Imposeks dalam siput haliah, Thais sp. sebagai penunjuk biologi pencemaran tributiltimah di perairan Semenanjung Malaysia

Abstract

Unintentional effects of the antifouling biocide tributyltin (TBT), produced mainly from marine paints, have been discovered in marine gastropods as an induction of male sex characters in females, a phenomena that is known as imposex. This imposex phenomenon is use d as a bioindicator of TBT contamination. TBT, the active ingredient of antifouling paints, is one of the most toxic chemicals that Man has ever introduced into the marine environment. TBT-based antifouling paints are widely used in Malaysia and there is as yet any rule or regulation in controlling the usage of these paints. Field studies on imposex in the rock shell, Thais sp., and butyltin (BT) compound contamination in it and its sediments were conducted along the coast of Peninsula Malaysia. The percentage occurrence of imposex in Thais sp ., was in the range of 6 – 100 % at all sites surveyed (19 sites). Observed values of the Relative Penis Size Index (RPSI), defined as the ratio of mean penis size found in imposexed females to that in normal males, were between 0 and 109.21 %. Vas Deferens Sequence Index (VDSI) values ranged from 0 – 5. In some study sites, the rock shell populations were male -biased and matured gastropods dominated the population. Levels of butyltin compounds in rock shells and sedime nts from 12 sites were determined using gas chromatograph-flame photometry detectors (GC -FPD). The results indicated widespread contamination of butyltin compounds in the surrounding water of the Straits of Malacca and South China Sea. TBT concentration in the rock shells and sediments ranged 3.9 – 650 ng g-1 wet weight and 0 – 700 ng g- 1 dry weight, respectively. High concentrations of TBT were detected in samples from areas with high shipping activity, ports, jetties, marinas and dockyards. A positive relation existed between the concentration of TBT in rock shells and the development of imposex. The mechanisms leading to annual input of TBT to the waters of the Straits of Malacca and the South China Sea from shipping was discussed and estimated at 70.23 tonnes.