Phytoplankton Diversity In Typical Lakes And Reservoirs In Northeast Region

China is a country with many lakes.Thousands of natural lakes and artificial reservoirs which were distributed within 5 great lake regions in our country,bear the function of drinking,irrigation,shipping,fishery,tourism and so on,and have played a pivotal role to the national economy and social development.In recent years,as urbanization and industrialization process accelerated,the economic development speeded up,resource utilization intensity increased,eutrophication and the resulting phytoplankton blooms gradually become one of the major problems facing Chinese lakes and reservoirs.It can help us to monitor lakes eutrophication level,make focused strategies for eutrophication and water bloom prevention and fundamentally solve the problem of lake eutrophication with systemic investigation of phytoplankton community diversity,spatiotemporal pattern analysis of phytoplankton population structure,and relationship analysis of both phytoplankton population struture and environmental factors.As a result,lakes can serve better for social production,human living,and economic development.At present,there are few studies focused on phytoplankton of the Northeast plain-mountain lakes region.These studies mainly rely on traditional morphological identification and the study object is often limited to one single lakes or reservoirs,or with limited sampling points,or with few sampling seasons,so lack of systematic and continuity.In order to systematicly and completely grasp the phytoplankton community structure and spatiotemporal distribution in the northeast plain-mountain lakes region,we select seven typical lakes and reservoirs distributed in the northeast region,and do samples collection and environmental data determination for multi-seasons,multi-points,and multi-depths during the period of May to December in 2011.In this study,a total of 26 times field sampling and investigation were done,a total of 32 sampling points were set,a total of 66 phytoplankton specimens were produced,and a total of 110 DNA samples were extracted from water samples.By the integration of microscopic identification technique based on morphology and DGGE technology based on molecular biology,we analyzed the spatiotemporal change pattern of phytoplankton from each lake or reservoir,and revealed the correlation between phytoplankton diversity and environmental factors with multivariate statistical analysis.The main resluts were as follows:Through microscopic examination analysis,the phytoplankton community compositiion of different seasons in 7 typical lakes and reservoirs from northeast region were identified.A total of 103 genera of phytoplankton were discovered,belonging to 57 families from 8 phyla.From seasons analysis,the peak of genus number and abundance were both occured in samples from summer,followed by spring,while the lowest genus number and abundance were both occurred in winter or autumn(part of the lakes or reservoirs didn’t collect the winter samples).From the aspect of phytoplankton genus distribution,the largest genus number identified was from Chlorophyta(40 genera in 21 families),followed by Bacillariophyta(24 genera in 11 families)and Cyanophyta(21 genera in 11 families).When comparing among lakes or reservoirs,the largest genus number identified was from Lianhuan lake,in which the phytoplankton genus were more than any other lakes or reservoirs during sping to autumn,he greatest abundance identified was from Xiquanyan reservoir,in which the phytoplankton abundance were more than any other lakes or reservoirs during sping to autumn,while both the lowest genus number and abundance were occurred in Songhua lake.The phytoplankton community structure of each lake or reservoir has a certain degree of correlation with the natural condition of lakes and reservoirs such as area size,depth,lake formation and so on.The PCR-DGGE technology system used for eukaryotic phytoplankton was established.With this system,the eukaryotic phytoplankton diversity of 3 seasons samples from 5 shallow lakes and reservoirs(Hongqi reservoir,Xiquanyan reservoir,Xinkai lake,Lianhuan lake,Taoshan lake),different depths samples from 2 deep water lakes(Jinbo lake and Songhua lake),and winter samples from 6 lakes and reservoirs were analyzed.Shannon index analysis and clustering analysis based on DGGE bands showed that the distribution of eukaryotic phytoplankton in 7 different lakes and reservoirs has obvious seasonal effect,vertical effect and level effect.Speak in detail,most lakes and reservoirs showed the highest eukaryotic phytoplankton diversity in summer or sping,while the lowest in winter;for the part of deep-water lake,it showed the highest eukaryotic phytoplankton diversity in middle or lower layers,while the lowest diversity in surface layer;the eukaryotic phytoplankton diversity in littoral zone was higher than that in the pelagic zone.Through both in situ and laboratory measurement of water samples,the main environmental factors of 7 typical lakes or reservoirs were determined.It was found that the main environmental parameters of each lake or reservoir show obvious seasonal effect.The method of comprehensive trophic state index was applied to do the comprehensive evaluation of the trophic levels of 7 lakes and reservoirs we investigated.The results showed that the trophic levels of the 7 lakes and reservoir were among mesotrophic to middle eutrophic,To understand the effects of different environmental factors on the phytoplankton diversity distribution,the multivariate statistical analysis was used to study the correlation between the eukaryotic phytoplankton diversity of 7 lakes and reservoirs in northeast region and the corresponding environmental factors.The main environmental factors influencing the eukaryotic phytoplankton diversity of all lakes and reservoirs were revealed.The main environmental factors influencing the eukaryotic phytoplankton diversity were not identical among different lakes and reservoirs,in which,water temperature,BOD5,the concentration of ammonia nitrogen,total nitrogen,and chlorophyll a were the main influencing factors.This study was the first to investigate phytoplankton species and abundance with the whole Northeast plain-mountain lakes region as the study object,and was the first to reveal phytoplankton spatiotemporal pattern in molecular level and the main environmental factors influenced in the Northeast plain-mountain lakes region.The results of this study will provide theoretical guidance for water resources protection and rational development and utilization of lakes and reservoirs in Northeast China.