Exergy as a Tool for Ecosystem Health Assessment

Abstract

Abstract:Exergy is demonstrated to be a useful measurable parameter reflecting the state of the ecosystem, and allowing estimation of the severity of its anthropogenous damage. Exergy is shown to have advantages such as good theoretical basis in thermodynamics, close relation to information theory, rather high correlation with others ecosystem goal functions and relative ease of computation. Nowadays exergy is often used in ecological assessment. This paper reviews the application of exergy in ecology in the fields of ecological modeling and natural ecosystem monitoring. Special attention is paid to the use of exergy for aquatic ecosystem studies, particularly, assessment of the lake Baikal ecosystem state.

Characterization of Ecological Exergy Based on Benthic Macroinvertebrates in Lotic Ecosystems

“…According to Marques et al [28] and de Wit et al [75], eutrophication (i.e., a high nutrient load) results in higher exergy and lower specific exergy because the biomass bulk has a low weighting factor. Unlike exergy, specific exergy is not dependent on biomass alone and expresses the ability of the ecosystem to accept and utilize external fluxes of energy while simultaneously serving as an indicator of ecosystem development, reflecting the complexity and level of evolutionary development of species in an ecosystem [10]. Accordingly, specific exergy reflects diversity (i.e., a more complex ecosystem), and a higher specific exergy represents more highly developed organisms (i.e., higher β values that represent more information) [34].…”

“…In this context, various ecological indicators have been developed, including maximum power [1], diversity [2], biomass [3], emergy [4], exergy [5], ascendency [6] and entropy [7]. Of these indicators, exergy and specific exergy have been used most recently to assess ecosystem health in freshwater ecosystems [8][9][10][11][12].…”

“…The effectiveness of exergy and specific exergy have been demonstrated in aquatic ecosystems [10,17,24] to assess natural disturbance [25], water quality (e.g., acidification, copper, oil, pesticide contamination [26] and eutrophication [15,20,[27][28][29]), course type [16], the food webs of phytoplankton, zooplankton and fish [11] and the temporal changes of aquatic ecosystems from yearly [30] and long-term monitoring [31].…”

“…Benthic macroinvertebrates employ a wide variety of structural and functional responses to various factors (e.g., longitudinal changes in energy sources, food webs, nutrient input and pollution gradients) [33] because macroinvertebrate species possess diverse life cycles and generation times and represent several trophic levels and different feeding behaviors. Exergy has typically been used in benthic studies [10] because it has been a useful functional indicator for the evaluation of the impacts of human disturbance on benthic communities [34].…”

Advantages and limitations of exergy indicators to assess sustainability of bioenergy and biobased materials

“…The principle link between information theory and entropy has been criticised and remains debated (Corning and Kline, 1998a,b;Kline, 1999). The direct inclusion of EE in cumulative exergy analysis is not warranted because it departs from the pure thermodynamical measure, and the information measure of EE, based on essential DNA strands, is debated among biologists (Silow and Mokry, 2010). It remains challenging to interpret these valuations of living ecosystems and organisms in relation with standard thermodynamical measurements, even if both are expressed in the same units.…”