Variability in microbial community and venting chemistry in a sediment-hosted backarc hydrothermal system: Impacts of subseafloor phase-separation

Abstract

Phase-separation and -segregation (boiling/distillation of subseafloor hydrothermal fluids) represent the primary mechanisms causing intra-field variations in vent fluid compositions. To determine whether this geochemical process affects the formation of microbial communities, we examined the microbial communities at three different vent sites located within a few tens meters of one another. In addition to chimney structures, colonization devices capturing subseafloor communities entrained by the vent fluids were studied, using culture-dependent and -independent methods. Microbiological analyses demonstrated the occurrence of distinctive microbial communities in each of the hydrothermal niches. Within a chimney structure, there was a transition from a mixed community of mesophiles and thermophiles in the exterior parts to thermophiles in the interior. Beside the transition within a chimney structure, intra-field variations in microbial communities in vent fluids were apparent. Geochemical analysis demonstrated that different vent fluids have distinctive end-member compositions as a consequence of subseafloor phase-separation and -segregation, which were designated gas-depleted, normal and gas-enriched fluids. In comparison to gas-depleted and normal fluids, gas-enriched fluids harbored more abundant chemolithoautotrophs with gaseous component-dependent energy metabolism, such as hydrogenotrophic methanogenesis. Subseafloor phase-separation and -segregation may play a key role in supplying energy and carbon sources to vent-associated chemolithoautotrophs and subvent microbial communities.

Quantification of Microbial Communities in Hydrothermal Vent Habitats of the Southern Mariana Trough and the Mid-Okinawa Trough

“…Gray indicates samples that did not exhibit significant differences conditions and high/low temperatures around the hydrothermal vent may produce various habitat conditions to induce a phylogenetically, functionally, and morphologically diverse microbial community. The high proportion of Epsilonproteobacteria inhabiting oxygenated and low-to mediumtemperature environments has been reported in previous studies (Huber et al 2003;Nakagawa et al 2005 (Fig. 6.3).…”

“…These studies demonstrated the prevalence of Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria, Bacteroidetes, Firmicutes, and various candidate divisions in the hydrothermal system. Due to fluctuations in the environmental conditions, microbial communities in hydrothermally influenced regions exhibit variability on various spatial and temporal scales, including large-scale intra-and inter-field variability (Flores et al 2012;Huber et al 2010;Nunoura and Takai 2009), short-term temporal and spatial variability (Perner et al 2009(Perner et al , 2013, and spatial variability on a small scale of a few centimeters to meters (Nakagawa et al 2005;Takai et al 2004). However, most studies focused on the variability of specific microbial populations in the zone adjacent to hydrothermal vents.…”

Understanding the Compositional Variability of the Major Components of Hydrothermal Plumes in the Okinawa Trough

“…The Okinawa Trough is a backarc basin in the rifting to spreading stage characterized by the development of normal faulting of transitional crust (atypical crust with mantle-derived material) and frequent magma intrusions, which provides a favorable geological environment for the development of seafloor hydrothermal systems [8,41,42]. As of 2016, there were at least 15 deep-sea hydrothermal fields reported in the Okinawa Trough based on the InterRidge data base, including the Minami-Ensei (e.g., [10]), Iheya North [9,11,43], Jade [7,13], Hakurei [8], Hatoma [44][45][46], Yonaguni Knoll IV [12,14,47], and Tangyin hydrothermal fields [48,49]. The Iheya North knoll hydrothermal field (27 ∘ 47.2 N, 126 ∘ 53.9 E) is located at a water depth about 1,000 m along the eastern slope of a small knoll, part of the Iheya North knoll volcanic complex ( Figure 1; [8]).…”

Hydrothermal Activity in the Okinawa Trough Back-Arc Basin: Geological Background and Hydrothermal Mineralization

“…Many of the mounds host active fluid venting and sulfide/ sulfate mineralization. A large mound of more than 30 m height associated with vigorous venting of clear fluid with the highest temperature of 311 C (called NBC (North Big Chimney) mound) appears to mark a center of the hydrothermal activity at the Iheya North Knoll (Nakagawa et al 2005). A diversity of fluid chemistry and temperature within the hydrothermal field has been attributed to subseafloor phase separation (Kawagucci et al 2011).…”