Comparing effects of berberine on the growth and photosynthetic activities of Microcystis aeruginosa and Chlorella pyrenoidosa

Berberine is a potent algicidal allelochemical of Microcystis aeruginosa. To optimize its application in the control of Microcystis blooms, the effects of berberine on the growth and photosynthetic activities of M. aeruginosa and a non-target green alga, Chlorella pyrenoidosa, were compared. The results showed that the algicidal activity of berberine on M. aeruginosa was light dependent. Berberine had no algicidal effects on C. pyrenoidosa with or without light exposure. Under light-dark conditions, berberine significantly decreased the chlorophyll fluorescence parameters in M. aeruginosa while no significant berberine-induced changes were observed under constant darkness. Significant reductions of photosystem II (PSII) and whole chain electron transport activities in M. aeruginosa exposed to berberine suggested that PSII was the important target site attacked by berberine. Contrary to M. aeruginosa, no berberine-induced inhibition in photosynthesis activities were observed in C. pyrenoidosa. The differences in photosynthetic apparatuses of these two algae might be responsible for their different sensitivities to berberine.