| Lianhuan Lake is the largest brackish water lake in Heilongjiang Province,which is composed of 18 lake bubbles.Among them,Amutabao and Yamenxipao are a comprehensive lake with a water area,which combines fishery,waterfowl hunting and tourism,forming a fishery mode mainly for the proliferation of large silver carp and bighead carp.In order to explore the zooplankton community structure and evaluate the status of hydroecology in Lianhuan Lake,we investigated eight samplings of water and zooplankton seasonaly from June,2018 to May,2019.This paper evaluates the current situation of fish bait biological resources and water ecology,and provides scientific basis for the protection of water ecological environment and sustainable utilization of fishery resources.In this study,conventional survey and analysis methods were used to statistically analyze the species composition,abundance,biomass,dominant species,and diversity index of plankton.Factor analysis,using Spearman correlation analysis and redundancy analysis(RDA)to analyze the correlation between plankton and environmental factors,using water quality factor evaluation method,comprehensive nutrition status index evaluation method,plankton abundance and biomass method and plankton biodiversity index evaluation method conducted a water pollution level and eutrophication evaluation of the two water bodies.The research methods and results are as follows.A total of 123 species of 62 genera and 8 phytoplankton were detected during the investigation.Among them,there were 44 species of phytoplankton in total.The second was diatomophyta,39 species.There were 21 species of cyanobacteria in total.There were 12 species of euglenophyta in total.However,cryptophyta,xanthophyta and jinzophyta were less common,with only 2 species.Dinoflagellates have the least number of species,only 1 species.There are 20 species of phytoplankton in 15 genera in the Lianhuan Lake,10 species in spring and autumn,8 species in summer and 5species in winter.The average annual abundance of phytoplankton was 9.28×10~5ind./L,and the average annual biomass was 0.357mg/L.The annual average of Shannon-Wiener,Pielou and Margalef diversity indices were 2.27,0.52 and 1.44respectively.Both of these diversity indices were different in different seasons,but not significantly different between the eight sampling sites.Correlation analysis showed that the water temperature,p H,DO and chlorophyll a were the major factors affecting the phytoplankton community.RDA analysis showed Total nitrogen(TN),DO,Chlorophyll a,TLI were also important factors affecting the phytoplankton community structure.As a result,75 species of zooplankton were identified,including 20 species of protozoa,21 species of rotifers,15 species of cladocerans,and 19 species of copepod;Dominant species included 12 Protozoa species,1 Rotifera species,1 Cladocerans species and 2 Copepod species.The zooplankton community structure showed a miniaturization trend.The annual average abundance and biomass of zooplankton was1060 ind./L and 2.930mg/L,respectively.Zooplankton abundance and biomass were both higher in summer than in other seasons.The annual average of Shannon-Wiener,Pielou and Margalef diversity indices were 1.09,0.36 and 1.56 respectively.Both of these diversity indices were different in different seasons,but not significantly different between the eight sampling sites.Correlation analysis showed that the water temperature and DO were the major factors affecting the zooplankton community.RDA analysis showed Total nitrogen(TN),Chlorophyll a,TLI were also important factors affecting the zooplankton community structure.The water quality and eutrophication of two consecutive water bodies were evaluated by water quality factor,TLI,plankton density,biomass index and diversity index.From TP and transparency indicators,it can be evaluated as the middle eutrophication level,from dissolved oxygen and total nitrogen indicators,it can be evaluated as the middle eutrophication level,from chlorophyll a,it can be evaluated as the middle eutrophication level;according to the comprehensive nutritional state index,the whole lake is in the light eutrophication state throughout the year;from the perspective of space,there is little difference in the annual TLI of various points,most of which are in the light eutrophication state;according to the abundance index of phytoplankton,the two water bodies are in the state of poor nutrition;according to the abundance and biomass of zooplankton,the two water bodies were in mesotrophic state.According to the index of phytoplankton diversity,the annual average water quality of Amutapao and Yamenxipao is of moderate pollution type.According to the zooplankton diversity index,the average water quality of the whole year was?-moderate pollution level.In general,the two water bodies of Lianhuan Lake are in the state of medium eutrophication all year round,and the water quality is of medium pollution type,and the difference between each station is not significant.In order to prevent the further deterioration of the water quality in the lake area,the principle of reasonable reclamation of agriculture should be adhered to,illegal reclamation should be prohibited,and attention should be paid to water ecological protection.At the same time,it is necessary to pay attention to adopting water purification ecological fishery technology to effectively control the nitrogen and phosphorus budgets and reduce the risk of water eutrophication.This study provides sufficient scientific basis for the fishery and aquaculture and water environment protection in Lianhuan Lake area,and has important guiding significance. |
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