西北印度洋卡尔斯伯格脊卧蚕热液羽流影响区细菌群落结构特征及其演化

Characteristics and evolution of bacterial communities in the Wocan hydrothermal plume-influenced zone,Carlsberg Ridge,northwestern Indian Ocean

【目的】热液羽流影响区包括热液羽流流经区域和羽流中性浮力层下方受热液颗粒物影响的区域。随着热液羽流的演化,热液羽流影响区内微生物群落的结构组成也会发生相应的变化,但是,由于观测和取样困难等原因,迄今热液羽流影响区不同空间位置微生物的群落结构特征及其在月际尺度上的演化尚不清楚。【方法】中国大洋49航次在卧蚕1号热液喷口东南侧300 m处投放了沉积物捕获器锚系,在不同离底高度开展了为期18个月的观测和时序采水。本文采用Illumina MiSeq高通量测序技术对水样中的微生物类群进行测序分析,结合现场实时探测的浊度异常资料,研究卧蚕热液区附近中性浮力羽流和热液颗粒沉降区细菌群落结构的特征和演化及其影响因素。【结果】结果表明,样品中细菌群落以γ-变形菌纲(Gammaproteobacteria)、弯曲菌纲(Camplylobacteria)、α-变形菌纲(Alphaproteobacteria)、拟杆菌纲(Bacteroidia)、梭菌纲(Clostridia)和脱硫叶菌纲(Desulfobulbia)为主。在时间上,优势类群的相对丰度随浊度起伏发生变化,当浊度异常值升高时,弯曲菌纲相对丰度增加,α-变形菌纲相对丰度减少;在空间上,热液颗粒沉降区样品(离底40 m)中弯曲菌纲的平均相对丰度更高,中性浮力羽流(离底300 m)γ-变形菌纲的平均相对丰度更高。【结论】研究区受到了热液羽流的动态影响,当热液活动增强时,弯曲菌纲相对丰度显著增加,α-变形菌纲相对丰度减少;下方羽流颗粒沉降区比上方中性浮力羽流区含有更丰富的弯曲菌纲,而γ-变形菌纲则在中性浮力羽流更加富集。热液输入物质和硫化物颗粒的含量差异可能是造成热液羽流影响区内微生物时空间异质性的主要因素。

[Objective] The zone influenced by the hydrothermal plume includes the waters within and underneath the hydrothermal plume.The structure of microbial communities in that zone varies with the evolution of the hydrothermal plume.However,due to the difficulty in observing and sampling,the diversity of microbes and how they evolve with time and in space are unclear.[Methods] During China DY49-5 cruise,a sediment trap mooring system was deployed approximately 300 m southeast of the Wocan-1 hydrothermal vent field.Eighteen months later,a total of 42 hydrothermal plume samples were retrieved from the areas 40 m and 300 m above the seafloor,respectively.In this paper,we used Illumina MiSeq combined with in-situ turbidity anomaly data to characterize the diversity and temporal evolution of bacterial communities within and beneath the neutrally buoyant plume,hoping to clarify the factors causing the spatial and temporal heterogeneity.[Results] The samples were dominated by Gammaproteobacteria,Camplylobacteria,Alphaproteobacteria,Bacteroidia,Clostridia,and Desulfobulbia.The relative abundance of Camplylobacteria increased when hydrothermal venting was more active as suggested by the anomaly high turbidity,while the relative abundance of Gammaproteobacteria and Alphaproteobacteria decreased.Spatially,Gammaproteobacteria and Camplylobacteria were more abundant within and beneath the hydrothermal plume,respectively.[Conclusion] The water column studied had been affected by the dynamics of hydrothermal plume from Wocan-1 hydrothermal field.When the hydrothermal influence was stronger,the relative abundance of Camplylobacteria was higher.The samples collected beneath the neutrally buoyant plume contained more Camplylobacteria species than those collected within the plume.It is suggested that the hydrothermal input and abundance of sulfide particles are likely the main factors causing the spatial and temporal heterogeneity of bacterial communities in the hydrothermal plume-influenced zone.