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International audience; Given the lack of background data on essential and non-essential trace elements in invertebrates and fish known to be the predominant prey of marine mammals and seabirds breeding at the Kerguelen Islands, this study intends to provide these results of great influence for predators in higher trophic levels. To this end, plankton organisms (9 species/4 phyla), mollusks (2 bivalves and 2 squid species) and fishes (8 benthic and 10 pelagic species) from Kerguelen waters were analysed for cadmium (Cd), copper (Cu), mercury (Hg), and zinc (Zn). Individual concentrations of non-essential elements (particularly Cd) showed larger variation in comparison with essential ones due to homeostasis. Cd ranged over 4 orders of magnitude; however, Hg ranged only 1, without significant correlation to trophic level. Instead, ecological parameters (benthic/mesopelagic habitat and feeding ecology) showed a more important influence on the results. Concerning seashore organisms, bivalves collected inside the Gulf of Morbihan had higher Cd concentrations compared to those from the Kerguelen shelf, suggesting a local source of Cd, such as runoff water from bird colonies. Comparison with literature showed metal concentrations in invertebrates and fishes from Kerguelen Islands somewhat lower than in the Antarctic area, with Hg prevailing in benthic species and Cd in pelagic ones. In contrast to Hg, Cd values of squids, jellyfish and the amphipod Themisto gaudichaudii were significantly higher than all other species. Finally, top predators foraging in this area that can be subject to potentially high Hg and Cd exposure through their diet at Kerguelen are reviewed.

Linear Alkylbenzene Sulfonates (LAS) are ubiquitous surfactants. Traces can be found in coastal environments. Sorption and toxicity of C(12)-LAS congeners were studied in controlled conditions (2-3500 μg C(12)LAS/L) in five marine phytoplanktonic species, using standardized methods. IC(50) values ranged from 0.5 to 2 mg LAS/L. Sorption of (14)C(12)-6 LAS isomer was measured at environmentally relevant trace levels (4μg/L) using liquid scintillation counting. Steady-state sorption on algae was reached within 5h in the order dinoflagellate>diatoms>green algae. The sorption data, fitted a L-type Freundlich isotherm, indicating saturation. Desorption was rapid but a low LAS fraction was still sorbed after 24h. Toxic cell concentration was 0.38±0.09 mg/g for the studied species. LAS toxicity results from sorption on biological membranes leading to non-specific disturbance of algal growth. Results indicate that LAS concentrations in coastal environments do not represent a risk for these organisms.

Zooplankton assemblages were studied from January 2007 to January 2008 along the salinity gradient of the Charente estuary (France). A Lagrangian survey was performed monthly at five sampling stations defined by salinity (freshwater, 0.5, 5, 15 and 25) in order to collect zooplankton and measure the main environmental parameters (concentrations of suspended particulate matter, particulate organic carbon, chlorophyll a and phaeopigments). A combination of multivariate cluster analysis, species indicator index and canonical correspondence analysis was used to relate the spatio-temporal patterns of the zooplankton assemblages with environmental drivers. The estuary was divided into three different zones by means of environmental parameters while four zooplankton assemblages were identified along the salinity gradient. The Charente estuary appeared as one of the most turbid systems in Europe, with suspended particulate matter (SPM) concentration reaching 3.5 g l-1 in the Maximum Turbidity Zone (MTZ). Algal heterotrophy and microphytobenthos resuspension from the wide mudflats could be responsible for the relatively high chlorophyll a concentrations measured within this MTZ. Salinity and SPM affected significantly the spatial distribution of zooplankton species while temperature and river flow seemed to control their temporal variations. From a zooplanktonic viewpoint, the highly turbid Charente estuary seemed to match an "ecotone-ecocline" model: the succession of species assemblages along the salinity gradient matched the concept of ecocline while the MTZ, which is a stressful narrow area, could be considered as an ecotone. Although such ecoclinal characteristics seemed to be a general feature of estuarine biocenoses, the ecotone could be more system-specific and biological compartment-specific. © 2010 Elsevier Ltd. All rights reserved.

International audience; Cd, Cu and Zn were analysed in the organs and tissues of the three scallop species from the Bay of Biscay, the variegated Chlamys varia L., the queen scallop Aequipecten opercularis L. and the common scallop Pecten maximus L. for interspecific comparisons. In P. maximus the greatest concentrations of Cd and Cu were found in the digestive gland, whereas the two other species showed similar levels of Cd between digestive gland and kidneys and higher renal Cu concentrations. However, the digestive gland of all Pectinidae species contained from 75 to 93 % and 52 to 74 % of the total body burdens of Cd and Cu, respectively. Whatever the species and the origin, kidneys displayed the highest Zn concentrations, which therefore contained from 53 to 97 % of the total body burden of this metal. Also using reported results, ratios between the concentrations in the digestive gland and that in the kidneys discriminated two groups of Pectinidae : 1) the Pecten group (P. maximus, P. jacobeus and Adamussium colbecki) with a Cd ratio ≥ 4, a Cu ratio ≥ 1 and a Zn ratio > 20.10-3 2) the Chlamys group with a Cd ratio ≤ 1, a Cu ratio ≤ 1 and a Zn ratio ≤ 6.10-3. However, no differences in the detoxification processes in the digestive gland were found between groups in this study. 72 to 80 % of the total Cd was found to be soluble, probably bound to metalloproteins such as metallothioneins, while Cu and Zn were mainly found associated to the insoluble fraction of the digestive gland cells whatever the species. Queen scallops from the Faroe Islands were also considered to examine variations of the metal concentrations due to the geographical origin. In this northern area, queen scallops displayed Cd concentrations 2, 4 and 6 times higher in kidneys, muscle and digestive gland, respectively, compared to those from the Bay of Biscay. Consequently, the Cd concentrations in the whole soft parts of the queen scallops were more than 6 times higher in the Faroe Islands than in the Bay of Biscay. In contrast to Cd, both Cu and Zn concentrations in the whole soft parts were 2 times lower in the Faroe Islands, suggesting lower bioavailability of these essential elements.

International audience; Concentrations of cadmium, mercury, copper and zinc were measured in muscle, kidney and liver tissues and in the main prey of five species of zooplankton-eating petrels: blue petrel (Halobaena caerulea), thin-billed (Pachyptila belcheri) and Antarctic (P. desolata) prions, and South Georgian (Pelecanoides georgicus) and common (Pelecanoides urinatrix) diving petrels. Since some of these species are closely related species with respect to body size, timing ofmoult and life span, their diet has been examined to evaluate its influence on heavy-metal bioaccumulation. Inter-specific differences were significant for Hg concentrations in the liver and for Zn concentrations in both liver and kidney tissues. Blue petrels exhibited the highest Hg concentrations in the liver (3.9±2.02 lg.g)1 wet weight). No significant differences were found in Cd concentrations between species. Exposure to heavy metals through the most important prey species in the diet during the breeding period was evaluated. The most evident result was the influence of fish prey on Hg levels. Although crustacean species exhibit different cadmium concentrations, the diet composition does not appear to be discriminant for Cd bioaccumulation within the small petrel community at Kerguelen.

Le littoral picto-charentais est une zone a fortes activites economiques liees a l'aquaculture, a la peche et au tourisme.. Toutes ces activites demandent une tres bonne qualite des eaux et de l'environnement en general. Or, cette zone littorale est soumise a de nombreux apports de micropolluants: metaux lourds, phytosanitaires, hydrocarbures, organochlores ... Les sources en sont nombreuses : apports fluviatiles et atmospheriques, rejets diffus et rejets directs. Les risques dus a cette pollution sont multiples que ce soit au niveau des organismes , au niveau des ecosystemes ou des consommateurs. De ce fait, les contaminants majeurs (metaux lourds, organochlores, hydrocarbures aromatiques polycycliques) et leurs impacts eventuels sur les ecosystemes font l'objet de veille environnementale (reseaux de surveillance ou d'observatoires de l'environnement) et de mesures de prevention se traduisant par la definition de normes de rejets ou de contamination decidees a l'echelle europeenne.

Polonium-210 (210Po) has been analysed in the soft parts of two bivalves species, the scallop Chlamys varia and the common mussel Mytilus edulis, from the Bay of La Rochelle and Re Island, on the French Atlantic coast. Between those sites, the highest 210Po concentrations have been found in whole scallop soft parts from La Rochelle, reaching 1181±29 Bq kg−1 dry weight (dwt), a size effect being related to the highest 210Po concentration in the smallest scallops. The results show a significant difference in concentrations for similar size individuals between species in each site ( C. varia>M. edulis ) and between sites for each species ( R e Island > Bay of La Rochelle ). Very high 210Po concentrations have been found in the digestive gland of C. varia, ranging 3150–4637 Bq kg−1 dwt. Thus, the digestive gland contains up to 60% of the radionuclide. Subcellular investigations have shown that approximately 40% of the 210Po contained in the digestive gland is in the cytosolic fraction, suggesting a high bioavailability of the 210Po from this fraction to the trophic upper level. Calculations will show that approximately 4 kg of scallops flesh intake would be necessary to reach the annual incorporation limit of 1 mSv.

International audience; The use of seabirds to assess marine contamination by trace elements in areas remote from pollutant emission points has already been done at various latitudes. Nevertheless, little information is available concerning the Southern Indian Ocean. Determining the contaminants levels, there appears necessary not only due to several deleterious effects reported in literature, but also as previous studies have highlighted elevated concentrations of cadmium (Cd) and mercury (Hg) in mollusks, crustaceans and fish. Within this context, the white-chinned petrel appears as a key species due to its lifespan, diet and trophic position. Thirty-three accidentally killed (collision with lights/bycatch in longline vessels) individuals collected in Kerguelen waters were analysed for Cd, copper (Cu), Hg, selenium (Se) and zinc (Zn) in liver, kidney, pectoral muscle, feathers and for mature males, testis. Elevated Hg concentrations (average 58.4 lg g-1 dw in liver) are likely due to the presence of mesopelagic prey in the diet of Procellaria aequinoctialis. Cd concentrations (average of 65.7 lg g-1 dw in kidney) can be attributed to a high level of fisheries offal consumption, as well as crustacean and squid ingestion. Correlation of Hg with Se indicates its detoxification by co-precipitation, and correlation of Cd with Zn suggests its displacement by Cd on metallothioneins binding sites. This work also indirectly confirms ecological data (range and diet composition) from the wintering period of the species, which is rather scarce. Seasonal diet change and moulting accounted more for the obtained results than sex of the birds.

The bioaccumulation of four metals (Cd, Cu, Pb, Zn) dissolved in water was assessed measuring the concentrations recorded within sea-urchin larvae (Paracentrotus lividus, Lmk.) after a 48-h exposure period. Concurrently, the frequencies of abnormalities were evaluated at the 48-h pluteus stage to check the actual toxicity of such contaminants with regards to larval development. Maximum metal concentrations in the larvae reached 43.8 +/- 6.7 micrograms Cd g-1 dry weight (d.w.), 1269 +/- 392 micrograms Cu g-1 d.w., 3106 +/- 679 micrograms Pb g-1 d.w., 534 +/- 62 micrograms Zn g-1 d.w. Bioconcentration factors (BCFs) reached very high values for Pb (maximum value: 16,282 +/- 973) and indicated that the concentrations of Pb and Cd were directly related to the water concentration at least in the range of concentrations tested. Zn appeared to be partially regulated above a certain threshold concentration (between 5 and 25 micrograms l-1). Cu was accumulated with an active uptake at least below lethal threshold level (100 micrograms l-1). Nevertheless, above these thresholds, high mortality of embryos prevent any interpretation of Zn and Cu bioconcentration factors. Concurrent studies carried out on embryotoxicity confirmed the high toxicity of Cu towards sea-urchin pluteus larvae and highlighted the different behaviour of Cd. The internal Cd concentrations were directly related to the external ones, comparable to other non-essential metals, but Cd had little toxic effect on the initial larval development.

Le Cd est un polluant remanent present naturellement dans notre environnement. Les apports dus aux activites anthropiques ont ete estimes a environ 500 000 T depuis 1817. Par le jeu des flux geochimiques, une grande partie de ce Cd atteint le milieu marin ou ce metal est bioaccumule par les organismes vivants. Afin d'evaluer le risque toxicologique encouru par les predateurs superieurs, homme compris, consommateurs de produits marins contamines par le Cd, nous nous sommes interesses a deux ecosystemes soumis a des apports chroniques de ce metal. 1) Les cotes de Charente-Maritime sont soumises a une pollution diffuse en Cd a partir de la Gironde. L'etude des concentrations en Cd de plus de 110 especes collectees sur ce littoral montrent que seules certaines especes appartenant toutes a l'embranchement des mollusques concentrent fortement ce metal. L'apport de Cd du a la consommation de ces especes qualifiees d'hyperbioaccumulatrices a ete estime pour les habitants de Charente-Maritime et compare a la Dose Hebdomadaire Tolerable de 7 μg/g de Cd/kg corporel defini pour l'homme par le JECFA. Bien que non negligeable, ces apports restent inferieurs a la DHT. Les petoncles sont les organismes susceptibles de transferer les plus fortes quantites de Cd. Les normes mises en place par la Commission Europeenne qui interdit la consommation de coquillages dont les concentrations en Cd depassent 5 μg/g de poids sec protegent les consommateurs. En effet, dans notre zone, ces concentrations sont depassees, notamment pour les huitres, seulement dans l'estuaire de la Gironde ou du fait de la contamination par le Cd, toute consommation de coquillages est interdite. C'est la seule zone de Charente-Maritime ou nos calculs montrent que la consommation de coquillages pourrait induire chez les gros consommateurs un depassement de la DHT. 2) Les zones polaires sont soumises a un enrichissement naturel de Cd. Dans ces environnements, les cephalopodes qui concentrent tres fortement le Cd dans leur glande digestive, nous y avons mesure des concentrations atteignant pres de 400 μg/g de poids sec, sont les principaux responsables du transfert de ce metal vers les predateurs superieurs, mammiferes marins et oiseaux de mer qui les consomment. Chez ces especes, le Cd se concentre tres fortement dans le foie et les reins. La prise hebdomadaire de Cd a partir des cephalopodes a, par exemple, ete calculee pour les globicephales noirs des Iles Feroe. Elle est de 7 a 100 fois superieures a celle qui a ete montree provoquer des desordres metaboliques chez l'etre humain. De ce fait, la question se pose du risque toxicologique encouru par ces predateurs. Il est probable, qu'exposes depuis de longues periodes au Cd ces animaux ont developpe des processus de detoxication du Cd qui les protege de cette impregnation. Neanmoins, la decouverte de granules enrichis en Cd dans les tubules renaux de delphinides des Iles Feroe presentant de fortes concentrations en Cd dans leurs reins relance cette problematique. Parmi les polluants, le Cd doit etre particulierement surveille dans notre environnement. En effet, du fait de sa presence naturelle dans notre alimentation, la Dose Hebdomadaire Tolerable pour cet element peut etre rapidement atteinte en cas d'apports anthropiques supplementaires.

The bioavailability of Cd, Cu, Pb and Zn was assessed in different harbours of the Atlantic coast (France). The responses of the two dominant meiobenthic groups (nematodes and copepods) to a heavy metal contamination gradient measured in similar subtidal sediments were observed in field surveys. Heavy metal concentrations were measured in nematodes and copepods. Nematodes have higher Cd, Cu, Pb and Zn transfer factors than copepods or other benthic species. The flux of heavy metal through nematodes was estimated and appears to be important compared to plankton in the process of heavy metal transfer to benthic or pelagic food webs.

Three hundred and fifty individuals of 12 species of cephalopods which differed in their feeding habitats were sampled from the French Atlantic coast to the sub-Arctic region (Bay of Biscay, English Channel, west Irish coast and Faroe Islands) and analysed for their cadmium contents. Comparison of the Cd levels of the cephalopods showed that those from the sub-Arctic area contained very high Cd concentrations compared to those from lower latitudes such as along the French Atlantic coast. High Cd levels in cephalopods from the sub-Arctic zone correspond closely to the reported high Cd concentrations in the tissues of top vertebrate predators from the same area. Comparison of the weekly Cd intakes for the Faroe Island pilot whales with the `Provisional Tolerable Weekly Intake' for humans recommended by the World Health Organisation, showed that top vertebrate predators are often subjected to Cd doses far in excess of those recommended for humans. Our limited survey results suggest that cephalopods constitute an important source of Cd for cephalopod predators, and that this bioaccumulation effect is most evident at high latitudes.

In this study, the toxicity of vanadium to three invertebrate larvae ( Artemia salina, Crassostrea gigas, Paracentrotus lividus ) was assessed. Two criteria were mainly observed: percentage of normal developed larvae and growth of normal larvae. After short term experiments (2 days), toxic effect of vanadium appears for a concentration of 50 μg l −1 ( C. gigas larvae), 100 μg l −1 ( P. lividus pluteus). A. salina are less sensitive, and toxic effects appear only after 8 days of contact with vanadium concentration of 250 μg l −1 . For the three species tested, growth of larvae was not affected by the introduction of vanadium up to 750 μg l −1 in the rearing medium, but high teratogenic effect occur on the development of sea urchin pluteus. The toxic effect of vanadium appeared at 50 100 μg l −1 for marine larvae, this observation was in contrast with results previously obtained with adult marine organisms.

Samples of seston, plankton and suprabenthic species were collected in the Seine estuary along the gradient of salinity (0 to > 30 PSU) during six cruises from September 1992 to September 1995. Concentrations of Cd, Cu, Pb and Zn were measured at different levels of the estuarian pelagic trophic web, such as organic detritus, diatoms, Copepods and suprabenthic organisms (mysids, shrimps and fish). Organic detritus, phytoplankton and Copepods showed heavy metal contamination due to biochemical processes along the gradient of salinity. For carnivorous species (shrimps and fish), this contamination may be found only for Zn and Pb. No bio-magnification may be described in the trophic web of the Seine estuary.

The larvae of three marine species (Artemia salina, Crassostrea gigas, Paracentrotus lividus) reared within the suspended particulate phases of contaminated sediments from harbours were used in bioassays firstly to assess their ability to accumulate four metals (Cd, Cu, Pb, Zn) and secondly to show the toxicity of such rearing media by recording delays in growth and possible abnormal larval development. The results show that resuspension processes of dredged harbour sediments may induce both a release of Cd, Cu and Pb which are bioavailable for larvae (levels of bioaccumulation depending on the species) and biological perturbations, i.e. abnormal development in C. gigas and P. lividus larvae for the more contaminated sediments and growth inhibition in all three larvae for slightly contaminated sediments. The concentrations of Pb reached in the C. gigas D-shaped larvae and the P. lividus pluteus were unusually high; in contrast, Zn was not accumulated by the three species. The impact of dumping operations thus appears to depend both on the metal considered and on the larvae used in such tests. In this context, Pb seems a more worrying metal than Zn and C. gigas and P. lividus are better indicator species than A. salina larvae.

Transplanted mussels, Mytilus edulis (L.), were used as bioindicators to assess the metal contamination and biological effects of the dredging activities in the harbour of La Rochelle-La Pallice which result in the dumping of sediment in the site of the ‘Le Lavardin’ located in the vicinity of two economically important shellfish farming zones. Immersion of dredged material appeared to have no influence on the growth of mussels within their first year of development, when compared to the size of individuals sampled from neighbouring farming zones (40 mm). The Dry Condition Indexes calculated from individuals present in the disposal site were similar to those found in mussels sampled from a natural population. After three months of immersion around the disposal site, copper and zinc concentrations were similar to those recorded in individuals from a natural population. In contrast, the cadmium concentration was lower. Mussels from the northern stations of the site exhibited lead contamination. However, the respective roles of both dredged material and coastal inputs in the disposal site could not be distinguished.

Concentrations of eight metals (Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn) were determined in the brown seaweed Fucus serratus and the limpet Patella vulgata collected every 2 weeks for 13 months on the rocky shore of Goury near the outlet of the nuclear reprocessing plant of La Hague (France). During this period, the heavy metal concentrations in both algae and gastropods showed large variations (a factor of 2–5). Statistical analysis of the data showed that the concentrations of Cd, Co, Cr, Fe, Ni and Pb in Patella, and those of Cd, Co, Cu, Fe, Ni and Zn in Fucus exhibit a seasonal pattern at Goury showing a maximum in winter. The highest values found in our samples are within the range of lower values reported for other regions of the world, indicating an area not, or only slightly, influenced by industrial activities.

10 páginas, 3 tablas, 2 figuras, This study investigated 14 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn) in the tissues of the giant squid Architeuthis dux from the Mediterranean and Atlantic Spanish waters. As for other families of cephalopods, the digestive gland and the branchial hearts of Architeuthis showed the highest concentrations of Ag, Cd, Co, Cu, Fe, Ni, Se, V and Zn, highlighting their major role in the bioaccumulation and detoxification processes. With the exception of Hg, the muscles showed relatively low trace element concentrations. Nevertheless, this tissue contained the main proportion of the total As, Cr, Hg, Mn, Ni, and Zn body burden because muscles represent the main proportion of the squid mass. These findings suggest that the metal metabolism is overall the same as other cephalopod families from neritic waters. In females, Zn concentrations increased in the digestive gland with the squid’s weight likely reflecting physiological changes during sexual maturation. Comparing the trace element concentrations in the tissues of Architeuthis, higher Ag, Cu, Hg and Zn concentrations in the squid from the Mediterranean reflected different exposure conditions. In comparison to other meso-pelagic squids from the Bay of Biscay, Cd concentrations recorded in the digestive gland suggest that Architeuthis might feed on more contaminated prey or that it displays a longer life span that other cephalopods., This study was supported financially by LIENSs (University of La Rochelle).

The effect of chronic exposure to a low concentration (0.5 mu g l(-1)) of cadmium ions was investigated on escape behaviour of sea bass, Dicentrarchus labrax, using video analysis. Observations were also performed on the microanatomy of lateral system neuromasts. When fish were exposed for 4 h per day over 8 days to the cadmium ions, most of both types of neuromasts observed remained intact. However, some of them presented damaged sensory maculae. Whereas before cadmium exposure, fish responded positively to nearly all the lateral system stimulations, after exposure they decreased by about 10% their positive responses to Stimulations. From the 15th day after the beginning of cadmium exposure, neuromasts presented progressively less damage, cadmium accumulation in gills and scales decreased significantly and fish escape behaviour had recovered. This study presents a new concept in ecotoxicology: using behavioural change to reveal the effects of pollution levels, scarcely detectable by currently used techniques (physiological responses). (C) 2007 Elsevier Ltd. All rights reserved.

Pacific oysters, Crassostrea gigas, are commonly reared in estuaries where they are exposed to anthropogenic pollution. Much research has been made on the toxicity of cadmium to aquatic organisms because the compound recurrently contaminates their environment. Our study examined the influence of cadmium on aneuploidy level (lowered chromosome number in a percentage of somatic cells) and hemocyte parameters in C. gigas at different stages of life. Adults and juveniles were exposed to two different concentrations of cadmium. The first concentration applied was equivalent to a peak value found in Marennes-Oleron bay (Charente-Maritime, France; 50 ng L-1) and the second was 10 times higher (500 ng L-1). Exposure to 50 ng L-1 cadmium caused a significant decrease in the survival time of C gigas, but exposure to 500 ng L-1 surprisingly affected the survival time positively. Significant differences in aneuploidy level were observed between the cadmium treatments and the control in adults but not in juveniles or the offspring of the adult groups. The effects of cadmium on hemocyte parameters were analyzed by flow cytometry. Several hemocyte parameters increased significantly after 21 days of cadmium exposure and subsequently decreased. Phenoloxidase-like activity, evaluated by spectrophotometry, varied over the time of the experiment and increased after 66 days of contact with 500 ng L-1 cadmium. Taken together, cadmium at environmentally relevant concentrations seems to have only moderate effects on aneuploidy and hemocyte parameters. (c) 2006 Elsevier B.V. All rights reserved.

The developmental changes in the concentration of 8 essential and non-essential heavy metals (Ag, Cd, Cu, Co, Fe, Pb, V, Zn) in the tissues (digestive gland, cuttlebone and whole animal) of the common cuttlefish Sepia officinalis collected in the bay of the river Seine were monitored from the end of the embryogenesis until the adult reproductive stage. Compared to embryos, juveniles after hatching displayed much higher concentrations of Ag, Cu, Fe and Zn, suggesting an efficient incorporation from seawater. Conversely, the amounts of Cd, Pb and V in hatchlings remained constant suggesting that these metals are barely bioavailable for juveniles. Once the juveniles start to feed, the digestive gland appears to play a major role in the storage of all metals. After only one month of benthic life, the digestive gland already contains up to 90% of the total metal body burden, indicating that it plays a major role in the storage and presumed detoxification of the selected metals. Metal concentrations in the digestive gland increase in a logarithmic fashion with age during the entire life of cuttlefish, except for Ag, which decreases as soon as cuttlefish migrate to open sea. This strongly suggests that (1) Ag is excreted from the digestive gland in relation to presumably lower exposure in less contaminated environments compared to coastal waters and (2) the digestive gland of cephalopods could be a very good indicator of Ag contamination in the marine environment. (c) 2005 Elsevier B.V. All rights reserved.

International audience; The Marennes-Oléron Bay is subject to chronic pollution by cadmium (Cd) from the Gironde watershed. An ecosystem approach was used to study the fate of cadmium in the different biological compartments. The median Cd concentration was 0.4 µg g–1 dry weight for the 63 benthic species measured. When combined with the respective biomasses for the different species studied, we estimated that 7 kg of Cd is partitioned into the soft tissues of the benthic species in the bay. The majority of this cadmium was distributed between primary producers, mainly microphytobenthos (40%), and suspension-feeders, mainly oysters (40%). All other benthic species measured were associated with negligible masses of Cd. Two trophic levels contained 98% of the Cd: 3 kg was partitioned into primary producers (of which 77% is associated with the microphytobenthos) and 3.2 kg of Cd was distributed among all suspension feeders. The carnivores, including scavengers, concentrated less than 0.2 kg of Cd, suggesting an absence of biomagnification of Cd in the trophic food web of the bay. The microphytobenthic compartment was estimated to control the largest quantity of Cd (ca. 188 kg yr–1), suggesting an important role for the microphytobenthos in the biogeochemical cycle of Cd in the bay. The quantities of Cd associated with annual biological production in other biological compartments were low: 2 kg yr–1 for eelgrass which could represent a vector of Cd transfer to winter populations of Brent geese and 1.4 kg yr–1 for all suspension feeders, principally the cultivated Pacific oysters (64%) representing a vector of Cd transfer to humans. An ecosystem-wide budget for the quantities of Cd present in all the biological and physical compartments showed that the majority of Cd (1 t) is trapped in the upper 5 cm of the bay sediments, representing a potential risk for the oyster and shellfish cultivation in the bay.

International audience; This study assess the potential of the scallop Chlamys varia as a biomonitor of metal contamination in the field. Cd, Cu, and Zn concentrations were determined in the soft tissues and organs of individuals from the French Atlantic coast sampled over a one year period and belonging to a large range of size. All metals were selectively distributed among the different considered body compartments, and their concentrations were influenced by the size of the specimens or the sampling-season. The present work shows the importance to consider the body compartment, the sampling period and the size as important factors in studies aiming to use this scallop as a biomonitor species. Among tissues, the digestive gland and kidneys exhibited the highest metal concentrations whatever the season or the size. The digestive gland contained 65 and 48 % of the whole Cd and Cu body burdens, respectively, and kidney accounted for 85 % of the Zn load. Those tissues are therefore particularly recommended for use in biomonitoring programs.

Behavioural responses of sea bass Dicentrarchus labrax were investigated after exposure to cadmium ions in laboratory-controlled conditions. The aim of this study was to discover whether environmental exposure to cadmium ions inactivates fish lateral line system neuromasts, and to determine the behavioural consequences of such a sensory blockage. For this, fish escape behaviour in response to an artificial water jet was recorded using a 25-frames s(-1) analog video camera before and after cadmium exposure. Experimental set up was tested with fish whose lateral line system was artificially inactivated by antibiotics (gentamicin and streptomycin). Histological analyses with scanning electron microscopy showed antibiotic treatment destroyed lateral line system neuromasts. In addition, these fish did not respond to stimulations provoked by the water jet after antibiotic treatment. Fish escape behaviour was then recorded before and after cadmium exposure at two different concentrations. When fish were exposed to the first concentration of cadmium tested (0.5 mu g l(-1), which represents the maximal cadmium concentration encountered in contaminated estuaries), no alteration in neuromast tissue was observed. In addition, before cadmium exposure, fish responded positively in 98.41 +/- 4.95% of lateral line system stimulations (escape behaviour in response to the water jet). After cadmium exposure, no behavioural modification could be detected: the fish responded positively in 95.16 +/- 9.79% of stimulations (chi(2) = 2.464, p = 0.116). In contrast, the high cadmium concentration used (5 mu g l(-1), which represents 10 times the concentration occurring in highly polluted estuarine areas) involved severe neuromast tissue damage. Just after such cadmium exposure, fish showed only 41.67 +/- 35.36% of positive responses to their lateral line system stimulations, while they responded positively in 95.93 +/- 9.10% of stimulations under control conditions (chi(2) = 224.562, p < 0.0001). Their lateral line system neuromasts seemed to regenerate about I month after cadmium exposure. Associated with this regeneration, from the 21st day after cadmium exposure, their escape behaviour had recovered and was not significantly different from that recorded under control conditions (86.74 +/- 20.82%, chi(2) = 2.876, p = 0.090). This study shows that although 5 mu g l(-1) cadmium is able to damage lateral line system neuromasts and causes fish behavioural alterations, fish exposed to 0.5 mu g l(-1) cadmium displayed neither tissue neuromast nor behavioural modification. (C) 2005 Elsevier B.V. All rights reserved.

Three pathways of exposure (sediment, seawater and food) were examined to determine transfer of 110mAg and 57Co in juvenile cuttlefish Sepia officinalis. Additional experiments were conducted on adult cuttlefish and their eggs/embryos in order to assess bioaccumulation patterns at different stages of the organism's life cycle. Eggs, juveniles and adults readily accumulated both Ag and Co from seawater. In eggs, both metals were predominantly adsorbed onto the capsule membrane (greater than or equal to60 % for Ag and greater than or equal to99 % for Co), indicating that the latter may act as an effective shield to limit exposure of embryos to soluble metals. Adult cuttlefish incorporated waterborne radiotracers mainly in their muscular tissues (greater than or equal to60 % of the whole-body burden); subsequent metal retention was greater for Co (biological half-life, Tb1/2 = 34 d) than for Ag (Tb1/2 = 7 d). Turnover of Co ingested with food was much more rapid in juveniles (Tb1/2 = 5 d) than in adults (Tb1/2 = 990 d), suggesting that the functional maturation of the digestive gland was not complete in the juveniles. With ingested Ag, retention was roughly similar for juveniles and adults (Tb1/2 = 13 and 9 d, respectively). Transfer from sediments was negligible for Co and Ag. Regardless of the exposure pathway, the digestive gland of juveniles and adults contained the major fraction of incorporated metal either following uptake or after depuration. This observation demonstrates that substantial metal transfer takes place from several organs to the digestive gland, and further highlights the major role this organ plays in metal storage and detoxification processes in these cephalopods.

Bioaccumulation of 65Zn and 109Cd by the cuttlefish Sepia officinalis L. was studied at different stages of its life cycle, i.e. in embryos, juveniles and adults, following exposures via sea water, sediments and food. Cuttlefish eggs efficiently accumulated both elements from seawater with bioconcentration factors of 79 for 65Zn and 46 for 109Cd after 11 d exposure. Most of the radiotracers were found in the capsule membrane of the eggs, demonstrating that the capsule acts as a shield to protect embryos against metals. Juveniles and adults efficiently bioconcentrated both radiotracers from seawater, with the muscular tissues containing 84% of the total 65Zn and 62% of the total 109Cd. Loss kinetics followed a single exponential function for 65Zn, while for 109Cd loss was best described by a double exponential model. Biological half-lives for elimination were ca. 2 mo for both elements. After 29 d depuration in uncontaminated seawater, 76 to 87% of the radiotracers were found in the digestive gland. For both elements, the dissolved phase can be considered as a significant source of accumulation. In an experiment with radiolabelled sediments, transfer factors were very low, even after 29 d exposure. Food-chain transfer experiments demonstrated that both juveniles and adults assimilated 65Zn and 109Cd very efficiently. Moreover, loss of ingested radiotracers was much slower than elimination of 65Zn and 109Cd taken up from seawater, indicating a very strong retention of dietary Cd and Zn by juvenile as well as by adult cuttlefish. As with direct uptake from seawater, ingested radiotracers were mainly found in the digestive gland, with fractions reaching 82% for 65Zn and 97% for 109Cd after 29 d depuration. These tracer experiments indicate that (1) food is the likely primary pathway for Zn and Cd bioaccumulation in S. officinalis, and (2) the digestive gland plays a major role in the subsequent storage and presumed detoxification of these elements regardless of the uptake pathway.

International audience; The high concentrations of cadmium recorded in the digestive gland of cephalopods from various temperate and subpolar waters suggest that these molluscs have developed efficient cadmium detoxification mechanisms. The subcellular distribution of cadmium in the digestive gland cells was investigated in seven cephalopod species from the Bay of Biscay (France) and the Faroe Islands. In most species, cadmium was mainly found in the cytosolic fraction of the digestive gland cells, reaching up to 86% of the total cadmium for the squid Loligo vulgaris from the Bay of Biscay. But species with the highest total level of cadmium showed a higher percentage of cadmium associated to insoluble compounds. The quantification of metallothioneins (MTs) by the polarographic method was performed in order to evaluate the involvement of these proteins in the detoxification of the high amounts of bioaccumulated cadmium. Metallothionein levels in cephalopods ranged form 742 ± 270 to 3478 ± 1572 µg/g wwt. No relationship could be established between total cadmium, cytosolic cadmium and MT levels suggesting the occurrence of other Cd-binding ligands. Although these proteins have not been characterised, as cadmium in the digestive gland of cephalopods is mainly associated with soluble ligands, a high potential transfer to predators can be predicted.

International audience; Top predators from the northern sub-polar and polar areas exhibit high cadmium concentrations in their tissues. In the aim to reveal possible adverse effects, samples of five Atlantic white-sided dolphins Lagenorhyncus acutus have been collected on the occasion of the drive fishery in the Faroe Islands, for ultrastructural investigations and energy dispersive X-ray microanalyses. Cadmium concentrations were less than the limit of detection in both immature individuals and ranged from 22.7 to 31.1 µg g-1 wet weight in the mature individuals. Two individuals with the highest cadmium concentrations exhibited electron dense mineral concretions in the basal membranes of the proximal tubules. They are spherocrystals made up of numerous strata mineral deposit of calcium and phosphorus together with cadmium. Cadmium has been detected with a molar ratio of Ca:Cd of 10:1 in the middle of these concretions. To our knowledge, this is the first report of such granules in a wild vertebrate. The role of these granules in the detoxification of the metal and the possible pathological effects are considered.

International audience; Soils in New Caledonia are particularly rich in metals among which Fe and Ni are intensively exploited. Due to important natural erosion in tropical latitudes and to mining activities, coastal waters are enriched in Co, Cr, Fe and Ni. In deeper waters lives a previous termcephalopodnext term species which is considered as a living fossil, the nautilus Nautilus macromphalus. In this study, 12 trace elements were analysed in the tissues of 4 nautilus specimens. Results showed high metal concentrations compared to data available for previous termcephalopodsnext term from temperate waters. These concentrations were often in the same order as those encountered in bivalves or gastropods from contaminated areas. Relatively high concentrations of Ni and Cr in the haemolymph strongly suggest a high exposure of N. macromphalus to these metals. Among the tissues, the digestive gland has the highest concentrations of Cd, Co, Fe, V and Zn while for Ag, Al, As, Cr and Ni, renal and pericardial appendages exhibited the highest values. Despite this, the digestive gland contained the largest quantities of all metals with the exception of As and Mn which were mainly found in the body muscular remains. These results highlighted the major role of digestive gland and excreting organs in the metabolism of metals in these previous termcephalopodnext term species.

International audience; Cadmium, copper and zinc have been analysed in some tissues and organs of Loggerhead, Kemp's Ridley (only muscle for this species) and Leatherback turtles stranded along the Atlantic coasts of France. The pancreas analysed only in Leatherback turtles exhibited the highest metal concentrations, which is very surprising for an organ which does not play a role in the detoxification processes. The distribution of these elements in kidney, liver and muscle were quite similar to that found in marine mammals or seabirds. Nevertheless, mean cadmium concentrations in the kidney were as high as 13.3 µg g-1 wet weight in the Loggerhead turtles and 30.3 µg g-1 wet weight in the Leatherback turtles. Such high concentrations in the Leatherback turtles have never been recorded before. The main source of cadmium for marine turtles is probably the food. The Leatherback turtles are known to feed mainly on jellyfish in this area. Ten times higher cadmium concentrations have been determined in jellyfish compared to fish. This would imply a greater exposure to cadmium for Leatherback turtles, which probably need to eat great quantities of jellyfish to cover their needs.

International audience; Concentrations of cadmium, copper and zinc were measured in 34 octopuses over a large range of size and weight, caught in the Kerguelen shelf waters. Compared with levels normally encountered in European cephalopods, Cd concentrations in both species were very high: 30.7-47.1 and 27.3-54.4 wg/g dry weight in Graneledone sp. and Benthoctopus thielei, respectively; Cu concentrations were generally low while Zn concentrations exhibited similar levels. Distribution of Cd in tissues showed that the high levels of Cd in Kerguelen octopuses resulted from very high levels of the metal in the digestive gland (369 and 215 wg/g dry wt in Graneledone sp. and Benthoctopus thielei, respectively). The digestive gland accumulated about 90% of the total Cd in the whole animal. Due to the very high concentrations of Cd in the Kerguelen octopuses, we hypothesize that these species play an important role in the process of Cd transfer throughout the food chain to top vertebrate predators in this area.

The report presents the results of analyses for ten trace metals (Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn) in marine surface sediments from Kuwait and discusses the effect of grain size and total organic content on the observed concentrations of these metals. (JMT)

International audience; The subcellular fractionation of the digestive gland cells of the common cuttlefish Sepia officinalis was performed in order to investigate the distribution of metals 1) between organelles and cytosol and 2) in the different cytosolic fractions separated by gel-filtration chromatography. Total metal concentrations vary over 3 orders of magnitudes, ranging from 2.2 µg.g-1 dwt for Pb to 612 µg.g-1 dwt for Zn. With the exception of Cd, Co and Cu, metals were mostly bound to the organelles. Whereas no specific organelle compartment was found for Mn, Pb and Zn, Fe was mainly associated to nucleus, brown body, and “boule” fraction (i.e. 52%) and 44% of the total Ag was contained in the lysosomal and mitochondria enriched fraction. The link of metals with hydrosoluble proteins in the cytosolic fraction was investigated at 254 and 280 nm. Direct relationship between cytosolic metal and metallothioneins could only be established for Ag and Cu whereas Cd and Zn seems to mainly bind high (>70kDa) and low (< 4kDa) molecular weight proteins

The increase of anthropogenic activities on coastal areas induces discharges of polycyclic aromatic hydrocarbons in aquatic ecosystem. PAHs effects depend on their concentration and the way of contamination, but also on the different developmental stages of the organism. In this context, the aim of our study was to observe the effects of an exposure to two PAHs mixes, pyrolytic and petrogenic, on the model species zebrafish Danio rerio. These chronicle exposures at sub-lethal concentrations were representative of contaminated areas. Biological responses of fish were estimated at individual levels through the assessment of aerobic metabolic scope, swimming and escape performance, which are considered to be relevant indirect measures of the fitness. Furthermore, measurements of cardiac frequency allowed observing PAHs impairments at sub-individual levels. These physiological performances were estimated (i) a several times of exposure (i.e. from 2-months juveniles to 6-months adults) and (ii) on their progeny, in order to observe parental effect of the PAHs exposure. An increase of aerobic metabolic scope was observed on the progeny of fish contaminated by pyrolytic mix. Regarding petrogenic PAHs exposure, the increase of aerobic metabolic scope was associated to increase of critical swimming speed in adults. This study will contribute to establishing a global vision of PAHs exposure impairments and to a better understanding of the regulating mechanisms of the main biological functions on which organism survival depends.; L’anthropisation croissante des zones côtières induit le rejet dans les écosystèmes aquatiques d’Hydrocarbures Aromatiques Polycycliques (HAP). En plus de la concentration et de la voie de contamination considérées, leurs effets dépendent du stade de développement de l’organisme. Dans ce contexte, l’objectif de cette étude était d’évaluer les effets d’une contamination par voie trophique à des concentrations sublétales de HAP sur une espèce modèle, le poisson zèbre Danio rerio. Deux types de mélanges de HAP, pyrolytique et pétrogénique, représentatifs de ce qui est rencontré en milieu contaminé ont été testés via des expositions chroniques. Au niveau individuel, les réponses biologiques ont été évaluées au travers de performances physiologiques considérées comme des mesures indirectes de la fitness : la capacité métabolique aérobie, les performances de nage et la réponse de fuite. A l’échelle sub-individuelle, l’exposition aux HAP a été évaluée sur le cœur via la mesure du rythme cardiaque. Ces paramètres biologiques ont été mesurés (i) à différents temps d’exposition des poissons ainsi que (ii) sur leur descendance dans le but d’évaluer l’effet parental de la contamination. Les résultats mettent en évidence une diminution de la capacité métabolique aérobie chez la descendance de poissons contaminés aux HAP d’origine pyrolytique. Chez les poissons adultes directement exposés aux HAP de type pétrogénique, une réduction de la capacité métabolique a également été observée, associée à une réduction de la vitesse de nage critique. Cette étude contribuera à établir une vision globale des effets de l’exposition aux HAP et à mieux comprendre les mécanismes régulant des fonctions biologiques clés dans la survie d’un organisme tout au long de son cycle de vie.

Estuaries are highly dynamic systems where complex biogeochemical greatly affect the fate of organic and non-organic matter. The physical mixing of freshwater and saltwater leads to high variability in the main drivers controlling organisms distribution and trace metals partitioning between the particulate and dissolved phases: eg. salinity gradient, suspended particulate matter concentration (SPM). This work aims thus at studying the Charente estuary, which is the main river discharging into the Marennes-Oléron Bay (first oyster producing area in France) in order to (i) characterize the zooplankton community structure and relate it to the main environmental parameters, (ii) identify the main organic matter sources contributing to the functioning of the planktonic food web and (iii) to characterize contamination of the biological compartment of this estuary. Although being one of the most turbid estuaries in Europe, the Charente estuary displays quite high organic matter contribution, especially through a spring phytoplankton bloom in the mesohaline area and microphytobenthic production. The maximum turbidity zone (MTZ) displays some ecotonal characteristics, controlling both organic matter fluxes and organisms distribution. The physical mixing of terrestrially and marine derived particles within the high load of resuspended estuarine particles leads to quite homogeneous isotopic and metallic signatures in particles all along the salinity gradient during summer and autumn. Salinity and SPM concentration significantly controls the spatial distribution of the four zooplankton assemblages identified while temperature and river discharge controls their temporal variations. Despite the quantitative dominance of terrestrially derived detrital organic matter, the five dominant planktonic and suprabenthic taxa studied (Eurytemora affinis, Acartia spp., Daphnia spp., Neomysis integer, Mesopodopsis slabberi) display strong selectivity toward different organic matter sources. At the annual scale, the exploitation of the available stock of organic matter seems optimized by this spatio-temporal succession of selective species that leads to multiple trophic pathways. In addition, the concentrations of Cd, Cu, Hg, Pb, V and Zn were measured in nearly 40 estuarine taxa (zooplankton, benthos, fishes). Although particulate and dissolved metal concentrations were somewhat low as compared to those measured in highly impacted European estuaries (Seine, Gironde), the contamination levels recorded in these biotic compartments were of the same order of magnitude. Moreover, brief events such as high water levels and phytoplankton blooms greatly affect this overall pattern by modifying the available organic matter sources and particulate trace metals concentrations (especially Cd).; Les estuaires sont des systèmes hautement dynamiques où interagissent des processus biogéochimiques complexes qui influent sur le devenir de la matière organique et non organique. La confrontation des eaux fluviales et marines induit des changements rapides des principaux facteurs structurant la distribution des organismes vivants et gouvernant la spéciation de certains éléments traces entre phase particulaire et dissoute, ex : gradient de salinité, teneurs en matières en suspension (MES). Ce travail vise à étudier l’estuaire de la Charente, principal fleuve influançant le bassin de Marennes-Oléron (première zone ostreicole française) afin (i) de caractériser la structure de la communauté zooplanctonique en relation avec les paramètres environnementaux, (ii) le fonctionnement de la base du réseau trophique de l’estuaire (identification des sources de matière organique exploitée par les organismes zooplanctoniques et suprabenthiques) et (iii) d’établir un état de contamination par les métaux des compartiments biotiques. L’estuaire de la Charente se distingue par des concentrations en MES extrêmement élevées, présentant néanmoins une contribution importante de la matière organique (efflorescence phytoplanctonique printanière en zone mésohaline et production microphytobenthique). La zone de turbidité maximale semble correspondre à un écotone qui contrôle les flux de matière organique et la distribution des organismes. Le mélange physique des particules issues des systèmes dulcicoles et marins adjacents à l’estuaire avec cette forte charge de matériel resuspendu conduit à une homogénéisation des signatures isotopiques et métalliques particulaires en été et automne le long du gradient de salinité. Les quatre assemblages zooplanctoniques identifiés sont structurés spatialement par la salinité et la concentration en MES et temporellement par les variations de température et de débit fluvial. Malgré la dominance quantitative du matériel détritique au sein du pool de matière organique particulaire (MOP), il semble que les 5 taxons planctoniques ou suprabenthiques dominants étudiés (Eurytemora affinis, Acartia spp., Daphnia spp., Neomysis integer, Mesopodopsis slabberi) présentent une sélectivité importante vis-à-vis de sources primaires distinctes. Cette succession spatio-temporelle d’espèces sélectives conduit à une multiplication des flux trophiques et semble ainsi optimiser à l’échelle annuelle l’exploitation de la MOP disponible. Les concentrations en Cd, Cu, Hg, Pb, V et Zn ont par ailleurs été mesurées dans près de 40 taxons estuariens (zooplancton, benthos, poissons). Malgré des concentrations en métaux dissous et particulaires plus faibles que dans les grands estuaires européens subissant une pression anthropique importante (Seine, Gironde), les niveaux de contamination mesurés dans les différents compartiments biotiques semblent globalement équivalents. Les évènements brefs (crue hivernale, efflorescence phytoplanctonique printanière) altèrent toutefois fortement ce schéma général en modifiant les sources primaires de matière organique disponibles et les concentrations métalliques particulaires (Cd notamment).

Estuaries are highly dynamic systems where complex biogeochemical greatly affect the fate of organic and non-organic matter. The physical mixing of freshwater and saltwater leads to high variability in the main drivers controlling organisms distribution and trace metals partitioning between the particulate and dissolved phases: eg. salinity gradient, suspended particulate matter concentration (SPM). This work aims thus at studying the Charente estuary, which is the main river discharging into the Marennes-Oléron Bay (first oyster producing area in France) in order to (i) characterize the zooplankton community structure and relate it to the main environmental parameters, (ii) identify the main organic matter sources contributing to the functioning of the planktonic food web and (iii) to characterize contamination of the biological compartment of this estuary. Although being one of the most turbid estuaries in Europe, the Charente estuary displays quite high organic matter contribution, especially through a spring phytoplankton bloom in the mesohaline area and microphytobenthic production. The maximum turbidity zone (MTZ) displays some ecotonal characteristics, controlling both organic matter fluxes and organisms distribution. The physical mixing of terrestrially and marine derived particles within the high load of resuspended estuarine particles leads to quite homogeneous isotopic and metallic signatures in particles all along the salinity gradient during summer and autumn. Salinity and SPM concentration significantly controls the spatial distribution of the four zooplankton assemblages identified while temperature and river discharge controls their temporal variations. Despite the quantitative dominance of terrestrially derived detrital organic matter, the five dominant planktonic and suprabenthic taxa studied (Eurytemora affinis, Acartia spp., Daphnia spp., Neomysis integer, Mesopodopsis slabberi) display strong selectivity toward different organic matter sources. At the annual scale, the exploitation of the available stock of organic matter seems optimized by this spatio-temporal succession of selective species that leads to multiple trophic pathways. In addition, the concentrations of Cd, Cu, Hg, Pb, V and Zn were measured in nearly 40 estuarine taxa (zooplankton, benthos, fishes). Although particulate and dissolved metal concentrations were somewhat low as compared to those measured in highly impacted European estuaries (Seine, Gironde), the contamination levels recorded in these biotic compartments were of the same order of magnitude. Moreover, brief events such as high water levels and phytoplankton blooms greatly affect this overall pattern by modifying the available organic matter sources and particulate trace metals concentrations (especially Cd).; Les estuaires sont des systèmes hautement dynamiques où interagissent des processus biogéochimiques complexes qui influent sur le devenir de la matière organique et non organique. La confrontation des eaux fluviales et marines induit des changements rapides des principaux facteurs structurant la distribution des organismes vivants et gouvernant la spéciation de certains éléments traces entre phase particulaire et dissoute, ex : gradient de salinité, teneurs en matières en suspension (MES). Ce travail vise à étudier l’estuaire de la Charente, principal fleuve influançant le bassin de Marennes-Oléron (première zone ostreicole française) afin (i) de caractériser la structure de la communauté zooplanctonique en relation avec les paramètres environnementaux, (ii) le fonctionnement de la base du réseau trophique de l’estuaire (identification des sources de matière organique exploitée par les organismes zooplanctoniques et suprabenthiques) et (iii) d’établir un état de contamination par les métaux des compartiments biotiques. L’estuaire de la Charente se distingue par des concentrations en MES extrêmement élevées, présentant néanmoins une contribution importante de la matière organique (efflorescence phytoplanctonique printanière en zone mésohaline et production microphytobenthique). La zone de turbidité maximale semble correspondre à un écotone qui contrôle les flux de matière organique et la distribution des organismes. Le mélange physique des particules issues des systèmes dulcicoles et marins adjacents à l’estuaire avec cette forte charge de matériel resuspendu conduit à une homogénéisation des signatures isotopiques et métalliques particulaires en été et automne le long du gradient de salinité. Les quatre assemblages zooplanctoniques identifiés sont structurés spatialement par la salinité et la concentration en MES et temporellement par les variations de température et de débit fluvial. Malgré la dominance quantitative du matériel détritique au sein du pool de matière organique particulaire (MOP), il semble que les 5 taxons planctoniques ou suprabenthiques dominants étudiés (Eurytemora affinis, Acartia spp., Daphnia spp., Neomysis integer, Mesopodopsis slabberi) présentent une sélectivité importante vis-à-vis de sources primaires distinctes. Cette succession spatio-temporelle d’espèces sélectives conduit à une multiplication des flux trophiques et semble ainsi optimiser à l’échelle annuelle l’exploitation de la MOP disponible. Les concentrations en Cd, Cu, Hg, Pb, V et Zn ont par ailleurs été mesurées dans près de 40 taxons estuariens (zooplancton, benthos, poissons). Malgré des concentrations en métaux dissous et particulaires plus faibles que dans les grands estuaires européens subissant une pression anthropique importante (Seine, Gironde), les niveaux de contamination mesurés dans les différents compartiments biotiques semblent globalement équivalents. Les évènements brefs (crue hivernale, efflorescence phytoplanctonique printanière) altèrent toutefois fortement ce schéma général en modifiant les sources primaires de matière organique disponibles et les concentrations métalliques particulaires (Cd notamment).

Mining activities constitute the major economic resource of New Caledonia. This doctoral research was realized in order to develop a programme for biomonitoring mining contamination inthe New Caledonia coastal waters using marine organisms as “bioindicators”: the brown alga Lobophora variegata, the oysters Malleus regula and Isognomon isognomon and the clam Gafrarium tumidum. In this context, the bioindicative value of these four organisms for Ag, As, Cd, Co, Cr, Mn, Ni and Zn has been investigated through both laboratory and field experiments.Laboratory investigations of the bioaccumulation behaviour of the four organisms using radiotracer techniques demonstrated their high bioaccumulation and retention capacities for the contaminants tested. Moreover, the organisms respond to the most relevant criteria of a bioindicator species: the contaminant concentrations in organisms actually reflect those occurring in the environment.Field experiments showed that the analysis of contaminant concentrations in resident populations of clams, oysters and algae allowed discriminating sites according to their degree of contamination. In addition, transplantations of organisms between clean and contaminated sites indicated that the species displayed efficient bioaccumulation capacities for the contaminants in situ, and consequently, they can be used to monitor sites where the species were not naturally present.Overall, it is concluded that L. variegata, G. tumidum and I. isognomon are efficient and reliable bioindicator species that may be used for active and passive biomonitoring of mining contamination in the lagoon of New Caledonia.; Les activités minières constituent la principale ressource économique de la Nouvelle-Calédonie. La présente recherche doctorale a été réalisée afin de développer un système de surveillance de la contamination minière des eaux lagonaires au moyen d’organismes marins « bioindicateurs » : l’algue brune Lobophora variegata, les huîtres Malleus regula et Isognomon isognomon et le clam Gafrarium tumidum. Dans ce contexte, la valeur bioindicative de ces espèces vis-à-vis de l’Ag, As, Cd, Co, Cr, Mn, Ni et Zn a été déterminée en laboratoire et in situ.L’étude en laboratoire du comportement bioaccumulateur des quatre organismes à l’aide des techniques de radiotraçage a démontré leur importante capacité de bioaccumulation et de rétention des contaminants sélectionnés. De plus, ces organismes répondent au principal critère que doit rencontrer un bioindicateur : les concentrations mesurées dans les tissus reflètent celles qui sont présentes dans l’environnement.Dans les expériences in situ, la mesure des concentrations corporelles en contaminants dans les populations résidentes de clams, d’huîtres et d’algues a permis de discriminer des sites selon leur degré de contamination. De plus, la transplantation d’organismes entre des sites propres et contaminés (et vice versa) a montré que les espèces sont capables de refléter le degré de contamination des sites et qu’elles peuvent être utilisées pour surveiller des sites où les espèces ne sont pas naturellement présentes.Ainsi, L. variegata, G. tumidum et I. isognomon sont des bioindicateurs fiables et très prometteurs qui peuvent être utilisés pour la biosurveillance passive et active de la contamination du lagon de Nouvelle-Calédonie.

Mining activities constitute the major economic resource of New Caledonia. This doctoral research was realized in order to develop a programme for biomonitoring mining contamination inthe New Caledonia coastal waters using marine organisms as “bioindicators”: the brown alga Lobophora variegata, the oysters Malleus regula and Isognomon isognomon and the clam Gafrarium tumidum. In this context, the bioindicative value of these four organisms for Ag, As, Cd, Co, Cr, Mn, Ni and Zn has been investigated through both laboratory and field experiments.Laboratory investigations of the bioaccumulation behaviour of the four organisms using radiotracer techniques demonstrated their high bioaccumulation and retention capacities for the contaminants tested. Moreover, the organisms respond to the most relevant criteria of a bioindicator species: the contaminant concentrations in organisms actually reflect those occurring in the environment.Field experiments showed that the analysis of contaminant concentrations in resident populations of clams, oysters and algae allowed discriminating sites according to their degree of contamination. In addition, transplantations of organisms between clean and contaminated sites indicated that the species displayed efficient bioaccumulation capacities for the contaminants in situ, and consequently, they can be used to monitor sites where the species were not naturally present.Overall, it is concluded that L. variegata, G. tumidum and I. isognomon are efficient and reliable bioindicator species that may be used for active and passive biomonitoring of mining contamination in the lagoon of New Caledonia., Les activités minières constituent la principale ressource économique de la Nouvelle-Calédonie. La présente recherche doctorale a été réalisée afin de développer un système de surveillance de la contamination minière des eaux lagonaires au moyen d’organismes marins « bioindicateurs » : l’algue brune Lobophora variegata, les huîtres Malleus regula et Isognomon isognomon et le clam Gafrarium tumidum. Dans ce contexte, la valeur bioindicative de ces espèces vis-à-vis de l’Ag, As, Cd, Co, Cr, Mn, Ni et Zn a été déterminée en laboratoire et in situ.L’étude en laboratoire du comportement bioaccumulateur des quatre organismes à l’aide des techniques de radiotraçage a démontré leur importante capacité de bioaccumulation et de rétention des contaminants sélectionnés. De plus, ces organismes répondent au principal critère que doit rencontrer un bioindicateur : les concentrations mesurées dans les tissus reflètent celles qui sont présentes dans l’environnement.Dans les expériences in situ, la mesure des concentrations corporelles en contaminants dans les populations résidentes de clams, d’huîtres et d’algues a permis de discriminer des sites selon leur degré de contamination. De plus, la transplantation d’organismes entre des sites propres et contaminés (et vice versa) a montré que les espèces sont capables de refléter le degré de contamination des sites et qu’elles peuvent être utilisées pour surveiller des sites où les espèces ne sont pas naturellement présentes.Ainsi, L. variegata, G. tumidum et I. isognomon sont des bioindicateurs fiables et très prometteurs qui peuvent être utilisés pour la biosurveillance passive et active de la contamination du lagon de Nouvelle-Calédonie.