Variation of Environmental Factors and Dominant Population Succession of Microalgae Planktonic in Closed Shrimp Pond

In order to investigate the influence of season changes of environmental factors in closed shrimp ponds on the community structure of planktonic microalgae,this paper conducted isolated tests to the temperature,pH,total nitrogen( TN),total phosphorus( TP) and chlorophyll a in the shrimp culture ponds,analyzed the planktonic microalgae community structure and changes of dominant species in water over the same period,with the aim to explain the responses of microalgae community to changes of environmental factors in the pond without foreign water sources.The results showed that pond water temperature and TP content gradually increased from April to the end of September and then declined in October; water pH first decreased and then increased; TN and chlorophyll a first increased and then decreased.The dominant species in the pond were Cyclotella sp.,Navicula sp.,Oocystis borgei and S.quadricauda in the early stage( Apirl-May),Chlamydomonas sp.,Chlorella sp.,S.quadricauda,Golenkinia radiata and Pseudanabeanain in medium stage( June-July),Microcystis,Pseudanabeana,Chlorella sp.And S.quadricaudain in the mid-late stage( August-September),Microcystis,Pseudanabeana,Oscillatoria sp.and Chlorella sp.in the late stage( October-December),and Chlorella sp.,Golenkinia radiate,S.quadricauda in the last stage.Diatoms and green algae were the dominant species in the early stage when the water had low temperature,low N and P nutrition but high N/P and a certain salinity.With the increase of temperature,water desalination and accumulation of N and P nutrition,algae became the dominant species.Cyanobacteria became the strong dominant stages in the mid-late stage when the water had high temperature in the state of eutrophication,and there were also some green algae which were fond of high temperature and had resistant to pollution.In the late stage,cyanobacteria were the absolute dominant stage,but with the decrease of water temperature in the last stage,green algae became the dominant species,and planktonic microalgae biomass in the pool decreased.