Abstract
To determine microbial community composition, community spatial structure and possible key microbial processes in the shallow-sea hydrothermal vent systems off NE Taiwan’s coast, we examined the bacterial and archaeal communities of four samples collected from the water column extending over a redoxocline gradient of a yellow and four from a white hydrothermal vent. Ribosomal tag pyrosequencing based on DNA and RNA showed statistically significant differences between the bacterial and archaeal communities of the different hydrothermal plumes. The bacterial and archaeal communities from the white hydrothermal plume were dominated by sulfur-reducing Nautilia and Thermococcus, whereas the yellow hydrothermal plume and the surface water were dominated by sulfide-oxidizing Thiomicrospira and Euryarchaeota Marine Group II, respectively. Canonical correspondence analyses indicate that methane (CH4) concentration was the only statistically significant variable that explains all community cluster patterns. However, the results of pyrosequencing showed an essential absence of methanogens and methanotrophs at the two vent fields, suggesting that CH4 was less tied to microbial processes in this shallow-sea hydrothermal system. We speculated that mixing between hydrothermal fluids and the sea or meteoric water leads to distinctly different CH4 concentrations and redox niches between the yellow and white vents, consequently influencing the distribution patterns of the free-living Bacteria and Archaea. We concluded that sulfur-reducing and sulfide-oxidizing chemolithoautotrophs accounted for most of the primary biomass synthesis and that microbial sulfur metabolism fueled microbial energy flow and element cycling in the shallow hydrothermal systems off the coast of NE Taiwan.
Highlights
Hydrothermal vents occur over a wide depth range, from the intertidal to the abyssal [1]
The silicon dioxide (SiO2) and dissolved inorganic carbon (DIC) concentrations increased along the gradient from the surface to the vents
Compared to deep-sea vents, sulfide (S22) concentration was relatively lower in this shallow vent system, whereas relatively higher concentrations of chlorophyll a and dissolved organic carbon (DOC) [12] were found here
Summary
Hydrothermal vents occur over a wide depth range, from the intertidal to the abyssal [1]. Shallow-sea hydrothermal vents, at depths of 200 meters or less, have been studied less. In hydrothermal fluids, reduced compounds, such as hydrogen sulfide (H2S), methane (CH4) and hydrogen (H2), are the most important for biological processes and, active sulfur and CH4 cycling are usually considered to occur in either deep-sea or shallow-sea hydrothermal systems. Besides chemotrophy based on sulfur and/ or CH4, phototrophy may be another important process in the shallow-sea vent fields since sunlight and hydrothermal energy cosupport these systems [1,2]. Unlike the deep-sea hydrothermal vent where the effect of venting is restricted to a very narrow zone near the discharge, the volcanic fluids affect the near-bottom water layer, and the surface in the shallow-sea vent fields, affecting whole ecosystems [1]
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