CELLULAR SITES OF IRON AND NICKEL ACCUMULATION IN ASCIDIANS RELATED TO THE NATURALLY AND ANTHROPIC ENRICHED NEW CALEDONIAN ENVIRONMENT

New Caledonia is particularly rich in heavy metals and there is large scale mining of iron and nickel. Natural erosion and mining thus incre ase the amount of Fe, Ni, Cr, and Co in coastal waters. The storage of these metals by several species of filter-feeding ascidians, known to sequester heavy metals, has been evaluated by cytological, microanaly tical and chemical techniques. Specimens of several cosmopolitan speci es of different families were studied at increasing distances from the shore in New Caledonia and compared to the same species collected in the Caribbean and Polynesian waters. Fe contamination was highest, Ni somewhat less, Cr and Co were not detected in ascidian tissues. Ascidi a sydneiensis has revealed to be the best species for this ecotoxicolo gical study. In this species, the Fe contamination of New Caledonian a nd Guadeloupean specimens is expressed by the presence of Fe(III) in t he body wall, branchial epithelium, vacuolar blood cells, oocytes and spermatocytes. Ni normally stored in pigment cells did not increase in polluted areas, but excess Ni was present in blood cells. The relatio nship of these findings to the available geochemical data from New Cal edonia is discussed. The biochemical state and ligands of the metals a re proposed and compared to the literature data.