Imposex in Bolinus brandaris from the Ria formosa lagoon (southern Portugal): usefulness of "single-site baselines" for environmental monitoring.

The present study aimed at creating a so called "single-site baseline" (SSB) of imposex in the purple dye murex (Bolinus brandaris) from the Ria Formosa lagoon (Algarve coast, southern Portugal), at the moment that the IMO Antifouling System Convention (banning globally the use of organotin compounds in antifouling paints on ships' hulls) entered into force (September 2008). In the context of monitoring long-term temporal trends of pollution levels, SSBs are proposed whenever it is difficult to obtain adequate numbers of bioindicator specimens in most of the study area or if significant short-term variability in imposex levels is likely to occur. In order to deal with these constraints, this study created a SSB by sampling on a monthly-basis (from October 2008 to September 2009) in a single site considered to be representative of the Ria Formosa as a whole (vicinities of the Culatra Island) and where B. brandaris is abundant all year round. The SSB provided a good characterisation of the monthly variation in the imposex indices, which ranged throughout the year between 72.7 < I% < 100; 0.08 < FPLI < 1.73; 1.20 < RPLI < 23.27; 1.29 < VDSI < 3.54. Only a SSB could have detected this large variability, which otherwise might have been unnoticed and would have produced biased temporal and spatial comparisons, leading to erroneous interpretations of environmental monitoring data. Therefore, this SSB of imposex in B. brandaris constitutes valuable reference data to assess the future trend of organotin pollution in the Ria Formosa, after the benchmark date of the complete eradication of organotin from antifouling agents was implemented worldwide.

Spatial and temporal evolution of imposex in dogwhelk Nucella lapillus (L.) populations from North Wales, UK.

Nucella lapillus imposex and organotin tissue contamination were assessed, during 2006, at twenty sites in North Wales, between Anglesey and Shell Island on the Lleyn Peninsula. Vas Deferens Sequence Index (VDSI), Relative Penis Size Index (RPSI) and the percentage of affected females (%I) were used to assess imposex levels which varied between 0.5 and 3.8 for VDSI, 0.0 and 11.5% for RPSI and 49 and 100% for %I. Tributyltin (TBT) and triphenyltin (TPT) concentrations in whole tissues varied between 0.8 and 39 and 0.4 and 2.1 ng Sn/g dry weight, respectively. TBT represented the higher fraction of butyltin compounds in the tissues, suggesting that TBT inputs continue to occur. Comparisons with nineteen years of data collected during previous studies demonstrated that there had been a significant reduction in imposex levels over the last two decades following the introduction of legislative restrictions in the U.K. regarding the use of organotin based antifouling paints.