Studies On The Relationship Between Zooplankton Community Structure And Water Environment In The Shanmei Reservoir

Due to the increasing shortage of water in cities,many reservoirs are listed as drinking water sources to solve the problem of urban water shortage.The Shanmei Reservoir is the drinking water source of Quanzhou City,Fujian Province,and it also provides water to Jinmen County,Taiwan Province.As an important primary consumer in the water ecosystem,zooplankton plays a very important role in water quality evaluation.In this study,zooplankton community and environmental factors were seasonally investigated in January,April,July,and October in 2020 and 2021 in the Shanmei Reservoir,and the variation characteristics of them were studied after fish community manipulation since 2020.The water quality of the Shanmei Reservoir was also evaluated by combined biological monitoring and physical and chemical factors.The present studies was mainly aimed to provide basic information of biological data of the Shanmei Reservoir,and also provide scientific guarantee for the smooth development of water environment protection and efficient utilization of fishery resources in The Water Resources Allocation Center of the Quanzhou Shanmei Reservoir.The results are as follows:1.A total of 102 zooplankton species belonging to 68 genera were identified,including 41 Rotifers species（40.2%）,41 Protozoans species（40.2%）,seven Copepods species（6.9%）and 13 Cladocerans species（12.7%）.The seasonal variation was mainly characterized by high species richness in April and July,but low in January and October.Protozoans is the main dominant species in January and April,while the rotifers are the main species in July and October The averaged density of zooplankton（1443.05±360.02ind./L）in eight seasons ranged from 418.72 to 3592.74 ind./L,and the averaged biomass（1.21±0.27 mg/L）ranged from 0.19 to 2.34 mg/L.After two years of fish community manipulation,the standing crop of zooplankton had significant differences in interannual changes.The standing crop of zooplankton in 2021 were significantly higher than those in2020.Among them,the density of four groups were significantly higher than that in 2020,the inflowing area in 2021 was significantly higher than that in 2020.The biomass of cladocerans in the middle,upper and lower section of the reservoir in 2021 was significantly higher than that in the corresponding areas in 2020,the copepods and protozoans in 2021 was significantly higher than that in 2020.Our results indicated that manipulation of fish assemblage structure increased density and biomass of zooplankton in the Shanmei Reservoir,and based on this,we proposed measures to change zooplankton community structure by manipulating fish assemblage structure and improve water quality,which could provide some scientific information for environment protection and efficient aquatic bio-resources utilization in lakes and reservoirs.2.The diversity index of zooplankton community in the Shanmei reservoir had significant differences among seasons.Thevalue of zooplankton in the Shanmei Reservoir ranged from 2 to 3 in each season and area;The′value of zooplankton was between 1～2 in all seasons and regions;Thevalue of zooplankton ranged from 0.42 to0.75 in all seasons and 0.58 to 0.64 in all areas.The three diversity indexes of zooplankton in the Shanmei Reservoir were mainly high in July and low in October;spatially,the three diversity indexes in the Shanmei Reservoir were mainly high in inflowing and upper section area,and low in lower area.The average values of the three diversity indexes in 2021 are significantly higher than those in 2020.3.The PCA analysis showed that p H,conductivity（Cond）,transparency（SD）,total nitrogen content（TN）,ammonia nitrogen content（NH₄⁺-N）,and chlorophyll content（Chl.a）were the key environmental factors affecting water environment of the Shanmei Reservoir;The RDA analysis showed that Conductivity（Cond）and water temperature（WT）had the greatest impact on the zooplankton community in the Shanmei Reservoir.Different physical and chemical factors had different effects on different groups,resulting in a higher occurrence rate of protozoans in January and April;The occurrence rate of rotifers was higher in April and July;Cladocerans and copepods appeared more frequently in October.4.Based on the monitoring data of water environmental factors and zooplankton community structure data.The comprehensive single factor evaluation method,comprehensive trophic level index evaluation method,zooplankton stock evaluation method,zooplankton indicator species evaluation method,and zooplankton diversity index evaluation method suggested that the Shanmei Reservoir was in a condition of oligotrophic～mesotrophic level,and the water quality was in the light～moderate pollution state.