Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations were measured by high-temperature (720ºC) combustion using a Shimadzu TOC-VCSH analyzer. Two consensus reference materials (CRM, from University of Miami, Dickson et al., 2007), Florida Strait 700 m-deep seawater (DSW) and low carbon water (LCW), were used.

Nitrate-plus-nitrite (N+N) analysis was carried out with a colorimetric flow injection analyzer (Grasshoff et al., 1999).

Ammonium concentrations were measured at the University of Hawaii with a flow injection-fluorometric method (Jones, 1991) and calibrated against gravimetrically prepared standards. The detection limit was 0.1 uM at the setting for measuring low concentrations of ammonium in the vent fluids. The analytical uncertainty was 0.03 uM.

Silicate was measured by colorimetry (Grasshoff et al., 1999).

Total dissolved iron (1-sigma precision 4%) in vent fluids was measured by atomic absorption at PMEL/Seattle on samples preserved shipboard with ultra-pure HCl (TraceMetal Grade).

The total iron of acidified plume samples was measured by a Ferrozine colorimetry method (Gibbs, 1976; Stookey, 1970).

The pH of was measured shipboard at laboratory temperature in a closed vessel using a glass pH electrode (Ross Sure-Flow) calibrated with NBS-certified buffers (Fisher Scientific). The precision of the measurement is 0.02 pH units.

The POC and particulate nitrogen (PN) and isotopic compositions of acidified (with 1 N HCl) GF/F samples were measured with a CN elemental analyzer (Costech, ECS 4010) connected in-line with an isotope ratio mass spectrometer (IRMS; Thermo Finnigan Delta XP) interfaced with a ConFloIV, at the University of Hawaii. The reference materials were extensively characterized with certified reference materials, including NBS 18, NBS 19, NIST 1547, NIST 3, USGS 32, USGS 34, and USGS 35.

BCO-DMO Processing notes:

Converted date and time columns to 1 datetime column (ISO format)
Longitude on western hemisphere were converted to negative (-180,180 scale)
Renamed fields to comply with database requirements

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