Euro-limpacs Deliverables

ABSTRACT - DELIVERABLE 65

Report describing the transfer of pollutants through the food web in lacustrine systems and modelling the influence of temperature - Interim report

This deliverable comprises two manuscripts, one published in Environmental Science and Technology (Catalan et al) and one published in Environmental Toxicology and Chemistry (Vives et al.).

Catalan et al.
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 (d13C and d15N). 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.

Vives et al.
We investigated the concentration of polycyclic aromatic hydrocarbons (PAHs) in the food web organisms included in the diet of brown trout from a remote mountain lake. The preferential habitat and trophic level of the component species have 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 that point to different capacities for uptake and metabolic degradation. Brown trout show an elevated capacity for metabolic degradation because they have lower PAH concentrations than food and they are enriched strongly in lower molecular weight compounds. The PAH levels in trout highly depend on organisms living in the littoral areas. Fish exposure to PAH, therefore, may vary from lake to lake according to the relative contribution of littoral organisms to their diet.

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