Characteristics of Water Quality in the Recreational Ponds Covered with Algal Blooms in Osaka City.

概要

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Changes of water quality indicators caused by algal blooms in the recreational ponds in Osaka city were investigated. The results of investigations showed that all ponds were eutrophic and concentrations of chlorophyll-a closely related to that of total phosphorus (T-P) . It was suggested that T-P concentration controlled the density of algal blooms in all ponds. Appearance of algal blooms in 1997 delayed from that in 1996, probably because the rainy season began later and continued longer than 1996.<BR>In a pond where dense algal blooms was observed, dissolved oxygen in the surface water was supersaturated in the daytime, but whole water became anaerobic at night, because of the oxygen consumption by algal respiration. It was suggested that oxygen consumption by dense populations of algae causes bad influence on the ecosystem when temperature of pond water kept over 24°C all night.
環境技術学会の論文