Element concentrations in cold-water gorgonians and black coral from Azores region

Seamounts are thought to support high biodiversity and special biological communities, including corals. Corals incorporate minor and trace elements and have been suggested as possible bioindicators of their availability in the environment. Forty specimens of five gorgonian species (Alcyonacea) and a black coral (Antipatharia) were collected in 12 sites in the Azores region. Concentrations of Ca, Mg, Cr, Mn, Co, Ni, Cu, Zn, Se, Cd and Pb were determined in skeleton and attached tissue of each individual from each species. Leiopathes sp. had higher Cr, Ni, Se and Pb concentrations than the gorgonians. Enhanced Cu and Cd values were registered in Leiopathes and Acanthogorgia hirsuta. Specimens of A. hirsuta also presented elevated concentrations of Zn and Co. Linear relationships between Cd and Cu, Zn and Se point to response mechanisms in corals, possibly related to the induction of proteins enlarging the capacity to incorporate further quantities of essential elements. Results obtained in this study suggest the existence of an additional source of Cd in waters off Azores Islands associated with natural hydrothermal activities.