Effects of nitrogen forms and supply modes on colony formation in Microcystis aeruginosa

摘要

Microcystis blooms can lead to a decline in water quality and ecological damage, and pose risks to human health. Therefore, studies on the mechanisms of Microcystis colony formation and bloom occurrence are of great significance for the aquatic ecosystem. In this study, Microcystis aeruginosa was cultured with nitrate, ammonium, or urea as the nitrogen source in the medium to investigate the effects of nitrogen forms on colony formation. Nitrogen was added as a single dose or in multiple doses to determine the effect of the nitrogen supply modes on colony formation. Compared with urea, nitrate significantly stimulated the growth of M. aeruginosa while ammonium inhibited growth. Among the three nitrogen forms, ammonium resulted in the highest concentrations of total dissolved nitrogen (TDN). Colonies larger than 10 mu m were significantly promoted in the ammonium treatment. Cells were generally smaller in the nitrate treatment than in the ammonium and urea treatments. The extracellular polysaccharide (EPS) contents were lower in the nitrate and urea treatments than in the ammonium treatments. Within the same nitrogen form, there was little difference in growth and colony formation between the single-dose and multiple-dose treatments. Our results demonstrated that ammonium significantly promoted M. aeruginosa colony formation, and that the nitrogen supply mode did not affect colony formation in M. aeruginosa.