Trends in concentrations of selected metalloid and metals in two

23 The concentrations of 9 elements (Ag, As, Cd, Co, Cr, Cu, Mn, Ni and Zn) were measured 24 in the oyster Isognomon isognomon and the edible clam Gafrarium tumidum from different 25 sites along the SW New Caledonian coast which is subjected to important chemical inputs due 26 to intense land-based mining activities (New Caledonia is the third world producer of nickel). 27 Results indicate that concentrations in the two organisms mirrored the geographical 28 differences in contamination levels as established through element analyses in sediment. On 29 the basis of organism analyses, two out of the seven investigated stations can be considered as 30 relative “reference” sites, except for As, for which very high levels were detected in clam and 31 oyster tissues (up to 441 μg g dry wt for clams). Overall, our results indicate that both 32 tropical organisms investigated could be used as valuable bioindicator species for surveying 33 metal contamination in the coastal waters of New Caledonia with reasonable perspectives of 34 wider application to other coral reef environments. 35 36