IMPORTANCE OF GELATINOUS PLANKTON ORGANISMS IN STORAGE AND TRANSFER OF TRACE-METALS IN THE NORTHWESTERN MEDITERRANEAN
Résumé
Concentrations of trace metals (Cd, Cu, Pb, Zn) were determined in gelatinous macroplankton collected from the northwestern Mediterranean Sea. Samples belonging to 4 different phyla - cnidarians, ctenophores, molluscs and tunicates (salps and pyrosomes) - were collected. Some amphipod crustaceans, living on gelatinous organisms, were also analysed, Metal concentrations were basically identical among the different phyla. For the cnidarian Velella velella, differences in cadmium and lead concentrations were noted for organisms of the same weight between those collected near the coast and those from the open sea. In the ctenophore Beroe ovata, copper and zinc concentrations appeared to be independent of weight, whereas some weight-dependency was found in V. velella. The most significant features in the trace metal concentration of salps were the elevated values found either in the viscera ('nuclei') or in the faecal pellets, compared to that found in whole animals. Due to their high defecation rate, salps seem to play an important role in the biogeochemical cycling of trace metals in the sea. Cadmium, copper and zinc linked to faecal material may be rapidly dissolved in the water column, whereas lead does not seem to be recycled.
Domaines
Océanographie
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