Sponges as biomonitors of heavy metals in spatial and temporal surveys in northwestern mediterranean: multispecies comparison

Contamination by heavy metals has increased drastically in the coastal Mediterranean during the last 20 years. A comparative study on metal bioaccumulation by four widespread sponge species (Crambe crambe, Chondrosia reniformis, Phorbas tenacior, and Dysidea avara) has been performed to select the most suitable species for metal monitoring. Copper bioaccumulation fits an accumulation strategy while Pb concentration seems to be regulated in most sponges. Crambe crambe was the only studied species that bioaccumulated Pb and Cu as a function of the available metal, proving its suitability for monitoring purposes. Then, we examined its effectiveness as a bioindicator at large spatial and temporal scales, comparing metal accumulation in this species and in sediments. Crambe crambe provided accurate information on the background levels of metals in the area at both spatial and temporal scales, and furthermore it reflected seasonal fluctuations of the bioavailable metals, which would be impossible to assess by means of a sediment survey.