LAKE EUTROPHICATION MODEL BASED ON THE IMPACT OF THE ZOOPLANKTON COMMUNITY ON PHYTOPLANKTON SUCCESSION

概要

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To estimate the long-term effects of ecosystem-manipulating lake restoration methods such as biomanipulation, we need a numerical model which can predict the succession of plankton community with sufficient accuracy. An accurate numerical model can be prepared based on an accurate data background. In this sense, two series of mesocosm (outdoor open-air pond) experiments that mimicked conditions in shallow and eutrophic water ecosystem were performed to clarify the effects of the zooplankton community on phytoplankton succession quantitatively. The experiments were carried out in both summer and winter periods. The results revealed that three types of zooplankton, namely rotifers, copepods, and cladocerans, have different effects on phytoplankton succession. Rotifers did not graze blue-green algae. Cladocerans suppress the growth of phytoplankton even for some blue-green algae effectively by their predation. The results of these experiments suggest that the amount of crustaceans, i.e., copepods and cladocerans, should be increased for the successful enforcement of biomanipulation. A model based on these quantitative outcomes, and its prediction of a biomanipulation for an eutrophic shallow lake is also mentioned.