Increasing input of nutrients is leading to significant eutrophication in aquatic systems across the globe. Toxin production in those blooms is correlated with high cell density. A study was done to investigate the effects of initial cell density on the growth rate of the potentially toxic cyanobacterium
Microcystis aeruginosa, in unfiltered lake water as well a common algal growth medium under laboratory conditions. Five treatments were established in the laboratory varying the initial cell density of M.
aeruginosa and the growth medium. Unfiltered lake water was inoculated with a low, medium, and high initial cell density and Bold’s medium was inoculated with low and high initial cell densities. There was a significant difference in final cell density between the lake water treatments with the high inoculum of cell treatment reaching the highest final cell density. There was also a significant difference in final cell density between the Bold’s medium treatments. These results indicate there is a relationship between initial cell density of M.
aeruginosa and final cell density, however, the results are similar when nutrients are available. Diverse algal communities can keep toxin producing algae in low density therefore precluding the need of toxin production.