Relationship between soft bottom macrofauna and polycyclic aromatic hydrocarbons (PAH) from smelter discharge in Norwegian fjords and coastal waters

Abstract

Data from monitoring surveys were used to test the responses of soft bottom fauna in Norwegian fjords and coastal waters affected by effluents from aluminium and manganese alloy smelters to effluent discharges. Generally, polycyclic aromatic hydrocarbons (PAHs) have been considered the main threat to the biota in the receiving waters. Data from a total of 57 quantitative stations, of which 30 were simultaneously sampled for sedimentary PAHs, were analysed. Canonical Correspondence Analysis (CCA) was used to evaluate species patterns in relation to sediment PAH concentrations and natural environmental variables such as depth, sediment characteristics and riverine input. The PAHs varied from very high concentrations (760 μg g-1 total PAH) at the most impacted sites to background levels in reference areas. Despite previous reports of little to no effects of the effluent discharges, the analyses identified significant species changes along PAH gradients, which could be associated with feeding modes. In particular, a number of carnivorous polychaetes had their distribution optima in the most affected areas. Based on species statistics calculated by CCA, response functions were fitted for the species on PAH and used to establish a generalised expression of trophic community structure in relation to PAH concentrations. At low PAH levels, the carnivores represented 15 to 20% of the specimens in the communities, but the proportion began to increase from about 10 μg g-1 and exceeded 50% at 100 μg g-1 total PAH. The faunal changes were most evident in shallow waters, possibly reflecting the effects of dissolved PAHs to which the species may react more directly than they do to sedimentary particle-associated PAHs.