Abstract

  Torsviken is a small bay close to the city of Gothenburg, Sweden. Part of the bay has been used for disposal of dredged harbor sediment since the 1970s. Other potential sources of contamination are a deposit site and treatment facility for hazardous waste. The area has been classified as ecologically sensitive and is of great ornithological interest. Birds are abundant and several rare species have been observed. In this study, pollution was assessed by analyzing concentrations of polycyclic aromatic hydrocarbons, polychlorinated biphenyls and heavy metals and by measuring toxicity of sediment samples to Daphnia magna, Nitocra spinipes, Chironomus riparius and Hyalella azteca. The combined exposure to several contaminants and solar light can enhance toxic effects, and since Torsviken is a shallow bay (maximum depth 2 in), organisms surviving the bioassays were exposed to simulated ultraviolet (DV) light of site-relevant intensity for 2 h to detect potential UV-enhanced toxicity. Torsviken is subdivided into three basins and the concentrations of most investigated contaminants, especially polycyclic aromatic hydrocarbons and polychlorinated biphenyls, were 2-5 times higher in the inner (western) area compared to the outer (eastern) areas. Acute sediment toxicity was found primarily in Nitocra, but there was no clear difference between the two areas of Torsviken. Ultraviolet-induced toxicity also occurred especially in Nitocra but only in the western area where organic pollutants are elevated in concentration. In the same sediment sampling site that caused the highest increase in mortality in Nitocra, there was also a significant response by Daphnia after UV treatment. Correlations between the toxicity enhancement (measured as % of surviving Nitocra from the bioassays that died after subsequent exposure to DV light) and chemical concentrations were found for several of the pollutants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls, mercury and lead, indicating that some of these substances were bioavailable and induced toxicity with DV irradiation. The results support the need to develop special sediment quality guidelines for shallow sites, where the phototoxic properties of pollutants should be accounted for. © 2000 Elsevier Science Ltd and AEHMS. All rights reserved.

Keywords: Photoinduced toxicity; Benthic invertebrates; Dredge disposal