IMPOSEX AS SURVEILLANCE BIOMONITORING TOOL OF POLLUTION BY THE ANTIFOULING AGENT, TBT AFTER ITS BAN: MALTA, A CASE STUDY

摘要

Tributyl tin (TBT) has been banned as an antifouling agent in the maritime sector over the past few years, due to its impact on a wide range of non-target marine species. This includes imposex induction in prosobranch gastro pods. The Maltese Archipelago was one of the first sites within the Mediterranean, where imposex in the marine snail, Hexaplex trunculus was first used as a biomonitor to assess environmental levels of TBT. Subsequently, this same species was used in several other Mediterranean coastal areas for the same purpose. Imposex levels in Hexa plex trunculus have been studied in Malta since 1993, and have been ongoing since then. The present study will report on the trends in such imposex biomonitoring over the past 18 years in popula tions of H. trunculus from 13 different inshore coastal areas around the Maltese islands (Malta and Gozo). It concludes that levels of imposex have been declining in this species. Furthermore, the incidence of normal females completely free from imposex in some places, has been on the increase (it is worthwhile to note that prior to 2005 all sampled females of this species showed evidence of im posex). Nonetheless, imposex is still being recorded, in cluding in marine protected areas. Furthermore, different imposex developmental expressions have been identified in some localities, with some of such expressions proba bly rendering female specimens more susceptible to early death.