Using Nucella lapillus (L.) as a bioindicator of tributyltin (TBT) pollution in eastern Canada: a historical perspective

Dogwhelks (Nucella lapillus), a universal bioindicator of tributyltin (TBT) pollution, were used to determine butyltin distribution in three Atlantic Canada harbours previously surveyed between 1995 and 2006. N. lapillus were analysed for the presence of TBT and its degradative products while imposex incidence and severity were compared with previous surveys to assess the efficacy of the Canadian regulations on TBT. Imposex was observed at two harbours that had dogwhelks, but not at surrounding reference sites. When comparing results with previous surveys in the same geographic area, there appears to be some improvement of affected N. lapillus populations, suggesting that the 1989 Canadian regulations have been effective in decreasing imposex severity for most sites as measured by the vas deferens sequence index (VDSI), but not the occurrence of imposex. The highest butyltin tissue concentration (63.75 ng Sn g (1), dry wt) was detected in imposex-affected females from Red Head in Saint John Harbour (New Brunswick), which is adjacent to an area frequented by large oil tankers that, under the 1989 regulations, are legally allowed to use TBT antifouling paint. This study is the first to illustrate a significant correlation between TBT levels and imposex on a spatial scale in Atlantic Canada.