Accumulation and trophic transfer of organotins in a marine food web from the Danish coastal waters

The presence of organotin compounds, e.g., tributyltin (TBT) and triphenyltin (TPhT) including the di- and monosubstituted breakdown products, was studied in a representative marine food web in order to assess the accumulation potential at different trophic levels in Danish coastal waters. This included samples of two species of seaweed, four species of invertebrates, four species of fish, five species of birds and two species of mammals. All organisms were sampled away from harbour areas and the organotin concentrations found in this study can therefore be considered to reflect a general level in organisms living in Danish coastal waters. All the samples analysed contained organotin compounds. The highest hepatic concentrations of butyltins were found in flounder (60-259 ng g-1 wet weight [ww], as Sn), eider duck (12-202 ng g-1 ww) and harbour porpoise (134-2283 ng g-1 ww). The lowest concentrations were found in seaweed and a plant-feeding bird. TPhT or its degradation products were also found in most of the samples with the highest concentrations in flounder (9.8-74 ng g-1 ww), cod (23-28 ng g-1 ww) and great black-backed gull (19-24 ng g-1 ww). This indicates an input of TPhT in the region, probably from the use as antifouling agent. A high variance in accumulation potential was found between the species, even between species at the same trophic level, which probably reflects the species-specific differences in exposure routes and the capabilities to metabolise and eliminate the organotin compounds. This study gives evidence of the importance of biomagnification of butyltin in harbour porpoises and, to a lesser extent, in fish and birds.