Interactions between eutrophication and contaminants. IV. Effects on sediment-dwelling organisms

Effects of organic enrichment, oxygen availability and the presence of contaminants on three sediment-dwelling invertebrates, the polychaete Nereis (Hediste) diversicolor, the bivalve Abra alba and the brittle star Amphiura filiformis, were assessed using growth, arm regeneration and biomarkers (metallothionein-like proteins, glutathione reductase, glutathione S-transferase) in a 93-day microcosm experiment. Moderate organic enrichment (approx. 40 g C m−2) increased growth and hypoxia (2.4–3.5 mg l−1) decreased growth in all three species. Effects of organic enrichment and low oxygen availability were additive for growth in N. diversicolor and A. filiformis, whereas there was an interaction between hypoxia and organic enrichment in their effects on growth in A. alba, reflecting a decreased ability of this species to utilize the available organic material under hypoxic conditions. Sediment-bound contaminants (4.8 mg kg−1 Cd and 1.32 mg kg−1 benzo[a]pyrene) had minor effects on growth and arm regeneration. Some biomarkers in N. diversicolor and A. filiformis reflected tissue contaminant concentrations, whereas there was no response of biomarkers in A. alba to any treatment or contaminant.