Physiological And Biochemical Responses Of Cyanobacteria To Phosphine In Lakes Under Elevated Atmospheric CO₂ Concentration

Phosphorus is one of the important factors of water eutrophication.Over the years,people have made some progress in the study of phosphorus,but most of these studies are limited to orthophosphate,polyphosphate,phosphite and other forms of phosphorus.However,phosphine,a low-valent phosphide in lakes,also plays an important role in lake eutrophication.Eutrophication is easy to cause the outbreak of cyanobacteria bloom,and Microcystis aeruginosa is the dominant algae species in cyanobacteria bloom outbreak.Phosphine also is highly toxic,on the one hand,it may have adverse effects on the growth of organisms.On the other hand,phosphine is easy to be oxidized to phosphite,hypophosphite and phosphate with lower toxicity.These different forms of phosphate may be absorbed by algae.In addition,CO₂ is an important carbon source for photosynthesis of cyanobacteria,it is also improtnt for the growth and reproduction of cyanobacteria.Therefore,the growth of cyanobacteria can be obviously affected by CO₂ and phosphine.Global climate change caused by elevated atmospheric CO₂ concentration is an important environmental problem in today's society.Phosphine has been proved to be ubiquitous in lake waters.Therefore,with the increase of atmospheric CO₂ concentration,it is of great significance to study the effect of phosphine on cyanobacteria and to clarify the factors of cyanobacteria bloom.In this study,M.aeruginosa was control cultured,and the physiological and biochemical response of M.aeruginosa to phosphine treatment under elevated atmospheric CO₂ concentration were mainly studied.The main conclusions are as follows:1.M.aeruginosa cells have certain acclimation to phosphine treatment.In the phosphine treatment groups with 2.48×10^-22 mg/L and 7.51×10^-33 mg/L,the growth and reproduction of algal cells are continuously promoted after acclimating to phosphine treatment,and the total antioxidant capacity?T-AOC?is improved.2.48×10^-22 mg/L phosphine can promote the growth of algae more than 7.51×10^-33 mg/L phosphine as a whole.From day 0 to day 12,high concentration?7.51×10^-22 mg/L?of phosphine promoted the growth and reproduction of algal cells to the greatest extent,and the overall chlorophyll a and carotenoid concentration of M.aeruginosa cells were higher than those of other treatment groups(7.51×10^-33 and 2.48×10^-2mg/L phosphine).However,long-term treatment with high concentration of phosphine can cause M.aeruginosa cells death.2.1000 ppm CO₂ can effectively promote the growth and reproduction of M.aeruginosa and improve the T-AOC of algae cells to resist phosphine,thus prolonging the resistance time of algae cells against high concentration of phosphine?7.51×10^-22 mg/L?.Under the coupling treatment of CO₂ and phosphine,the higher the concentration of phosphine treatment,the more it can promote the growth and reproduction of M.aeruginosa.3.Treatment with phosphine alone and coupling treatment with 1000 ppm CO₂ and phosphine can effectively promote the growth and reproduction of M.aeruginosa in delayed period.The coupling treatment with CO₂ and phosphine can make dissolved oxygen and pH in the culture medium in a dynamic change.