TROPHIC TRANSFER OF A SEDIMENT-ASSOCIATED ORGANOPHOSPHATE PESTICIDE FROM MEIOBENTHOS TO BOTTOM FEEDING FISH

Experiments were conducted to examine the dynamics of a sediment-assoc iated pesticide azinphosmethyl (APM) using a sublethal benthic based t rophic transfer model (meiobenthic copepods to juvenile fish). Two pre dominant pathways for contaminant transfer during feeding, prey ingest ion and sediment ingestion, were examined to determine their relative contributions to APM transfer and subsequent effects on fish brain ACh E inhibition. Experiments were conducted in 1993 and in 1994. Field co llected benthic copepods were exposed to 14-C labeled APM, a potent ac etylcholinesterase (AChE) inhibitor, in sediments for 96 h. APM burden s were measured in the copepods, and these contaminated copepods were fed to the juvenile fish predator Leiostomus xanthurus in uncomtaminat ed sediments. After gut clearance, fish were examined for brain AChE a ctivity and APM residues in the liver, heart, gut, muscle, gill, and r emains. Similar experiments were conducted in which meals of uncontami nated copepods were fed to spot in APM contaminated sediments, to dete rmine the relative contribution of contaminated sediments to APM trans fer. Copepods exposed to APM at a mean sediment concentration of 1223 ng/ g dry weight accumulated APM at the level of 2.5 mu g/g dry tissue . Brain AChE activity was significantly depressed (23%) in the 1993 fi sh fed one meal of contaminated copepods, however there was no signifi cant decline in AChE activity in the fish tested during 1994. APM accu mulation in fish feeding in contaminated sediments was generally great er than in fish feeding on contaminated prey. Significant accumulation was found in bodily remains, gills, gut, and muscle in fish that fed in contaminated sediments. No significant APM accumulation was found i n fish fed the contaminated copepods.