Dataset: Sediment methane and sulfate concentrations and radiotracer anaerobic methane oxidation and sulfate reduction rates in the Gulf of California during R/V Atlantis cruise AT50-22 in 2024

Sediment samples were collected by the HOV Alvin using PVC push cores. Upon arrival at the surface, the cores were described and cataloged prior to being sectioned into discrete 3 cm depth intervals. Methane samples were collected first.  Porewater was separated from the sediment using a manually-actuated porewater press as described by Joye et al., 2004. Whole sediment subsamples for radiotracer sulfate reduction rates and anaerobic oxidation of methane rates were collected in triplicate from a parallel core and were handled, injected, incubated, and analyzed using the methods described in Joye et al., 2004.

CH4: Methane samples (3 cc whole sediment) were collected into a glass serum vial, preserved with 2 mL 2 M N₂-purged NaOH, crimp-sealed with a butyl rubber stopper and stored at room temperature until analysis. Concentrations were determined by headspace analysis using an SRI 8610 GC-FID with Agilent J&W HP-PLOT Al2O3 S Capillary Column, 50 m, 0.53 mm, 15.00 μm (Prod. No. 19095P-S25E). See Joye et al., 2004.

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 with a Dionex Integrion HPIC using KOH eluent supplied by a Dionex EGC 500 KOH Eluent Generator Cartridge (Prod. No. 075778), Dionex CR-ATC Continuously Regenerated Trap Column (Prod. No. 088662), Dionex ADRS 600 Dynamically Regenerated Suppressor (Prod. No. 088666), Dionex IonPac AG18 Guard Column (Prod. No. 060551), Dionex IonPac AS18 Analytical Column (Prod. No. 060549) and Dionex CRD 200 Carbonate Removal Device (Prod. No. 062983). See Weston et al., 2006.