Description of aquatic ecosystem's development by eco-exergy and exergy destruction

Abstract

The respiration rate (energy used for maintenance as g detritus equivalents/m 2 y, and the stored eco-exergy as g detritus equivalents/m 2 have been found for 26 different aquatic ecosystems. It was shown that the respiration rate has a maximum value for a given type of aquatic ecosystem: 30 g detritus equivalents/m 2 y for coral reef, about 12 fertile estuaries or coastal lagoons and about 5 g detritus equivalents/m 2 y for fertile ponds and lakes (according to Odum [Odum, E.P., 1969. Fundamentals of Ecology, third ed. W.B. Saunders Company, Philadelphia, London and Toronto, 575 pp.]). As ecosystem in addition to the growth of biomass also can develop by increasing the ecological network and the information content of the ecosystem, it is possible for ecosystems to move further away from thermodynamic equilibrium – increase the content of eco-exergy, even the maximum respiration rate has been achieved. The result is a Michaelis–Menten like graph for eco-exergy, used for respiration versus eco-exergy storage in the ecosystem. The same shape has been found for the graph, when observations from terrestrial ecosystems are applied. The results may be considered a support of the description of ecosystem development by the three growth form and the so-called tentative Ecological Law of Thermodynamics (see Jørgensen, S.E., Patten, B.C., Straskraba, M., 2000. Ecosystem emerging: 4. Growth Ecol. Modell. 126, 249–284; Jørgensen, S.E., 2002. Integration of Ecosystem Theories: A Pattern, third ed. Kluwer Academic Publisher, Dordrecht, 428 pp. (first edition, 1992; second edition, 1997); Jørgensen, S.E., Svirezhev, Y.M., 2004. Towards a Thermodynamic Theory for Ecological Systems. Elsevier, 366 pp.).