In Situ Simulation Study On The Growth And Decline Of Three Species Of Cyanobacteria

Water bloom,which means due to adequate nutrition a large number of phytoplankton breed in a period.In result,the surface of water is obviously covered with visible accumulation.Cyanobacteria water bloom not only can affect the normal balance of ecological environment,but also can do harm to human health.What's more,it will seriously restrict the development of economic where water bloom happens.At present,the frequency of cyanobacteria water bloom in our country is high.And there are many kinds of cyanobacteria which can lead to water bloom.For example,Anabaena,Microcystis,Aphanizomenon,all of them can form water bloom under different environmental conditions.Therefore,We choose Anabaena,Microcystis and Aphanizomenon as experimental materials.We set 6 kinds of different concentration of nitrogen and phosphorus in 6 big pools.There are low N,middle N,high N(set concentration of nitrogen as 0.5,1.0,1.5 mg/L,set concentration of phosphorus as 0.03 mg/L)and low P,middle P,high P(set concentration of phosphorus as 0.03,0.04,0.05 mg/L,set concentration of nitrogen as 1.5 mg/L).We study on population dynamics of three species of bloom-forming cyanobacteria in spring,summer and autumn by in situ experiment.At the same time we set cooling experiment and heating experiment in the room,to simulate the process of lowering the temperature and increasing the temperature of the outdoor environment under low temperature,in order to simulate the overwintering stage and recruitment of cyanobacteria.The indoor experiments use 6 kinds of sterilized pool water as medium.In addition,we also set different temperature indoor experiments,as a reference for outdoor in situ experiments.Results are as follows:(1)In spring,in the water of different concentrations of nitrogen,the growth of three kinds of cyanobacteria from fast to slow is Microcystis,Anabaena,Aphanizomenon,and all these three species have the fastest growth in middle N.In the water of different concentrations of phosphorus,Aphanizomenon has the fastest growth.All these three species have the fastest growth in middle P.(2)In summer,in the water of different concentrations of nitrogen,all these three species have the fastest growth in middle N water and Aphanizomenon has the fastest growth during the day.And Anabaena has the fastest growth in low N and high N,and Aphanizomenon has the fastest growth in middle N during 24hours.In the water of different concentrations of phosphorus,Aphanizomenon has the fastest growth in low P and middle P,Microcystis has the fastest growth in high P during the day.And Microcystis has the fastest growth in middle P and high P,and Aphanizomenon has the fastest growth in low P during 24hours.(3)In autumn,in the water of different concentrations of nitrogen,Microcystis died and all these three species died faster in low N.Only Anabaena and Aphanizomenon grew little in middle N.In the water of different concentrations of phosphorus,Aphanizomenon has the fastest growth in low P during the day.During 24hours,only Aphanizomenon grew little in low P,Microcystis and Anabaena all had negative growth,and all these three species had faster negative growth in high P.(4)During cooling experiment,potential maximum photosynthetic capacity of Anabaena and Aphanizomenon weakened slowly.potential maximum photosynthetic capacity of all these three species weakened slowly in middle N.Microcystis has the weakest potential maximum photosynthetic capacity.In middle N,number of living cells of all these three species decreased slowly,and number of living cells of Aphanizomenon decreased most slowly.In the water of different concentrations of phosphorus,potential maximum photosynthetic capacity from strong to weak is Anabaena,Aphanizomenon,Microcystis.Number of living cells of Aphanizomenon decreased most slowly.(5)During heating experiment,in the water of different concentrations of nitrogen,potential maximum photosynthetic capacity of Anabaena is the strongest,and number of living cells of Aphanizomenon is the most.Number of living cells of all these three species is the most in middle N.In the water of different concentrations of phosphorus,potential maximum photosynthetic capacity of Anabaena and Aphanizomenon are stronger than Microcystis.Only number of living cells of Aphanizomenon increased,number of living cells of Microcystis and Anabaena decreased.(6)In different temperature indoor experiments,when 22?,Microcystis has the fastest growth when concentration of TP is different.When 28?,Microcystis has the fastest growth,and potential maximum photosynthetic capacity of Microcystis is the strongest.When 16?,potential maximum photosynthetic capacity of Anabaena and Aphanizomenon are stronger than Microcystis,and the negative growth of Microcystis is the fastest.When 10?,potential maximum photosynthetic capacity of Anabaena and Aphanizomenon are stronger;the negative growth of Microcystis is faster than the negative growth of Anabaena and Aphanizomenon.Through the experiments,we can conclude that population dynamics of three species of bloom-forming cyanobacteria is different in different seasons and in different water bodies.In addition,because the tolerance of three species of bloom-forming cyanobacteria is different when temperature is reduced,as well as the ability of recovering growth is different when temperature is raised.In result,germplasm resources of different cyanobacteria differs a lot in winter.In all,when water bloom happens,population dynamics of different species of cyanobacteria is different,sometimes population alternation happens.