Deconvolution of trace element (As, Cr, Mo, Th, U) sources and pathways to surface waters of a gold mining-influenced watershed.
The Upper Isle River (SW France) drains the second most productive gold-mining district of France. A high resolution survey during one hydrological year of As, Cl(-), Cr, Fe, Mn, Mo, SO(4)(2-), Th and U dissolved concentrations in surface water aimed to better understand pathways of trace element export to the river system downstream from the mining district. Dissolved concentrations of As (up to 35000 ng/L) and Mo (up to 292 ng/L) were about 3-fold higher than the regional dissolved background and showed a negative logarithmic relation with discharge. Dissolved concentrations of Cr (up to 483 ng/L), Th (up to 48 ng/L) and U (up to 184 ng/L) increased with discharge. Geochemical relationships between molar ratios in surface water, geochemical background as well as rain- and groundwater data were combined. The contrasting behavior of distinct element groups was explained by a scenario involving three seasonal components: (i) The high flow component is poorly concentrated in As and Mo but highly concentrated in Cr, Th, U. This has been attributed to diffuse sources such as water-soil interactions, atmospheric inputs, bedrock and bed sediment weathering. Although this component probably also includes a contribution by weathering of sulfide veins, this signal is masked by dilution. (ii) One low flow component presents high SO(4)(2-), Fe, As and Mo and moderate Cr, Th and U concentrations. This component has been attributed to point sources such as mine gallery effluents, mining waste weathering and groundwater inputs from natural and/or mining-induced sulfide oxidation in the ore deposit. (iii) A second low flow component showing high As plus Mo concentrations associated with very low SO(4)(2-), Fe, Cr, Th and U concentrations, probably reflects trace element scavenging by ferric oxyhydroxide formation in the adjacent aquifer. This is supported by the decrease of Fe, Cr, Th and U in surface waters. Flux estimates suggest contrasting element-specific impacts on annual dissolved fluxes. Runoff may account for the major part of annual dissolved As, Mo, Th and U fluxes in the Upper Isle River. Inputs related to sulfide oxidation respectively contributed approximately 30% and approximately 24% to annual As and Mo fluxes. The formation of ferric oxyhydroxides strongly retained Cr, Th and U during the low flow, limiting their dissolved concentrations in surface waters. If this process may eventually decrease As mobility, its impact on dissolved As concentrations in surface water may be limited or/and counterbalanced by As release during sulfide oxidation.
(Science of the Total Environment. vol. 407, n° 0048-9697, pp. 2063-76, 01/03/2009)
GRESE, UNILIM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Impact of lateral transport on organic proxies in the Southern Ocean
K′ Sea-surface temperature BIT index Southern Ocean Lateral transport of fine-grained organic carbon particles can complicate the interpretation of paleoclimate records based on organic proxies. Here we investigated the effect of lateral transport on newly developed temperature and soil organic matter proxies, TEX 86 and BIT index, respectively, in core MD88-769 recovered from the South East Indian Ridge. Our results show that TEX 86 and BIT records in comparison to diatom and foraminifera records were representative for more local climate changes while alkenones and n-alkanes originated from distant areas by oceanic and atmospheric transport, respectively. This suggests that TEX 86 and BIT paleoclimate records are primarily influenced by local conditions and less subjected to long-distance lateral transport than other organic proxies in the Southern Ocean.
(Quaternary Research. vol. 71, n° 0033-5894, pp. 246-250, 01/03/2009)
NIOZ, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, NIOZ
Stable isotopes changes in the adductor muscle of diseased bivalve Ruditapes philippinarum
In this article, we show how a disease could bias stable isotope analyzes of trophic networks and propose a strategy in the choice of tissues to be analyzed. In the past few years, a new pathology (brown muscle disease or BMD) affecting the posterior adductor muscle of Ruditapes philippinarum has emerged in Arcachon Bay. BMD induces a necrosis of muscle tissues which become infused by conchiolin and hence calcified. As muscle of mollusks are often used for trophic food webs studies through stable isotopic analyzes, this work investigated the effect of BMD on carbon and nitrogen isotopic ratios of anterior and posterior adductor muscles of clams collected in February and August 2007. Infected clams displayed a lower condition index and a posterior adductor muscle δ13C enrichment of 1.2‰ in February and 0.7‰ in August. δ15N of posterior muscles was however not affected by the disease. Anterior muscle of diseased clams remained healthy and displayed the same isotopic signature as both posterior and anterior muscular tissues of healthy clam. Acidification significantly depleted δ13C in posterior muscles of infected clams, suggesting calcification, contrary to anterior muscles of infected clam and to both muscles of healthy clams, where no effect was observed. An X-ray diffractometry analysis confirmed the presence of CaCO3 (aragonite). Trophic food web studies relying on stable isotope ratios should utilize only healthy animals or anterior adductor muscles when expertise in mollusk pathology is lacking.
(Marine Biology. vol. 156, n° 0025-3162, pp. 611 - 618, 01/03/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER, LIENSs, INSU - CNRS, ULR, CNRS
Sensory structures of Archaeostraca (Phyllocaridida, Crustacea)
The carapace of some Archaeostraca exhibits two kinds of structures that are best interpreted as corresponding to sensory organs. Dorsal ones are located either along the dorsal margin of the valves of the carapace, or on the median dorsal plate. Anterolateral ones are located in the anterior region of both valves. Both structures are respectively homologous of the anterior and posterior sensory organs known from extant Leptostraca and other Crustacea. These structures are described in adult Archaeostraca from the Ordovician to the Carboniferous. It is expected that they could have baroreceptor, mechanoreceptor, and/or chemoreceptor functions in some cases, and a function in osmotic regulation in others.
(Evolution & Development. vol. 11, n° 1525-142X, pp. 225-232, 24/02/2009)
MNHN, UPMC, CNRS, LDO, INSU - CNRS, UBO EPE, CNRS, NRM
A new phyllocarid crustacean from the Famennian of Belgium
A single carapace of an echinocaridid phyllocarid found in the uppermost part of the Evieux Formation at Arbre near Namur of late (latest ?) Famennian age lacks both the posterocentral and posterodorsal ridges, both characters considered to be derived ones. This makes it a member of the E. punctata group. However the lack of any spine or tubercle on the dorsal lobes, along the hinge line, or on the peripheral margin of the carapace, makes the Belgian specimen distinct from all other Famennian echinocaridids. A new genus and species Nervicaris belgica is proposed for this first late Famennian echinocaridid representative from continental Western Europe. This occurrence extends both the vertical range and geographic distribution of echinocaridid phyllocarids.
(Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. vol. 251, n° 0077-7749, pp. 147-153, 19/02/2009)
LDO, INSU - CNRS, UBO EPE, CNRS, UEB, MNHN, UPMC, CNRS, CR2P, MNHN, UPMC, CNRS
Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum
Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations(1). The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2,3). Since that time, several shortcomings of that earlier effort have become apparent(4). Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project(5). We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present(6,7).
(Nature Geoscience. vol. 2, n° 1752-0894, pp. 127-132, 01/02/2009)
PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, ICTA, UAB, ICREA, SCIB - UMR E3, INAC, CEA, UGA [2016-2019], CNRS, CEREGE, IRD, AMU, CdF (institution), INSU - CNRS, CNRS, INRAE, UB, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, BCCR, BIO / UiB, UiB, AWI, CALTECH, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, FSS, CEBC, CNRS, MARUM, NOC
Development of a multimetric approach to assess perturbation of benthic macrofauna in Zostera noltii beds
Biotic indices based on soft-bottom macrozoobenthic communities are currently used throughout Europe to assess the ecological quality of coastal and transitional water bodies according to the European Water Framework Directive. However, the performance of the currently available biotic indices still has to be tested against a variety of different impact sources. In particular, physical perturbations have received much less attention than other kind of disturbances. This study consisted in testing the capacity of currently available uni- (BOPA, AMBI and BENTIX) and multivariate (M-AMBI) Biotic Indices to assess the ecological impact of the destruction of a Zostera noltii seagrass bed in Arcachon Bay (France) following sediment deposits. Changes of habitat after this physical perturbation were hardly assessed by any of these Biotic Indices whereas analysis of the benthic community showed drastic changes of structure following the perturbation and no recovery after 15 months. This study demonstrates that these Biotic Indices must be integrated into a multimetric approach which describes better the biological integrity of the benthic community by including a complementary set of metrics. A new multimetric approach, named MISS (Macrobenthic Index of Sheltered Systems) is proposed. MISS correctly highlighted the destruction of the seagrass beds, by using 16 metrics describing the biological integrity of the macrofauna.
(Journal of Experimental Marine Biology and Ecology. vol. 368, n° 0022-0981, pp. 101-112, 31/01/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Sediment transport particular events and beach profile response
A field campaign was carried out as part of the ECORS project on the macro-tidal beach of Truc Vert (France, March-April 2008). Velocities, sediment concentrations and bed evolutins recorded at the mid intertidal zone are presented, covering calm (Hs~0.5m)and energetic (Hs~1m) conditions. Cross-shore transport rates were estimated using the BAILARD (1981) model for the total load transport, beach profile changes for the net transport and suspended sediment fluxes. Under energetic wave forcing the undertow was large and sediment transport was directed offshore whereas under calm conditions the undertow was weaker and sediment transport was directed onshore.
(Journal of Coastal Research, n° 0749-0208, pp. pp 1766-1770, 01/01/2009)
LCPC/EAU, LCPC, UNAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGI, UJF, Grenoble INP, CNRS
Distance decay of similarity among parasite communities of three marine invertebrate hosts
The similarity in species composition between two communities generally decays as a function of increasing distance between them. Parasite communities in vertebrate definitive hosts follow this pattern but the respective relationship in intermediate invertebrate hosts of parasites with complex life cycles is unknown. In intermediate hosts, parasite communities are affected not only by the varying vagility of their definitive hosts (dispersing infective propagules) but also by the necessary coincidence of all their hosts in environmentally suitable localities. As intermediate hosts often hardly move they do not contribute to parasite dispersal. Hence, their parasite assemblages may decrease faster in similarity with increasing distance than those in highly mobile vertebrate definitive hosts. We use published field survey data to investigate distance decay of similarity in trematode communities from three prominent coastal molluscs of the Eastern North-Atlantic: the gastropods Littorina littorea and Hydrobia ulvae, and the bivalve Cerastoderma edule. We found that the similarity of trematode communities in all three hosts decayed with distance, independently of local sampling effort, and whether or not the parasites used the mollusc as first or second intermediate host in their life cycle. In H. ulvae, the halving distance (i.e. the distance that halves the similarity from its initial similarity at 1 km distance) for the trematode species using birds as definitive hosts was approximately two to three times larger than for species using fish. The initial similarities (estimated at 1 km distance) among trematode communities were relatively higher, whereas mean halving distances were lower, compared to published values for parasite communities in vertebrate hosts. We conclude that the vagility of definitive hosts accounts for a high similarity at the local scale, while the strong decay of similarity across regions is a consequence of the low probability that all necessary hosts and suitable environmental conditions coincide on a large scale.
(Oecologia. vol. 160, n° 0029-8549, pp. 163-173, 01/01/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
At environmental doses, dietary methylmercury inhibits mitochondrial energy metabolism in skeletal muscles of the zebra fish (Danio rerio).
The neurotoxic compound methylmercury (MeHg) is a commonly encountered pollutant in the environment, and constitutes a hazard for human health through fish eating. To study the impact of MeHg on mitochondrial structure and function, we contaminated the model fish species Danio rerio with food containing 13 μg of MeHg per gram, an environmentally relevant dose. Mitochondria from contaminated zebrafish muscles presented structural abnormalities under electron microscopy observation. In permeabilized muscle fibers, we observed, a strong inhibition of both state 3 mitochondrial respiration and functionally isolated maximal cytochrome c oxidase (COX) activity after 49 days of MeHg exposure. However, the state 4 respiratory rate remained essentially unchanged. This suggested a defect at the level of ATP synthesis. Accordingly, we measured a dramatic decrease in the rate of ATP release by skinned muscle fibers using either pyruvate and malate or succinate as respiratory substrates. However, the amount and the assembly of the ATP synthase were identical in both control and contaminated muscle mitochondrial fractions. This suggests that MeHg induced a decoupling of mitochondrial oxidative phosphorylation in the skeletal muscle of zebrafish. Western blot analysis showed a 30% decrease of COX subunit IV levels, a 50% increase of ATP synthase subunit α, and a 40% increase of the succinate dehydrogenase Fe/S protein subunit in the contaminated muscles. This was confirmed by the analysis of gene expression levels, using RT-PCR. Our study provides a basis for further analysis of the deleterious effect of MeHg on fish health via mitochondrial impairment.
(International Journal of Biochemistry and Cell Biology. vol. 41, n° 1357-2725, pp. 791-799, 01/01/2009)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, U1211 INSERM/MRGM, UB, INSERM, IBGC, UB, CNRS