| In recent years,the shallow sea cage aquaculture model of sea cucumber has been rapidly promoted in the coastal areas of Liaoning and Shandong.However,the lack of background data on the aquaculture environment and insufficient scientific data on aquaculture directly affect the sustainable development of this new aquaculture model.This study focuses on the Dalien Island sea area in Wafangdian City,Liaoning Province,where shallow sea cages are most concentrated.The annual changes in environmental factors and the structural characteristics of environmental microbiota were analyzed,and the structural characteristics of water and sediment microbiota in two types of ponds(semi open and closed large surface ponds)were further analyzed.The impact of aquaculture activities on environmental microbiota was also explored.In addition,the correlation between the intestinal microbiota of sea cucumber and environmental microbiota was also explored,In order to gain a more comprehensive and in-depth understanding of the microbial community structure characteristics of the sea cucumber shallow sea cage aquaculture system,provide basic data for the scientific layout and upgrading of shallow sea cage aquaculture technology and technology,and ensure the sustainable development of the industry.The main research results are as follows:1.Annual changes in environmental factors and bacterial community structure in the sea area of sea cucumber cage aquacultureIn this study,three major sites,namely,the offshore area of Dalien Island,semi open pond non cage culture area and closed pond non cage culture area,were taken as the research objects,and the investigation and evaluation analysis of environmental factors of water quality and sediment in the cage culture of stichopus japonicus were completed.Further,the high-throughput sequencing method was used to complete the analysis of the diversity of water and sediment flora and the characteristic flora of differences in different seasons,and the correlation between environmental factors and flora structure was analyzed.The research results indicate that the phosphate content in the water bodies of non cage aquaculture areas in semi open ponds in winter does not meet the national Class III seawater quality standards,while other indicators comply with the national Class III water quality standards and sediment quality standards for aquaculture.There are significant seasonal and regional differences in the abundance and diversity of water and sediment microbiota in the Dalien Island sea area,manifested as the lowest abundance and diversity of water microbiota in summer,the highest abundance and diversity of sediment microbiota in spring,and the higher abundance and diversity of offshore water microbiota among all sites.The PCo A analysis results show that seasonal differences have a significant impact on the microbial community structure of water and sediment,and there are significant differences between the microbial community structure of water and sediment.The statistical results of dominant bacterial communities show that at the phylum level,the top three dominant bacterial phyla with relative abundance in water are Proteobacteria,Bacteroidota,and Cyanobacteria.The top two dominant bacterial phyla with relative abundance in sediment are Proteobacteria and Desulfobacteriota;At the family level,Rhodobacteriaceae,Flavobacteraceae,Clade＿I、SAR86＿Clade and Methylophilaceae are the main dominant bacterial families in water bodies,while Woeseiaceae,flavobacteriaceae,Thermoanaerobiaceae,and Sva1033 are the main dominant bacterial families in sediments.The LEf Se analysis results showed that 79 and 50 significantly different bacteria were screened from water and sediment samples in different seasons(P<0.05).RDA analysis results showed that among the environmental factors,temperature,dissolved oxygen,phosphate and nitrate concentration were the dominant environmental factors affecting the microbial community structure of sea cucumber cage culture water,and Total organic carbon and sulfide were the dominant environmental factors affecting the microbial community structure of sea cucumber cage culture sediment.2.Annual changes in bacterial community structure in sea cucumber cage aquaculture areas and the impact of aquaculture activities on environmental microbial communitiesThis study took the semi open pond cage culture area and the closed pond cage culture area as the research object,completed the annual change investigation and evaluation analysis of the environmental factors of water quality and sediment in the sea cucumber cage culture area,further completed the analysis of the diversity of water and sediment flora and the characteristic flora of different seasons by high-throughput sequencing,and analyzed the impact of aquaculture activities on the structure of shallow sea environmental flora.The research results indicate that the phosphate content in the water bodies of the semi open pond cage aquaculture area in winter does not meet the national Class III seawater quality standards,while other indicators comply with the national Class III water quality standards and sediment quality standards for seawater aquaculture.There are significant seasonal and regional differences in the abundance and diversity of water and sediment microbiota in the sea cucumber cage culture area.The diversity of water microbiota is higher in autumn,higher in spring and winter,and higher in sediment microbiota in spring.The richness and diversity of water and sediment microbiota in the semi open pond cage culture area are generally higher than those in the closed pond cage culture area.The results of PCo A analysis show that seasonal differences have a significant impact on the microbial community structure of water bodies,and there is a high similarity in the microbial community structure of sediment at different locations in different seasons;Except for the high similarity in the microbial community structure between the semi open pond cage water and sediment in autumn,there are significant differences in the microbial community structure between sediment and water in other seasons.The statistical results of dominant bacterial communities show that at the phylum level,the top three dominant bacterial phyla with relative abundance in water are Proteobacteria,Bacteroidota,and Cyanobacteria.The top two dominant bacterial phyla with relative abundance in sediment are Proteobacteria and Desulfobacteriota;At the family level,Rhodobacteriaceae,Flavobacteraceae,Clade＿I、SAR86＿Clade and Methylphiliaceae are the main dominant bacterial families in water bodies,while Woeseiaceae,Thermoanaerobiaceae,Desulfobulbaceae,Desulfosarcinaceae,and Anaerolinaceae are the main dominant bacterial families in sediments.The results of LEf Se analysis of the microbial communities in water and sediment samples from four seasons showed that71 and 50 significantly different bacteria were screened from water and sediment samples from different seasons(P<0.05).The cultivation of sea cucumber in net cages has a significant impact on the microbial community structure in the semi open pond environment.LEf Se analysis of the water and sediment microbial communities in autumn semi open ponds screened 72 and 78 significantly different bacteria(P<0.05),respectively.3.Structural characteristics and correlation analysis of gut microbiota in shallow sea cage culture of sea cucumber and aquaculture environmentThe study on the correlation between the gut microbiota of sea cucumber in shallow sea cage culture and the aquaculture environment(water,sediment,and cage attachment)showed significant differences in microbial richness and diversity between water,sediment,cage attachment,and sea cucumber gut samples.Among all samples,sediment microbiota richness and diversity were the highest;The richness of the gut microbiota of sea cucumber is the lowest,but its diversity is relatively high;The diversity of the bacterial community in the attachment of the cage is the lowest,but the richness is relatively high.The PCo A analysis results showed that the similarity between the gut microbiota structure of sea cucumber and the attachment of net cages was the highest,while the similarity with the sediment microbiota structure was the lowest.The statistical results of the dominant microbiota show that at the phylum level,Proteobacteria is the first dominant phylum among different samples,with a relative abundance of over 32.5%.At the family level,the first dominant bacterial family in water bodies and cage attachments is Rhodobacteriaceae,while the first dominant bacterial family in sediments and sea cucumber intestines are Woeseiaceae and Sphingomonadaceae,respectively.The results of LEf Se analysis showed that there were significant differences(P<0.05)in 34 bacterial groups screened from the intestinal tract of S.japonicus,which mainly belonged to Acidobacteria,Actinobacteriota and Firmicutes.The representative differential bacteria were Vicinalibacteriae,Actinobacteria and Lactobacillus,respectively.In summary,under the shallow sea cage aquaculture model,there is both mutual connection and relative independence between the gut microbiota and environmental microbiota structure of sea cucumber.Related research provides basic data for the regulation of intestinal microbiota in cage culture of sea cucumber and healthy farming. |
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