Biological indicators used to map organotin contamination in Cork Harbour, Ireland

In 1993 TBT contamination in areas of aquaculture and small boat activity about Ireland was found to have improved significantly since 1987, but in areas of shipping, contamination remained. Cork Harbour, a sea inlet with heavy shipping traffic, was examined in 1994 to determine the extent of contamination, using imposex and intersex in two prosobranch snails. Both Nucella lapillus (dogwhelk) and Littorina littorea (periwinkle) provided data on the varying levels of TBT contamination throughout Cork Harbour. N. lapillus is particularly sensitive to TBT and has become extinct in some areas of the harbour since 1968. Littorina littorea tolerates lower salinities, is less affected by TBT, and so can be used to monitor in more brackish and heavily contaminated areas. Intersex is used for the first time to map areas of TBT contamination. Shell thickness in the Pacific oyster, Crassostrea gigas, from 1985–1987 and 1994 was also compared. All three indicator species are consistent in terms of the pattern of TBT contamination in Cork Harbour. TBT contamination in the western side is greater than in the eastern side of the harbour, reflecting the inputs. Contamination levels generally decline with increased distance from the harbour.