SUP05 niche partitioning in meso- and bathypelagic plumes. Kermadec SO253

Hydrothermal plumes are highly diluted fluids which introduce reduced chemical species up to thousands of kilometres away from the source into the deep sea. Despite their considerable spatial scale and the impact they have on the ocean biogeochemical cycles, plume-based studies are scarce. Here we analysed the plume microbial ecology of a deep-sea and a mesopelagic volcano, Brothers and Macauley, on the Kermadec intra-oceanic Arc (South Pacific Ocean). Based on on-board 16S rRNA gene analysis, CARD-FISH, multi-omics approach and an extensive geochemical dataset, we report a SUP05-clade niche differentiation. Niche partitioning was evident in plumes emanating from caldera and the cone of Brothers volcano, potentially owing to the ability of SUP05 to adapt the metabolism to fluctuating environmental conditions. Low-abundant SUP05 was omnipresent, expressing a wide variety of transporters and displaying a heterotrophic lifestyle. Moreover, the mesopelagic plume was dominated by a new SUP05 species, provisionally named Candidatus Thioglobus vadi (CTV), which is found habiting coastal waters. We hypothesise that CTV could be oxidizing iron due to its occupancy of high dFe niches and highly expressed cytochromes. Taken together, we propose that the niche partitioning between SUP05 derives from small variation of environmental parameters and depth across large spatial scales.

热液羽流（Hydrothermal plume）是一类高度稀释的流体，可将还原性化学物质从喷发源头输送至距离可达数千公里的深海海域。尽管热液羽流具有可观的空间分布范围，并对海洋生物地球化学循环具有显著影响，但针对羽流的相关研究仍较为匮乏。本研究以南太平洋克马德克洋内弧上的Brothers深海火山与Macauley中层火山的羽流微生物生态为研究对象展开分析。本研究基于船载16S rRNA基因分析、催化报告沉积荧光原位杂交（CARD-FISH）、多组学方法及大规模地球化学数据集，揭示了SUP05演化支的生态位分化现象。Brothers火山破火山口与锥状喷口产生的羽流中存在明显的生态位分区现象，这可能源于SUP05类群能够调整自身代谢以适应波动的环境条件。低丰度SUP05类群广泛存在，其可表达多种转运蛋白并呈现异养生活方式。此外，中层羽流的优势类群为一种新型SUP05物种，暂命名为候选种Candidatus Thioglobus vadi（CTV），该类群此前被记录栖息于近岸海域。研究推测，CTV或可通过占据高溶解态铁（dFe）生态位并高表达细胞色素来实现铁氧化过程。综上，本研究提出SUP05类群的生态位分化源于大空间尺度下环境参数与水深的细微差异。