Combining sediment quality criteria and sediment bioassays with photoactivation for assessing sediment quality along the Swedish West Coast

Abstract

Sediments from 48 sites along the Swedish West Coast were sampled for determination of priority pollutants (metals, polycyclic aromatic hydrocarbons and chlorinated hydrocarbons). Toxicity to two crustaceans ( Daphnia magna and Nitocra spinipes) were also determined within 2 weeks and after 12 months of storage at 4°C. Since, according to earlier studies, polycyclic aromatic hydrocarbons may exhibit photoinduced toxicity, all test vessels (including exposed test organisms) were subjected to ultraviolet irradiation after immobility/lethality was recorded. Thereafter, the vessels were recorded again for immobility/lethality and the data were compared with phototoxicity data of analyzed substances, in order to estimate the bioavailability of phototoxic hydrocarbons in these sediments. Immobility of Daphnia exposed to 16% sediment (wet weight) ranged from 0 to 80% both before and after photo treatment. Nitocra 96-h LC 50s (% wet weight of sediment) ranged from 1.9 to >32% before, and from 1.0 to >32% after ultraviolet treatment. The sensitivity to the different sediments as well as the photo-activation was species dependent and differed between fresh and stored sediments. Photoactivation in Daphnia was generally low but significant in an analysis of variance test. Compared with two different sediment quality guidelines it was found that some sediments would be classified as moderately or strongly polluted. These values did not always coincide with toxicity to any of the two species. The guidelines were thus of no value in predicting sediment toxicity. Correlations between toxicity and chemicals measured in the sediments were also highly variable and inconsistent. Photo-induced toxicity in Nitocra did not correlate (p<0.01) to any of the analyzed substances, and a clear pattern between ultraviolet-induced toxicity to Daphnia and polycyclic aromatic hydrocarbon concentrations in the sediments was not obtained, possibly because most sediments contained relatively low amounts of bioavailable material. However, the sediment sample with the highest concentrations of photoactive PAHS such as pyrene did demonstrate the greatest increase in toxicity (39%) following ultraviolet irradiation.