Microbial Communities Under Distinct Thermal and Geochemical Regimes in Axial and Off-Axis Sediments of Guaymas Basin.

Andreas Teske,Daniel Lizarralde,Dirk De Beer,Matthew A Saxton,Dylan White,Gunter Wegener,Guangchao Zhuang,Daniel Hoer,S Adam Soule,Samantha B Joye,S Emil Ruff,Jeffrey P Chanton,Barbara Macgregor

doi:10.3389/fmicb.2021.633649

Abstract

Cold seeps and hydrothermal vents are seafloor habitats fueled by subsurface energy sources. Both habitat types coexist in Guaymas Basin in the Gulf of California, providing an opportunity to compare microbial communities with distinct physiologies adapted to different thermal regimes. Hydrothermally active sites in the southern Guaymas Basin axial valley, and cold seep sites at Octopus Mound, a carbonate mound with abundant methanotrophic cold seep fauna at the Central Seep location on the northern off-axis flanking regions, show consistent geochemical and microbial differences between hot, temperate, cold seep, and background sites. The changing microbial actors include autotrophic and heterotrophic bacterial and archaeal lineages that catalyze sulfur, nitrogen, and methane cycling, organic matter degradation, and hydrocarbon oxidation. Thermal, biogeochemical, and microbiological characteristics of the sampling locations indicate that sediment thermal regime and seep-derived or hydrothermal energy sources structure the microbial communities at the sediment surface.

Highlights

Over 700 marine hydrothermal vent sites are currently known (Beaulieu and Szafranski, 2020), including sedimented hydrothermal systems at coastal and continental margin locations (Price and Giovanelli, 2017)
The bathymetry of the hydrothermally active graben segment in southern Guaymas Basin was mapped by AUV Sentry during dives 407-409, 413-417; the bathymetry of Octopus Mound at the Central Seep site was mapped during Sentry dive 412 (Figure 1)
During expedition AT37-06 to Guaymas Basin, AUV Sentry and submersible Alvin mapped and sampled hydrothermally active sediments within the southern Guaymas Basin spreading center, at an off-axis sill-driven vent site (Ringvent) with hybrid seep/vent biota on the northwestern flanking regions near Isla Tortuga (Teske et al, 2019), and at the off-axis Central Seep site on the northwestern Guaymas flanks (Geilert et al, 2018) that is approximately equidistant from the Sonora and Baja California coasts (Figure 1)

Summary

Introduction

Over 700 marine hydrothermal vent sites are currently known (Beaulieu and Szafranski, 2020), including sedimented hydrothermal systems at coastal and continental margin locations (Price and Giovanelli, 2017). The diversity of hydrothermal regimes in Guaymas Basin selects for microbial communities with adaptations to different thermal and geochemical niches (McKay et al, 2016; Teske et al, 2016). We compare thermal gradients, porewater geochemistry, and microbial community composition in the surface layer of different hydrothermal, cold seep, and background sediments (Table 1) to determine whether sediments with distinct porewater geochemistry and thermal regimes harbor particular bacterial and archaeal populations. The Guaymas Basin background sediments harbor the five globally distributed marine benthic archaeal groups of MBG-A, MBG-B (Lokiarchaeota), MBG-C (Bathyarchaeota), MBG-D (Thermoprofundales), and MBG-E (Thermoplasmata subgroup) that were originally discovered in cold North Atlantic seafloor sediments (Vetriani et al, 1999)

Methods

Results

Conclusion