A decadal study of biometric and imposex indices in two gastropods

We have monitored tributyltin (TBT) pollution in Galicia (NW Spain) for more than a decade by means of assessing gastropod imposex in populations of Nucella lapillus (N ≥ 34) and Tritia reticulata (N ≥ 18) at regular intervals. Several thousand specimens were processed to obtain their shell height (SH), penis length (PL) and vas deferens sequence (VDS); imposex indices (including the VDS index, VDSI) were subsequently calculated. The regional mean SH of both females and males has not changed significantly in either species throughout the study. This also applies to the mean male PL in N. lapillus, but male T. reticulata penises surprisingly enlarged. On the contrary, the regional mean female PL (MFPL) and all imposex indices significantly decreased in both snails. Results confirm previous conclusions based on the chemical analyses of tissues and partial imposex observations. In addition, the close correlations between MFPL and VDSI show some potential applications to TBT biomonitoring.

Shell shape as indicator of pollution in marine gastropods affected by imposex

Tributyltin (TBT) and other pollutants are present in Patagonia, and are associated with maritime traffic and human activities. Cause–effect relationship between TBT and imposex development in females of marine gastropods is well documented. We tested whether the imposex incidence associated with TBT pollution is related to detectable shell-shape variations in the edible marine snail (Buccinanops globulosus). We compared shell shape of B. globulosus in six contiguous sites on a gradient of imposex and maritime traffic, by using geometric morphometric analysis. Our results indicated that the registered differences in shell shape are associated to imposex incidence in the harbour zone where previous works have detected TBT pollution. Gastropods from areas of high maritime traffic presented a rounded shell with a shorter spire, and a smaller relative size of the shell aperture, whereas the opposite shape (fusiform shape, elongated-spired shell and bigger relative size of the shell aperture) occurred in gastropod shells from areas of low maritime traffic. Shell variation registered here could be useful to detect TBT pollution in populations of B. globulosus and another neogastropod species.

Organotin pollution at Arraial do Cabo, Rio de Janeiro State, Brazil: increasing levels after the TBT ban

Imposex, an endocrine disruption phenomenon, is a biomarker of tributyltin (TBT) exposure in marine gastropod populations. The occurrence and intensity of the syndrome in populations of the neogastropod Stramonita haemastoma were ascertained at nine sampling stations in October 2008 at Arraial do Cabo, a very important tourist resort in Rio de Janeiro state (Brazil) and part of the Marine Extractive Reserve of Arraial do Cabo. The results obtained made it possible to evaluate the changes which had occurred since the last biomonitoring campaign, undertaken in 2001, at these same stations. Despite the ban on the use of TBT imposed by the Brazilian Navy in 2003, the controls on the use of this agent in Brazil resulting from the establishment of NORMAM 23 by the Navy in 2007 and the complete ban of organotin compounds in antifouling paint formulae by the IMO on a global scale in 2008, imposex was still detected. Instead of the expected reduction, an increase was observed in the areas affected by imposex. Furthermore, populations in the areas seriously affected by imposex in 2001 were absent in the 2008 sampling campaign. These results suggest an increase in TBT pollution in the study area, indicating the inefficacy of legislative measures.

Using Nucella lapillus (L.) as a bioindicator of tributyltin (TBT) pollution in eastern Canada: a historical perspective

Dogwhelks (Nucella lapillus), a universal bioindicator of tributyltin (TBT) pollution, were used to determine butyltin distribution in three Atlantic Canada harbours previously surveyed between 1995 and 2006. N. lapillus were analysed for the presence of TBT and its degradative products while imposex incidence and severity were compared with previous surveys to assess the efficacy of the Canadian regulations on TBT. Imposex was observed at two harbours that had dogwhelks, but not at surrounding reference sites. When comparing results with previous surveys in the same geographic area, there appears to be some improvement of affected N. lapillus populations, suggesting that the 1989 Canadian regulations have been effective in decreasing imposex severity for most sites as measured by the vas deferens sequence index (VDSI), but not the occurrence of imposex. The highest butyltin tissue concentration (63.75 ng Sn g−1, dry wt) was detected in imposex-affected females from Red Head in Saint John Harbour (New Brunswick), which is adjacent to an area frequented by large oil tankers that, under the 1989 regulations, are legally allowed to use TBT antifouling paint. This study is the first to illustrate a significant correlation between TBT levels and imposex on a spatial scale in Atlantic Canada.