IN SITU COMPARATIVE STUDY OF SEVERAL MEDITERRANEAN SPONGES AS POTENTIAL BIOMONITORS OF HEAVY METALS

Abstract

The heavy metals content of sponges is investigated in order to assess their suitability as biomonitors. The concentration of 10 elements is determined in six species of massive Demosponges well represented in a polluted and a clean site: Cliona viridis, Cacospongia scalaris, Chondrosia reniformis, Spongia officinalis, Spongia agaricina and Agelas oroides. Wide interspecific variations are observed between them, no doubt as a result of their morphological and physiological differences. Cliona viridis appears to be unique with regard to the higher concentrations found for several elements, especially Cd that is from 42 to 375 times more concentrated than in the other species. However, this species displays highly variable results and gives a rather poor image of the level of contamination of the sites, as only three trace elements out of ten have a significantly higher concentration in the polluted site. Three species, S. officinalis, S. agaricina and A. oroides, which give a consensual indication of the metals’ bioavailability, with sufficiently high and homogenous concentrations, appear to be well suited for consideration in the overall assessment of the marine environment quality.