Toxicity and metabolism of copper pyrithione and its degradation product, 2,2′-dipyridyldisulfide in a marine polychaete

We conducted acute toxicity tests and sediment toxicity tests for copper pyrithione (CuPT) and a metal pyrithione degradation product, 2,2′-dipyridyldisulfide [(PS)2], using a marine polychaete Perinereis nuntia. The acute toxicity tests yielded 14-d LC50 concentrations for CuPT and (PS)2 of 0.06 mg L−1 and 7.9 mg L−1, respectively. Sediment toxicity tests resulted in 14-d LC50 concentrations for CuPT and (PS)2 of 1.1 mg kg−1 dry wt. and 14 mg kg−1 dry wt., respectively. In addition to mortality, sediment avoidance behavior and decreases in animal growth rate were observed; growth rate was the most susceptible endpoint in the sediment toxicity tests of both toxicants. Thus, we propose lowest observed effect concentrations of 0.3 mg kg−1 dry wt. and 0.2 mg kg−1 dry wt. for CuPT and (PS)2, respectively, and no observed effect concentrations of 0.1 mg kg−1 dry wt. for both CuPT and (PS)2. The difference in the toxicity values between CuPT and (PS)2 observed in the acute toxicity test was greater than the difference in these values in the sediment toxicity test, and we attribute this to (PS)2 being more hydrophilic than CuPT. In addition to the toxicity tests, we analyzed conjugation activity of several polychaete enzymes to the toxicants and marked activity of palmitoyl coenzyme-A:biocides acyltransferase and UDP-glucuronosyl transferase was observed.