Effects of dissolved organic matter from different sources on Microcystis aeruginosa growth and physiological characteristics.

The roles dissolved organic matter play when managing watersheds and controlling cyanobacteria blooms have been overlooked. We assessed the effects of dissolved organic matter extracted from biochar, paddy soil, pectin, and rice husks, at carbon concentrations of 0, 1, 3, 5, and 10 mg L on Microcystis aeruginosa growth, photosynthesis, and physiological characteristics. The dissolved organic matter derived from paddy soil and rice husks increased M. aeruginosa growth by promoting photosynthesis. Biochar at low carbon concentrations (1, 3, and 5 mg L) also improved M. aeruginosa growth by increasing the maximum photosynthesis II quantum yield. However, biochar at a high concentration decreased the protein and RNA concentrations in M. aeruginosa and therefore inhibited the increase in M. aeruginosa biomass. Pectin did not affect M. aeruginosa photosynthesis, protein concentration, RNA concentration, or growth. The results suggested that M. aeruginosa growth was improved by the amino acids tryptophan and tyrosine, decreased by abundant humic-acid-like substances, and unaffected by polysaccharides.