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

Abstract:

[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.