Ignored effects of phosphite (P) on the growth responses of three typical algae species.

Nowadays, the ubiquitous distribution and increasing abundance of P in waterbodies have caused serious concerns regarding its bioavailability and potential toxicity. However, our knowledge on these issues is relatively limited. We addressed previously unknown effects of P on three dominate algae species i.e. Microcystic aeruginosa (M. aeruginosa), Chlorella pyrenoidesa (C. pyrenoidesa) and Cyclotella. sp in eutrophic waterbodies in China. Remarkable declines in biomass, specific growth rate and Chl-a of algae cells treated with 0.01-0.7 mg/L P as sole or an alternative P source were observed, indicating P had an inhibitory effect on the algal growth. Besides, the intracellular enzyme activities e.g superoxide dismutase (SOD) and malondialdehyde (MDA) were significantly increased with P stress. M. aeruginosa and Cyclotella. sp cells seemed to be more sensitive to P toxicity than C. pyrenoidesa since cell membrane suffered more serious stress and destruction. These findings combined, it confirmed P could not be utilized as bioavailable P, but had certain toxicity to the tested algae. It indicated that the increased P abundance in eutrophic waterbodies would accelerate the algal cell death, which could have a positive effect against algal blooms. Our results provide new insights into assessing the ecological risks of P in aquatic environments.