Table of Contents

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

Coordinates of sample locations, depths and analyses conducted during the biogeochemical hot spot study.

These data are reported and discussed in Mattes et al., 2013.

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).

Samples for nutrients, DOC and TDN analyses were stored frozen in 60 mL HDPE bottles until analysis within 2 months of the completion of the cruise. Nutrient concentrations were assessed by follow the protocols of the WOCE Hydrographic Program using a Technicon AAII system at the University of Washington. DOC and TDN concentrations were assessed by high temperature combustion using a Shimadzu TOC-csh with auto injection (Dickson et al 2007). Four point standard curves using KHP and KNO3 were run daily to calibrate the response of the high temperature combustion system. Measurements were quality controlled using Consensus Reference Materials (CRM’s) distributed to the international community by the Hansell laboratory (Hansell 2005). The CRMs were analyzed at regular intervals during each analytical day. Low C reference water was employed to determine system blanks. DON was determined as the difference in concentrations of TDN and DIN. (See Supplementary Figure One (pdf))

Description from NSF award abstract:
The ocean serves an immense reservoir of carbon, nitrogen, phosphorus, sulfur, and other elements required for all life. The active and diverse microbial populations that inhabit the oceans are responsible for mediating nutrient transformations that maintain the chemistry of seawater. A recent study identified a ubiquitous group of marine bacteria from the Arctic96BD-19 gamma-proteobacterial sulfur oxidizer (GSO) lineage that is closely related to known sulfur oxidizing species that fix inorganic carbon and oxidize sulfide in low-oxygen waters. The potential for GSOs to use reduced forms of sulfur in oxygenated waters suggests that they are a keystone species that link the marine carbon and sulfur cycles. The only known isolates from the Arctic96BD-19 lineage of GSOs are now in culture, allowing fundamental questions about their roles in carbon and sulfur cycling to be investigated. Preliminary data suggest that they use energy from the oxidation of sulfur to assimilate carbon. This project seek to address the overarching hypothesis that sulfur transformations provide the Arctic96BD- 19 lineage of GSOs with energy for organic and inorganic carbon cycling throughout the water column.

Three specific hypotheses will be tested.
1. Arctic96BD-19 cells assimilate either organic carbon or fixes inorganic carbon, depending on environmental conditions.
2. Arctic96BD-19 cells oxidize thiosulfate via formation of a tetrathionate intermediate, or using the branched thiosulfate oxidation pathway.
3. Arctic96BD-19 cells are ubiquitous sulfur oxidizers that assimilate organic and inorganic carbon through the Pacific Northwest.

A combination of laboratory growth studies of the investigator's pure cultures and comparative genomic analyses will be used. The genomic data will be used to determine whether the Arctic96BD-19 cultures possess the genetic potential to oxidize reduced sulfur to sulfate (based on possession of known core and ancillary sulfur oxidation genes), which potential oxidation pathways are used, and whether they can fix inorganic carbon. These data will help guide the physiology studies by determining the most likely forms of inorganic and organic compounds that can be utilized.

Marine bacteria are critical players in global nutrient cycles, but many of their individual and community functions in the ecosystem are not well understood. Future oceanographers will need to use cultivation-dependent and cultivation-independent methods to identify metabolic process that shape microbial communities and impact biogeochemical cycles. Student education, scientific advancement, and public awareness are all important components of this project.