| Zooplankton can accelerate the transfer of solar energy fixed by phytoplankton photosynthesis to the water ecosystem,which is important for the energy transfer between phytoplankton and fish.In this paper,we investigated and analyzed the zooplankton of two water source reservoirs in Liaoning Province,Baishi Reservoir and Guanyinge Reservoir,from 2018 to 2020,integrated the physicochemical indexes of water bodies with zooplankton data,screened the intrinsic connection between each physicochemical factor and zooplankton community characteristics;explored a two-year real-time monitoring to compare the two reservoirs The spatial and temporal variation of zooplankton in the two reservoirs was explored,and the relationship between fish stocking and zooplankton production potential in the reservoirs was integrated to provide a scientific basis for the development of ecological fisheries in the reservoirs.The results of the study are as follows.1.During the survey period,a total of 61 genera and 107 species of zooplankton were detected in Baishi Reservoir,which is slightly lower than that in Guanyinge Reservoir 61 genera and 113 species.The number of species in both reservoirs was dominated by small zooplankton-protozoa and rotifers.The number of protozoan species in Baishi Reservoir was slightly higher than that in Guanyinge Reservoir(18genera and 32 species),and the number of rotifers was higher in Guanyinge Reservoir(25 genera and 55 species)than in Baishi Reservoir(25 genera and 49 species);the number of species of branchiostomes and copepods in the water bodies of both reservoirs was low during the survey period,and the number of large zooplankton species in Baishi Reservoir was slightly lower than that in Guanyinge Reservoir.The number of branch and horn species in Baishi Reservoir and Guanyinge Reservoir are8 genera and 15 species and 7 genera and 17 species respectively,while the number of copepods are 10 genera and 11 species and 11 genera and 13 species respectively.2.The average annual zooplankton density from 2018 to 2020 in Baishi Reservoir was 1043.85 ind./L,while that in Guanyinge reservoir was only 379.44 ind./L,which was lower than that in Baishi reservoir.On the contrary,the averagevannual biomass in Guanyinge reservoir was higher,which was 2.08 mg/L and that in Baishi reservoir was only 1.77 mg/L.The seasonal variation in density was relatively similar in both reservoirs,with extreme values The seasonal variation of zooplankton biomass was similar in both reservoirs,with extreme values occurring during the highest and lowest temperature periods of the year.The seasonal variation of zooplankton biomass was quite different,with the zooplankton biomass in Baishi Reservoir being higher in summer than in other periods and lowest in winter,while Guanyinge Reservoir showed the highest in autumn and the lowest in spring.The spatial distribution of zooplankton density in Baishi Reservoir was the highest in the middle and upper reaches and decreasing from the inlet to the downstream dam entrance,and the biomass in the middle and upper reaches was higher than that in the downstream in spring and autumn,while the opposite was true in summer and winter.3.The number of dominant species in Guanyinge Reservoir is much higher than that in Baishi Reservoir,with 21 genera and 27 species,while the dominant species in Baishi Reservoir is only 16 genera and 18 species.The dominant species in both reservoirs are mainly small zooplankton,and the dominant species of protozoa in Baishi Reservoir is the most,with 9 genera and 10 species,followed by 4 genera and5 species of rotifers,while the dominant species of rotifers in Guanyinge Reservoir is the most,with 7 genera and 10 species,followed by 6 genera and 7 species of protozoa.The dominant species of large zooplankton in both reservoirs are less,and the dominant species of large zooplankton in Guanyinge Reservoir are slightly more than those in Baishi Reservoir,in which the dominant species of copepods in Baishi Reservoir and Guanyinge Reservoir are 2 genera and 2 species and 6 genera and 6species,respectively,and the dominant species of branch and horn are the least,2genera and 4 species and 1 genus and 1 species,respectively.Among them,the frequency and dominance of Tintinnopsis wangi were higher in both reservoirs as the absolute dominant species.4.During the survey period,the range of variation and mean value of Shannon-Wiener(H’)diversity index of zooplankton in Guanyingo Reservoir were0.62 ～ 3.34 and 2.19,respectively,higher than those of 0.46 ～ 3.18 and 2.05 in Baishi Reservoir.The range of variation and mean value of uniformity index of Pielou(J)in Baishi Reservoir were lower than those of 0.16 ～ 0.80 and 0.54 in Guanyingo Reservoir with 0.13 ～ 0.91 and 0.49,respectively.the range of variation and mean value of Shannon-Wiener(H’)diversity index and Marglef richness index(D)seasonal trends are relatively similar,the lowest values are in winter;while Shannon-Wiener(H’)diversity index and Marglef richness index(D)seasonal trends of Guanyinge reservoir are different,August 2020 H’ decreased while D increased.The seasonal variation of Pielou(J)evenness index was not obvious in both reservoirs.5.The results of Pearson correlation analysis showed that water temperature was the main physicochemical factor causing changes in zooplankton community structure in both Baishi and Guanyinge reservoirs from 2018 to 2020,in which the number of species,density and biomass were all highly positively correlated with water temperature.The results of multiple linear regression analysis showed that water temperature,ammonia nitrogen and total phosphorus were selected in the regression equation for the number of species in Baishi reservoir;water temperature and transparency were selected in the regression equation for density;dissolved oxygen,chemical oxygen demand and nitrite were selected in the regression equation for biomass.The regression equation of species number of Guanyinge Reservoir had water temperature,p H and chemical oxygen demand selected;the regression equation of density had p H,chlorophyll a and nitrite selected;the regression equation of biomass only had nitrite selected.6.Redundancy analysis showed that the eigenvalues of the first two ranking axes of Baishi Reservoir were 1.46 and 1.28,and the explanation rate was 69.48%.The zooplankton density distribution was mainly influenced by water temperature,dissolved oxygen,total nitrogen and nitrate nitrogen,and all environmental factors were positively correlated except for dissolved oxygen and axis I,which were negatively correlated.The eigenvalues of the first two ranking axes of Guanyinge Reservoir were 0.88 and 0.57,and the explanation rate was 79.49%.The zooplankton density distribution was mainly influenced by water temperature,p H and dissolved oxygen,among which only dissolved oxygen was negatively correlated with axis I,and the rest of environmental factors were positively correlated with axis I.The zooplankton density distribution was mainly influenced by water temperature,p H and dissolved oxygen.7.The average annual zooplankton biomass in both reservoirs was much larger in 2018-2019 than in 2020,and the fish production potential was also much larger in2018-2019 than in 2020.The average annual zooplankton biomass in Baishi Reservoir was lower than that in Guanyinge Reservoir,with Baishi Reservoir at 2.264 mg/L(2018-2019)and 0.784 mg/L(2020)and Guanyinge Reservoir at 2.705 mg/L(2018-2019)and 0.836 mg/L(2020),respectively;the fish production potential in Baishi Reservoir was also lower than that in Guanyinge The fish production potential of Baishi Reservoir was 773.964 t(2018-2019)and 267.792 t(2020),respectively,and that of Guanyinge Reservoir was 1148.620 t(2018-2019)and 355.065 t(2020),respectively. |
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