K. Ha et al., Microcystis bloom formation in the lower Nakdong River, South Korea: importance of hydrodynamics and nutrient loading, MAR FRESH R, 50(1), 1999, pp. 89-94
A cyanobacterial bloom in the lower part of the Nakdong River was investiga
ted during the dry summer of 1994. High levels of phytoplankton biomass, ma
inly Microcystis aeruginosa, in the surface waters (chl. a 193 +/- 436 mu g
L-1, mean +/- s.d.; >10(5) cells mL(-1), n = 15) were maintained for three
months from mid July to mid October. After the last major rainfall in mid
June, water temperature increased sharply within three weeks (18 June, 24 d
egrees C; 9 July, 33 degrees C). The highest cell density (5 x 10(6) cells
mL(-1)) and highest concentration of chi. a (>500 mu g L-1) in the surface
water were recorded in the early phase of the bloom (21-26 July) as the dro
ught persisted. Concentrations of dissolved inorganic nitrogen (DIN) and to
tal phosphorus (TP) during the bloom were high (DIN 2.5 +/- 0.9 mg L-1; Tp
155 +/- 98 mg L-1; n = 23). pH was low (similar to 7) until the initial sta
ge but was high (pH >9) as the bloom formed. Elevated water temperature (>3
0 degrees C) along with low discharge and high irradiance were major factor
s contributing to the Microcystis spp. bloom in this river-reservoir system
.