西北印度洋卡尔斯伯格脊卧蚕热液羽流影响区古菌群落动态变化特征

Spatio-temporal variations of archaeal communities in the Wocan hydrothermal plume-influenced zone, Carlsberg Ridge, northwest Indian Ocean

摘要:

【目的】热液羽流在浮力上升和非浮力侧向迁移过程中与背景海水不断进行物质和能量的交换。因海底热液活动和洋流的流速流向均存在动态变化性，热液羽流的高度、物理化学参数和微生物群落也随时空发生演化。然而，由于缺乏热液羽流的长期监测和时序取样，微生物群落(尤其是古菌)的多样性及其时空演化尚不清楚。【方法】2018年7月-2019年6月，在卧蚕1号热液喷口东南300 m处放置了一套带有2个沉积物捕获器(分别距海底300 m和40 m)和一个浊度仪(距海底150 m)的锚系潜标，对热液羽流和热液羽流下方颗粒物沉降区的近底水样进行了为期18个月的观测和时序采样。本研究采用16S rRNA基因高通量测序技术研究了水样中古菌群落的多样性，以了解羽流层和近底沉降层古菌群落结构的特征与时空演化。【结果】热原体纲(Thermoplasmata)、甲烷八叠球菌纲(Methanosarcinia)和甲烷杆菌纲(Methanobacteria)等热液来源古菌，当浊度异常值较高时，它们的丰度也增加。从空间上看，热液羽流区和近底沉降区古菌群落结构在门和纲水平上具有相似性，但在目水平上表现出差异性，而且各主要类群的相对丰度也存在差异，其中热原体纲在羽流层中的丰度普遍高于近底沉降层，而氨氧化古菌和甲烷八叠球菌纲在沉降层的丰度较高。【结论】卧蚕热液区东南300 m热液羽流层和近底沉降层均受到了热液的影响，羽流层受热液影响的程度相对更显著，而近底沉降层除了受到一定程度的热液影响外，还可能受到了再悬浮沉积物的影响。热液贡献大小的动态变化和底层沉积物再悬浮可能是造成热液区近端水体古菌群落时空异质性的主要因素。本研究深化了对热液影响区古生菌群落结构及其月际尺度时空分布特征的认识。

Abstract:

[Objective] Hydrothermal plumes exchange matter and energy with background seawater during the processes of buoyant rising and non-buoyant lateral migration. Due to the dynamic variability of both hydrothermal activity and ocean currents, the pattern, physico-chemical parameters, and microbial communities of hydrothermal plumes experience spatio-temporal variations. However, due to the lack of long-term monitoring and time-series sampling of hydrothermal plumes, the diversity and spatio-temporal variations of microbial communities, especially archaea, remain unclear.[Methods] From July 2018 to June 2019, a mooring system with two sediment traps (one for collection of hydrothermal plume samples 300 m above seafloor and the other for collection of near-bottom water 40 m above seafloor) and a turbidity sensor (150 m above seafloor) was deployed at 300 m southeast of the active Wocan-1 hydrothermal field for 18 months. We employed 16S rRNA gene high-throughput sequencing to study the diversity and spatio-temporal variations of archaeal communities in the samples on the monthly scale.[Results] The abundance of hydrothermal plume-associated archaea including Thermoplasmata, Methanosarcinia, and Methanobacteria increased when turbidity anomalies were higher. Spatially, the archaeal community structures in the hydrothermal plume and near-bottom water were similar at the phylum and class levels but showed differences at the order level. The relative abundance of Thermoplasmata was generally higher in the plume, whereas ammonia-oxidizing archaea and Methanosarcinia were more abundant in the near-bottom water. [Conclusion] Both the hydrothermal plume and the near-bottom water from 300 m southeast of the Wocan-1 hydrothermal field were affected by hydrothermal fluids, with the plume layer being more significantly affected. The near-bottom layer was affected by re-suspended sediments in addition to hydrothermal fluids. Dynamic changes of hydrothermal contributions and re-suspension of sediments were probably the main factors responsible for the spatial and temporal heterogeneity of archaeal communities. This study gives insights into the structure and spatio-temporal evolution of the archaeal community in the hydrothermal-influenced zone on a monthly scale.