Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 24

Report on modelling the distribution of organochlorine compounds in the food-web of a high mountain lake (Redo, Pyrenees)

This deliverable comprises a paper submitted to Environmental Toxicology and Chemistry and a paper published in Environmental Science and Technology.

1. Distribution of Polycyclic Aromatic Hydrocarbons in the Food Web of a High Mountain Lake (Pyrenees) Environmental Toxicology and Chemistry (Vives et al, in press) − Concentrations of polycyclic aromatic hydrocarbons (PAHs) in organisms included in the diet of brown trout from a remote mountain lake have been investigated. The preferential habitat and trophic level of the component species has been assessed from the signature of stable isotopes (δ13C and δ15N). Subsequently, the patterns of accumulation and transformation of these hydrocarbons in the food chain have been elucidated. Most of the organisms exhibit PAH distributions largely dominated by phenanthrene, which agrees with its predominance in atmospheric deposition, water and suspended particles. Total PAH levels are higher in the organisms from the littoral habitat than from the deep sediments or the pelagic water column. However, organisms from deep sediments exhibit higher proportions of higher molecular weight PAH than those in other lake areas. Distinct organisms exhibit specific features in their relative PAH composition suggesting different capacities for uptake and metabolic degradation. Brown trout shows an elevated capacity for metabolic degradation since they have lower PAH concentrations than found in their food and they are strongly enriched in lower molecular weight compounds. The PAH levels in trout are highly dependant on organisms living in the littoral areas. Fish exposure to PAH may therefore vary from lake to lake according to the relative contribution of littoral organisms to their diet.

2. The roles of food and water in the bioaccumulation of organochlorine compounds in high mountain lake fish. Environmental Science and Technology (Catalan et al, 2004) − An integrated study encompassing the distribution of organochlorine compounds (OC) in water, food web (chironomids, terrestrial insects, cladocerans, molluscs, 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 their transport routes into fish. Food diets have been estimated by analysis of fish stomach content and food web stable isotopes (δ13C and δ15N). OCs with octanol−water partition coefficient (Kow) higher than 106 showed lower concentrations in food than expected from theoretical octanol−water partition, indicating that the 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.

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