SELENIUM CONCENTRATIONS IN THE MARINE-INVERTEBRATES MACOMA-BALTHICA, MYTILUS-EDULIS, AND NEREIS-DIVERSICOLOR

Waders residing in the Dutch Wadden Sea had high selenium concentratio ns in the tissues. These high concentrations may be a result of a cont amination in the food chain, and a selection of marine invertebrate pr ey animals, the bivalves Macoma balthica and Mytilus edulis and the po lychaete Nereis diversicolor, were analyzed for selenium. Selenium con centrations varied by year, season, location, species and size, but th e average concentrations (2-6 mg/kg ash free dry weight) remained with in the range of known background concentrations in marine invertebrate s (1-10 mg/kg DW). However, the highest concentrations approximate the general (sub)toxic level of dietary selenium. The importance of the d etermination of the selenium compound(s) in marine biota is stressed M acoma had a seasonal variation in selenium concentration that may para llel the reproductive cycle; the highest concentrations (4-5 mg/kg AFD W) were found in the spawning period, the concentration dropped after spawning and in the recovery phase the bivalves were lowest in seleniu m (2-3 mg/kg AFDW). Intermediate concentrations (3-4 mg/kg AFDW) were measured during the gametogenesis. Concentration changes in Mytilus co rresponded with this pattern.