Growth inhibition of bloom‐forming cyanobacterium Microcystis aeruginosa by rice straw extract

Aims:  To inhibit the growth of the bloom-forming cyanobacterium Microcystis aeruginosa using a rice straw extract. Methods and Results:  The cell numbers of the algal strain M. aeruginosa UTEX 2388 significantly decreased after treatment with different concentrations (0·01, 0·1, 1 and 10 mg l−1) of a rice straw extract for an 8-day cultivation period. Among seven tested allelochemicals from rice straw, salicylic acid at 0·1 mg l−1 exhibited the highest allelopathic activity (26%) on day 8. A synergistic effect on algal growth inhibition was found when adding two or three phenolic compounds from the rice straw. Conclusions:  The growth of M. aeruginosa was inhibited by rice straw extract concentrations ranging from 0·01 to 10 mg l−1. This activity was due to the synergistic effects of various phenolic compounds in the rice straw. Significance and Impact of the Study:  The identification of rice straw as an effective material for the growth inhibition of M. aeruginosa implies it may have the potential to be used as an environment-friendly biomaterial for controlling the algal bloom of M. aeruginosa in eutrophic water.