Abstract
There are still notable gaps regarding the detailed distribution of microorganisms between and within insular habitats such as deep-sea hydrothermal vents. This study investigates the community composition of black smoker vent microorganisms in the Southern Hemisphere, and changes thereof along a spatial and chemical gradient ranging from the vent plume to surrounding waters. We sampled two hydrothermal vent fields, one at the South West Indian Ridge (SWIR), the other at the East Scotia Ridge (ESR). Samples were collected across vent fields at varying vertical distances from the origin of the plumes. The microbial data were sequenced on an Illumina MiSeq platform for the 16SrRNA gene. A substantial amount of vent-specific putative chemosynthetic microorganisms were found, particularly in samples from focused hydrothermal venting. Common vent-specific organisms from both vent fields were the genera Arcobacter, Caminibacter and Sulfurimonas from the Epsilonproteobacteria and the SUP05 group from the Gammaproteobacteria. There were no major differences in microbial composition between SWIR and ESR for focused plume samples. However, within the ESR the diffuse flow and focused samples differed significantly in microbial community composition and relative abundance. For Epsilonproteobacteria, we found evidence of niche-specificity to hydrothermal vent environments. This taxon decreased in abundance by three orders of magnitude from the vent orifice to background water. Epsilonproteobacteria distribution followed a distance–decay relationship as vent-effluents mixed with the surrounding seawater. This study demonstrates strong habitat affinity of vent microorganisms on a metre scale with distinct environmental selection.
Highlights
Hydrothermal vents are ubiquitous along mid-ocean ridges, back-arc basins and volcanically active seamounts
The environmental setting at the South West Indian Ridge (SWIR) and East Scotia Ridge (ESR) vents reflects their respective positions north and south of the polar front based on temperature [53]
As has been shown previously, most of them are common deep-sea bacteria, such as Halomonas and Marinobacter mixed with abundant Epsilonproteobacteria such as Arcobacter, Sulfurimonas and Caminibacter
Summary
Hydrothermal vents are ubiquitous along mid-ocean ridges, back-arc basins and volcanically active seamounts. Other non-symbiotic vent microorganisms namely the free-living planktonic microorganisms dwell in the unpredictable fluid environment around the vents, with unstable physicochemical conditions and immense variation in temperature and availability of compounds These conditions offer a variety of microhabitats that potentially could be occupied by diverse microorganisms. The Epsilonproteobacteria are known to have diverse metabolic properties but are commonly found to be meso- or thermophilic hydrogen-oxidizing and sulfurreducing chemolithotrophs [15] Because of their preferences and high abundance in hydrothermal vent systems, Epsilonproteobacteria serve as an ideal taxon for examining vent-specific microbial community structures [7]. 0 background seawater plume had a high relative abundance of genera Halomonas and Alteromonas, which resembles some of the diffuse vent samples from the ESR. This is further verified by the NMDS (figure 6), where the vent samples mostly clustered together and the diffuse samples and background samples from the SWIR and ESR clustered together
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