Etude de l'impact des contaminants métalliques et organiques chez l'anguille européenne (Anguilla anguilla) et américaine (Anguilla rostrata) au moyen d'approches transcriptomiques
En milieu naturel, évaluer l’effet des contaminants sur les organismes aquatiques s’avère difficile dû aux nombreux facteurs (température, oxygénation, prédation, parasitisme, …) agissant sur les organismes. Le but de ces travaux de thèse était alors de tester la possibilité de détecter et hiérarchiser les effets de divers facteurs naturels et anthropiques sur des individus prélevés in situ. Le modèle d’étude utilisé était l’anguille Européenne (Anguilla anguilla) et Américaine (Anguilla rostrata). Pour appréhender les effets in situ des polluants, nous avons tenté d’identifier des gènes pour lesquels le niveau de transcription était spécifiquement corrélé à un polluant ou un facteur naturel mesuré sur le terrain au moyen de deux outils transcriptomiques : le séquençage haut débit et la puce à ADN. Les profils transcriptomiques obtenus à partir des foies d’anguilles directement prélevées sur le terrain ont été comparés dans un deuxième temps, à ceux obtenus à partir d’individus exposés au laboratoire à divers facteurs naturels et anthropiques de façon séparée. La comparaison de ces profils a montré une différence notable des réponses des individus exposés en laboratoire et ceux prélevés in situ, soulevant un effet non négligeable du stress induit par la captivité en mésocosme. La réalisation d’une étude similaire en utilisant la nageoire caudale comme méthode non invasive s’est révélée pertinente dans la capacité de cet organe à discriminer les différentes conditions expérimentales et de terrain. L’utilisation de la puce sur des gonades d’anguilles européennes maturées artificiellement a indiqué que la pollution pourrait affecter les capacités de reproduction des futurs géniteurs et contribuer alors au déclin massif de cette espèce observé depuis les dernières décennies.
(10/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Anobothrus amourouxi sp. nov., a new species of Ampharetidae (Polychaeta) from the Capbreton Canyon (Bay of Biscay, NE Atlantic Ocean)
A new species of Ampharetidae, Anobothrus amourouxi sp. nov., has been identified from bathyal depths of the Capbreton Canyon, Bay of Biscay (NE Atlantic Ocean). This new species is characterized by inner branchiae with transversal ciliated ridges, notochaetae from modified eighth thoracic unciniger with hirsute tips, uncini from thoracic unciniger with 6–7 teeth in lateral view arranged in two vertical rows in frontal view, fused segments II + III with paleae from SII and reduced notopodia without chaetae from SIII. An identification key for all hitherto described species of the genus Anobothrus is provided.
(Journal of the Marine Biological Association of the United Kingdom. vol. 95, n° 0025-3154, pp. 961-969, 09/02/2015)
LECOB, OOB, UPMC, CNRS, UPMC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UDC
Approche intégrée des conditions physico-chimiques affectant les cortèges biologiques de la partie fluviale de l'estuaire de la Gironde
Les estuaires, situés à l’interface entre les domaines continental et marin, constituent des zones essentielles dans les échanges de matières. Ils jouent dès lors un rôle capital pour les cycles biogéochimiques et biologiques et subissent, par ailleurs, des pressions climatiques et anthropiques croissantes depuis plusieurs décennies. Le présent travail a été focalisé sur les peuplements benthiques et pélagiques présents dans la partie fluviale (Garonne et Dordogne) de l’estuaire de la Gironde, zone àtrès faible salinité où ces peuplements n’avaient encore jamais été étudiés. Alors que la méiofaune, composée principalement de Nématodes, s’est avérée relativement abondante dans les domaines intertidal et subtidal, le macrobenthos est apparu composé essentiellement d’Oligochètes en intertidal et complètement absent en subtidal. La grande plasticité du copépode dominant Eurytemora affinis a été confirmée, celui-ci occupant une niche écologique différente dans la partie fluviale de l’estuaire par rapport à la zone haline. L’importance de la température plutôt que la qualité du pool nutritif sur la productivité d’E. affinis a été démontrée, mettant en évidence une fois de plus la grande adaptabilité de cette espèce dans un habitat très fluctuant. L’étude de l’habitat benthique et pélagique, notamment en terme de qualité du pool nutritif disponible pour les organismes, a démontré que la contribution de la matière organique réfractaire d’origine terrestre est dominante. La contribution du micro phytobenthos à la composition de la matière organique sédimentaire et pélagique a aussi été mise en évidence. Enfin,l’étude des communautés planctoniques dans la partie fluviale de l’estuaire de la Gironde a montré que l’espèce E. affinis y occupe une position clef.
(04/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Exposures of zebrafish through diet to three environmentally relevant mixtures of PAHs produce behavioral disruptions in unexposed F1 and F2 descendant.
The release of polycyclic aromatic hydrocarbons (PAHs) into the environment has increased very substantially over the last decades. PAHs are hydrophobic molecules which can accumulate in high concentrations in sediments acting then as major secondary sources. Fish contamination can occur through contact or residence nearby sediments or though dietary exposure. In this study, we analyzed certain physiological traits in unexposed fish (F1) issued from parents (F0) exposed through diet to three PAH mixtures at similar and environmentally relevant concentrations but differing in their compositions. For each mixture, no morphological differences were observed between concentrations. An increase in locomotor activity was observed in larvae issued from fish exposed to the highest concentration of a pyrolytic (PY) mixture. On the contrary, a decrease in locomotor activity was observed in larvae issued from heavy oil mixture (HO). In the case of the third mixture, light oil (LO), a reduction of the diurnal activity was observed during the setup of larval activity. Behavioral disruptions persisted in F1-PY juveniles and in their offspring (F2). Endocrine disruption was analyzed using cyp19a1b:GFP transgenic line and revealed disruptions in PY and LO offspring. Since no PAH metabolites were dosed in larvae, these findings suggest possible underlying mechanisms such as altered parental signaling molecule and/or hormone transferred in the gametes, eventually leading to early imprinting. Taken together, these results indicate that physiological disruptions are observed in offspring of fish exposed to PAH mixtures through diet.
(Environmental Science and Pollution Research. vol. 22, n° 0944-1344, pp. 16371–16383, 03/02/2015)
BE, IFREMER, LRHBL, HMMN, IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INERIS, Irset, UA, UR, EHESP, INSERM, Biosit : Biologie - Santé - Innovation Technologique, IMB Sinica, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique
Disentangling direct and indirect effects of a legume shrub on its understorey community
Direct and indirect interactions among plants contribute to shape community composition through above- and belowground processes. However, we have not disentangled yet the direct and indirect soil and canopy effects of dominants on understorey species. We addressed this issue in a semi-arid system from southeast Spain dominated by the legume shrub Retama sphaerocarpa. During a year with an exceptionally dry spring, we removed the shrub canopy to quantify aboveground effects and compared removed-canopy plots to open plots between shrubs to quantify soil effects, both with and without watering. We added a grass removal treatment in order to separate direct from indirect shrub effects and quantified biomass, abundance, richness and composition of the forb functional group. With watering, changes in forb biomass were primarily driven by indirect shrub effects, with contrasting negative soil and positive aboveground indirect effects; changes in forb abundance and composition were more influenced by direct shrub soil effects with contrasting species composition between open and Retama patches. As community composition was different between open and Retama patches the indirect effects of Retama on forb species did not concern forbs from the open community but forbs from Retama patches. Indirect effects are, thus, important at the functional group level rather than at the species level. Without watering, there were no significant interactions. Changes in species richness between treatments were weak and seldom significant. We conclude that shrub effects on understorey forbs are primarily due to their influence on soil properties, directly affecting forb species composition but indirectly affecting the biomass of the forbs of the Retama patches, and only with sufficient water.
(Oikos. vol. 124, n° 0030-1299, pp. 1251-1262, 01/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Cockle infection by Himasthla quissetensis – I. From cercariae emergence to metacercariae infection
The European cockle (Cerastoderma edule) is an exploited bivalve along the North-Eastern Atlantic semi-sheltered ecosystems. Its population dynamics are driven by numerous environmental factors, including parasitism, particularly by trematodes. The complex life cycle of trematodes includes a free living stage (cercaria) between the first (a mollusk) and the second (an invertebrate or a vertebrate) intermediate hosts. Taking the example of Himasthla quissetensis, a dominant trematode in Arcachon Bay (France) utilizing Nassarius reticulatus as first intermediate host and the cockle as second intermediate host, we investigated the correlation between cockle infection and cercariae emergence by N. reticulatus, including the role of water temperature and light. Experimental and field data provided evidence that cercariae emergence from N. reticulatus took place during the night and for water temperature comprised between 15 °C and 22 °C (optimum at 20 °C). The lifespan of cercariae did not exceed 48 h and 50% of them were no more infectious after 7 h. A model was designed (emergence = f(water temperature)) in order to calculate an average monthly cercarial emergence rate according to water temperature that was daily recorded for 5 years (1998–2002). Concomitantly, non-infected cockles were transplanted each of these years in order to assess the infection rate by H. quissetensis. Infection occurred strictly for the same water temperatures (and dates) as those expected for cercariae emergence. Within each year, there was often (but not always) a good correlation between the predicted number of emerging cercariae and the observed number of cercariae transformed into metacercariae in cockles. However, the among-years variability of cockle infection (× 4.4 range) was not explained by the predicted annual number of emerging cercariae. This study highlights the importance of water temperature and light in stimulating cercariae emergence which is closely related to the occurrence of cockle infection. Accordingly, climate change would be expected to alter certain parasite transmission traits. Conversely, the lack of correlation between the total number of metacercariae in cockles and the expected number of cercariae suggests that other factors contribute to infestation variability.
(Journal of Sea Research (JSR), n° 1385-1101, 01/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Wind-driven modifications to the residual circulation in an ebb-tidal delta: Arcachon Lagoon, Southwestern France
A combination of observations and analytical solutions were used to determine the modifications caused by wind forcing on the residual or non-tidal circulation in an ebb-tidal delta. Observations were obtained in the lower Arcachon Lagoon, southwestern France. The basic non-tidal circulation was established with acoustic Doppler current profilers (ADCPs) that were i) moored in the delta's two deepest channels, and ii) towed along a cross-lagoon transect. The bathymetry of the lower lagoon, or ebb-tidal delta, featured two channels: North Pass (>9 m) and South Pass (>20 m). The basic non-tidal circulation consisted of mostly inflow with weak surface outflow in the South Pass, and laterally sheared bidirectional flow, dominated by outflow, in the North Pass. Analytical solutions and comparison of observed dynamical terms suggested that, in addition to the conventionally accepted influence of tidal nonlinearities, density gradients contributed to the basic non-tidal circulation in the lagoon. Observations also indicated that wind forcing altered the basic circulation by driving simultaneous upwind flows in both passes. This response was supported by an analytical solution to wind-driven flows over the bathymetry of the transect sampled. The response to seaward winds was to enhance inflow in South Pass and reduce outflow in North Pass. Landward winds caused diminished inflow in South Pass and increased outflow in North Pass. This article is protected by copyright. All rights reserved.
(Journal of Geophysical Research. Oceans. vol. 120, n° 2169-9275, pp. 728-740, 01/02/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Anisotropic surfaces detection using intensity maps acquired by an airborne LiDAR emitting in near-IR over coastal environments
(. vol. 8, pp. 727 - 739, 01/02/2015)
M2C, UNICAEN, NU, INSU - CNRS, UNIROUEN, NU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, ISCR, UR, INSA Rennes, INSA, ENSCR, INC-CNRS, CNRS
Papuadocus blodiwai gen. nov., sp. nov. (Crustacea: Amphipoda: Maeridae), a new bathyal species associated with sunken wood in the Bismarck Sea (Papua New Guinea)
A new species belonging to a new genus of Maeridae, Papuadocus blodiwai gen. nov., sp. nov., is described from bathyal bottoms of the Bismarck Sea (Papua New Guinea). This genus/species can be distinguished from most other known maerids by right and left maxillas 1 with asymmetrical palps and by gnathopod 2 not sexually dimorphic. Its closest relative is the genus Bathyceradocus also characterized by asymmetrical maxillas 1, but differing by the presence of gill on coxae 7. These observations lead to the conclusion that the diagnosis of the family Maeridae has to be amended to receive both Bathyceradocus and Papuadocus genera. All the collected specimens lived in association with sunken wood, at 500–580 m depth.
(Zootaxa. vol. 3914, n° 1175-5326, pp. 406, 29/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Arctic warming will promote Atlantic-Pacific fish interchange
Throughout much of the Quaternary Period, inhospitable environmental conditions above the Arctic Circle have been a formidable barrier separating most marine organisms in the North Atlantic from those in the North Pacific1,2. Rapid warming has begun to lift this barrier3, potentially facilitating the interchange of marine biota between the two seas4. Here, we forecast the potential northward progression of 515 fish species following climate change, and report the rate of potential species interchange between the Atlantic and the Pacific via the Northwest Passage and the Northeast Passage. For this, we projected niche-based models under climate change scenarios and simulated the spread of species through the passages when climatic conditions became suitable. Results reveal a complex range of responses during this century, and accelerated interchange after 2050. By 2100 up to 41 species could enter the Pacific and 44 species could enter the Atlantic, via one or both passages. Consistent with historicalandrecent biodiversity interchanges5,6, this Exchange of fish species may trigger changes for biodiversity and food webs in the North Atlantic and North Pacific, with ecological and economic consequences to ecosystems that at present contribute 39% to global marine fish landings.
(Nature Climate Change. vol. 5, n° 1758-678X, pp. 261-265, 26/01/2015)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS