Bioaccumulation of mercury in starfish from contaminated mussels

Abstract

In the course of our works on mercury metabolism in marine organisms, we investigated in laboratory the technical feasibility and the scientific relevance of the simple benthic food chain ‘particles-mussel-starfish’. Mature starfish, Leptasterias polaris, fed over 45 days with contaminated mussels ( Mytilus edulis), bioaccumulated organic mercury in all their tissues. The absorption rate of mercury in the first weeks of the experiment was respectively 0.238, 0.094, and 0.015 μg.g −1 d −1 (wet wt) in pyloric caeca, stomachs and body walls. Starfish retained about 50% of the organic mercury ingested mostly in pyloric caeca and calcerous skeleton (96–98%). After four weeks of regular accumulation, an auto-depuration process took place and mercury concentration in digestive organs was reduced even if the contaminated food was still provided. Coelomic fluid seems to be a barrier to the rapid dispersion of methylmercury into the whole animal and may play a role in the depuration process. These results provide evidence for the strong interest in the mussel-starfish food chain for fundamental studies of metal biotransfer in invertebrate marine organisms.