rapidly after the beginning of exposure and persisted in the long term. Reproduction was also impaired, and we established 28-day EC50s for sexual maturation and fecundity of 831 and 339 mg Hg kg(-1), respectively, for food and 1719 and 53 mg Hg kg(-1), respectively, for soil. Total Hg analyses in snails exposed to contaminated matrices revealed important bioaccumulation capacities up to 2000 mg Hg kg(-1) viscera. Critical limits in internal Hg concentration of about 500 and 1000 mg Hg kg(-1) were determined as thresholds for the induction of growth toxicity through food and soil exposure, respectively. These different values underlined differences in the uptake and toxicological dynamics of Hg according to its bioavailability in the source of exposure.
(Environmental Science and Pollution Research. vol. 23, n° 0944-1344, pp. 3165-75, 31/01/2016)
LCE, CNRS, UFC, UBFC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact des obstacles aquatiques sur la migration des jeunes stades d’Anguilla anguilla
L’anguille européenne Anguilla anguilla est une espèce catadrome avec un cycle de vie complexe incluant des migrations entre la mer de Sargasses et l’Europe et l’Afrique du Nord. On a noté une baisse drastique de sa population depuis les 30 ans et on la considère aujourd’hui comme ‘en danger critique’. Une des causes principales de ce déclin est la fragmentation de l’habitat.Nous avons étudié si les obstacles aquatiques peuvent exercer un pression de sélection sur les jeunes anguilles en migration. On a utilisé une approche sans a priori, où une large liste des gènes a été analysée dans trois tissus de chaque poisson provenant des zones amont/aval de l’obstacle (article 1). On a détecté les différences de transcription des gènes du cerveau des poissons, ces gènes étant liés à la plasticité neuronale. On a également trouvé que ces différences se maintiennent à long terme (article 2). Finalement, on a étudié la relation entre le comportement d’escalade et la transcription des gènes (article 3). Les anguilles provenant des zones amont possèdent une tendance d’escalade la plus forte. De plus, certains poissons classés comme ‘leaders’ d’escalade présentaient des niveaux de transcription de gènes liés à la cognition plus faibles que les ‘suiveurs’. Ces résultats peuvent être associés au concept de coping style et de la personnalité animale. En effet, on suggère que les leaders agissent comme des individus proactifs et téméraires, contrairement aux suiveurs, plutôt réactifs et timides.L’implication des notre étude est discutée dans le contexte écologique, car la présence des obstacles peut modifier les patterns de distribution de phénotypes dans les réseaux aquatiques.
(29/01/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IRSTEA, UR EABX, IRSTEA
Improvement of biostratigraphic and paleoenvironmental reconstruction tools based on cretaceous dinoflagellate cysts from the tethys and the atlantic
In the first chapter, dinocysts are used to recognize the Upper Cretaceous and Paleocene stage boundaries in the ODP Hole 959D, on the Côte d’Ivoire–Ghana transform margin. The comparison of my own results with two previous studies of the same cores highlights uncertainties of biostratigraphic approach when dinocyst markers have low occurrence frequencies. The second chapter analyzes the dinocyst distribution along an inshore-offshore transect on the western Iberian Margin during the Albian. Contrasting the dinocyst occurrence data with the sedimentological and paleontological data allow identifying dinocyst associations with common environmental preferences and tolerances. The main factors contributing to the dinocyst distribution are the stability and predictability gradient and the nutrient availability. Paleoceanographic and paleogeographic evolution of the western Iberian margin during the Albian are clearly recorded in the spatiotemporal occurrence patterns of dinocyst associations. The third chapter compares Aptian dinocyst distribution from the Central Atlantic and northwestern Tethys. It is used to test the methodology and the paleoenvironmental preferences of dinocyst issued from the second chapter. The recognized paleoenvironmental preferences and tolerances of the Aptian dinocysts precisely match those proposed for the Albian species. The Aptian dinocyst associations reflect the evolution of carbonate platforms of both the Southern Provence Basin and the western Iberian margin, combined with the sedimentary organic matter allows the identification of regional and global oceanic changes; the demise of carbonate platforms, the OAE 1a and the Fallot level.
(22/01/2016)
CR2P, MNHN, UPMC, CNRS
Climate variability across the last deglaciation in NW Iberia and its margin
(Quaternary International. vol. 414, n° 1040-6182, pp. 9 - 22, 08/01/2016)
Unifesp, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, ACE-CRC, AWI
Cockle population dynamics: recruitment predicts adult biomass, not the inverse
Bivalves are an essential component of marine ecosystems, playing an important role in community maintenance. The abundance of an exploited bivalve population depends on the balance between inputs (reproduction/recruitment and growth) and outputs (mortality and fishery removals). Reproduction and subsequent successful recruitment are crucial for population sustainability. In the present study, the reciprocal relationship between recruitment (operationally defined as retention on a 1-mm sieve) and adult stock size was studied using a 17-year database (1997–2014) on an unexploited Cerastoderma edule population in a national nature reserve in Arcachon Bay, France. Results showed that cockle recruitment in a temperate climate with mild winters is rather unrelated to temperature in the previous months, but depends on recruitment timing. When temperature reached 14 °C in May, stimulating early recruitment, recruit density was high (500–1000 ind m−2), and the resulting cohort had a relatively long lifespan (>1 year) with high associated secondary production. Conversely, when temperature reached 14 °C in June, recruitment occurred later (June), recruit density was lower (0–500 ind m−2), and the cohort had a shorter lifespan (<4 months) with a consequent low secondary production. Adult spawner biomass was not positively correlated with recruitment, and the spawner biomass at the time of recruitment did not negatively affect recruitment. More than previous studies, the present study showed that factors driving cockle recruitment success are highly site-dependent, temperatures at the site being only one component.
(Marine Biology. vol. 163, n° 0025-3162, 07/01/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Bacterial and macrofaunal communities in the sediments of the West Gironde Mud Patch, Bay of Biscay (France)
Changes in (1) main sediment characteristics, and (2) benthic bacterial and macrofaunal communities were simultaneously addressed along an inner–outer transect within the West Gironde Mud Patch (Bay of Biscay, NE Atlantic), through the sampling of three stations (E: inner part, C: central part and W: outer part) during July 2010. Except in the top centimetre where a sandy layer was found at station E, all sediments were muddy and tended to be coarser and richer in photosynthetic pigments and particulate organic carbon and nitrogen at stations C and W than at station E. Maximum oxygen penetration depth was also lower at station E than at stations C and W. These results are consistent with: (1) the occurrence of strong hydrodynamics precluding current sedimentation in the inner part of the WGMP, and (2) conversely, inputs of particles originating from the Gironde Estuary in its central and outer part. Prokaryotic cell abundances were lower at station E than at stations C and W. Bacterial community composition also differed more clearly at station E as compared to stations C and W. Conversely, macrofaunal abundances and species richness decreased monotonously from station E to station W (i.e., along the inner–outer gradient). Macrofaunal composition strongly differed at station E on one side, and stations C and W on the other side. These results are consistent with the current paradigm regarding the long term effect of major rivers on benthic macrofauna given that strong hydrodynamics at station E precludes the sedimentation of fine particles originating from the Gironde Estuary. At last, we found no overall correlation between benthic bacterial and macrofaunal compositions, which may however clearly result from limitations in our sampling design.
(Estuarine, Coastal and Shelf Science, n° 0272-7714, 01/01/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
First record of the non-indigenous Melita nitida Smith, 1873 (Crustacea: Amphipoda: Melitidae) in the Bay of Biscay (NE Atlantic)
The non-native amphipod Melita nitida Smith, 1873 was collected between 2013 and 2016 in Arcachon Bay, Hossegor Lake and the Gironde Estuary (SW France) in intertidal oyster reefs and under stones. This species, native to the Atlantic coast of North America, is considered as a non-indigenous species on the Pacific coast of North America. Recently, the presence of M. nitida was reported in Europe, both in The Netherlands and in Germany. This species may have been accidentally introduced to Arcachon Bay with oyster transfers. An identification key for species belonging to the genus Melita and closely related species in European waters is also provided.
(BioInvasions Records. vol. 5, n° 2242-1300, pp. 85-92, 01/01/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Using recent high-frequency surveys to reconstitute 35 years of organic carbon variations in a eutrophic lowland river
Concentrations of dissolved and particulate organic carbon (DOC and POC), total suspended solids (TSS), were measured daily, and phytoplankton pigments (chlorophyll-a and pheopigments) were measured every 3 days at three strategic stations along the eutrophic Loire River between November 2011 and November 2013 marked by a high annual and seasonal variability in hydrological regimes. This unique high-frequency dataset allowed to determine the POC origin (autochthonous or allochthonous). Some strong relationships were evidenced between POC, total pigments and TSS and were tested on a long-term database with a lower frequency (monthly data) to reconstitute unmeasured algal and detrital POC concentrations and estimate annual total organic carbon (TOC) fluxes from 1980 onwards. The results were subjected to only ≈25 % uncertainty and showed that the annual TOC fluxes at the outlet of the Loire River decreased from 520 103 tC year−1 (i.e. 4.7 t km−2 year−1) in the early 1990s to 150 103 tC year−1 (i.e. 1.4 t km−2 year−1) in 2012. Although DOC always dominates, the autochthonous POC represented 35 % of the TOC load at the basin outlet by the end of the 1980s and declined to finally represent 15 % only of the TOC. The control of phosphorus direct inputs and the invasion by Corbicula clams spp. which both occurred since the early 1990s probably highly reduced the development of phytoplankton. Consequently, the autochthonous POC contribution declined and TSS concentrations in summertime significantly decreased as well as a result of both less phytoplankton and less calcite precipitation. At the present time, at least 75 % of the POC has allochthonous origins in the upper Middle Loire but downstream, autochthonous POC dominates during summer phytoplanktonic blooms when total pigments concentrations reach up to 70 μg L−1 (equivalent to 75 % of the total POC).
(Environmental Monitoring and Assessment. vol. 188, n° 0167-6369, pp. 41, 01/01/2016)
GéHCO, UT, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Structure of Manila Clam (Ruditapes philippinarum) Microbiota at the Organ Scale in Contrasting Sets of Individuals
Marine invertebrate microbiota has a key function in host physiology and health. To date, knowledge about bivalve microbiota is poorly documented except public health concerns. This study used a molecular approach to characterize the microbiota associated with the bivalve Manila clam (Ruditapes philippinarum) by determining (1) the difference among organs either or not under the influence of host habitat, (2) small-scale variability of microbiota, and (3) the experimental response of the Manila clam microbiota submitted to different lateral transmissions. These questions were investigated by sampling two groups of individuals living in contrasting habitats and carrying out a transplant experiment. Manila clam microbiota (i.e., bacterial community structure) was determined at organ-scale (gills, gut, and a pool of remaining tissues) by capillary electrophoresis DNA fingerprinting (CE fingerprinting). The Manila clam microbiota structure differed among organs indicating a selection of Manila clam microbiota at organ scale. Habitat strongly influenced gill and gut microbiota. In contrast, microbiota associated with remaining tissues was similar between group individuals suggesting that these communities are mostly autochthonous, i.e., Manila clam specific. Transplant experiment showed that improving living condition did not induce any change in microbiota associated with remaining tissues. In contrast, the reduction in individual habitat quality led to individuals in declining health as strongly suggested by the increase in phagocytosis activity and decrease in condition index together with the change in internal organ microbiota. This study provides a first description of the Manila clam holobiont which can withstand disturbance and respond opportunistically to improved environmental conditions.
(Microbial ecology. vol. 71, n° 0095-3628, pp. 194-206, 01/01/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, DFO-MPO, LEMAR, IRD, IFREMER, UBO EPE, CNRS
Danio rerio ABC transporter genes abcb3 and abcb7 play a protecting role against metal contamination
ATP‐binding cassette (ABC) proteins are efflux transporters and some of them are involved in xenobiotic detoxification. The involvement of four zebrafish ABC transporters in cadmium, zinc and mercury detoxification was characterized in a metal hypersensitive mutant of Escherichia coli. The E. coli tolC mutant expressing ABCB3 or ABCB7 transporters exhibited higher survival ratios and lower metal accumulation under a metal exposure condition than the controls. For instance, in the presence of 8 and 10 μM of HgCl2, the survival ratios of bacteria expressing ABCB3 were four and six‐times higher than the control whereas the mercury concentrations were 2.5 and 2‐times lower than in the control. This work provides new data on the function of zebrafish ABCB3 and ABCB7 transporters and highlights their significance in metal detoxification
(Journal of Applied Toxicology. vol. 36, n° 0260-437X, pp. 1551-1557, 01/01/2016)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS