Succession Of Phytoplankton Community And Their Driving Mechanism In The Artifical Lakes Formed From Land Subsidence In The Coal Mine Areas

The study explored the structure composition,succession law of lake phytoplankton community and its relationship with environmental factors.In addition,based on the results of the field phytoplankton survey,we selected dominant functional groups to represent species to experiment on the restriction of pure species dynamics,and further explored the driving mechanism of phytoplankton succession.The results above is not only the scientific basis of ecological restoration in mining area,but also provide theoretical guidance for regional economic development.Selected two mall lakes at PXPJ site and PXXQ site in Huainan Panxie coal mine subsidence area and the nearby city of Huainan HXH as resarch sites.The water quality of the lake and the phytoplankton community structure were investigated.The details are as follows:?1?To investigate water quality,phytoplankton community structure and the relation phytoplankton community with aquatic environmental factors in 2016-2018 23months for the three lakes.A total of 89 species of phytoplankton were identified,which belong to 6 phyla,53 genera in HXH site,93 species belong to 7 phyla,52 genera in PXPJ site and 101 species belong to 7 phyla,52 genera in PXXQ site.Phytoplankton at 3 research sites all dominated by Cyanophyta in summer,in other months,Phytoplankton dominated by Cryptophyta species in HXH site and appear alternately by Cryptophyta and Diatom in PXPJ and PXXQ site.The annual phytoplankton density and biomass of the HXH site are much higher than those of the other two sites.?2?According to the functional group?FGs?classification method,HXH site identified 22 FGs,12 FGs are dominant functional groups.The main advantage FGs of the trend for the year is C,X2,Y?L0?Y,C?X2,Y?C,X2,Y?L0?X2,Y?P.In summer,L0?Merismopedia miniam G.Beck as a representative?was dominant functional group,In other months,C,X2,Y,and P functional groups dominated.The representative species were Cyclotella Beijierinck,Chroomonas caudata Geitler,Cryptomonas ocata Ehr.and Melosira granulate?Ehr.?Ralfs.PXPJ site identified 21FGs,the main advantage FGs of the trend for the year is C,X2?S1,X2?D,X2,Y?S1,S2?C,Y?C,X1,X2?S1,Y?Y,X2,In summer,it is dominated by the functional group of S1?Pseudanabaena sp.as a representative?.PXXQ site identified 23 FGs,The main advantage FGs of the trend for the year is C,X2,Y?S1,J?S1,S2,L0?C,Y?C,E?D,S1?S1?S1,Y?Y,C.In summer,it is dominated by the functional group of S1.Phytoplankton functional groups complexity and stability:PXPJ>PXXQ>HXH.The dominant functional groups of phytoplankton in the three lakes are C,X2,Y,L0,and S1,which reflect the typical environmental features of eutrophication,low light,and low transparency of the collapsed lake.The main factors affecting the structure change and succession of phytoplankton functional groups in collapsed lakes are nutrient content and ratios?TN/TP?,water temperature,pH and SD.?3?The experiment on dominant phytoplankton in the lakes was carried out by controlling indoor nutrition,temperature and light.The results show:in the N limit training,the?maxS of Chroomonas Caudata Geitler,Cyclotella Beijierinckand Pseudanabaena sp.were 0.66 d^-1,0.37 d^-1,0.71 d^-1,the Ks were 1.66 mg/L,1.06 mg/L,2.26 mg/L.Furthermore,in the P limit conditions,the?max S of Chroomonas Caudata,Anabaena Cyclotella and Pseudanabaena mucicola were 0.51 d^-1,0.31d^-1,0.90 d^-1,the Ks were 0.023 mg/L,0.035 mg/L and 0.015 mg/L.That is,In the case of sufficient N,Pseudanabaena sp can form the advantage in the competition and easily become the dominant species under the restriction of P.In the temperature limiting culture,the?_maxTaxT of Chroomonas Caudata Geitler,Cyclotella Beijierinckand Pseudanabaena sp.were0.35d^-1,0.32d^-1,0.81d^-1,the T_opt were 24.5?,24.4?,35.4?,respectively.The high temperature is more suitable for Pseudanabaena sp.Under the light restriction,the?_maxax of Chroomonas Caudata Geitler,Cyclotella Beijierinckand Pseudanabaena sp were0.37d^-1,0.34d^-1,0.75 d^-1,and the I_k were 3227Lux,3300Lux,2780Lux respectively.The low light is more suitable for its growth.?4?Establishing an ecological model based on kinetic parameters of phytoplankton growth,The fitting results show that the succession of phytoplankton community structure in the collapsed lake is mainly driven by temperature and light.In spring and autumn,the water temperature is low,and the illumination is sufficient.Phytoplankton mainly takes advantage of the species of Cryptophyta.In summer,the temperature increases and the phytoplankton changes to the species of Cyanophyta.In winter,low temperature,low light,and adaptability to low temperature and high transparency of Diatoms dominate.