Imposex status associated with organotin contamination in Reishia clavigera after reciprocal transplantation between clean and polluted sites in Hong Kong

Recent biomonitoring studies have showed that contaminations of triphenyltin (TPT), relative to levels of tributyltin, have become more serious in Hong Kong and other South China coasts. However, there is a lack of field-based evidence to demonstrate the casual relationship between TPT and imposex development in the rock shell Reishia clavigera in this region. This study aimed to investigate the temporal changes of imposex development and tissue concentration of six organotins (OTs) in tissues of R. clavigera after their reciprocal transplantation between relatively clean and polluted sites in Hong Kong for six months. The results revealed a significant increase of tissue concentration of total OTs, in particular TPT, in the rock shells transplanted from a clean site to a polluted site, while a decrease of tissue OT concentrations was observed in those treated conversely. Vas Deferens Sequence Index, one of the imposex indices, only increased slightly for rock shells transplanted from clean to polluted sites, while Relative Penis Size Index elevated remarkably for the same treatments. In general, the rock shells had lower tissue concentrations of OTs in winter than that in summer, though the exact mechanism is still unknown. This study has further confirmed that OT contamination is still prevalent in Hong Kong's coastal marine waters, which necessitates tightened management controls on this group of chemicals especially on TPT compounds.