Dataset: Sulfur Oxidizers Sample Collection and Nutrient Information
Deployment: TN268

All samples were collected onboard the R/V Thomas G. Thompson during a University of Washington led research cruise in support of the National Science Foundation’s Ocean Observatory Initiative-Regional Scale Nodes cruise (August 19 – September 1, 2011) from Seattle, WA to Hydrate Ridge and Axial Seamount (Figure 1). Water samples for microbial and chemical analyses were collected using a Conductivity, Temperature, and Depth (CTD) rosette profiler equipped with 12 L Niskin bottles. Samples were collected from 5 different stations (CTD7 Cascadia Basin (lat: 45.8602/lon:-127.9353), CTD8 base of Axial Seamount (lat:45.8202/lon:-129.7567), CTD11 ASHES vent field (lat:45.9339/lon:-130.0136), CTD13 Coquille vent (lat:45.9264/lon:-129.9803), and CTD 17 ASHES vent field (lat: 45.9340/lon:-130.0138)).

Contextual data and site description

Partial and full water column profile measurements were conducted using a rosette-mounted instrument package that included a Seabird 9plus CTD with dual temperature and conductivity sensors, a Seabird 43 oxygen sensor (calibrated to onboard Winkler titrations), and a WET Labs C-Star transmissometer. Using the down-cast profile measurements, the position and extent of the hydrothermal plume was identified by large negative deflections in beam transmission (corresponding to the high particulate load generated from precipitating metal sulfides in the hydrothermal fluid), and subtle positive anomalies in temperature (corresponding to the heat input from high-temperature fluids), following well established plume identification practices (Baker et al 1993). At the summit of Axial seamount, hydrothermal plumes were 30-100 meters thick, with the neutrally buoyant plume having a typical rise height of 75-200 meters above the seafloor.

During the profile up-cast, 12 L Niskin water sampling bottles (General Oceanics) were triggered at depths determined to be within the hydrothermal plume, and at regular intervals in the water column above the plume. Water samples were analyzed for methane (CH4) and hydrogen (H2) concentrations using shipboard gas chromatography. Samples were headspace extracted and inlet into a gas chromatograph (SRI Instruments) configured with a helium carrier, a 30 meter 5Å mol sieve column, a 50°C isothermal temperature program, and flame ionization (FID) and pulse discharge (PDD) detectors. This method provided the sensitivity to measure the low gas concentrations of background seawater (CH4 0.5-1 nM, H2 0.1-0.5 nM). Hydrothermal fluids are enriched in both CH4 and H2 (Lilley et al 1982, Proskurowski et al 2008).