Table of Contents

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

Geochemical measurements of CTD and Alvin Niskin samples collected in the Gulf of California during R/V Falkor cruise FK190211 in 2019.

Locations:

Gulf of California
Guaymas Basin, 27 00.00 N, -111 24.00 W
Sonora Margin, 27 35.00 N, -111 28.00 W
Pescadero Basin, 24 00.00 N, -108 51.00 W

Sampling and analytical procedures:

1) Nutrients (DOC, TDN, NOx, NO2, NH4, PO4, TDP): Water 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 (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.
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) Alkalinity - Water sample was filtered through a pre-rinsed 0.2 μm regenerated cellulose Target2 syringe filter (Thermo Scientific, Prod. No. F25047) into a 15 mL centrifuge tube and stored at 5°C until analysis.   Alkalinity was determined using the spectrophotometric method described by Sarazin et al., 1999.

3) H2S: 5 mL water sample was collected into a 15 mL centrifuge tube containing 200 uL of 20% zinc acetate and stored at 5°C until analysis.  H2S was determined using the colorimetric method described by Cline, 1969.

4) SO4: Water 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.

5) Cl - Water 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) Dissolved oxygen: - DO was measured with a Thermo Orion DO probe (Prod. No. 083005MD) while sample was constantly stirred.

7) Salinity: Salinity was determined with a refractometer.

8) pH - pH was measured using a Ross electrode (Thermo Fisher, Prod. No. 8103BNUWP) calibrated with standard pH buffers of pH 4, 7, and 10.

9) CH4: - Gas samples were collected by overflowing a 1 L PETG bottle and closing headspace-free with a Teflon septum cap. A modified 1 L glass media bottle was evacuated to a pressure of 0.2 Torr or below. A 0.7 L aliquot of sample from the PETG was pulled into the evacuated bottle. The 0.7 L sample was shaken and sonicated 3x before the pressure was equilibrated by the addition of brine purged with UHP nitrogen. Extracted gases were collected from the top of the modified media bottle using a syringe and stored in 20 mL serum vials filled with brine. Methane concentrations were determined by injecting gas samples from the brine vials onto an SRI 8610 GC-FID and SRI Hayesep D 6’x1/8” column (Prod. No. 8600-PKDB). See Schmitt, 1991 and Lammers, 1994. 

10) 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:
* Extracted data submitted in Excel file FK190211 Water Column Summary - with MOx.xlsx to csv
* added a conventional header with dataset name, PI name, version date
* modified parameter names to conform with BCO-DMO naming conventions: only A-Za-z0-9 and underscore allowed.  Can not start with a number.  (spaces, +, and - changed to underscores). 
* blank values in this dataset are displayed as "nd" for "no data."  nd is the default missing data identifier in the BCO-DMO system.
* longitude and latitude converted from degrees decimal mintues to decimal degrees,  rounded to five decimal places
* Date converted to ISO 8601 format YYYY-MM-DD
* comment lines explaining what BD and ND mean were removed and added to the parameter descriptions
* The second occurance of column named "NH4" was removed from the dataset at the request of the submitter. 

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.