CHOLINESTERASE ACTIVITY IN THE COMMON SCA LLOP AND THE QUEEN SCALLOP FROM THE BAY OF BREST (FRANCE) - A TOOL FOR THE DETECTION OF EFFECTS OF ORGANOPHOSPHOROUS AND CARBAMATE INSECTICIDES

Among the priority contaminants in the marine environment, insecticide s can cause serious ecotoxicological problems because of their strong persistance (organochlorines) or high toxicity (organophosphates [OP] and carbamates [C]). OPs and Cs are toxic to most organisms by their a bility to inactivate the cholinesterases (ChEs) and especially acetylc holinesterase (AChE), by taking the place of the natural substrate of the enzyme. In order to assess the potential effects of OPs and Cs on organisms in the Bay of Brest, levels of cholinesterases and especiall y levels of a sensitive isoform of acetylcholinesterase (AChE) of the common scallop (Pecten maximus) and the queen scallop (Aequipecten ope rcularis) were measured. The specific activity of AChE was determined for the adductor muscle of six to ten shellfish from three stations in the Bay, four times in 1994 (February, May, September and November). These results were compared to the activity measured in animals from t he Bay of Erquy (North Brittany). No variation in the levels of cholin esterase activity was observed between animals from the Bay of Brest a nd the control (Bay of Erquy) except a slight but significant depressi on in AChE activity in animals from l'Auberlac'h in February 1994. Thi s observation was not confirmed by samples from the same station in Ma y, September and December. In conclusion no evidence of important diff erence in cholinesterase activity in scallops between the Bay of Brest and the control site was observed, that would indicate the presence o f organophosphorous or carbamate in the Bay.