Species richness and composition of the epifauna on Pinna bicolor, a large benthic bivalve mollusc, were examined near a lead smelter. P. bicolor were collected from areas of high sediment metal concentrations near the smelter and from other nearby areas with lower sediment metal concentrations. Two independent gradients were discerned in the species composition of the epifauna. The first gradient extended from the contaminated to the less contaminated areas, while the second gradient passed from shallower sites towards deeper sites. Despite the apparent relationship between contaminant sediment metal concentrations and faunal change, the first faunal gradient correlated with numerous sediment parameters (Ca, Ni, TOC, clay and ‘undissolved’) as well as the contaminant metals Cu, Mn, Pb and Zn. Thus, although the mechanisms are not clear, the faunal gradient may result from the effects of both contaminant metals and solids resuspended from the sediments. Thirteen of the 55 taxa of epifauna are associated with the faunal gradient between metal-contaminated and uncontaminated areas. Compared with their overall distribution, more bryozoan and sponge species than mollusc species correlate to this change, suggesting different sensitivities to the causal factors.