Evolution of tributyltin (TBT) pollution in the Ria de Aveiro (NW Portugal): 25 years of biomonitoring and current status

• Main Author: Pereira, Daniel Alexandre Coelho Lopes
• Publication Date: 2023
• Format: Master thesis
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10773/41122
• topic: Tributyltin; TBT; Imposex; Biomarker; Bioindicator; Peringia ulvae; Tritia reticulata; Sediments; Ria de Aveiro

Peringia ulvae and Tritia reticulata imposex levels were assessed jointly to monitor tributyltin pollution in the entire area of the Ria de Aveiro coastal lagoon (NW Portugal) in 2023 and then compare the current levels of this type of pollution with historical data available since 1998, allowing the analysis of its temporal evolution in the last 25 years. Male and female mean shell heights (SH♂, SH♀, respectively), mean male penis length (MPL), mean female penis length (FPL), relative penis length index (RPLI), vas deferens sequence index (VDSI) and imposex incidence (%I) were determined in the current work for a total of 9 and 11 sampling sites for P. ulvae and T. reticulata, respectively. Statistical analysis between the data obtained here and the available in the literature was performed and results are described. Despite the different temporal evolution of imposex levels registered in the two bioindicators in the mentioned period (1998-2023), a considerable decline in imposex intensity was observed in both species: significant reductions in FPL and VDS levels were detected. Quantification of TBT and its metabolites in tissues and sediments as a complement to imposex assessment was planned. Samples were collected, sent for analysis and the results are awaited in order to verify the effective reduction in TBT concentrations in both matrices (gastropod tissue and surface sediment). In general, the expected overall decrease in TBT pollution is finally evident in Ria de Aveiro. The local shipyards seem to be the exception to this beautiful picture, since the gastropods sampled there continue to exhibit high levels of imposex, possibly due to historical contamination of the sediments (a fact that is awaited confirmation by chemical analysis).