Effect of the Pulsed Addition of Phosphorous on the Growth and Toxin Production of the Bloom-Forming Cyanobacterium Chrysosporum Ovalisporum (forti) Zapomelová Et Al.

Eutrophication and global warming boost the outbreak of cyanobacterial blooms and the spread of invasive cyanobacterial species such as Chrysosporum ovalisporum. Different from the often steady-state conditions under laboratory cultivation, the external input of nutrients in natural water is often intermittent and pulsed, which may affect the response of cyanobacteria. In this study, we cultured C. ovalisporum under two phosphorus treatment patterns: a one-time treatment and a five-time pulsed treatment with the same total dosing. Our results showed that phosphorus deficiency in the water inhibits the growth of C. ovalisporum, thereby significantly reducing its biomass and photosynthetic activity (p < 0.05). In addition, phosphorus deficiency led C. ovalisporum to secrete more exopolysaccharides and alkaline phosphatase. Compared with the one-time treatment, the multiple pulses promoted the absorption of phosphorus by C. ovalisporum and inhibited the synthesis of alkaline phosphatase but had no significant effect on the release of cylindrospermopsin (CYN). We also found that multiple pulses had a more significant growth-promoting effect on C. ovalisporum under low phosphorus concentrations. Our results indicated the overall strong adaptability of C. ovalisporum to dynamic changes in phosphate levels in the water column and provide new insight into the outbreak and dispersal strategies of C. ovalisporum.