Phototoxic evaluation of marine sediments collected from a PAH-contaminated site

The phototoxicity potential of PAH-contaminated field sediment was evaluate d and compared to standard sediment toxicity test results, Marine sediments were collected from 30 sites along a presumed PAH sediment pollution gradi ent in Elliot Bay, WA. Standard 10-day acute and 28-day pra chronic sedimen t toxicity tests were conducted with the infaunal amphipods Rhepoxyninus ab ronius and Leptocheirus plumulosus using mortality and the ability to rebur y as endpoints. The survivors of these tests were then subjected to 1-h exp osures to UV radiation with mortality and reburial again determined. The mo st highly toxic sediments identified in these experiments were evaluated fu rther for toxicity and phototoxicity by serially diluting them with unconta minated sediment and repeating the toxicity tests. Standard 10-day toxicity test results indicated that over 70% of the sites sampled in Elliot Bay ex hibited measurable toxicity with nine sites being highly toxic to both spec ies of amphipods. Results of standard 28-day chronic sediment toxicity test s were similar. In contrast, almost all of the sites were found to be highl y phototoxic. Results indicated that exposure to UV increased toxicity five - to eightfold. This suggests that standard toxicity tests underestimate th e potential ecological risk of PAH-contaminated sediments in animals expose d to sunlight. However, only when PAH contamination was between 0.05 and 1. 0 toxic units would conducting a phototoxicity evaluation add information t o that gained from conducting a standard sediment toxicity test alone.