Adaptation Characteristics Of Typical Aquatic Organisms To Phosphite

The traditional theory of phosphorus cycle in lakes thought that phosphorus in nature is dominated by+5 valence and the migration and transformation process is limited to liquid phase or solid phase,ignoring the existence of low phosphorus(phosphite,hypophosphite,phosphine),which the valence state of phosphorus is lower than+5 valence.Phosphite(P,+3)is a kind of reduced phosphorus widely existed in the environment,especially in the lake hypoxic area sediment with a high detection rate.The entry of reduced phosphorus into the aquatic ecosystem may cause potential effect to the lake ecological environment system.The study is a typical aquatic organism adapt to the characteristics of the study of low-valence phosphorus,select advantage lake aquatic plants Vallisneria natans,three kinds of algae(Cyanophyta,Chlorophyta,Bacillariophyta)and sediment microbial community in Lake Tai,observation and determination of different concentration of phosphite and orthophosphate aquatic biological growth morphology and physiological indicators.The results are as follows:1.The experiment of phosphite exposure to the dominant aquatic plant Vallisneria natans was designed by using the self-designed experimental device.In pot experiments A,B and C,treatment groups had significant inhibitory effect on the leaf elongation of officinalis(p<0.05).B and C had significant inhibitory effects on the root elongation(p<0.05),but A had slight stimulative effect on root elongation.Phosphite had little effect on the number of leaves and growth rate of Vallisneria natans.With the increase of phosphite exposure concentration,the photosynthetic pigment content in general showed a trend of decreasing first and then increasing.Roots were more sensitive than leaves to phosphite stress.The antioxidant system is activated,which is manifested by the increase of total protein,SOD and MDA,to remove excess ROS in the cell.By changing its own morphology and improving the antioxidant defense system based on enzyme and non-enzyme substances,Vallisneria natans can resist the stress of adverse environment,so as to improve its tolerance to the external environment.2.The bioavailability and physiological and biochemical reactions of low phosphorus to Cyanobacteria(Microcystis aeruginosa),Chlorobacteria(Chlorella)and Bacillariophyta(Cyclococcus)were studied by single phosphite treatment and combined with phosphorus.The results showed that 0.01 mg/L,0.07 mg/L and 0.7 mg/L phosphite treatment could not be used as the only direct phosphorus source for Microcystis aeruginosa,Chlorella and Cyclococcus.In the phosphite combined with phosphorus,or pentavalent phosphorus,phosphite may be toxic and thus inhibit chlorophyll a production in algal cells.Phosphite treatment caused stress to all three kinds of algal cells,and the stress degree was different.Will result in the decrease of total protein,the production of reactive oxygen species(ROS),and the increase of SOD enzyme activity.3.The effects of anaerobic growth of sediments at different phosphite concentrations on the microbial community in the sediments were simulated in laboratory.The results showed that phosphite increased the diversity,homogeneity and richness of microorganisms in sediments,and phosphite played a synergistic role in this case.After 30 days of culture,the diversity,homogeneity and richness of microorganisms increased.The addition of phosphite did not change the composition of major species at the phylum level,but did change their relative abundance.Phosphite promoted the abundance increase of Archaea,and it was speculated that it mainly played a synergistic role.Phosphite reduce the abundance of bacteria.There was little correlation between CK in blank group,0.1 mg/L in low concentration group and 10 mg/L in high concentration group.The study illustrated the impact of phosphite on aquatic organisms in lake ecosystem by the aquatic plants,algae and microorganisms,discussed the lack of phosphorus cycle process is an important link,and provided a theoretical basis for exploring the biochemical geocycle of phosphite in aquatic system.