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Imposex is is a well-documented deleterious effect caused by tributyltin (TBT) in females of hundreds of Caenogastropoda species and it is a well-established way of predicting BTs occurrence in marine systems. This study presents the very first information on the presence and distribution of imposex in Stramonita brasiliensis (Claremont and Reid, 2011) in the Brazilian Legal Amazon, within a Ramsar site, during a 6-year appraisal after the TBT global ban in 2008 (2012–2017). Imposex was evidenced in six out of the seven sampling sites, with 39.7% of the total affected females, most of them showing VDSI <1. The temporal appraisal allowed the identification of the introduction of new sources of TBT in some sites, as well as populational recovery in other sampling points. In addition, the dilution effect present in São Marcos Bay was also likely to play an important role in the imposex distribution. [Display omitted] • The first appraisal of imposex in Stramonita brasiliensis from Brazil's Legal Amazon. • Imposex was ubiquitous in most of the sampling sites. • Dilution effect may have influenced imposex distribution. • Levels of imposex represent concerns in the region. [ABSTRACT FROM AUTHOR]

This study evaluates tributyltin (TBT) pollution on a spatial-temporal scale using imposex occurrence in Stramonita brasiliensis in a coastal region of the southeast Brazil, between 2007 and 2018, and tests the viability of this species as a tool to evaluate the environmental quality through the Ecological Quality Ratio (EQR). Imposex indexes varied during the monitoring period, with I% varying from 0% to 100%, Vas Deference Sequence Index (VDSI) from 0 to 4.11 and Index of Relative Penis Length (RPLI) from 0 to 51. The EQR indexes indicated high levels of contamination by TBT in the first years of the study (2007 to 2011), followed by an improvement in the ecological status in the last two years (2017 and 2018). This study confirmed the viability of the use of EQR to evaluate the environmental status in a tropical region by means of an endemic species. Our results indicate that the Espírito Santo coastline is still contaminated with TBT, especially in areas close to ports and fishing activity. • Regions with intense vessel traffic still show high imposex levels in Brazil. • Stramonita brasiliensis is a viable species for the use of Ecological Quality Ratio. • EQR and imposex indexes indicate a decrease in the effects caused by TBT. [ABSTRACT FROM AUTHOR]