Imposex in Morula Granulata as Bioindicator of Tributyltin (TBT) Contamination in the Dampier Archipelago, Western Australia

Abstract

This study was undertaken to examine the use of imposex in the tropical neogastropod whelk Morula granulata as bioindicator of tributyltin (TBT) contamination. Samples were collected from sites throughout the Dampier Archipelago; both impact sites close to intensive shipping activity and remote control sites. TBT in this area originates mainly from commercial vessels using the Port of Dampier that are >25 m in length and exempt from legislation controlling the use of TBT in antifouling paints. A field survey was undertaken in July 1997; 100 M. granulata were taken at each of 18 sites with varying vessel activity, and examined for imposex. The level of TBT contamination in the Archipelago was low; ranging from <0.3 to 25 ng Sn l −1 in water,<0.3 to 80 ng Sn g− 1 in oyster tissue ( Saccostrea cuccullata – prey of M. granulata), and <0.3 to 33 ng Sn g −1 in whelks. Percentage of imposex in M. granulata ranged from 0% to 57%, and was correlated with distance to vessel activity ( r=0.646, p<0.05). The only significant relationship of imposex with butyltin concentrations was with TBT in oysters ( r=0.826, p<0.05), and dibutyltin (DBT) in whelks ( r=0.783, p<0.05). It is postulated that this is because of interspecies variation in ability to metabolize TBT to DBT and MBT (monobutyltin), as well as induction of imposex in earlier life stages, so that imposex in adults could be a reflection of prior contamination. M. granulata is a suitable bioindicator of TBT contamination in the Dampier Archipelago, which could be used throughout the Indo-Pacific given its abundance in the region.