Shell alterations in the limpet Bostrycapulus odites: A bioindicator of harbour pollution and mine residuals

Molluscs are commonly used as bioindicators because of their abundance, low motility and the information their shells record. Although in harbour areas gastropod shell deposition would be affected at an endocrinal level, which may increase their vulnerability, studies on the shell of gastropods are scarce. Bostrycapulus odites is a limpet species that possess those characteristics as well as a wide distribution. Limpets were collected in 2001 and 2011, in a channel polluted by both, harbour activities and leaching mine residuals, to compare to a 2011 sample from an unpolluted area within San Antonio Bay. The sensitivity to pollution of this species and the possibility of it use to detect changes in the environmental situation of an area in a 10 years period were investigated. Soft body wet weight and shell morphological variables were measured while shells were also analyzed through scanning electron microscopy and energy dispersive spectroscopy for microstructure and elemental composition, respectively. Maximum likelihood ratio test showed shells from the polluted channel were thicker as well as the same shells presented microstructure malformations and changes in elemental composition (lower Ca and O levels, higher C and Fe levels). The present results indicate that B. odites can be considered a useful bioindicator species to study these kinds of pollution and the potential processes implicated in shell alterations are discussed.