ACCUMULATION OF ORGANOTIN IN LITTORINA-LITTOREA AND MYA-ARENARIA FROMDANISH COASTAL WATERS

Organotin concentrations were determined in seawater, sediment and sel ected molluscs collected from the vicinity of the island of Fyn, Denma rk. The extent of organotin contamination varied with the proximity of sampling sites to marinas and commercial shipping activities. Seasona l reductions in environmental TBT concentrations coincided with remova l of pleasure craft from marinas during the winter season. At marina s ites, concentration factors for TBT were 150-1500 for sediment and 500 -10 000 for Littorina littorea (compared with seawater concentrations) . Away from marina sites, Mya arenaria concentrated TBT by a factor of 57000 to 220000. The concentrations of TBT in M. arenaria from relati vely clean sites were more than 10 times higher than found in L. litto rea from heavily polluted marinas. M. arenaria were absent from marina sites and their immediate surroundings. Of the total organotin found in M. arenaria throughout the year, 80-90% was in the form of TBT. In contrast, in L. littorea approximately 60-70% of the total organotin w as present as TBT in spring, but this proportion fell to 20-40% during autumn and winter. M. arenaria shows potential as a bioindicator orga nism of TBT pollution as it appears to have a very limited ability to metabolise and eliminate TBT, yet can tolerate quite high levels of TB T exposure. L. littorea might be used as a bioindicator of short-term fluctuations in TBT concentrations at heavily polluted sites. It is co ncluded that continued presence of TBT in the Danish coastal ecosystem may still pose an ecotoxicological threat.