MEPS 326:195-205 (2006)  -  doi:10.3354/meps326195

ABSTRACT: Single-species toxicity studies have been criticised for their inability to test for the effects of pollution on interacting species in field conditions. Pollution may have indirect effects on organisms due to changes in the abundance of competitors, predators or species that act as habitat. In marine hard substrate assemblages, pollution from the heavy metal copper causes predictable changes in the composition of sessile organisms in field conditions. The effects on mobile invertebrates associated with these habitats, however, are unknown. We tested the effects of copper on the entire assemblage of mobile and sessile invertebrates that colonise fouling plates, and demonstrated strong changes in the composition of mobile taxa due to the presence of copper. Manipulative field experiments partitioned the direct effects of water-borne copper from possible indirect effects mediated through changes to their habitat. Sessile assemblages were selectively gardened in the absence of copper to create habitats typical of polluted and unpolluted habitats, and then exposed to copper. The assemblages of mobile invertebrates varied between manipulated habitats, indicating that copper can indirectly affect mobile fauna via habitat change. The mechanisms of these effects were then examined with artificial habitats that mimicked the physical structure of polluted and unpolluted habitats. The composition of the mobile fauna was again dependent on habitat. In both experiments, there were interactions between the effect of habitat and the presence of copper, demonstrating the need for multi-species, field experiments to fully identify the effects of pollutants in natural conditions.

KEY WORDS: Ecotoxicology · Copper pollution · Mobile epifauna · Hard-substrate assemblages · Disturbance · Indirect effects