Allelopathic influence of low concentration Microcystis aeruginosa on Egeria densa under different light intensities.

In this study, Egeria densa plants were exposed to a low concentration of (OD730 = 0.04) Microcystis aeruginosa for seven days, under different photosynthetically active radiation (PAR) intensities (0, 50, 100, 200, and 300 µmol m−2 s−1). Experiments were conducted under controlled conditions inside incubators. The H2O2 content, antioxidant responses, pigmentation, and chlorophyll fluorescence parameters were measured. The biochemical parameters of E. densa varied with PAR intensity; under the 50 and 100 µmol m−2 s−1 PAR intensities, E. densa performed relatively better than under other intensities. When exposed to M. aeruginosa, the levels of the measured biochemical parameters reduced in E. densa. Under unfavourable light conditions, the optical density of M. aeruginosa was also reduced when E. densa was also present. Even at low concentrations, the presence of M. aeruginosa in the water can have a negative effect on E. densa pigmentation and physiological parameters, though E. densa also has negative effects on M. aeruginosa growth. Further studies are recommended to evaluate the responses of E. densa after prolonged exposure to M. aeruginosa and the effects of E. densa on M. aeruginosa. [ABSTRACT FROM AUTHOR]