During Alvin Dive 4905, May 8, 2017, 5 major samples were collected at the diffuse-flow vent Crab Spa. The fluid from these samplers was used in an on-deck Vent-SID incubation. The purpose of the incubation was to simulate a sea-floor incubation of the Vent-SID. Upon arrival of majors on the ship, we transferred fluid from the majors into N2 flushed 1L Restek bags. The bags were stored at 4\u02daC and taken out as needed for setting up a new Vent-SID incubation. In total,\u00a0six incubations were conducted, all at 25(+/-2)\u02daC.
\nMicrobial cell counts: Samples for cell numbers were fixed with formaldehyde (1% final concentration) and then counted on the board the ship after staining with acridine orange by fluorescence microscopy as described in McNichol et al. (2016).
\nCarbon fixation rates: 13C-labeled bicarbonate was added to the incubation chambers to assess chemoautotrophic production.\u00a0At the beginning and the end of the incubation, fluids were filtered onto pre combusted GFF filters, which were frozen until analysis back in the shore lab. Gas chromatography combustion (Fisons 1108 Elemental Analyzer equipped with a Costech \"Zero Blank\" sample carousel) coupled to an isotope ratio mass spectrometer (GC-IRMS) (Finnigan-MAT Conflo-II interface attached to a DeltaPlus Isotope Ratio Mass Spectrometer) was used to measure the incorporation of 13C-labelled bicarbonate into biomass during the incubations to determine chemoautotrophic production.
\nNitrate concentrations:\u00a0\u00a0Vent fluid from the Crab Spa site was incubated on the deck of the ship in the Vent-SID reaction chamber, in the dark at a temperature of 25(+/- 2)\u00b0C. Incubations consisted of a vent fluid with added NO3- (10 \u00b5mol/L), NO2- (1 \u00b5mol/L) and H13CO3- (0.7 mmol/L) and time-point samples were taken for nitrate+nitrite measurements at 0, 3, and 6 hours. Six incubations were conducted that varied in combinations of 15NO3-/14NO3 or 15NO2-/14NO2-, keeping the total concentration of added NO3- and NO2- constant across incubations.\u00a0
\nNitrate concentrations were measured in time-point samples utilizing the vanadium(III) reduction of nitrate and nitrite method described by Braman and Hendrix, 1989. Samples were injected into a heated Vanadium acid solution whereby NO3- and NO2- were reduced to NOx gases. The NOx then passed into a Teledyne T200 NOx analyzer where a photodetector measured the light produced from the chemiluminescent reaction of NOx and instrument generated ozone.
\nAfter initial collection, vent fluid samples were stored in 15 mL conical tubes at -20C until analyzed on the Teledyne NOx analyzer. Once thawed, samples were injected using Hamilton 1700 series gastight syringes and Nitrate concentrations were calculated alongside standards generated from a Ricca Nitrate Nitrogen Standard (CAT#5459-16, 1000 ppm N, 4427 ppm NO3). The series of standards ranged from 1 uM to 50 uM and were made up by diluting the Ricca standard in Milli-Q water.
\nPeak Simple Version 4.49 was used to generate chromatographs from the photodetector and raw data was further processed in Microsoft Excel.
This dataset includes microbial cell abundance, carbon fixation rates, and nitrate concentrations during shipboard incubations of vent fluids at the diffuse-flow vent Crab Spa site, East Pacific Rise in the Eastern Tropical North Pacific (ETNP) on RV/Atlantis cruise AT37-12, May 2017.\u00a0Crab Spa is\u00a0at 9.8398N, 104.2913W, and depth 2503 meters.
BCO-DMO Processing
\n- combined cell abundance, carbon fixation rates, and nitrate concentration excel tables into a single table