The Guaymas Basin Subseafloor Sedimentary Archaeome Reflects Complex Environmental Histories.

Gustavo A Ramírez,Carlos Mortera,Andreas P Teske,Christian Hensen,Ana Christina Ravelo,Matthew W Fields,Luke J Mckay,Andrew Buckley

doi:10.1016/j.isci.2020.101459

Abstract

SummaryWe explore archaeal distributions in sedimentary subseafloor habitats of Guaymas Basin and the adjacent Sonora Margin, located in the Gulf of California, México. Sampling locations include (1) control sediments without hydrothermal or seep influence, (2) Sonora Margin sediments underlying oxygen minimum zone water, (3) compacted, highly reduced sediments from a pressure ridge with numerous seeps at the base of the Sonora Margin, and (4) sediments impacted by hydrothermal circulation at the off-axis Ringvent site. Generally, archaeal communities largely comprise Bathyarchaeal lineages, members of the Hadesarchaea, MBG-D, TMEG, and ANME-1 groups. Variations in archaeal community composition reflect locally specific environmental challenges. Background sediments are divided into surface and subsurface niches. Overall, the environmental setting and history of a particular site, not isolated biogeochemical properties out of context, control the subseafloor archaeal communities in Guaymas Basin and Sonora Margin sediments.

Highlights

Guaymas Basin, located in the Gulf of California, Mexico, is a young marginal rift basin where active seafloor spreading generates northeast-to-southwest trending axial troughs surrounded on both sides by extensive flanking regions (Lizarralde et al, 2007)
SUMMARY We explore archaeal distributions in sedimentary subseafloor habitats of Guaymas Basin and the adjacent Sonora Margin, located in the Gulf of California, Mexico
Sediment and Porewater Geochemistry We surveyed archaeal distribution at six sites on the northwestern and southeastern off-axis regions of Guaymas Basin and on the Upper Sonora Margin (Figure 1, Table S1). These locations represent four different environmental settings: (1) Sediments on the Guaymas Basin flanking regions without hydrothermal or seep activity, represented by cores ContP03, ContP10, and ContP13; (2) the oxygen minimum zone (OMZ) on the upper Sonora Margin (Calvert, 1964), represented by core OMZP12, (3) compacted, highly reducing seep sediments from a pressure ridge, running along the transform fault that is cutting across the base of the Sonora Margin (Paull et al, 2007; Simoneit et al, 1990), represented by core SeepP06, and (4) the Ringvent site, characterized by off-axis hydrothermal circulation (Teske et al, 2019), represented by core RNVP11 (Figure 1)

Summary

Introduction

Guaymas Basin, located in the Gulf of California, Mexico, is a young marginal rift basin where active seafloor spreading generates northeast-to-southwest trending axial troughs surrounded on both sides by extensive flanking regions (Lizarralde et al, 2007). Since the sediments act as a heat-retaining thermal blanket, magmatic activity and organic matter alteration and mobilization are limited to the spreading center and occur at considerable distance, up to 50 km off-axis (Lizarralde et al, 2010). Many of these off-axis sites resemble cold seeps, where methane advection is linked to pathways formed by deeply buried magmatic sills (Geilert et al, 2018). If the underlying sill is sufficiently shallow and hot, the hydrothermal underpinnings of these off-axis sites becomes visible; the recently described Ringvent site provides an example (Teske et al, 2019)

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