Study On Influence Of Nitrogen And Phosphorus Concentrations On The Growth Of Four Dominant Species Of Algae In Taipu River

Water eutrophication and water security are the major environmental problems faced by all over the world.China is a world power,its large population and rapid development of economy brings many environmental pollution problems,especially the shortage of water resources and the frequent occurrence of deterioration of water.In recent years,the degree of the water eutrophication becomes more and more serious and the outbreak of water bloom becomes more and more frequently in our country, especially the algal toxins when cyanobacterial blooms are seriously affected drinking water security.In order to reduce the impact of sudden water pollution accidents,many large and medium-sized cities are constructing the back up water source.Shanghai as the largest city and economic center of China,has been chosen as one of the six cities of serious lacking of drinking water across the world in 21 century,water safety problem is very serious.As a result,in October,2013,<<The water source planning of the upper reaches of Huangpu River>> decided to construct a small ecological storage reservoir in the north of the Taipu River.When sudden water pollution accidents occur,it can solve the problem of water security and improve the security of drinking water supply in Shanghai.In this study,we used a methodology of a combination of field investigation and laboratory experiment and did a monitoring research on the phytoplankton in Taipu River.We have discussed how to control the growth of algae from the angle of nutrients and how to apply the ecological dynamics model to provide the theory basis for water quality monitoring and early warning of harmful algal bloom of the Taipu River.And the main conclusions are listed as follows:1. The common dominant species in Taipu River include 7 species of Cyanophyta,4 species of Bacillariophyta and 8 species of Chlorophyta. We screened Cyclotella sp.,Ankistrodemus sp., Pseudanabaena sp. and Microcystis aeruginosa from the dominant species for isolation,purification and extended culture,the growth characteristics in different nitrate and phosphate concentrations were studied by single facter experiment.2. Cyclotella meneghiniana has a relatively fast growth rate, the maximum cell densities and the Chl-a increased with the increasing concentrations of N and P,when the concentration of phosphate is higher than 0.24 mg/L,the added value is no longersignification;The specific growth rate（μ） varied from 0.39⁰.59 d^-1 under different nitrate concentrations and 0.33⁰.36 d^-1 under different phosphate concentrations; Ks N is higher than Ks P;Compared to phosphorous, C. meneghiniana was a species more easily subjected to growth-limitation of nitrogen,high concentration of nitrogen is beneficial to maintain its sustainable growth.3. Microcystis aeruginosa has a relatively slow growth rate, the specific growth rate（μ） of it varied from 0.279⁰.354 d^-1 under different nitrate concentrations and0.283⁰.318 d^-1 under different phosphate concentrations; Ks N is higher than Ks P;The specific growth rate increases continuously when concentration ranges of nitrogen and phosphorus are 0⁵.6 mg/L and 0⁰.96 mg/L respectively,when the phosphate concentration is higher than 0.96 mg/L,the two values begin to fall;It has a competitive advantage under low N/P conditions.4. Pseudanabaena sp. can not live in the experimental group without nitrogen and phosphorus,in the group with adequate nitrogen and phosphorus concentration of0.96 mg/L and 1.92 mg/L,the the maximum cell densities and μ are both the highest and the growth curve showed a significant exponential growth period.This indicates that the growth of it is higher for nitrogen and phosphorus,especially the increase of phosphorus can greatly promote the growth of it; It has more competitive advantages in the higher phosphorus concentration.5. The maximum cell densities and the Chl-a of Ankistrodemus sp. increased with the increasing concentrations of N and P,the added value is more significant under the higher nitrogen concentration; The specific growth rate varied from 0.32⁰.44 d^-1under different nitrate concentrations and 0.28⁰.34 d^-1 under different phosphate concentrations; Ks N is higher than Ks P; It has more competitive advantage in the higher nitrogen concentration.