낙동강 수계의 식물플랑크톤 침강속도

초록

Settling velocity is one of major parameters determining algal biomass in water quality modeling. In this study, the settling velocity of phytoplankton was measured in reservoir and stream sites of the Nakdong River, Korea. Settling velocities of various phytoplankton species were determined by measuring algal cell biomass settled in a sedimentation cylinder. Mean settling velocities were 0.22 m day-1 in reservoir sites and 0.33 m day-1 in stream sites, which were relatively higher compared with other default values suggested by water quality models (e.g. 0.1 m day-1 in CE-QUAL-W2). The lower settling velocity in reservoirs than in stream implies the adaptation of phytoplakton to low turbulence in lentic environments. Cyanobacteria showed lower settling velocity (0.2 m day-1) than diatoms (0.3 m day-1), and this phenomenon may have resulted from buoyancy mechanisms of cyanobacteria. Cell volume did not show a significant correlation with settling velocity in this study, implying that conformation factors of colonies or other factors had large effects on settling velocity of algal cells as well as cell size. The result of this study may suggest proper coefficients of settling velocity of phytoplankton in the calibration of water quality model.

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