Aquatic ecosystem assessment using exergy

The recent work is dedicated to the study of behaviour of exergy and structural exergy in physical models of aquatic ecosystems-mesocosms and microcosms and in Lake Baikal. The results of field experiments with mesocosms on Lake Baikal, containing natural plankton assemblage, and laboratory experiments with microcosms containing Daphnia magna and Chlorella vulgaris demonstrated decrease of the structural exergy of the communities after the addition of allochtonous compounds-peptone, diesel oil, o-biphenyl, CdCl2 to mesocosms assemblage of Lake Baikal and after the addition of toxicants to microcosms. Structural exergy decreased in microcosm experiments proportionally to a value of the added toxicant (phenol, COCl2 and CUSO4) concentration, while other parameters (biomasses of components, total biomass of community, total exergy) fluctuated. Comparison of exergy content for benthos in pure and affected by the discharges of Baikalsk Pulp & Paper Combine also showed significant decrease of structural exergy in polluted area. It points to the possibility of using structural exergy as reflecting ecosystem health. (C) 2004 Elsevier Ltd. All rights reserved.