Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Methodology:

Sediment samples were collected from hydrothermal areas of Guaymas Basin in the Gulf of California during cruise AT3706 of R/V Atlantis in December 2016. Push cores were obtained using the human-occupied deep diving vehicle Alvin during dives 4867 to 4872. Porewater was extracted from the sediment by centrifugation and then filtered through a 0.2 μm syringe filter. Samples for quantification of concentrations of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), volatile fatty acids and alcohols were immediately frozen and stored at −20 °C or −80 °C (i.e. alcohols) before analysis.

Instruments:

The in situ temperature in the sediment was measured with Alvin’s external heatflow probe (McKay et al., 2012). DIC was measured with: Shimadzu Instruments GC-2014 Gas Chromatograph with FID Detector and Methanizer. The concentration of DOC was measured with a Shimadzu TOC-V equipped with a nondispersive infrared detector (Joye et al., 2004). The concentrations and stable carbon isotopic compositions of VFAs were analyzed by a liquid chromatography coupled to isotope ratio mass spectrometry (DELTA Plus XP IRMS) via a LC Isolink interface (ThermoFinnigan) (Heuer et al., 2006). Methanol and Ethanol were measured with: a purge and trap system connected to an SRI Instruments 8610C Gas Chromatograph with FID Detector.

Issues of note:

Due to the limited volume of porewaters, methanol and ethanol were not determined for most of the samples collected from Dives 4867 to Dive 4870.

Missing data identifiers:
* B.D.: Below detection limit.
* nd：Not determined. nd is the default missing data identifier in the BCO-DMO data system.

BCO-DMO Data Manager Processing Notes:
* added a conventional header with dataset name, PI name, version date
* modified parameter names to conform with BCO-DMO naming conventions (spaces, +, and - changed to underscores). Units in parentheses removed and added to Parameter Description metadata section.
* Data submitted in Excel file "Data submission OCE.xlsx" sheet "Geochemistry" extracted to csv
* The defualt missing identifier in the original file N.D. for "not determined" is displayed as "nd" in the data. nd is the default missing data identifier in the BCO-DMO system.
* removed metadata notes at the bottom of the file and moved to parameter descriptions. E.g. "B.D.: Below detection limit."
* Date formats converted to ISO 8601 yyyy-mm-dd
* Lat/lon converted to decimal degrees from degrees decimal minutes

Description from NSF award abstract:
Hydrothermally active sediments in the Guaymas Basin are dominated by novel microbial communities that catalyze important biogeochemical processes in these seafloor ecosystems. This project will investigate genomic potential, physiological capabilities and biogeochemical roles of key uncultured organisms from Guaymas sediments, especially the high-temperature anaerobic methane oxidizers that occur specifically in hydrothermally active sediments (ANME-1Guaymas). The study will focus on their role in carbon transformations, but also explore their potential involvement in sulfur and nitrogen transformations. First-order research topics include quantifying anaerobic methane oxidation under high temperature,in situ concentrations of phosphorus and methane , and with alternate electron acceptors; sulfate and sulfur-dependent microbial pathways and isotopic signatures under these conditions; and nitrogen transformations in methane-oxidizing microbial communities, hydrothermal mats and sediments.

This integrated biogeochemical and microbiological research will explore the pathways of and environmental controls on the consumption and production of methane, other alkanes, inorganic carbon, organic acids and organic matter that fuel the Guaymas sedimentary microbial ecosystem. The hydrothermal sediments of Guaymas Basin provide a spatially compact, high-activity location for investigating novel modes of methane cycling and carbon assimilation into microbial biomass. In the case of anaerobic methane oxidation, the high temperature and pressure tolerance of Guaymas Basin methane-oxidizing microbial communities, and their potential to uncouple from the dominant electron acceptor sulfate, vastly increase the predicted subsurface habitat space and biogeochemical role for anaerobic microbial methanotrophy in global deep subsurface diagenesis. Further, microbial methane production and oxidation interlocks with syulfur and nitrogen transformations, which will be explored at the organism and process level in hydrothermal sediment microbial communities and mats of Guaymas Basin. In general, first-order research tasks (rate measurements, radiotracer incorporation studies, genomes, in situ microgradients) define the key microbial capabilities, pathways and processes that mediate chemical exchange between the subsurface hydrothermal/seeps and deep ocean waters.