The toxicity of the anti-sea lice pesticide AlphaMax® to the polychaete worm Nereis virens

Polychaete worms have been suggested as a commercially valuable, extractive species to use in Integrated Multi-Trophic Aquaculture (IMTA) to remove organic materials (fish feces) released from salmon aquaculture. However, pesticides used to control parasitic sea lice infestations on salmon are also released from fish farms and non-target organisms may be exposed to these chemicals. In laboratory studies, the polychaete Nereis virens was exposed via water and sediment to the anti-sea lice pesticide AlphaMax® (active ingredient, deltamethrin). Worms exposed in water for 48h exhibited mortality and impaired mobility in up to 100% of organisms, only at greater than 2-times the prescribed aquaculture treatment concentration. This would suggest negligible risk to worms from acute environmental exposure to AlphaMax® in water. Low mortality (≤20%) occurred in 7- or 30-d tests with sand or sediment spiked at relatively high concentrations (up to 0.72μgdeltamethrin/g), but sublethal effects related to burrowing behavior and worm condition were observed at concentrations as low as 11μg/g. Therefore, the long-term survival, growth, and ability of worms to perform their ecosystem function of processing organic waste could be affected, depending on the extent of deltamethrin accumulation in sediment. Environmental concentrations of deltamethrin in sediment near aquaculture sites are not presently known and are needed to assess risk to non-target organisms.