The toxicity of emamectin benzoate, an aquaculture pesticide, to planktonic marine copepods.

The acute and sublethal toxicity of emamectin benzoate to non-target planktonic marine copepods was determined. Emamectin benzoate is the active ingredient in Slice((R)), an in-feed pesticide formulation used to control parasitic sea lice in salmon aquaculture. The comparative sensitivity of three life stages (nauplii, copepodites, adults) of four common marine copepods (Acartia clausi, Pseudocalanus elongatus, Temora longicornis and Oithona similis) was assessed in 48-h exposures followed by a recovery period in toxicant-free sea water. The calanoid copepods responded similarly to emamectin benzoate and EC50 values were significantly lower than those for the cyclopoid O. similis. Nauplii and copepodite 48-h EC50 values were generally lower than those for the adults. EC50 values ranged from 0.12 mug/l (P. elongatus nauplii) to 232 mug/l (O. similis adults). The primary toxic effect, immobilisation, was generally irreversible. A 7-day sublethal test with adult A. clausi females measured a significant reduction in egg production at higher concentrations. The no-observed-effect-concentration (NOEC) and lowest-observed-effect-concentration (LOEC) values were 0.05 and 0.158 mug/l, respectively. Concentrations causing toxicity to planktonic copepods were considerably higher than Predicted Environmental Concentrations (PEC) in the vicinity of treated salmon farms and suggest that the use of emamectin benzoate for lice control is unlikely to adversely affect plank-tonic copepods. (C) 2003 Elsevier Science B.V. All rights reserved.