Community Structure Of Zooplankton And Its Influencing Factors In Xiaolonghu Lake And Qijia Lake In Daqing

In this study,Xiaolonghupao and Qijiapao zooplankton of Lake Group in Songnen Plain and large silver carp cultured in Xiaolonghupao were taken as research objects.The species,density,biomass and quantity distribution of zooplankton community were investigated,and the feeding habits of large silver carp were investigated and analyzed.The purpose of this study was to investigate and clarify the plankton of Xiaolonghupao and Qijiapao.Seasonal variation and spatial-temporal distribution of phytoplankton,as well as the correlation between water environmental factors and zooplankton,in order to find out the law of zooplankton community structure changing with environmental changes.Combining with the feeding data of small dragon tiger bubbles and big silver fish,the correlation between species number,density,biomass and community changes of small dragon tiger bubbles and changes of feeding habits was preliminarily discussed.In February,April,June,August and December 2017,five sampling points were set up in Xiaolong Hupao and Qijiapao respectively.The average water depth of Xiaolong Hupao and Qijiapao was more than 2 m in the last ten days of each bimonthly period.Therefore,stratified sampling was used at each sampling point,and5 L of Middle-Upper water and lower-middle water were taken respectively.Then,plankton network No.25 was used for zooplankton sampling.After filtration,the collected zooplankton samples were fixed with Bonn reagent solution on the spot,and the water temperature,p H and transparency were measured at various sampling points.At the same time,zooplankton samples were collected synchronously.500 ml of mixed water in the upper and lower water layers was collected by 5L water collector.The water samples were fixed with sulfuric acid stationary liquid in the field and brought back to the laboratory to determine the concentration of nutrients.In August and October 2017,large silver carp samples were collected and fixed with 5%formalin for food analysis.The zooplankton samples collected in Xiaolong Hubu in 2017 were analyzed and identified.A total of 22 genera and 36 species of zooplankton were detected,including7 genera and 15 species of rotifers,9 genera and 12 species of Cladocera and 6 genera and 9 species of copepods.There are 19 dominant species,including 8 cladocera,7rotifers and 4 copepods.The average annual density and biomass of zooplankton are356.7 ind./ L and 5.45 mg/L respectively.The highest species number,density and biomass of zooplankton occur in August and the lowest in February.The annual average values of Shannon-Wiener diversity index H_and Margalef richness index D were 1.99 and 2.88,respectively,with significant seasonal differences in diversity.Pearson correlation analysis of zooplankton species number,density,biomass and water environment factors showed that water temperature was a decisive positive correlation factor affecting the species,density and biomass of zooplankton in Xiaolonghu Bubble,and TP and NH3-N contents were important positive correlation factors affecting zooplankton density.PH value and TN were negative correlation factors of species number.The zooplankton samples collected in Qijiabuo in 2017 were analyzed and identified.A total of 34 species belonging to 20 genera were detected,of which 22 species belonging to 12 genera were rotifers,accounting for 64.70% of the total species;7 genera and 7 species were cladocera,accounting for 20.59% of the total species;copepods were the least,totaling 5 species belonging to 2 genera,accounting for 14.71% of the total species.There are 19 dominant species of zooplankton in Qijiabuo,including 11 dominant species of rotifers,3 dominant species of cladocera,the least copepods and 2 dominant species.The average annual density of zooplankton is 106.56 ind./ L,the highest and lowest density occur in June and December respectively,and the average annual biomass is 2.44 mg/L.The highest density occurs in August and the lowest density occurs in October.The annual average values of Shannon-Wiener diversity index H_and Margalef richness index D are 1.85 and 2.96,respectively.There are seasonal differences between the two values.Pearson correlation analysis of zooplankton species number,density and biomass with water environmental factors showed that the number of zooplankton species was significantly correlated with water temperature and total phosphorus;zooplankton density was significantly positively correlated with water temperature and total phosphorus;zooplankton biomass was positively correlated with water temperature and negatively correlated with total nitrogen.Therefore,water temperature is a common determinant of zooplankton species,density and biomass,and plays a decisive role in the change of zooplankton community structure.The feeding habits of big silver carp in June,August and October 2017 were investigated.The results showed that Cladocera had the highest frequency and the highest relative importance index in the feeding habits analysis of big silver carp.In August and October,the intestinal tract of the big silver carp showed intact large silver carp and beautiful white shrimp.On the one hand,it indicated that the big silver carp would eat fish and shrimp,while on the other hand,it indicated that the big silver carp would eat the same kind of fish.To some extent,this study supplemented the data gaps in the study of zooplankton community structure in saline-alkaline lakes and the multiplication of giant silver carp in saline-alkaline lakes,and provided basic theoretical data for further management of the multiplication of large silver carp in saline-alkaline lakes.