Water column nitrate plus nitrite isotope measurements from seawater collected November 2019 aboard R/V L’Atalante in the Western Tropical South Pacific (NCEI Accession 0278504)

This dataset contains physical data collected on R/V L'Atalante during cruise TONGA_2019 in the South Pacific Ocean from 2019-11-05 to 2019-11-30. These data include depth and sigma-theta. The instruments used to collect these data include CTD, GO-FLO Bottle, Isotope-ratio Mass Spectrometer, Niskin bottle, and Trace Metal Bottle. These data were collected by Angela N. Knapp of Florida State University and Sophie Bonnet of Mediterranean Institute of Oceanography as part of the "Collaborative Research: Dissolved organic phosphorus controls on marine nitrogen fixation and export production (DOP N2 fixation and export production)" project. The Biological and Chemical Oceanography Data Management Office (BCO-DMO) submitted these data to NCEI on 2022-03-04.

The following is the text of the dataset description provided by BCO-DMO:

TONGA 2019 NO3 d15N

Dataset Description:
Acquisition Description:
Duplicate water column samples were collected by Niskin or GoFlo rosette on one of the following types of casts:

‘CTD’, ’TMC’ (Trace Metal Clean), or ’TWO’ (small classical CTD with 12 x Niskin bottles) cast.

Nitrogen isotopic analysis (d15N of NO3-+NO2-) was by the “denitrifier method” and followed the methods described by Sigman et al. (2001), Casciotti et al. (2002), McIlvin and Casciotti (2011), and Weigand et al. (2016).

Briefly, NO3-+NO2- was quantitatively reduced to N2O by Pseudomonas aureofaciens , which was then cryogenically focused and analyzed on an isotope ratio mass spectrometer. A volume of sample was added to each bacterial vial to achieve a final quantity of 10 or 20 nmols N2O, which was then purged from the vial using a helium carrier gas. The d15N of N2O in samples was calibrated with the international isotopic reference materials.

Calibration:
NO3-+NO2- d15N analyses were calibrated with IAEA N3 and USGS 34 NO3- d15N isotopic reference materials as described in McIlvin and Casciotti, 2011.

Precision:
The average precision of NO3-+NO2- d15N measurements was < 0.2 per mil.