Simulation for Algal Bloom Occurrence&Disappearance and Its Variation Process of Dissolved Oxygen

Microcystis blooms were simulated in the experiments through controlling the initial pH value, water temperature,illumination intensity and time respectively. Analysis of chlorophyll a concentration showed that when the initial pH value was about 8, Microcystis bloom occurred with the highest peak of chlorophyll a as 199.17 mg/m3. Water temperature higher than 24 ℃ could enhance Microcystis cells to grow fast with strong enzymatic activity, which led to bloom, with the peak of chlorophyll a more than 500 mg/m3. Illumination intensity and time have the similar positive effects on Microcystis growth and bloom; wherein peaks of chlorophyll a are 1 065.007 mg/m3 and 740.561 mg/m3 respectively, higher than others. The variation of dissolved oxygen corresponded to that of chlorophyll a in the experiments, which indicated that the dissolved oxygen was mainly affected by photosynthesis of algae. The dynamic model for dissolved oxygen based on the growth kinet-ics of phytoplankton could be displayed by the exponential model, which could be used to forecast the dissolved oxygen.