Table of Contents

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

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 (Dissolved Organic Carbon) 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 (Total Dissolved Nitrogen) 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 (Nitric oxides) 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 (Nitrite) 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 (Ammonium) 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 (Phosphate) 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 (Total Dissolved Phosphorous) 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).

2) H2S (Hydrogen Sulfide): Water 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).

3) Alkalinity was determined colorimetrically by the method described in Sarazin, 1999 (A rapid and accurate spectroscopic method for alkalinity measurements in sea water samples. Water Research 33: 290-294).

4) CH4 (Methane): A 1L water sample was collected from the Niskin bottle using gas tight tubing and standard collection methods for dissolved gases. Subsequently in the lab, a 700 mL sub-sample was transferred to an evacuated 1L media bottle. The water was sonicated under vacuum for 1 minute and then shaken; this process was repeated twice to transfer dissolved gases into the bottle headspace. The bottle pressure was equilibrated with helium purged saturated salt brine and the volume of recovered dissolved gas was recorded. The gas sample was transferred to an evacuated serum vial for storage until analysis on the gas chromatograph. CH4 was determined by headspace analysis using an SRI 8610C gas chromatograph equipped with a flame ionization detector (Crespo-Medina et al. 2014, Nature Geoscience, 7:423-427).

5) Salinity and pH: Salinity was determined with a refractometer, and pH was measured with a Ross electrode calibrated with NBS standard buffers.

6) 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 Processing Notes:
- data submitted in Excel file "AT42-05_WC_geochem_dataset.xlsx" sheet 1 extracted to csv
- joined chemistry data with metadata table
- 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
- converted date from m/d/y to ISO format, yyyy-mm-dd
- added ISO datetime column
- changed blank cells to 'nd' for 'no data'
- columns Sulfate and Chloride removed as requested by the submitter, columns included in the file AT42-05_WC_geochem_dataset_V2.xlsx by mistake. 

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.