Correlation Analysis Of Metazoan Zooplankton Functional Groups And Water Environmental Factors In Zhalong Nature Reserve

Zhalong National Nature Reserve belongs to wetland ecosystem type.The reserve consists of a large permanent seasonal freshwater marsh and numerous small shallow lakes in the lower reaches of the Wuyuer river.The wetland is surrounded by grassland,farmland and artificial fish ponds.The main objects of protection are wetland ecosystem and rare birds such as red-crowned crane.It is the most intact,most primitive and most open wetland ecosystem in north China.In recent years,due to the influence of natural and human factors such as climate change,population increase,reclamation and expansion,factory sewage,etc.,the precipitation in the protection zone and the surrounding river basin has been reduced,the water environment has been deteriorated,the local fishery has been affected,and the water quality has been polluted.In this study,a total of 24 sampling sites were set up according to the hydrological conditions and sampling feasibility of Zhalong nature reserve in spring(May),summer(August)and autumn(October)of 2019.The correlation between metazoan zooplankton functional groups and water environment factors was analysis and discussed,and the water quality of Zhalong Nature Reserve was evaluated by physi-chemical indicators and biological indexes.The results were as follows:During the investigation,a total of 52 species of 25 genera of metazoan zooplankton were identified in Zhalong Nature Reserve,including 36 species of 17 genera of Rotifers,8 species of 6 genera of Cladocerans and 8 species of 2 genera of Copepods.The total number of species was summer>spring>autumn.The number of Rotifers was the majority in all sampling sites and seasons,while the number of Cladocerans and Copepods was relatively small.The abundance and biomass of metazoan zooplankton had significant seasonal changes.Rotifers were dominant in all seasons and sampling sites.The abundance value is between 300.6 ind/L and 22148.05 ind/L,and the annual average is 6417.79 ind/L.The change of abundance is summer>autumn>spring.The biomass ranged from 0.1454 mg/L to 11.2951 mg/L,and the annual average was 3.5231 mg/L.The biomass change wassummer>autumn>spring.A total of 9 dominant species were found,including 7 species of Rotifers:Asplanchna brightwel,Asplachna priodonta Gosse,Brachionus angularis,Brachionus calyciflorus Pallas,Keratella cochlearis,Trichocerca pusilla,Polyarthra trigla,and 2 species of Copepods:Nauplii and Thermocyclops hyalinus.There were 7 metazoan zooplankton functional groups in Zhalong Nature Reserve:Rotifers filter feeders(RF),Rotifers camivora(RC),Middle copepods and claocera filter feeders(MCF),Small copepods and claocera filter feeders(SCF),Large copepods filter feeders(LCF),Large copepods carnivora(LCC)and Middle copepods and claocera carnivora(MCC).The change of average biomass of functional groups was summer>autumn>spring,presenting a seasonal succession rule of RF/RC/SCF?RF/RC/MCC? RF/RC/LCC.Redundancy Analysis(RDA)was carried out between water environmental factors and metazoan zooplankton functional groups.The results showed that the main water environmental factors affecting the distribution of metazoan zooplankton functional groups were water temperature(WT),biological oxygen consumption(BOD5),ammonia nitrogen(NH4+-N,total phosphorus(TP)and chloride(Cl-).The biodiversity index was used to evaluate the water quality of the reserve.The results showed that the community structure of metazoan zooplankton was stable,and the water quality of Zhalong Nature Reserve was slightly or moderately polluted.