Simulation of Nutrient Competition between Bluc-green Algae in Chemostat under Gradient of N:P Ratio

摘要

Competition of blue-green algae Microcystis aeruginosa and Phormidium tenue in chemostat was simulated to determine what was the cause of species shift among them. The model consists of 8 equations including Droop's equation, growth of algae depends on in tern al nutrient con tent. Simulation of growth of M. aeruginosa and P.tenue at N:P supply ratio 5 to 40 almost agreed with experimental data. It was suggested that outcome of competition in chemostat could be predicted by the simulation model. Differences in kinetic constants such as Q_min (minimum cell quota) and ρ_max(maximal nutrient uptake rate) were assumed to be causes of change in weight ratio of each algae with increase in N:P supply ratio in chemostat, suggesting species shift among blue-green algae in lakes occurs de to differences in kinetic constants for growth and nutrient uptake. At N:P supply ratio <60 (P was fixed), total dry weight of M. aeruginosa and P.tenue in com petition calculated with the model increased with increase in N:P supply ratio.