Abstract:

This dataset contains water column process rate measurements from water collected aboard the R/V Endeavor cruise EN559 in the northern Gulf of Mexico from 2015-05-31 to 2015-06-02. Samples were collected during cruise EN559 using a CTD-rosette. The objective was to determine water column process rates at ECOGIG seep and other study sites. The ship departed Gulfport, Mississippi on 2015-05-29 and collected samples at ECOGIG sites before returning to Gulfport on 2015-06-21. Water samples collected with the CTD-rosette were incubated under simulated in-situ conditions after addition of 15N2 and either 13C-bicarbonate or 13C -methane tracers for 24 (DIC label) or 48h (CH4 label). Experiments were terminated by gentle pressure filtration onto a 10 µm sieve and pre-combusted GF/F filters to collect the small and large size fractions of particles. Filters were dried, then pelletized in Sn (tin) capsules for isotopic analysis. N and C isotopic abundances were measured by continuous-flow isotope ratio mass spectrometry using a Micromass Optima IRMS interfaced to a CE NA2500 elemental analyzer. Rates were calculated using a mass balance approach (Montoya et al. 1996). The dataset also includes the date, depth, and locations (latitudes and longitudes) of the sample collection.

Suggested Citation:

Montoya, Joseph P. and Erica K. Strope. 2021. Water column process rate measurements from water collected aboard the R/V Endeavor cruise EN559 in the northern Gulf of Mexico from 2015-05-31 to 2015-06-02. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-eg90-tk58

Purpose:

Determination of water column process rates at ECOGIG seep and other study sites.

Data Parameters and Units:

Date (sampling date, m/dd/yyyy); NFix# (sequential experimental ID); Station (Station event number from cruise EN559 aboard the R/V Endeavor); Latitude and Longitude (decimal degrees); Depth (m); C Substrate [13C-labelled substrate, either 13C-bicarbonate (DIC) or 13C-methane (CH4)]; PN concentrations (µmole L^-1); PC concentrations (µmole L^-1); Vat% (NFix) [h^-1]; RhoAt% (N Fix) [µmole L^-1 h^-1]; Vat% (CFix) [h^-1]; RhoAt% (C Fix) [µmole L^-1 h^-1]. Rates are reported for both the small (<10 µm) and large (> 10 µm) size fractions of particles. The dataset also includes the cruise documentation with the cruise information for the R/V Endeavor cruise EN559 (2015-05-29 to 2015-06-21) led by chief scientist Dr. Joseph Montoya.

Methods:

Water samples collected with the CTD-rosette were incubated under simulated in-situ conditions after addition of 15N2 and either 13C-bicarbonate or 13C-methane tracers for 24 hours (DIC label) or 48 hours (CH4 label). Experiments were terminated by gentle pressure filtration onto a 10 µm sieve and precombusted GF/F filters to collect the small and large size fractions of particles. Filters were dried, then pelletized in Sn capsules for isotopic analysis. N and C isotopic abundances were measured by continuous-flow isotope ratio mass spectrometry using a Micromass Optima IRMS interfaced to a CE NA2500 elemental analyzer. Rates were calculated using a mass balance approach (Montoya et al. 1996).

Instruments:

The elemental and isotopic composition of samples was measured by continuous-flow isotope ratio mass spectrometry using a CE NC2500 elemental analyzer interfaced to a Micromass Optima and Isoprime 100 IRMS systems.

Provenance and Historical References:

Montoya, Joseph P., Maren Voss, Paul Kahler, Douglas G. Capone. 1996. A simple, high-precision, high-sensitivity tracer assay for N2 fixation. Applied Environmental Microbiology 62(3):986-993. doi:10.1128/aem.62.3.986-993.1996

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