A Study On The Community Structure Of Zooplankton Resting Eggs In Liuye Lake Of Changde City

The spawning and hatching of resting eggs is an important survival strategy for zooplankton.In order to study the community structure of zooplankton resting eggs in sediments of the Changde City,the temporal and spatial distribution of species composition and resting egg number in sediments of the Liuye Lake,Chuanzi River,Yuan River and Baima Lake were studied from December 2016 to December 2017.The main results were as following:1.Surface sediments of Liuye Lake were treated in three ways:cold storage,air-drying and directly hatching,and the numbers and hatching rates of zooplankton resting eggs were compared.The results showed that the hatching numbers of copepods,cladocerans,a nd rotifers were different with different pre-hatching methods.The hatching number of cladoceran resting eggs after air-drying was significantly higher than those with the other two treatments,and the hatching number of rotifer resting eggs was significa ntly higher than that with directly hatching.The hatching rates were at a high level,and the hatching rate of resting eggs with air-drying was significantly higher than that with the other two methods.However,the hatching rate of copepod resting eggs with cold storage was significantly higher than that treated by the other two methods,and the hatching rate of rotifer resting eggs after cold storage was significantly higher than that with directly hatching.2.Resting eggs of thirty-five species of zooplankton were found in the sediments of Liuye Lake,including 6 species of copepods,13 species of cladocerans,and 16 species of rotifers.The number of species showed seasonal differences in winter and summer,of which dominant species were Sinocalanus dorrii,Alona sp.,and Synchaeta sp.3.The average potential recruitment of zooplankton resting eggs in sediments of Liuye Lake was(25.4±7)×10~5 ind./m~3.The range of the potential recruitment of copepod resting eggs was(0.5~62.5)×10~5 ind./m~3,and the range of cladocera was(0.5~14.5)×10~5 ind./m~3,and the range was(0.5~19.5)×10~5 ind./m~3 for rotifers.The potential recruitment of zooplankton eggs was significantly different among different months,and it was higher in the summer and autumn compared to those in the winter and spring,and the highest was in summer and lowest in spring.Statistical analysis showed that the community structure of zooplankton resting eggs was significantly positively correlated with water temperature,chlorophyll a,total nitrogen and total phosphorus in the major waters of the Changde City.4.The results of core sediments showed that the number of zooplankton resting eggs was higher in the 0~6 cm sediments,and the density of resting eggs gradually decreased as t he depth increased.The potential recruitment of copepods resting eggs was significantly higher than that of cladoceran and rotifers.