Table of Contents

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

Sediment geochemistry from push cores obtained using the human-occupied deep-diving vehicle (HOV) Alvin dives 4991-5000 during the R/V Atlantis cruise AT42-05 in Guaymas Basin, Gulf of California (27 00.00 N, -111 20.00 W) in November  2018.

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 using a manually-actuated pore water press.  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 (A high-temperature catalytic oxidation method for the determination of non-volatile dissolved organic carbon in seawater by direct injection of liquid sample. Mar. Chem., 24: 105-131). 

TDN was determined using high temperature combustion and a chemiluminescence detector following the method described in Watanabe et. al, 2007 (Conversion efficiency of the high-temperature combustion technique for dissolved organic carbon and total dissolved nitrogen analysis.  Intern. J. Environ. Anal. Chem., 87: 387-399).

NOx was determined using chemical reduction and a nitric oxide detector following the method described by Garside, 1982 (A chemiluminescent technique for the determination of nanomolar concentrations of nitrate and nitrite in seawater. Mar. Chem. 11: 159-167). 

NO2 was determined using the colorimetric method described by Bendschneider and Robinson, 1952 (A new spectrophotometric method for the determination of nitrite in sea water. J. Mar. Res., 11: 87) as reproduced by Parsons, Marta, and Lalli, 1984 (Determination of Nitrite.  A manual of chemical and biological methods for seawater analysis pp. 7-9).

NH4 was determined using the colorimetric method described by Solorzano, 1969 (Determination of ammonia in natural waters by the phenolhypochlorite method.  Limnol. Oceanogr., 14: 799-801).

PO4 was determined using the colorimetric method described by Strickland and Parsons, 1972 (Determination of reactive phosphorus. A practical handbook of seawater analysis. Fisheries Research Board of Canada, pp. 49-52).

TDP was determined using the colorimetric method described by Solorzano and Sharp, 1980 (Determination of total dissolved phosphorous and particulate phosphorous in natural waters.  Limnol. Oceanogr., 25: 754-758).

Sediment pH was determined using a sediment probe (Oakton, Prod. No. 35634-50) and measured immediately during core sectioning; the probe was calibrated using NBS standards.

Pore water pH was determined using a Ross electrode (Thermo Fisher, Prod. No. 8103BNUWP) that was calibrated using NBS standards.

2) Alkalinity: Porewater alkalinity was determined using the spectrophotometric method described by Sarazin et al., 1999 (A rapid and accurate spectroscopic method for alkalinity measurements in sea water samples. Water Research 33:290-294)./

3) CH4: Sediment samples (3 cubic centimeters) were collected into a glass serum vial, preserved with 1M NaOH (3 milliliters), crimp-sealed with a butyl rubber stopper and stored at room temperature until analysis.  CH4 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).

4) 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 (Spectrophotometric determination of hydrogen sulfide in natural waters.  Limnol. Oceanogr., 14: 454-458).

5) Sulfate (SO4): Porewater sample was filtered through a pre-rinsed 0.2 μm regenerated cellulose Target2 syringe filter (Thermo Scientific, Prod. No. F25047) into a 7 mL scintillation vial. Samples were acidified with 10 μL of concentrated HNO3 per 1 mL sample, sealed with a PTFE lined cap, and stored at room temperature until analysis. 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). Reference - Weston et al. 2006, Biogeochemistry 77: 375-408.

6) Chloride (Cl): Porewater sample was filtered through a pre-rinsed 0.2 μm regenerated cellulose Target2 syringe filter (Thermo Scientific, Prod. No. F25047) into a 7 mL scintillation vial. Samples were acidified with 10 μL of concentrated HNO3 per 1 mL sample, sealed with a PTFE lined cap, and stored at room temperature until analysis. 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). Reference - Weston et al. 2006, Biogeochemistry 77: 375-408.

7) Calculated Values: Values for NO3, DIN, DON, DOP were calculated as follows:
NO3 = NOx - NO2
DIN = NOx + NH4
DON = TDN - DIN
DOP= TDP - PO4

BCO-DMO Processing Notes:
- data submitted in Excel file "Joye_OCE_1357360_Data_Submission_AT4205_sediment.xlsx" sheet 1 extracted to csv
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions: spaces, +, and - changed to underscores; changed µ to u; removed #, (, )
- converted latitude and longitude from degrees-decimal-minutes to decimal-degrees, rounded to 4 decimal places
- re-formatted date from d/m/yy to yyyy-mm-dd
- extracted strings from numeric columns and added to new adjacent columns: OLW from depth and bdl from O2_uM, DOP_uM, H2S_mM, PIC_pcent
- changed blank cells to 'nd' for 'no data'

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.