Experimental study on the ecological efficiencies of plankton communities

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The present study was conducted to determine the ecological efficiencies of conversion through food chain structure of planktonic organisms in aquatic environments. Most of the microorganisms used in this study were isolated from lake environment and successfully mainteined in culture conditions. This study also revealed effects of ultraviolet radiation on the dissolved organic matter which affect bacterial metabolism in lake ecosystems.1.A method was established for determination of dissolved organic carbon (DOC) in lake water. Vertical profile of DOC in several lakes was elucidated and dicussed with underwater attenuation of ultraviolet radiation.2.Seasonal change of protozoan plankton in a lake was studied and their grazing rate of bacteria, as well as their predatory loss by zooplankton were estimated.3.Several strains of bacteria, protozoa, rotifers, and crustacean plankters were isolated and cultivated successfully.4.This study demonstrated that the ecological efficiency is 40-48% from phytoplankton excreted organic matter to bacterial cellular organic matter in lake water.5.Nitrogen in aquatic anvironment and the related bacterial metabolisms were considered and summarized.