The Effects of Nutrient Release from Sediments on the Formation of Water Blooms,

Simulation of the formation of water blooms dominated by Microcystis blue-green algae was carried out by using the mathematical model on the vertical migration, phosphorus uptake, and growth of the algal colonies in a water column under the coexistence of nonmigrating algae. Phosphorus supplies both through the inflow of water and sediment release were considered in the model. Numerical solutions of the model were in agreement qualitatively with the observations reported on Microcystis behavior in eutrophic lakes. Phosphorus release from sediments did not enhance the growth of Microcystis nor that of the nonmigrating algae in cases of abundant inflow of phosphorus. In the absence of phosphorus inflow, however, phosphorus release from sediments enhanced only the growth of Microcystis without significant stimulation of the growth of Microcystis without significant stimulation of the growth of the nonmigrating algae. Daily vertical mixing from 1200 to 1700 in the upper layer of the water column had little effect on the dominancy of Microcystis over the nonmigrating algae.