인북천에서 부착조류 현존량의 시･공간적 변동

초록

Eutrophication is a well-known phenomenon in lentic habitats, however it is receiving increasing attention in shallow streams of Korea due to the increase of periphyton to a nuisance level. In this study temporal and spatial variation in periphyton standing crop and nutrient concentrations were surveyed in the upper reach of the Han River (the Inbuk Stream) that used to be a pristine rural stream until 1980s. Chlorophyll-a concentration per unit surface area of bottom substrate was examined monthly for one year period at nine sites along the Inbuk Stream together with environmental factors such as phosphorus, nitrogen, and water velocity. The standing crop of periphytic algae ranged from 4~242 mgChl.a/m2 with a median of 55 mgChl.a/m2, often exceeding the nuisance level criterion. Along the stream periphyton increased significantly from 39±48 mgChl.a/m2 to 94±49 mgChl.a/ m2 after merging of a tributary in an intensive agricultural basin with high phosphorus concentrations. Seasonally periphyton biomass was highest in autumn (median 171±76 mgChl.a/m2) from October through December when water flow velocity was low (median 0.4±0.3 m/s), while it was higher in flood season (median 1.2±0.4 m/s) and freezing season (median 0.2±0.3 m/s) was lower. The result shows that this rural stream often shows characteristics of eutrophication according to periphyton standing crop and it may be regulated by phosphorus and water velocity.

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