The geographic variation of silver in the black tuban snail, Tegula funebralis

The geographic variation of silver concentrations in the black turban snail, Tegula funebralis, along the California coastline indicates an anthropogenic influence. Relatively elevated levels of the metal occur in organisms adjacent to major wastewater outfalls compared to those from less populated areas. This parallels the distributions of silver concentrations in other molluscs within the area. It, therefore, substantiates the proposal that the pattern is primarily due to external factors, such as wastewater discharges, rather than intraspecific differences among the samples.