The effect of nitrogen concentration and its interaction with light intensity on population dynamics and polysaccharide content of Microcystis aeruginosa.

Cultures of Microcystis aeruginosa were inoculated into media with different nitrogen concentrations (5%, 10%, 25%, 100% N of standard BG-II media) and cultured under two light intensities for 35 days. The populations of M. aeruginosa tended to increase with decreased nitrogen concentrations in both the high light intensity and the low light intensity. Cell densities in high light intensity were significantly higher than those in low light intensity under lower nitrogen concentrations (5%, 10%, 25% N), whereas the result was reversed under the high nitrogen concentration (100% N). A four-parameter logistic model fitted all the population dynamics well. Soluble extracellular polysaccharide content of M. aeruginosa cultured in the 100% N media was significantly higher than in M. aeruginosa cultured in the lower nitrogen media; however, the bound polysaccharide and total polysaccharide of M. aeruginosa cultured in 5% N media were significantly higher than those of M. aeruginosa cultured in all other nitrogen concentration media. Significant differences in bound polysaccharide and total polysaccharide were also detected between the high light intensity and the low light intensity. There was a statistically significant interaction between light intensity and nitrogen concentration on the soluble extracellular polysaccharide content but not on bound polysaccharide or total polysaccharide. [ABSTRACT FROM AUTHOR]

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