Study on the water quality conservation in ponds used abundant waterfowl and/or Common Cormorant

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It was reported that water quality in many ponds using abundant migratory waterfowl in winter period in Japan were deteriorated. However, there are few study on the effect of waterfowl and other waterbird to the water environment. In order to clarify the effect of waterfowl to water quality, we studied the relationship between water quality and waterfowl biomass at several lakes, such as L. Miyajimanuma (M), Feeding Pond near L.Izunuma (I), Fresh Water Pond in Tokyo -port Bird Sanctuary (T), Katano Kamoike Pond (K), and brackish pond in Yonago Waterbird Sancutuary. These ponds were typical ponds using abundantly waterfowl in Japan.TN, DTN and NH_4-N concentrations were increased with the increase of waterfowl biomass, except Pond K. TP and Chl-a concentrations increased in spring, soon after waterfowl fly away. NH_4-N concentration related directly with waterfowl biomass. NO_3-N concentration also increased in several pond in winter period with residence of waterfowl, however, the origin of the NO_3-N seemed to be agriculture land. COD and DOC concentrations also increased after waterfowl fly away in several ponds.The effect on Common Cormorant to water quality was also studied at Yamada-Onuma Pond in the Mushashiyuryo Forest Park. Water quality of this pond was deteriorated by Common Cormorant, and heavy water bloom by Microcystis sp. continued from June to October. Above 400mg/m^3 of Chl-a concentrations were observed in this period.