Marine bacterial richness increases towards higher latitudes in the eastern Indian Ocean@en

Abstract: We investigated the bacterial community structure in surface waters along a 2500 km transect in the eastern Indian Ocean. Using high throughput sequencing of the 16S rRNA gene we measured a significant latitudinal increase in bacterial richness from 800 to 1400 OTUs (42% increase; r2=0.65; p<0.001) from the tropical Timor Sea to the colder temperate waters. Total dissolved inorganic nitrogen, chl a, phytoplankton community structure and primary productivity strongly correlated with bacterial richness (all p<0.01). Our data suggest that primary productivity drives greater bacterial richness. Because, N2-fixation accounts for up to 50% of new production in this region we tested whether higher N2-fixation rates are linked to a greater nifH diversity. The nifH diversity was dominated by heterotrophic Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria. We did not found any mechanistic links between nifH amplicon data, bacterial richness and primary productivity due to the overall low nifH evenness in this region. […]摘要： 本研究针对东印度洋沿2500公里样带的表层水体细菌群落结构开展了调查。通过16S rRNA基因高通量测序技术，本研究测得从热带帝汶海至寒温带水域的纬度梯度上，细菌群落丰富度显著提升，范围介于800至1400个操作分类单元（Operational Taxonomic Units，OTU），增幅达42%，决定系数r²=0.65，p<0.001。总溶解无机氮、叶绿素a（chl a）、浮游植物群落结构及初级生产力均与细菌群落丰富度呈显著相关（所有p<0.01）。本研究数据显示，初级生产力是驱动细菌群落丰富度提升的核心因素。鉴于该区域新生产力中高达50%来源于固氮作用，本研究进一步探讨了较高的固氮速率是否与更高的nifH基因多样性存在关联。nifH基因多样性主要由异养型α-变形菌纲、β-变形菌纲及γ-变形菌纲类群主导。由于该区域nifH基因整体均匀度偏低，本研究未在nifH扩增子数据、细菌群落丰富度与初级生产力之间发现任何机制性关联。……