Temporal evolution of imposex and butyltin contamination in Gemophos viverratus from São Vicente (Cabo Verde) - a countercurrent trend on the world scenario.

Organotin (OT) based Antifouling Systems (AFS) were globally banned by the AFS Convention since 2008, but the Republic of Cabo Verde did not ratify this Convention, nor did it develop a national legislation to control OT-AFS. Gemophos viverratus imposex and butyltin tissue contamination were assessed around the São Vicente Island (Cabo Verde) in 2019 and compared with the data available from 2012. The vas deferens sequence index (VDSI), the relative penis length (RPL), the percentage of females with imposex (%I) and the percentage of sterilized females (%S) in 2019 ranged from 0 to 4.0, 0-84.4%, 0-100% and 0-5.1%, respectively, whilst TBT reached maximum values of ≈30 ng TBT-Sn g-1 dw in the whelk tissues. These values are very similar to those registered in 2012, which indicates that TBT pollution has not decreased over the years, in contrast to the declining trend observed worldwide.

Long-term monitoring of Nucella lapillus imposex in Ria de Aveiro (Portugal): When will a full recovery happen?

Nucella lapillus imposex has been monitored in Ria de Aveiro (Portugal) in order to understand the evolution of organotin (OT) pollution after the EU ban on OT-based antifouling systems (OT-AFS). A rapid decrease of imposex occurred, but a countercurrent tendency upsurged recently (2018-2019) with a slight increase of imposex at some sites, instead of a continuous decline towards a complete recovery. In 2018 the vas deferens sequence index ranged between 0.6 and 1.0 across stations and the percentage of females with imposex varied from 63 to 100%. In 2019 these parameters varied between 0.4 and 1.0 and 37-100%, while the concentration of butyltins (TBT, DBT, MBT) in the dogwhelk tissues were < 1 ng Sn g-1 dw. Although N. lapillus imposex levels are low they are indicative of OT pollution. The full recovery of N. lapillus imposex in the future is uncertain and a cause for concern.