Ecosystem health assessment of the plant-dominated Baiyangdian Lake based on eco-exergy

Thermodynamic indicators, including eco-exergy and structural eco-exergy, have been widely applied to lake ecosystem health assessment in recent decades. In this paper, the index system, including phytoplankton biomass, microzooplankton biomass, trophic state index (TSI), eco-exergy, structural eco-exergy and ecological buffer capacity to total phosphorus for phytoplankton, were applied to assess the health states of fourteen typical water areas in the plant-dominated Baiyangdian Lake. Different types of organisms, including zooplankton, benthonic animals and macrophytes with various denotative meanings, were differentiated to some extent and the latest weighting factors, were used in the eco-exergy and structural eco-exergy calculations for a better characterization of health state. The results showed that only the water area in site 4, with relatively high eco-exergy, structural eco-exergy, ecological buffer capacity and low phytoplankton biomass, microzooplankton biomass and TSI, is in healthy state. Health states of the other water areas were all deteriorated at various degrees due to the human disturbances. The health states of the northeast and southeast water areas were better than those of the northern, central and southern water areas with aquaculture and villages and western water areas close to the Fu River. For the plant-dominated Baiyangdian Lake, combining eco-exergy with structural eco-exergy could better characterize the health state of ecosystem with macrophytes hypermorphosis and meanwhile based on the distinguishing of various organism components, specifically benthonic animals, to some extent for eco-exergy and structural eco-exergy calculations, spatial variations of health state obtained better description, which indicated eco-exergy and structural eco-exergy were the robust indicators for ecosystem health assessment of the plant-dominated lake.