A Competitive Growth Model for the Simulation of Cyanobacterial Blooms Under Eutrophic Conditions

Abstract

This study presents a novel competitive growth model between Microcystis sp. (cyanobacteria) and Cyclotella meneghiniana (bacillariophyta) as a function of nitrogen and phosphorus concentrations, and dilution rate. The growth model was developed by combining the Droop and the Lotka–Volterra models to make it applicable to highly eutrophic conditions. Following the model development, cyanobacterial growth patterns in a monoxenic culture experiment were simulated, and the factors influencing the suppression of cyanobacterial blooms were discussed. Results from the monoxenic culture experiment simulation showed that a more accurate prediction of growth pattern was provided by the model developed in this study, when compared with our previous model. Specifically, the overestimation of cell densities under high nutrient conditions by the previous model was corrected. The simulation results also revealed that the initial nitrogen and phosphorus concentrations were decisive factors in determining which nutrient was critical to the cyanobacterial growth. It was also discovered that the crucial nutrient (nitrogen or phosphorus) for cyanobacterial growth switched at around an initial nitrogen and phosphorus mass ratio of 11. When the ratio was above 11, phosphorus was observed to be critical for cyanobacterial growth, while nitrogen was more critical when the ratio was below 11. These findings provide an ability to predict which nutrient is more important for cyanobacterial growth, and targeting its management or reduction in a water body can be promising toward the suppression of cyanobacterial blooms.