Study On Zooplankton Community Structure And Correlation Of Water Environment Factors In Long-Distance Raw Water Transmission Project

Water quality and zooplankton communities change along the long-distance pipeline during the water transfer process.In this study,water quality and zooplankton community(species,abundance and diversity)of a reservoir water conveyance project were investigated by field sampling,in situ monitoring,and indoor analysis during October 2020 to October 2021.The evolution characteristics of water quality,zooplankton community structure and diversity during the longdistance transmission of raw water were investigated from both temporal and spatial perspectives;the influence of the transmission pipeline on water quality and zooplankton community was analyzed by comparing the water bodies along the transmission pipeline with those at the water intake;meanwhile,the causes of zooplankton breeding and community structure dynamics in the pipeline were revealed by combining relevant factors.This study supports the clarification of the responsibilities of different units(water supply head and distribution station)in the water supply system from the perspective of water quality and water ecological safety.The measurement of water environmental factors in the water supply head and along the water pipeline revealed that the temperature of the water body in the pipeline was closely related to the air temperature,and dissolved oxygen had the opposite trend;p H was weakly alkaline,while turbidity values were lower in summer;redox potential was stable except in late May 2021;ammonia nitrogen,total nitrogen,total phosphorus and permanganate index were stable in spatial and temporal variation;chlorophyll was low in spring and low in summer and autumn during the monitoring period.Chlorophyll showed a trend of low in spring and high in summer and autumn during the monitoring months.Through principal component analysis,it was found that dissolved oxygen,water temperature,ammonia nitrogen,total nitrogen and total phosphorus contributed more to the water quality.The Pearson correlation analysis found that the correlations between the water environment factors of different water supply units differed.The zooplankton community structure in the water transmission project was investigated,and 4 families,7 genera and 16 species of branchiopods and 2 families,10 genera and 18 species of flexipods were identified in the first part of the water supply;4 families,4 genera and 10 species of branchiopods and 2 families,9 genera and 22 species of flexipods were identified along the water transmission pipeline.Among them,there were 10 genera and 14 species of zooplankton in the first part of the water supply,including 4 genera and 7 species of branchiopods and 6 genera and 7 species of flexipods;there were 8 genera and 12 species of zooplankton in the pipeline,including 2 genera and 4 species of branchiopods and 6 genera and 8 species of flexipods.Overall,the zooplankton density in the first part of the water supply increased with water depth,and the density of zooplankton decreased during the long distance transport of raw water;it is worth noting that the density of zooplankton decreased more between the transport distance of 60.76 km and 116.95 km.Temporally,the maximum values of zooplankton density in the first part of the water supply and along the transmission pipeline occurred in September,and the minimum values occurred in March.The alpha diversity analysis of zooplankton revealed that the Shannon-Weaner diversity index was highest temporally in June(3.39)and lowest in March(2.09)at the head of the water supply,and higher spatially in the lower and middle layers.It was highest temporally in June(3.07)and lowest in September(2.25)in the alongroute pipeline;it was higher spatially when the transmission distance was close.The Pielou uniformity index in the first part of the water supply was highest in time(0.75)in June and lowest(0.49)in March;spatially it was higher in the surface layer.In the along-route pipeline,it was highest in March(0.68)and lowest in September(0.61);spatially it was higher at long transport distances.The abundance index in the first part of the water supply was highest temporally in June(2.69)and lowest in September(1.54),and higher spatially at 15 m to 25 m water depth.The spatially higher values were found at long distances.The β-diversity analysis of zooplankton showed that the similarity coefficients of zooplankton composition in the first part of the water supply ranged from 0.226 to0.417;the similarity coefficients of zooplankton composition in the along-route pipeline ranged from 0.258 to 0.533.The similarity of zooplankton in the first part of the water supply and the along-route pipeline was moderately similar in June(similarity coefficient of 0.581),while the rest of the months were mildly similar.The redundancy analysis revealed that the zooplankton community in the head of water supply was mainly negatively correlated with dissolved oxygen and p H,and positively correlated with environmental factors such as total nitrogen,ammonia nitrogen and turbidity,and there was spatial and temporal heterogeneity in different environmental factors.The zooplankton community in the pipeline was positively correlated with water temperature and chlorophyll,and negatively correlated with redox potential and ammonia nitrogen.And there is spatial and temporal heterogeneity of different environmental factors in the pipeline with different distance transmission distance.