The Control Of Water Eutrophication By Xenocypris,Silver Carp And Bighead Carp Joint Manipulation Ecosystem

This study involved the control of eutrophication caused by algae biomass,nitrogen and phosphorus nutrient concentrations in lakes,supported by the national major water pollution treatment project"Shallow Lake Wetland Reconstruction and Ecological Restoration Technology and Engineering Demonstration"?2012ZX07101-007?and the basic scientific project of the central public welfare for research institute"Migration law and ecological effects research?GYZX160105?".Aiming at the problem of algae biomass and nitrogen and phosphorus nutrient concentration in eutrophic water,indoor simulation experiments were conducted with Microcystis aeruginosa,Plagiognathops Microlepis Bleeker?Xenocypris?,Hypophthalmichthys molitrix?Silver carp?and Aristichthys nobilis?Bighead carp?at the core food web structure.The effects of Xenocypris,Silver carp and Bighead carp joint manipulation system on algal blooms,nitrogen and phosphorus migration and transformation of microbial community structure were explored,and could provide a theoretical and scientific basis for the treatment of eutrophic water.The main conclusions of the study are as follows:?1?The ¹⁵N stable isotope tracer technique was used to investigate the effects of polyculture of Xenocypris,Silver carp and Bighead carp on nitrogen migration and transformation in the system through indoor static simulation experiments.The results showed that the pathway of migration of ¹⁵N marker Microcystis into the system was mainly as follows:?1?About 20%of the ¹⁵N marker sinks and deposits humus into the water by the action of microorganisms,and the ¹⁵N in the water is absorbed by the phytoplankton Microcystis.?2?Sedimentary humus and Microcystis were ingested by Xenocypris,Silver carp and Bighead carp respectively,and the marker ¹⁵N was assimilated into components of fish organisms.The percentage of storage and conversion in Silver carp and Bighead carp was 7.15%and 6.73%respectively in Xenocypris,Silver carp and Bighead carp team,while the Xenocypris also reached the maximum percentage of 7.85%.?3?Part of ¹⁵N was moved out of the system by microorganisms.?2?On the basis of analysis of different forms of phosphorus in water environment and sediment,the effects of polyculture of Xenocypris,Silver carp and Bighead carp on the migration and transformation of phosphorus in the system were investigated.It was found that the polyculture of Xenocypris,Silver carp and Bighead carp reduced the phosphorus content in the system,accelerated the circulation of phosphorus,and caused the phosphorus migrating to the biological phase.At the end of the experiment,the total phosphorus content in the substrate and the total phosphorus concentration in the water of Xenocypris,Silver carp and Bighead carp group was 37.58mg/kg and 0.187 mg/L,which was 70.72% and 85.39% respectively of the Silver carp and Bighead carp group,and the removal rates were 52.36%and 7.43%respectively.?3?The bacterial 16S high-throughput sequencing method was used to investigate the effects of polyculture of Xenocypris,Silver carp and Bighead carp group on microbial community structure.The results showed that the polyculture of Xenocypris,Silver carp and Bighead carp group can stabilize its species community structure,make the individual distribution of objects more uniform,and at the same time could affect the relative abundance of species in the Silver carp and Bighead carp group system and enhance its purification effect on the water environment.At the end of the test,the relative proportions of Bacillus in the Silver carp and Bighead carp group and the Xenocypris,Silver carp and Bighead carp group were 19.67% and 33.70%respectively,and the increase of the Xenocypris,Silver carp and Bighead carp group was obvious.At the same time,the TP,TN and NH₃-N in the control group were closely related to the distribution of Proteobacteria and Firmicutes.Concentration of TP and NH₃-N in the Silver carp and Bighead carp group and Xenocypris,Silver carp and Bighead carp were positively correlated with Chlorobi and Planctomycetes,and the interpretation amount was large.