紫菜养殖对养殖水体中细菌多样性分布及环境因子的影响

Effect of Pyropia Farming on Bacterial Communities and Marine Environmental Factors

中文关键词: 条斑紫菜  环境因子  细菌  16S rDNA

英文关键词: Pyropia yezoensis  Environment factors  Bacteria  16S rDNA

中文摘要:

      采用基于16S rDNA的高通量测序技术对山东长岛紫菜养殖区的细菌多样性分布进行了研究，并与环境因子进行关联分析，以探究紫菜养殖对环境的影响。结果显示，长岛海区水环境细菌多样性较丰富，呈现由近岸区(CDCNS)、养殖区(CDPF)、外海区(CDCOS)递减的趋势。分别基于所有细菌组成以及相对丰度最高的前20个属/种的聚类结果均显示，CDCNS和CDCOS区聚在一起，明显区别于CDPF区。CDPF区的特异优势菌包括鼠尾菌属(Muricauda)、假单胞菌属(Pseudomonas)、盐单胞菌属(Halomonas)、赤杆菌属(Erythrobacter)、海杆菌属(Marinobacter)。3个区域均未检测到河豚毒素假交替单胞菌(Pseudoalteromonas tetraodonis)、柠檬假交替单胞菌(Pseudoalteromonas citrea)等疑似紫菜致病菌。溶解氧(DO)和pH呈现由近岸向外海逐渐降低的趋势，总颗粒悬浮物(TSS)反之。CDPF区氨氮(NH4+-N)含量最低，盐度最高。关联分析发现，环境因子与环境微生物之间具有一定的相关性，如嗜氨菌属(Ammoniphilus)的丰度与NH4+-N 浓度具显著正相关性，CDPF区最低，CDCOS区最高；盐单胞菌属的分布与盐度具显著正相关性，CDPF区盐单胞菌属含量显著高于其他2个海区。研究表明，紫菜养殖海区细菌群落结构特征与环境因子具有关联性，其间的互作机制尚需进一步深入研究。

英文摘要:

      Pyropia is one of the most economically important seaweeds, which is mainly cultured in China. In recent years, water quality deterioration caused by long-term and intensive culture have led to problems for Pyropia aquaculture, such as disease outbreaks, decreased yields, and lower product quality. Microorganisms are important components of the environment and have important effects on the growth of other organisms. In this study, the microbial community structure in a Pyropia yezoensis aquafarm in Changdao, China, was studied using 16S rDNA-based high-throughput sequencing technology. Whether there were correlations between different environmental factors and the abundance of some predominant bacterial taxa was also tested to explore the environmental impacts of Pyropia farming. The results showed that microbial diversity was rich in the surveyed marine area. The abundance of Proteobacteria was the highest among all of the identified bacterial phyla. When the Pyropia farming area was compared with nearby non-farming areas, it was found that the highest abundances of microbial species occurred in the near-shore area (CDCNS), followed by the Pyropia farming area (CDPF), and the microbial diversity was the lowest in the offshore area (CDCOS). Cluster analysis of the samples was carried out based on Bray-Curtis similarity coefficient values calculated among them. The microbial community structure of CDCNS and CDCOS formed a clade that was separated from CDPF. Furthermore, the twenty genera with the highest abundances were used for a further cluster analysis, and the results showed that CDCNS and CDCOS clustered together, with more genera being especially abundant in CDPF. The predominant bacteria from CDPF included Muricauda, Pseudomonas, Halomonas, Erythrobacter, and Marinobacter. Suspected pathogenic bacteria of Pyropia, such as Pseudoalteromonas tetraodonis and Pseudoalteromonas citrea, were not identified in the surveyed areas. Indeed, the abundance of the genus Pseudoalteromonas was lower than 0.1%, suggesting that the environment was safe for Pyropia farming. Dissolved oxygen (DO) and pH decreased gradually from CDCNS to CDCOS, and TSS increased gradually from CDCNS to CDCOS. The content of NH4+-N was the lowest in CDPF and the highest in CDCOS, while the salinity was the highest in CDPF. Correlation analyses showed that there were relationships between environmental factors and environmental microorganisms. The abundance of Ammoniphilus was positively correlated with the content of NH4+-N, which was the lowest in CDPF and the highest in CDCOS. The distribution of Halomonas was related to salinity, and the abundance of Halomonas was significantly higher in CDPF than in the other two areas. Halomonas functions in denitrification, and thus can promote the conversion of N from an oxidized state to reduced forms that are more easily absorbed by algae. In conclusion, this study represented the first report of the structure of the microbial community in a Pyropia aquafarm and its correlation with environmental factors. The results showed that farming Pyropia had significant influences on the environmental microbial community, which were closely related to variations in environmental factors caused by Pyropia farming. Such changes in environmental factors and microbial structure had corresponding effects on Pyropia growth. The mechanisms of these interactions between environmental microorganisms and Pyropia growth should be further investigated in the future.