Study On The Structure Of Phytoplankton-microbial Community In Several Aquaculture Systems In Ningxia

Our country has a long history of aquaculture and is rich in aquaculture species.With the rapid development of aquaculture,it has brought ideal economic benefits,but also accompanied by many ecological problems.Phytoplankton and microorganism are the main bearers of material circulation and energy flow in the aquaculture system,and their community composition structure has an important impact on the aquaculture water environment.There are many complex relationships between phytoplankton and microorganisms,such as symbiosis,mutual benefit,competition and antagonism.Exploring their interaction mechanism is the basis of studying water ecological balance.This study explored the structure of phytoplankton and microbial communities in shrimp culture system,fish pond culture system,In-pond raceway system and ecological ditches in Ningxia,and discussed the correlation between phytoplankton and microbial communities by network,in order to provide data support for ecological culture in Ningxia.The main results and conclusions of this study are as follows:1.From May 2021 to August 2021,the phytoplankton-microbial community structure of Penaeus vannamei culture system was studied.A total of 129 species of phytoplankton in 8 phyla were detected in this study,of which 55 species were the largest,followed by 25 species of Euglenophyta,23 species of Cyanophyta,and the variation range of phytoplankton density was 10.21×10⁷cells·L^-1～143.65×10⁷cells·L^-1.Phytoplankton diversity indicates that the water of the shrimp pond is in a clean or less polluted state.A total of 31 phyla,85 classes,221 orders,391 families,675 genera and 1049 species of water microorganisms were detected.The dominant categories of microorganisms in different culture periods include Firmicutes,Proteobacteria,Actinobacteria,and the abundance changes of Proteobacteria,Actinobacteria,and Cyanobacteria in different culture periods are significantly different（P<0.05）;Microbial diversity increased with the incubation time.The level of microbial community in shrimp pond water is affected by water quality factors,and the composition of microbial community is affected by dissolved oxygen,temperature and nitrite in the early stage of culture.At the end of culture,the composition of microbial community is significantly related to p H.Through the analysis of the symbiotic network between phytoplankton and microorganisms,it is found that the relationship between phytoplankton and microorganisms is mostly competition or inhibition,and Spirulina,Pseudoanabaena and a variety of bacteria have correlation.2.From June 2021 to October 2021,the phytoplankton-microorganism study was conducted on the fish pond culture system in the rice-crab symbiosis-aquaculture coupling system.A total of 103 species of phytoplankton in 8 phyla were detected in this study,of which the Chlorophyta and Euglenophyta were dominant,with 35 and 34species respectively.The density of phytoplankton in the fishpond changes to 1.54×10⁷cells·L^-1～31.75×10⁷cells·L^-1,the highest value of phytoplankton density in the pond appeared in June,and the lowest value appeared in October.Phytoplankton diversity indicates that the fish pond water is in a state of low pollution.The microorganisms in the water were classified and summarized,and a total of 32 phyla,92 classes,245 orders,393 families,674 genera and 1124 species of microorganisms were detected.Microbial diversity showed a trend of increasing first and then decreasing.The main phyla during the study period included Actinobacteria,Proteobacteria and Firmicutes.The microbial community structure of pond is mainly affected by water temperature,p H and dissolved oxygen.Through the symbiosis network analysis of phytoplankton and microorganisms,a total of 82 correlations between phytoplankton and microorganisms were found,with more positive correlations.Algae with more connection points include Chlorella,Chlamydomonas,Microcystis and Chroococcus tenax.Bacteria with more relationships with algae include Alsobacter,which is positively correlated with most algae,Mycobacterium,Paludinobacter,Dominbacillus was negatively correlated with most algae.3.From July 2021 to September 2021,the phytoplankton-microorganism study was conducted on the In-pond raceway system in the rice-crab symbiosis-aquaculture coupling system.A total of 7 phyla and 84 species of phytoplankton were detected in the flume culture system,with the largest number of 35 species in the Chlorophyta,followed by Euglenophyta and Cyanophyta.The variation range of phytoplankton density is 4.65×10⁷cells·L^-1～11.13×10⁷cells·L^-1,the highest value of phytoplankton abundance appeared in July,and the lowest value appeared in August.Phytoplankton diversity indicates that the water of the In-pond raceway is slightly polluted.There are36 kinds of microorganisms,93 classes,220 orders,342 families,536 genera and 874species of microorganisms in the water of the convection tank system.The main microbial groups are Actinobacteria,Proteobacteria,Firmicutes and Bacteroides,of which actinomycetes and Proteobacteria were dominant during the study period.RDA analysis of microorganisms in the water of the convection tank found that the environmental factors affecting the bacterial community structure of the water were mainly water temperature,ammonia nitrogen and nitrite.The symbiotic network of phytoplankton and water microorganisms shows a total of 103 correlation relationships,with more negative correlation.The algae with more connection points include Synedra ulna,Pseudoanabaena,Nitzschialongissima,Crucigenia tetrapedia,and Phormidiun tenue.norank＿f＿Gemmatimonadaceae,CL500-29＿marine＿group,unclassified＿c＿Actinobacteria,hgcl＿Clade have positive correlation with many kinds of algae;Rhodoluna,Conexibacter,norank＿f＿norank＿o＿Saccharimonadales,norank＿f＿Paracaedibacteraceae are negatively correlated with many kinds of algae and inhibits each other.4.From September 2021 to October 2021,the phytoplankton and microbial community structure of the ecological ditch system in the rice-crab co-culture-aquaculture coupling system was studied.A total of 89 species of algae from 4 phyla were detected during the experiment.Chlorophyta is the largest,with 32 species.Followed by Bacillariophyta and Euglenophyta.The density of phytoplankton decreased with the sampling time,and the average density of phytoplankton in the ecological ditch in September was 14.52×10⁷cells·L^-1,the average phytoplankton density in October is 8.72×10⁷cells·L^-1.There are 29 phyla,90 classes,238 orders,382 families,658 genera and 1119 species of microorganisms in ecological ditch water.During the study period,the main phyla included Proteobacteria,Actinobacteria,Firmicutes and Bacteroidetes.The microbial diversity index in September was significantly higher than that in October.RDA analysis of water microorganisms found that the microbial community structure was mainly affected by water temperature,phosphate,ammonia nitrogen,nitrite and p H.The symbiotic network of phytoplankton and microorganisms shows 97 correlation relationships,mainly positive correlation.Algae that have more relationship with microorganisms include Chlorella,Microcystis robusta,Chlamydomonas and Spirulina.CL500-3,norank＿f＿norank＿o＿Microtrichales,norank＿f＿Sphingomonadaceae,norank＿f＿67-14,Ottowia,norank＿f＿JG30-KF-CM45 and Acidobacter have positive correlation with most phytoplankton.