The Significance of Imposex Levels and TBT Contamination in the Red Whelk, Neptunea antiqua (L.) from the Offshore Irish Sea

The extent to which open seas and oceanic waters have been contaminated by TBT is unclear since most sampling programmes have concentrated on inshore areas, particularly near harbours. Accordingly, the red whelk, Neptunea antiqua L. (Mollusca: Prosobranchia), a sublittoral and dioecious prosobranch species, was selected to investigate the potential effects of TBT-induced imposex in the central western Irish Sea. The presence of imposex was noted in >90% of all female whelks that were examined on a monthly basis over a 12-month period. However, the proliferation of the vas deferens was not considered severe enough to affect the reproductive capabilities of the population. Low concentrations of butyltins were detected in the soft tissues of all whelks examined, ranging from 0.009 to 0.112 μg g−1 Sn dry wt There was no significant correlation between the documented imposex stages and total butyltin contamination, indicating that the species is not a reliable bioindicator species of the effects of this contaminant.