Interactive relationships of Microcystis aeruginosa and three species of Chlorella under the condition of coexistence

The interactive relationships of toxic and bloom-forming Microcystis aeruginosa and three common green algae (including Chlorella pyrenoidosa, Chlorella vulgaris, Chlorella ellipsoidea) were investigated under the condition of coexisting cultivation. To inoculate the log-phase cells of C. pyrenoidosa and M. aeruginosa, the cocultivation results showed that M. aeruginosa under low initial densities could stimulate the growth of C. pyrenoidosa but its growth was inhibited; however, the growth of C. pyrenoidosa could be significantly inhibited while the growth of M. aeruginosa was pretty well with its initial density reaching up to 1×106 cells·mL⁻¹. Stable-phase M. aeruginosa caused more apparent phenomenon on C. pyrenoidosa but lost the competitiveness itself. Similar phenomena were observed when M. aeruginosa was coexisted with C. vulgaris or C. ellipsoidea. These results provided evidence in support of algal relationship in waterbodies, pointed out that restriction of harmful algal bloom in a certain range of density or growth stage might be beneficial to restoration of water environment, and proposed that all the three chlorella species had competitive advantage to be used to protect against M. aeruginosa bloom.