The Detrimental Effect of High Salinity on the Growth and Microcystins Contamination of Microcystis aeruginosa

Abstract

The occurrence of cyanobacterial species, especially toxic ones, poses a great threat to coastal and estuary areas. In this study, the toxigenic Microcystis aeruginosa (M. aeruginosa) FACHB-905 was exposed to BG-11 medium with different salinities (1, 4, 7, 10 and 15 ppt) to investigate the physiological responses of this species in terms of oxidative stress, chl a fluorescence and microcystins (MCs) contamination. The results showed that low salinity (≤7 ppt) favored the electron transfer of photosystem II, which promoted the growth and photosynthesis of M. aeruginosa and induced MCs production. However, increased salinity (≥10 ppt) suppressed the growth and photosynthesis of M. aeruginosa and aggravated the oxidative stress of the strain. Salinity of 15 ppt reduced MCs contamination and caused irreversible damage to the photosynthetic system of M. aeruginosa, leading to the lysis and death of algal cells. These results indicated that changes in salinity exerted important regulations on the growth and MCs contamination of the toxic M. aeruginosa, which may provide a reference for the risk assessment of the harmful cyanobacterial species in the coastal and estuary areas.