Biological indicators used to map organotin contamination from a fishing port, Killybegs, Ireland

Contamination by organotins in areas of aquaculture and small boat activity about Ireland has generally decreased since legislation was introduced in 1987, but in many port areas contamination increased. The fishing port of Killybegs lies within a small sheltered inlet in Donegal Bay on the N-W Irish coast and is the main source of contamination for several kilometers. This area has been studied using imposex of dogwhelks, Nucella lapillus, since 1987. Dogwhelks are particularly sensitive to TBT and have become extinct within the Harbour, and remaining populations near the Harbour entrance are likely to die-out. Periwinkles, Littorina littorea, are less affected by TBT and have a condition, intersex, which was used to determine the relative levels of contamination within the Harbour in areas where dogwhelks no longer exist. Both indicator species compliment each other; but periwinkles, useful for areas where there is high contamination, can provide some unexpected results in areas of low contamination. For such areas dogwhelks are better indicators. Imposex and intersex values decline with distance from source; low levels of contamination were found 12 km from Killybegs port. Decrease of these biological indices with distance from source was generally consistent with TBT body burdens. Fishing vessels that are greater than 25 m are permitted to use organotin antifoulant paints and high levels of contamination are expected to remain in the immediate area of the Harbour for some years even if its use is discontinued.