广西北部湾茅尾海夏冬季浮游细菌群落结构及其影响因子

海洋浮游细菌在生物地球化学循环过程中具有不可替代的作用。为解析广西北部湾茅尾海夏冬季浮游细菌群落结构及其关键环境影响因子，于2017年6月(夏季)和2017年12月(冬季)在该海域设置7个站点，采集0.5m处表层海水样品，利用16S核糖体RNA (16S rRNA)基因高通量测序技术，分析茅尾海浮游细菌群落结构与多样性。结果表明：茅尾海海域浮游细菌隶属于11个门、36个纲、86个目、188个科和506个属；主要浮游细菌类群为变形菌门(Proteobacteria, 52.47%)、厚壁菌门(Firmicutes, 17.34%)、放线菌门(Actinobacteria, 16.39%)、拟杆菌门(Bacteroidetes, 7.54%)和蓝细菌门(Cyanobacteria, 5.38%),共占浮游细菌总丰度的99.12%。北部湾茅尾海夏季浮游细菌群落Chao 1指数和Richness指数均显著(P<0.05)高于冬季。主坐标分析(PCoA)和相似性分析(ANOSIM)结果表明，不同季节浮游细菌群落结构存在极显著差异(R=0.586,P<0.001)。在目分类水平上进行组...

Community structure and influencing factors of planktonic bacteria across summer and winter in the Maowei Sea of Beibu Gulf, Guangxi

Planktonic bacteria play a key role in biogeochemical cycling in marine environment. To investigate the community structure of planktonic bacteria across summer and winter and their key environmental drivers, the surface seawater samples at 0.5m depth from seven stations were collected in June and December, 2017, respectivly, in the Maowei Sea, Beibu Gulf, Guangxi. We then analyzed the community structure and diversity of planktonic bacteria using 16S rRNA gene high-throughput sequencing. Our results showed that the planktonic bacteria community in the Maowei Sea belonged to 11 phyla, 36 classes, 86 orders, 188 families, and 506 genera. Proteobacteria (52.47%), Firmicutes (17.34%), Actinobacteria (16.39%), Bacteroidetes (7.54%), and Cyanobacteria (5.38%) were the major phyla, which accounting for 99.12% of the total abundance of the planktonic bacteria. The Chao 1 Index and Richness Index of the planktonic bacterial community in summer samples were significantly higher than that in winter in the Maowei Sea of Beibu Gulf (P<0.05). Additionally, the results of PCoA analysis based on Bray-Curtis distance and ANOSIM (R=0.586, P<0.001) indicated that there were significant differences in the planktonic bacterial community structure between the two seasonal groups. The Welch''s t-test indicated that the abundance of 15 orders significantly varied between summer and winter (P<0.05). Among them, Euzebyales, Rhodobacterales, SAR11, Flavobacteriales, Lactobacillales, Bacillales, and Pseudomonadales were significantly increased in summer group, Oceanospirillales, Propionibacteriales, Nevskiales, Vibrionales, Burkholderiales, Mycobacteriales, Rhodospirillales, and Nitrosomonadales were significantly increased in winter group. The co-occurrence network analysis based on SparCC indicated that a more complex topological feature of the bacterial co-occurrence network was found in summer than that in winter. Furthermore, the inter-species interactions of the co-occurrence network were mainly positive relationships, which were greater in summer than that in winter. And the proportion of positive correlation inter-species is 70.3% in summer group, and that is 68.9% in winter group. The partial Mantel test demonstrated that the planktonic bacterial community was significantly positively (P<0.05) correlated with temperature, salinity, dissolved oxygen, total dissolved nitrogen, and total dissolved phosphorus. Among these factors, temperature (R=0.326, P<0.001) and total dissolved phosphorus (R=0.512, P<0.001) with the highest correlation degree with the community structure of the planktonic bacteria in the Maowei Sea, Beibu Gulf, which were identified as the key factors that affecting the community structure of planktonic bacteria. Overall, this work provides a scientific basis for revealing marine planktonic bacteria diversity in Beibu Gulf, as well as solid evidences for ecological restoration and resource utilization in the Maowei Sea.