Table of Contents

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

Location: Guaymas Basin, Gulf of California, 27 00.00 N, -111 20.00 W

Sediment samples were collected by the DSV Alvin using PVC push cores.  Upon arrival at the surface the cores were described and cataloged prior to being sectioned into discrete depth intervals.  Porewater was separated from the sediment by centrifugation.  Porewater and sediment samples were preserved and analyzed as follows: 

1) Nutrients (DOC, TDN, NOx, NO2, NH4, PO4, TDP): Porewater sample was filtered through a pre-rinsed 0.2 um regenerated cellulose Target2 syringe filter (Thermo Scientific, Prod. No. F25047), collected into an HDPE bottle and stored frozen at -20°C until analysis.  Individual analytes were analyzed as follows:
DOC was determined using high temperature catalytic combustion and an NDIR detector following the method described in Sugimura and Suzuki, 1988.  
TDN was determined using high temperature combustion and a chemiluminescence detector following the method described in Watanabe et. al, 2007.
NOx was determined using chemical reduction and a nitric oxide detector following the method described by Garside, 1982.  
NO2 was determined using the colorimetric method described by Bendschneider and Robinson, 1952 as reproduced by Parsons, Marta, and Lalli, 1984.
NH4 was determined using the colorimetric method described by Solorzano, 1969.
PO4 was determined using the colorimetric method described by Strickland and Parsons, 1972.
TDP was determined using the colorimetric method described by Solorzano and Sharp, 1980.

2) C1-C3 (CH4, C2H6, C3H8): Sediment sample was collected into a glass serum vial, preserved with 1M NaOH, crimp-sealed with a butyl rubber stopper and stored at room temperature until analysis.  C1-C3 was determined by headspace analysis using an SRI 8610C gas chromatograph equipped with a flame ionization detector and SRI Hayesep D 6’x1/8” column (Prod. No. 8600-PKDB).

3) H2S: Porewater sample was collected into a 15 mL centrifuge tube containing 2M zinc acetate and stored at 5°C until analysis.  H2S was determined using the colorimetric method described by Cline, 1969.

4) SO4: Porewater sample was collected into a 7 mL scintillation vial, acidified with 10 uL concentrated hydrochloric acid per mL sample and sealed with a PTFE lined cap.  SO4 determination was made after Cl removal using a Dionex OnGuard Ag cartridge (Prod. No. 039637).  Sample analysis was performed using KOH eluent supplied by a Dionex EGC III KOH Eluent Generator Cartridge (Prod. No. 074532), Dionex CR-ATC Continuously Regenerated Trap Column (Prod. No. 060477), Dionex AERS 500 Electronically Regenerated Suppressor (Prod. No. 082541), Dionex IonPac AG19 Guard Column (Prod. No. 062888), Dionex IonPac AS19 Analytical Column (Prod. No. 062886) and Dionex CRD 200 RFIC Carbonate Removal Device (Prod. No. 062986).

5) TPN: The pressed sediment sample (mud-cake) was dried at 60°C and then homogenized via grinding. TPN was determined by the method described by Gordan, Jr., 1969 as reproduced by Sharp, 1974. Samples were analyzed on a ThermoFinnigan FlashEA 1112 series NC Soil Analyzer. 

6) TPC: The pressed sediment sample (mud-cake) was dried at 60°C and then homogenized via grinding. TPC was determined by the method described by Gordan, Jr., 1969 as reproduced by Sharp, 1974. Samples were analyzed on a ThermoFinnigan FlashEA 1112 series NC Soil Analyzer. 

7) POC: The pressed sediment sample (mud-cake) was acidified with 1 N HCl, dried at 60°C, and then homogenized via grinding. POC was determined by the method described by Gordan, Jr., 1969 as reproduced by Sharp, 1974. Samples were analyzed on a ThermoFinnigan FlashEA 1112 series NC Soil Analyzer. 

8) Calculated Values (NO3, DIN, DON, DOP):  These values were calculated as follows:
NO3 = NOx - NO2
DIN = NOx + NH4
DON = TDN - DIN
DOP= TDP - PO4

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 "AT37-06 Sediment Summary submit.xlsx" Sheet1 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
* OLW flag for sediment sampling depth (OLW = overlying water) moved from a value in the Depth column to a new Depth_OLW column

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.