Trophic-dynamic modeling in a shallow eutrophic river ecosystem

In this study, eutrophication control in shallow streams is analyzed from the viewpoint of a trophic chain. A trophic-dynamic model for aquatic ecosystems is established to resolve the interactions between all trophic species. The simulated taxa are algae, aquatic insects and fish, and the major relationship among them is predation. The trophic-dynamic model is built on the mass balance of each trophic level in terms of growth, respiration, and predation. The results of simulation show that algae are limited by nutrients in one-link and three-link systems and by predators in a two-link food chain. These conclusion is in good agreement with other theoretical predictions. As a result, bio-management of predators to regulate excessive algae only works in two-link and four-link food chains. The impact of the trophic cascade on dissolved oxygen (DO) level also is simulated. DO variation is greatly affected by the population of algae. (C) 1998 Elsevier Science B.V.