The roles of food and water in the bioaccumulation of organochlorine compounds in high mountain lake fish.

An integrated study encompassing the distribution of organochlorine compounds (OC) in water, food web (chironomids, terrestrial insects, cladocerans, mollusks, and cyanobacteria), and fish (brown trout) from a high mountain lake (Redon, Pyrenees) is reported. OC distributions in these compartments have been determined to assess theirtransport routes into fish. Food diets have been estimated by analysis of fish stomach content and food web stable isotopes (delta13C and delta15N). OCs with octanol--water partition coefficient (Kow) higher than 10(6) showed lower concentrations in food than expected from theoretical octanol--water partition, indicating thatthe distribution of these compounds does not reach equilibrium within the life span of the food web organisms (ca. 1 year). On the other hand, the degree of biomagnification in fish increased with Kow, except in the case of the largest compound analyzed (seven chlorine substituents, PCB #180). OC exchange at fish gill and gut has been evaluated using a fugacity model based on the water, food, and fish concentrations. All compounds exhibited a net gill loss and a net gut uptake. A pseudostationary state was only achieved for compounds with log(Kow) < 6. Calculation of fish average residence times for the compounds in apparent steady state gave values of days to a few weeks for HCHs, 1 year for HCB and 4,4'-DDE, and 2-3 years for 4,4'-DDT and PCB#28 and PCB#52. Residence times longer than one decade were found for the more chlorinated PCB.