Study On Nutrient Restriction Of Algae Based On Nutrient Enrichment In Situ(NEB) Simulation Experiment

In recent years,with the intensification of human activities,lead to a large number of nitrogen and phosphorus nutrient into the lake water in the library,the library cause lake eutrophication has become increasingly severe,the continuous deterioration of water quality and eutrophication problem has been a hotspot of research on ecology,environmental rich nutrition method appeared one after another,but at home and abroad to eutrophication and algal blooms are still outstanding.It has long been the main way to control the lake lake eutrophication and the algal bloom by controlling the nutrient salt into the lake,but whether the algal growth should be controlled by controlling nitrogen or phosphorus is still a controversial issue.In order to explore the response of phytoplankton to the enrichment of different nutrients in Baihua reservoir and to reveal the limiting factors of algae during the alga-prone bloom season?spring and autumn?in Baihua reservoir,the in-situ simulation experiments were conducted in May and August 2019 respectively in Baihua reservoir.The main results are as follows:?1?A total of 32 species of phytoplankton were identified in 7 phyla and 39 species of phytoplankton were identified in 7 phyla in the experiment of nutrient salt enrichment in baihua reservoir and 7 phyla in autumn.Phytoplankton communities in spring and autumn were all cyanobacteria-chlorophyta-dinoflagellates.?2?A total of 27 species of zooplankton were identified in spring.The community structure of zooplankton in spring was dominated by small zooplankton,which accounted for a large proportion of the total abundance.A total of 37 species were identified in autumn,mainly copepods,and the dominant species were Schizocerca diversicornis,Brachionus forficula and Mesocyclops sp.There were 18 species in the two seasons,among which Polyarthra remata and Mesocyclops sp were the dominant species.?3?In spring,when the nutrient salt was enriched in baihua reservoir,the phytoplankton increased the fastest and the zooplankton increased the abundance in the phosphorus group,indicating that the phytoplankton in baihua reservoir was phosphorus restricted.?4?In autumn,when nutrient salt was enriched in baihua reservoir,phytoplankton?plants and animals?grew fastest in the phosphorus+nitrate,phosphorus+ammonia groups,which proved that the common limit of nitrogen and phosphorus was in autumn,and the abundance of phosphorus+ammonia group was greater than that of phosphorus+nitrate.?5?Age season after the nutrient enrichment of phytoplankton,zooplankton diversity index showed a trend of lower,at the beginning of the experiment,the diversity index at a higher level,that nutrient after join the plankton has a certain role in promoting,but as the nutrient consumption,increased competition between species and eventually lead to the late community diversity index compared with a downward trend.?6?Through RDA analysis of dominant phytoplankton species and environmental factors in different seasons in baihua reservoir,it was found that TP and TN were the main environmental factors affecting phytoplankton community structure change in spring,and the changes of P-PO₄,N-NO₃ and Chla concentrations in autumn were the leading factors affecting phytoplankton community structure change.?7?Through RDA analysis of dominant zooplankton species and environmental factors in different seasons in baihua reservoir,it was found that TP and Chla were the main environmental factors affecting the change of zooplankton community structure in spring,and the changes of TN,N-NO₃ and Chla concentrations in autumn were the leading factors affecting the change of zooplankton community structure.