Heavy Metals in the Sea Cucumber Holothuria tubulosa (Echinodermata) from the Mediterranean Posidonia oceanica Ecosystem: Body Compartment, Seasonal, Geographical and Bathymetric Variations

摘要

The concentrations of Cd, Cu, Fe, Pb and Zn were measured in holothuroids Holothuria tubulosa collected during different seasons and at several depths in three N W Mediterranean Posidonia oceanica meadows (Calvi, Corsica; Ischia, Italy; Marseille, France). Metals were found to be selectively distributed among the holothuroid body compartments (i.e. body wall, gut, and haemal system). Among the sources of variation taken into account, the major part of the variability observed in metal concentrations was associated to the body compartment factor, then to the seasonal one and, finally, to the geographical and bathymetric factors. Our results suggest that, if one uses H. tubulosa as a bioindicator species for surveying and monitoring metal contamination in the Mediterranean P. oceanica meadows, attention should be paid to compare only concentrations measured in the same body compartments of individuals collected during the same period of the year. Body compartments that should be preferably considered for metal analyses are the haemal system and, secondarily, the gut (i.e. the compartments concentrating metals most efficiently). Due to the peculiar ecological characteristics of H. tubulosa (i.e. a deposit feeder living in close relationships with the sediments), this species could be effectively used to complement the small set of bioindicators available so far for surveying metal contamination in the P. oceanica ecosystem (viz. the phanerogam P. oceanica itself and the grazing echinoid Paracentrotus lividus).