魚の水質, 物質環境に及ぼす影響に関する実験的研究

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The influences of fish (goldfish) on water quality and nutrients cycle (carbon, nitrogen, phosphorus) were investigated during 39 days in the summer of 1993, using six outdoor experimental ponds (36 m3) with the same water residence times and nutrient inputs. Blue-green algae dominated the ponds with fish. Compared with ponds without fish, the ponds with high densities of fish had standing stocks of zooplankton and macrozoobenthos nearly one order of magnitude lower, about twice the concentrations of chlorophyll a and twice the rate of primary production. Settling rates of particulate substances in the high density ponds were nearly half those observed in ponds with no fish. The processes of sedimentation and exchange with air played important roles in the nutrient budgets as well as the in- and outflows and the changes in nutrient standing stocks. The high concentrations of chlorophyll a in the fish ponds were attributed in part to the lower zooplankton grazing pressure and in part to the higher nutrient concentrations due to lower settling rates and rapid nutrient recycling between biomass and dissolved components.
社団法人　日本水環境学会の論文
1995-11-10