Influence Of Phytoplankton Community And Nitrogen Phosphorus Ratio On Phytoplankton Community In Baihuahu Reservoir

Baihua reservoir,built in 1966,is an important reservoir for Guiyang residents to gather drinking water,power generation,agricultural irrigation,aquaculture,flood control,ecological environment guarantee and other functions.Baihua reservoir in the northwest suburb of Guiyang city is located between Zhuchang town and Baihua Lake Township,guanshanhu District,Guiyang City,which is connected with Hongfeng Reservoir.It is located at the lower reaches of Hongfeng Reservoir,the upper reaches of Maotiao River,and belongs to Wujiang River system,the main tributary of the Yangtze River.The catchment area is 299km2,the total drainage area is 1895km2,the normal water area is 14.5km2,the storage capacity is 1.82 × 108m3,the annual average rainfall is about1175 mm,and the annual average temperature is about 13.8 ℃.It belongs to subtropical monsoon climate,characterized by hot summer and warm winter,four distinct seasons and developed monsoon(Sun Ting,2019).In order to further understand the corresponding impact mechanism of changes in water environment factors on phytoplankton community in Guizhou reservoir,a monthly sampling survey will be conducted from winter to autumn in 2019 to investigate the dynamic change characteristics of phytoplankton community structure in the reservoir.Atthe same time,in order to understand the effect of different N / P ratio on phytoplankton growth in Guizhou reservoir,in-situ simulation experiments with different N / P ratio were carried out in Baihua reservoir in September.The results show thatIn Baihua reservoir,64 species(genera)of phytoplankton(7 phyla)were detected,with the most 28 species(genera)of Chlorophyta(43.75%),11 species(genera)of cyanobacteria(17.19%),17 species(genera)of Bacillariophyta(26.56%),2 species(genera)of Pyrrophyta(3.12%),1 species(genera)of Cryptophyta(1))2 species(genera)of Chrysophyta(3.12%)and 3 species(genera)of Euglenophyta(4.69%).Anabaena Pseudosciaena,Chlorella and Chlorella are dominant species in four seasons.The seasonal characteristics of phytoplankton community structure in Baihua reservoir are as follows: pseudoanabaena in winter,pseudoanabaena in spring,pseudoanabaena in summer and pseudoanabaena in winter.Anabaena Pseudosciaena was the first dominant species in spring,summer and autumn,while Chlorella and microcyclic algae were the dominant species in winter.Although the first dominant algae species are stable,phytoplankton community structure is single and diversity index is low in Baihua reservoir,which is harmful to reservoir health.In situ simulation experiments of different nitrogen phosphorus ratios in Baihua Reservoir show that the total nitrogen concentration in Baihua reservoir is high,and a small amount of phosphorus will change the nitrogen phosphorus ratio greatly.When the ratio of nitrogen to phosphorus is less than 10:1,the amount of plankton of green algae and diatom increases with the increase of phosphorus.There was a significant positive correlation between the activity of alkaline phosphatase and the total abundance of phytoplankton(P < 0.01,n = 130).