Experimental and field studies of effects of dichlorvos exposure on acetylcholinesterase activity in the gills of the mussel, Mytilus edulis L

Dichlorvos (DDVP) is an organophosphate medicine, used to treat ectoparasitic sea lice infestations of farmed salmon. Effects of this chemical on a non-target organism were investigated. Experimental exposure of mussels ( Mytilus edulis L.) to dichlorvos (DDVP) resulted in changes in gill acetylcholinesterase (AChE) activity with a hormetic increase at lower concentrations, and 50% inhibition at 3.6 μg l −1 after 24 h exposure. Repeat exposures resulted in cumulative inhibition. Twenty-four hour exposure to DDVP impaired the ability to close shells (EC 50 of 1700 μg l −1) and caused mortalities at high concentrations (LC 50 of 8200 μg l −1). AChE levels in mussels collected from sea lochs were indicative of DDVP inhibition related to the quantities of DDVP used. The use of AChE as a sublethal indicator of DDVP usage in the field is discussed.