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Entropy 2013, 15(6), 2319-2339; doi:10.3390/e15062319
Article

Characterization of Ecological Exergy Based on Benthic Macroinvertebrates in Lotic Ecosystems

1
, 1
, 2
 and 1,3,4,*
1 Department of Biology, Kyung Hee University, Seoul 130-701, Korea 2 Alterra, Green World Research, Department of Freshwater Ecosystems, P.O. Box 47, 6700 AA Wageningen, The Netherlands 3 Research Institute for Basic Science, Kyung Hee University, Seoul 130-701, Korea 4 Department of Life and Nanopharmaceutical Sciences, Kyung Hee University, Seoul 130-701, Korea
* Author to whom correspondence should be addressed.
Received: 21 March 2013 / Revised: 30 May 2013 / Accepted: 1 June 2013 / Published: 7 June 2013
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Abstract

The evaluation of ecosystem health is a fundamental process for conducting effective ecosystem management. Ecological exergy is used primarily to summarize the complex dynamics of lotic ecosystems. In this study, we characterized the functional aspects of lotic ecosystems based on the exergy and specific exergy from headwaters to downstream regions in the river’s dimensions (i.e., river width and depth) and in parallel with the nutrient gradient. Data were extracted from the Ecologische Karakterisering van Oppervlaktewateren in Overijssel (EKOO) database, consisting of 249 lotic study sites (including springs, upper, middle and lower courses) and 690 species. Exergy values were calculated based on trophic groups (carnivores, detritivores, detriti-herbivores, herbivores and omnivores) of benthic macroinvertebrate communities. A Self-Organizing Map (SOM) was applied to characterize the different benthic macroinvertebrate communities in the lotic ecosystem, and the Random Forest model was used to predict the exergy and specific exergy based on environmental variables. The SOM classified the sampling sites into four clusters representing differences in the longitudinal distribution along the river, as well as along nutrient gradients. Exergy tended to increase with stream size, and specific exergy was lowest at sites with a high nutrient load. The Random Forest model results indicated that river width was the most important predictor of exergy followed by dissolved oxygen, ammonium and river depth. Orthophosphate was the most significant predictor for estimating specific exergy followed by nitrate and total phosphate. Exergy and specific exergy exhibited different responses to various environmental conditions. This result suggests that the combination of exergy and specific exergy, as complementary indicators, can be used reliably to evaluate the health condition of a lotic ecosystem.
Keywords: ecosystem health assessment; exergy; self-organizing map; random forest; stream size; nutrients ecosystem health assessment; exergy; self-organizing map; random forest; stream size; nutrients
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Bae, M.-J.; Li, F.; Verdonschot, P.F.; Park, Y.-S. Characterization of Ecological Exergy Based on Benthic Macroinvertebrates in Lotic Ecosystems. Entropy 2013, 15, 2319-2339.

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