Environmental quality status of the Portuguese coast regarding TBT pollution - Recommendations for considering imposex monitoring within the scope of the Marine Strategy Framework Directive

The recent years witnessed an increasing society consciousness on subjects concerning aquatic pollution. In Europe, several legislative pieces have been implemented to improve and protect the aquatic environment like the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD), as well as the specific strategies adopted by Regional Sea Conventions. Here we assess the quality status of the Portuguese coastal and transitional waters regarding TBT pollution, using imposex as biomarker, aiming its integration as an indicator of environmental quality assessment under the MSFD. Imposex data available for two gastropod bioindicators, Nucella lapillus and Nassarius reticulatus, are used for that purpose, applying the classification previously proposed for the WFD (described elsewhere) and the OSPAR Assessment Criteria. A good quality status was achieved in most of the stations located in coastal waters while a worse ecological status was perceived in stations located in transitional water bodies, due to the proximity of TBT contamination sources. The comparison between the WFD classification proposal and the OSPAR Assessment Criteria shows a similar temporal trend in the study area however, slight differences can be perceived and are discussed. Both the WFD and OSPAR should be considered on the MSFD implementation but they differ in their objectives regarding TBT pollution. Therefore, this work allows the integration of imposex monitoring within the MSFD and recommends the use of the WFD assessment criteria also in this directive.