The environmental fate and effects of anti-sea lice chemotherapeutants used in salmon aquaculture

The active ingredients from 5 chemotherapeutant formulations (Slice (R) [active ingredient [AI] emamectin benzoate), Salmosan (R) (AI azimethiphos), Alphamax (R) (AI deltamethrin), Excis (R) (AI cypermethrin), and Interox (R) Paramove 50 (AI hydrogen peroxide) that have been used or continue to be used to treat sea lice in-festations in salmon aquaculture were examined to generate data on their environmental partitioning and persistence in water-sediment microcosms, as well as their acute and subchronic toxicity to representative classes of marine organisms. Emamectin benzoate, cypermethrin and deltamethrin partitioned mainly to the sediment phase; azimethiphos and hydrogen peroxide remained mainly in the water phase. The persistence of chemicals in water was: CP > DM > AZ > HP (half-lives: 19.8, 17.9, 12.7 d, and 8.9 h, respectively). In sediments, the following trend in calculated half-lives was observed: CP > EB > DM (half-lives: 557, 230 and 45 d, respectively). Toxicity test results with a wide variety of marine organisms (macroalgae, echinoderms, bivalves, crustaceans and fish) showed no susceptibility trend for any species, or inherent toxicity trend for any chemical, although DM tended to be the most toxic and HP the least toxic to the majority of species. This information is useful for identifying risks; specifically, toxicological parameters calculated for several of the non-target marine organisms examined, indicate that recommended treatment concentrations could result in non-target organism toxicity following release in the immediate vicinity of aquaculture sites before significant dilution. This study provides valuable data on the environmental fate and associated risks of chemotherapeutant use to non-target marine organisms whose habitat coincides with salmon aquaculture sites.