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Hedouin L.,International Atomic Energy Agency | Hedouin L.,Institute Of Recherche Pour Le Developpement Ird Noumea Center | Hedouin L.,CNRS Coastal and Marine Environment Laboratory | Metian M.,International Atomic Energy Agency | And 3 more authors.
Marine Pollution Bulletin | Year: 2010

The clam Gafrarium tumidum and the oyster Isognomon isognomon have been proposed as potential biomonitor species of metal contamination in the New Caledonia lagoon. The influence of dissolved concentrations of As, Cd, Co, Cr, Mn, and Zn on uptake and depuration kinetics, tissue and subcellular distribution of these elements was investigated in both species. Results indicate that both bivalves take up elements proportionally to the dissolved concentration for Cd, Cr and Mn in the surrounding water over the entire range of concentrations tested (three orders of magnitude), and up to the second and third highest added metal concentration tested for Co (23ngl-1) and Zn (700ngl-1), respectively. All elements were efficiently retained in bivalve tissues (estimated Tb1/2 ranging from 16d to ∞), suggesting that both species should be able to preserve a record of contamination events over a long period of time. Considering the specific range of concentrations examined here, G. tumidum and I. isognomon would therefore serve as adequate biomonitor species to monitor dissolved metal contamination in the New Caledonia lagoon waters. © 2010 Elsevier Ltd. Source


Hedouin L.,International Atomic Energy Agency | Hedouin L.,CNRS Coastal and Marine Environment Laboratory | Hedouin L.,Institute Of Recherche Pour Le Developpement Ird Noumea Center | Metian M.,International Atomic Energy Agency | And 5 more authors.
Marine Pollution Bulletin | Year: 2010

Bioaccumulation of Ag, Cd, Co, Cr and Zn was studied in the oysters Isognomon isognomon and Malleus regula, using highly sensitive radiotracer techniques. Metals were readily bioconcentrated from the dissolved phase. Sediment exposures indicated a low bioavailability of sediment-bound metals (3-5 orders of magnitude lower than dissolved metals). In both seawater and sediment experiments, the two oysters displayed similar bioaccumulation behaviour towards all metals but Ag. Indeed, Ag was much more efficiently incorporated and retained in I. isognomon. Metals ingested with food (phytoplankton) were efficiently assimilated (34-77%) and strongly retained in oyster tissues (Tb≥ 20d). Estimation of the relative contribution of each exposure pathway indicated that for both species sediment was the dominant pathway for Co and Cd, whereas food was the major source of Zn. Regarding Ag, seawater was the main source for I. isognomon (86%), whereas sediment was the predominant route for M. regula (92%). © 2010 Elsevier Ltd. Source


Hedouin L.,International Atomic Energy Agency | Hedouin L.,CNRS Coastal and Marine Environment Laboratory | Hedouin L.,Institute Of Recherche Pour Le Developpement Ird Noumea Center | Metian M.,International Atomic Energy Agency | And 7 more authors.
Marine Pollution Bulletin | Year: 2010

The present study aimed at examining the influence of food quality and quantity on the assimilation efficiency (AE) of metals in two abundant bivalves in the New Caledonia lagoon, the oyster Isognomon isognomon and the clam Gafrarium tumidum. Bivalves were exposed via their food to the radiotracers of three metals of concern in New Caledonia (54Mn, 57Co and 65Zn) under different feeding conditions (phytoplankton species, cell density, and cell-associated metal concentration). When bivalves were fed Heterocapsa triquetra, Emiliania huxleyi and Isochrysis galbana, AE of Mn, Co and Zn was strongly influenced by the phytoplankton species and by the metal considered. In contrast, when fed one given phytoplankton species previously exposed to different concentrations of Co, phytoplankton-associated Co load had no influence on the AE and on the retention time of the metal in both bivalves. Metals ingested with I. galbana displayed generally the highest AE in both bivalve species, except for Mn in clams for which the highest AE was observed for H. triquetra. Influence of food quantity was investigated by exposing bivalves to different cell densities of I. galbana (5×103, 104 or 5×104cellml-1). As for food quality, food quantity was found to influence AE of Mn, Co and Zn, the highest AE being observed when bivalves were fed the lowest cell density. Overall, results indicate that the two bivalve species are able to adjust their feeding strategies according to the food conditions prevailing in their environment. © 2010 Elsevier Ltd. Source

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