Hope for sex disturbed snails – monitoring of imposex and intersex show that banning TBT has had a positive effect

Summary

Tributyltin (TBT) was introduced as an active agent in antifouling paint on ships in the 1960s. TBT also caused significant hormonal effects inducing male sex characteristics on female marine snails. The phenomenon is called intersex in common periwinkle (Littorina littorea) and imposex in netted dogwhelk (Nassarius reticulatus) and dogwhelk (Nucella lapillus). Populations of dogwhelk in several areas of the North Sea were critical reduced in the 1990s. Thus, TBT containing paint was banned in 1990 on boats less than 25 m and on larger ships internationally from 2003. After 2008, sale and use was completely prohibited. During 2005-2012, our results show clear improvements of intersex and imposex were observed both in time and distance from an assumed source of pollution close to Grimstad. Common periwinkle showed a more rapid improvement than mud snail, but the levels closest to the source of contamination are still so high that both common periwinkle and netted dogwhelk were in bad condition. In 2011, no signs of imposex in dogwhelk were found in the previously contaminated coastal area outside Grimstad