Effects of tributyltin pollution on the mud snail, Ilyanassa obsoleta, from the York river and Sarah creek, Chesapeake bay

Abstract

Abstract Mud snails, Ilyanassa obsoleta , were collected along gradients of tributyltin (TBT) pollution in the York River-Sarah Creek region of Chesapeake Bay. Development of imposex (the imposition of male characters on female snails) was assessed. Frequencies of imposex and intensities of penis expression were either zero or very low at 3 sites in the York River where water concentrations of TBT were of the order of 2 ng l −1 . In the northwest branch of Sarah Creek, with water concentrations of around 20 ng l −1 , the frequency of imposex was 100% and the intensity of penis expression was high. Tissue concentrations of TBT were similar in both sexes and ranged from less than 20 ng g −1 dry wt at the 3 York River sites to 620–730 ng g −1 dry wt at a site in the northwest branch of Sarah Creek. An appreciable degree of imposex is induced in I. obsoleta at a seawater TBT concentration of about 10 ng l −1 and imposex is probably initiated at about 2 ng l −1 . No evidence was found for the sterilization of I. obsoleta by imposex, but the percentages of females in the samples declined significantly with increasing frequency of imposex.