Role of a dense bed of Ophiothrix fragilis (Abildgaard) in the transfer of heavy metals at the water-sediment interface

The role of a dense bed of suspension-feeders (Ophiothrix fragilis) on the biogeochemical cycle of five major metals has been studied in the English Channel (Fe, Mn, Pb, Cu, Cd). Metal concentrations in ophiurids, their food (=suspended matter) and their faeces did not show any significant time variation. After their transit between food, organisms and faeces, metal concentrations were poorly modified, but relations between them changed. A lot of trace elements have been detected in the stomach, some of them typical of the waste inputs above the site. So, the ophiurid O. fragilis can be considered as a biological indicator of the elemental composition of the water mass entering the North Sea.