Imposex in Nucella lapillus, a bioindicator for TBT contamination: re-survey along the Portuguese coast to monitor the effectiveness of EU regulation

Imposex, a bioindicator of TBT contamination, was re-examined in 2000, five years after the first survey, in populations of the dogwhelk Nucella lapillus sampled along the Portuguese coast, in order to monitor the effectiveness of the 1993 Portuguese legislation based on EU regulation to restrict the use of TBT-based antifouling paints on ships not longer than 25 m. The results obtained during this study indicate that TBT contamination has increased along the Portuguese coast over the five-year period, indicating an inefficacy of the partial ban. The degree of imposex had increased more near small harbours than near ports supporting commercial vessels.