Live (stained) benthic foraminifera from the Cap-Ferret Canyon (Bay of Biscay, NE Atlantic): A comparison between the canyon axis and the surrounding areas
(Deep Sea Research Part I: Oceanographic Research Papers. vol. 74, n° 0967-0637, pp. 98-114, 01/04/2013)
BIAF, UA, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, CEFREM, UPVD, INSU - CNRS, CNRS, CEMAGREF
Réserve Naturelle Nationale des prés salés d'Arès et de Lège-Cap Ferret (33) : connaissance et suivi des peuplements benthiques, supra-benthiques, ichtyologiques et des fonctions écologiques du compartiment tidal (programme de recherche Biamar 2012)
Les objectifs de cette étude étaient : • Le développement et l’expérimentation de méthodes réplicables pour l’étude du «couple» benthos/poissons, dans une optique à la fois de connaissance, de suivi et de gestion/conservation • La caractérisation des peuplements étudiés, en termes de richesses spécifiques, d’abondances relatives et de biomasses • L’étude de la dynamique spatio-temporelle (habitats/saisons) des peuplements étudiés • L’identification et la caractérisation des fonctions écologiques jouées par ces marais maritimes pour les poissons amphihalins.
(pp. 1, 28/03/2013)
IRSTEA, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EPBX, IRSTEA, IRSTEA
Relative potency of PCB126 to TCDD for sublethal embryotoxicity in the mummichog (Fundulus heteroclitus).
The relative potency (ReP) of 3,3',4,4',5-pentachlorobiphenyl (PCB126) to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) for sublethal responses was assessed in Fundulus heteroclitus embryos. Eggs were treated with intravitelline injections of graded sublethal doses of PCB126 (312-5000 pg g(-1) wet weight, ww) or TCDD (5-1280 pg g(-1) ww). At 16 days post-fertilization (DPF), craniofacial deformities were observed in larvae hatched from eggs treated with the two highest doses of PCB126 (2500-5000 pg g(-1) ww). Both compounds caused a dose-responsive reduction of larval growth and prey capture ability (at ≥1250 pg g(-1) ww), and induction of ethoxyresorufin-O-deethylase (EROD) activity (at ≥80 pg g(-1) ww). The dose-response relationships for EROD activity for PCB126 and TCDD had similar slopes and the ReP of PCB126 to TCDD for EROD activity was estimated at 0.71. This is 140-fold higher than the World Health Organization (WHO) TCDD equivalency factor (TEF) of PCB126 for fish (0.005), which is based on rainbow trout (Oncorhynchus mykiss) embryolethality data. The slope of the dose-response relationship for prey capture ability for PCB126 was steeper than for TCDD, suggesting different mechanisms of action. Expression levels of several genes were also studied by quantitative real-time polymerase chain reaction (qPCR) following exposure to single doses of TCDD or PCB126 (1280 and 1250 pg g(-1) ww, respectively) causing similar EROD induction. A different pattern of responses was observed between PCB126 and TCDD: PCB126 appeared to induce antioxidant responses by inducing sod2 expression, while TCDD did not. These results suggest that relative potencies are species-specific and that the current ReP for PCB126 underestimates its toxicity for some fish species. It is recommended to develop species-specific RePs for a variety of sublethal endpoints and at environmentally relevant doses.
(Aquatic Toxicology. vol. 128-129, n° 0166-445X, pp. 203-14, 15/03/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Silver behaviour along the salinity gradient of the Gironde Estuary
Dissolved and particulate Ag concentrations (Ag D and Ag P , respectively) were measured in surface water and suspended particulate matter (SPM) along the salinity gradient of the Gironde Estuary, South West France, during three cruises (2008-2009) covering contrasting hydrological conditions, i.e. two cruises during intermediate and one during high freshwater discharge (~740 and~2,300 m 3 /s). Silver distribution reflected non-conservative behaviour with 60-70 % of Ag P in freshwater particles being desorbed by chlorocomplexation. The amount of Ag P desorbed was similar to the so-called reactive, potentially bioavailable Ag P fraction (60±4 %) extracted from river SPM by 1 M HCl. Both Ag P (0.22±0.05 mg/kg) and Ag P /Th P (0.025-0.028) in the residual fraction of fluvial and estuarine SPM were similar to those in SPM from the estuary mouth and in coastal sediments from the shelf off the Gironde Estuary, indicating that chlorocomplexation desorbs the reactive Ag P. The data show that desorption of reactive Ag P mainly occurs inside the estuary during low and intermediate discharge, whereas expulsion of partially Ag P-depleted SPM (Ag P /Th P 0.040) during the flood implies ongoing desorption in the coastal ocean, e.g. in the nearby oyster production areas (Marennes-Oléron Bay). The highest Ag D levels (6-8 ng/ L) occurred in the mid-salinity range (15-20) of the Gironde Estuary and were decoupled from freshwater discharge. In the maximum turbidity zone, Ag D were at minimum, showing that high SPM concentrations (a) induce Ag D adsorption in estuarine freshwater and (b) counterbalance Ag P desorp-tion in the low salinity range (1-3). Accordingly, Ag behaviour in turbid estuaries appears to be controlled by the balance between salinity and SPM levels. The first estimates of daily Ag D net fluxes for the Gironde Estuary (Boyle's method) showed relatively stable theoretical Ag D at zero salinity (Ag D 0 0 25-30 ng/L) for the contrasting hydrological situations. Accordingly, Ag D net fluxes were very similar for the situations with intermediate discharge (1.7 and 1.6 g/day) and clearly higher during the flood (5.0 g/day) despite incomplete desorption. Applying Ag D 0 to the annual freshwater inputs provided an annual net Ag D flux (0.64-0.89 t/year in 2008 and 0.56-0.77 t/year in 2009) that was 12-50 times greater than the Ag D gross flux. This estimate was consistent with net Ag D flux estimates obtained from gross Ag P flux considering 60 % desorption in the estuarine salinity gradient.
(Environmental Science and Pollution Research. vol. 20, n° 0944-1344, pp. 1352-1366, 01/03/2013)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Disentangling the effects of water and nutrients for studying the outcome of plant interactions in sand dune ecosystems
Questions What is the relative role of water vs nutrients in driving changes in plant interactions in a dry and nutrient-poor dune system, where facilitation has been shown to highly contribute to the diversity and composition of plant communities? Location Atlantic coastal sand dune system, Aquitaine region, France. Methods We manipulated water (water addition) and nutrient (fertilizer addition) availabilities in a full-factorial experiment that lasted from September 2005 to September 2006. The responses of plants to neighbours were assessed through transplanting six target species within each experimental plot in the presence or absence (removal procedure) of the dominant shrub Helichrysum stoechas. We also measured changes in H. stoechas biomass among treatments. Results Watering mainly affected survival of the target species without neighbours and the direction of their responses to the shrub, whereas fertilization strongly increased the biomass of the shrub and intensity of the responses of the targets to the effects of the shrub. We did not observe any occurrence of biotic interactions (either positive or negative) for most of the target species in the unfertilized plots. In contrast, three of the six species exhibited significant facilitation in fertilized and un-watered plots, and significant competition in fertilized and watered plots. Conclusions Our results highlight the co-limitation of water and nutrients in coastal sand dunes. Nutrient availability mainly drove the neighbour effect of the shrub, whereas water availability affected the responses of the target species. Although further measurements of resource modifications by the shrub are needed to firmly conclude neighbour effects, our results provide new insights to the contrasting results in the literature on plant–plant interactions in unproductive communities. We propose that, depending on the system, changes in a given direct stress factor may either induce a collapse of interactions by decreasing neighbour performances and their effects, or a shift in the direction of interactions by affecting target species responses.
(Journal of Vegetation Science. vol. 24, n° 1100-9233, pp. 375-383, 01/03/2013)
ECODIV, UNIROUEN, NU, BioGeCo, INRA, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
MMHg production and export from intertidal sediments to the water column of a tidal lagoon (Arcachon Bay, France)
Hg cycling in biologically productive coastal areas is of special importance given the potential for bioaccumulation of monomethylmercury (MMHg) into aquatic organisms. Field experiments were performed during three different seasons in Arcachon Bay, a mesotidal lagoon (SW France), to assess the variability of the water column concentrations, sediment-water exchanges and potential formation and degradation of MMHg. The objectives were to evaluate the contribution of intertidal mudflats to MMHg production and the various pathways of Hg species export. Dissolved and bulk concentrations of Hg species in the water column downstream of tidal flats were measured throughout several tidal cycles. The Hg benthic fluxes at the sediment-water interface were determined by means of benthic chambers for three different stations. Hg methylation and demethylation potentials were determined in surficial sediments and the water column using isotopic tracers. The tidal surveys demonstrated that benthic remobilization of Hg occurs primarily in association with sediment erosion and advection during ebb tide. However, elevated dissolved Hg concentrations observed at low tide were found to be caused by a combination of pore-waters seeping, benthic fluxes and methylation in the water column. Benthic fluxes were more intense during late winter conditions (median MMHg and inorganic Hg (IHg) fluxes: 64 and 179 pmol m-2 h-1, respectively) and subsequently decreased in spring (median 0.7 and -5 pmol m-2 h-1, respectively) and fall (median -0.4 and -1.3 pmol m-2 h-1, respectively). The trends in methylation and demethylation potentials were at the opposite of the fluxes, two times lower during winter than for spring or fall conditions. In this tidal environment, MMHg production in surface sediments and its subsequent release is estimated to be the major source of MMHg to the water column during winter and spring time. However, during the more productive summer period, the Hg methylation extent in the water column may be very significant and equivalent to the sediment contribution.
(Biogeochemistry. vol. 114, n° 0168-2563, pp. 341-358, 26/02/2013)
LCABIE, UPPA, CNRS, LEMAR, IRD, IFREMER, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UBO EPE
Comparative effects of two water-accommodated fractions from light and heavy crude oils on early life stage of zebrafish Danio rerio
Session: Aquatic ecotoxicology AT16 Comparative effects of two water-accommodated fractions from light and heavy crude oils on early life stage of zebrafish Danio rerio.
(pp. 82, 11/02/2013)
IFREMER, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LIENSs, INSU - CNRS, ULR, CNRS, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique
Late Quaternary megaturbidites of the Indus Fan: Origin and stratigraphic significance
The Indus sedimentary basin forms one of the largest "source-to-sink" systems of the Quaternary and extends over 106 km2 offshore. It is characterized by a complex tectonic setting marked by the Himalayan active orogenic belt in the source area, and the active strike-slip India-Arabia plate boundary (Owen Fracture Zone; OFZ) in its distal reaches. This paper focuses on a Late Quaternary channel-levee system from the Indus Fan captured by the recent opening of the 20°N pull-apart basin, located at 850 km off the present-day Indus Delta, along the OFZ. In this area the channel-mouth deposits consist of a set of up to 23 m thick megaturbidites trapped in the basin. These deposits form "ponded" lobe deposits in a tectonically-active confined basin. Age determination from radiocarbon dating and extrapolation of local deformation rates show that the older deposits observed on the seismic profiles are up to 358 ka BP old (MIS 10). The origin of these Late Quaternary deposits are investigated in the context of the Indus "source-to-sink" system and their significance is placed in a sequence stratigraphic framework. Integration of the stratigraphic architecture of the 20°N Basin megaturbidites with previous work in the area suggests that the Indus Fan evolved from a delta-fed turbidite system with several active canyons and channel-levee during the forced regressive conditions of the last falling stage of sea-level (122-25 ka BP), to a point source turbidite system during the sea-level lowstand (Last Glacial Maximum) and early transgressive stages (25-12 ka BP). This work sheds new light on the recent evolution of the Indus sedimentary system and illustrates the importance of the delta/river evolution during the fall of sea-level (e.g., incised valley formation) on the timing of sedimentary transfer and sediment distribution at the basin-scale.
(Marine Geology. vol. 336, n° 0025-3227, pp. 10-23, 01/02/2013)
UWA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, iSTeP, UPMC, CNRS, LGENS, INSU - CNRS, CNRS, ENS-PSL, PSL, SHOM, LDO, INSU - CNRS, UBO EPE, CNRS
A mesocosm study of fate and effects of CuO nanoparticles on endobenthic species (Scrobicularia plana, Hediste diversicolor)
The fate and effects of CuO nanoparticles (CuO NPs) were examined in endobenthic species (Scrobicularia plana, Hediste diversicolor), under environmentally realistic conditions in outdoor mesocosms (exposure to Cu at 10 μg L−1 in particulate (CuO NPs) or soluble salt (CuNO3) forms) for 21 days. Labile Cu was determined in water and sediment by using diffusive gradient in thin films. No labile Cu being detected from CuO NPs; the observed effects in invertebrates exposed to CuO NPs were mainly attributed to the toxicity of nanoparticulate rather than dissolved Cu toxicity. Bioaccumulation of CuO NPs was observed in both species. Biomarkers were examined at different levels of biological organization: biochemical markers of defense and damage, biomarkers of genotoxicity (comet assay), and behavioral biomarkers (feeding and burrowing). Behavioral biomarkers, antioxidant defenses (catalase, glutathion S-transferase, metallothionein), and genotoxicity are the most sensitive tools to highlight the effect of soluble or nanoparticulate metal forms. Concerning other biomarkers of defense (superoxide dismutase, lactate dehydrogenase, laccase) and damage (thiobarbituric acid reactive substances, acetylcholinesterase, acid phosphatase), no significant effects were detected. This experiment shows the suitability of mesocosms for studying the environmental effects of nanoparticles.
(Environmental Science and Technology. vol. 47, n° 0013-936X, pp. 1620-1628, 01/02/2013)
MMS, UM, UN UFR ST, UN, UFR SPB, UN, LIENSs, INSU - CNRS, ULR, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BE, IFREMER, ECOMERS, UNS, CNRS, UniCA, NHM, MMS UCO, UCO, UNAM
A three-year time series of mineral dust deposits on the West African margin: Sedimentological and geochemical signatures and implications for interpretation of marine paleo-dust records
Mineral dust deposits in the Northeastern Tropical Atlantic Ocean (NETAO) are an important contribution for reconstructing paleoenvironments and paleoclimates of West Africa. However, the interpretation of the changes in the sedimentological and geochemical characteristics of the dust deposits recorded in the marine sediments from the NETAO remains incomplete. In order to improve our understanding of dust proxies, in particular its mineralogical and geochemical provenance tracers, present-day dust deposition has been monitored at Mbour (∼80 km south of Dakar) on the Senegalese margin. Here we report a multi-proxy investigation of a unique three-year continuous time series of mineral dust deposits collected at a weekly (or better) temporal resolution over the March 2006–March 2009 period. Mass deposition flux and mean modal grain size display marked but reverse seasonal features, with higher flux during the winter/spring seasons and coarser grain size mode in summer when flux is minimal, reflecting contrasting transport patterns throughout the year. Similarly, clay mineralogy, the illite/kaolinite ratio in particular, shows seasonal fluctuations, manifesting the latitudinal displacement of the contributing domains of provenance in response to the seasonal migration of the ITCZ position and the associated wind systems. Our three-year record also reveals the occurrence of major deposition events superimposed on the seasonal pattern, generally during the winter/spring dry seasons and most frequently during the month of March. Our study shows that these major events, which contribute a large fraction of the total annual deposition flux, all originate from the western Sahara–Sahel (a major area of emission in the region beside the Bodele Depression, stretching from the Mauritanian and Western Saharan coasts to the Hoggar Mountains). Combined with air mass tri-dimensional back-trajectories and satellite images, the mineralogical and Sr–Nd isotopic compositions of these large dust events enable us to identify several mineralogically and geochemically distinct provenance sectors within this vast western area. Unlike the background dust deposits, the 87Sr/86Sr and the εNd isotopic signatures of the major dry events closely match that of the NETAO Late Holocene sediments, supporting the hypothesis that these events account for most of the aeolian terrigenous supply reaching the ocean floor. Although this database needs to be expanded, our results already provide useful constraints for the interpretation of the dust proxies' variations in marine sedimentary archives off Mauritania/Senegal in terms of changes in wind regimes and aridity over West Africa.
(Earth and Planetary Science Letters. vol. 364, n° 0012-821X, pp. 145-156, 01/02/2013)
LOG, INSU - CNRS, ULCO, CNRS, IRD [Ile-de-France], CNRS, MPIC, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IMAGO, IRD