Dataset: Nitrate 15N/14N measurements in two adjacent mesoscale eddies in the North Pacific Subtropical Gyre

Name: Nitrate 15N/14N measurements in two adjacent mesoscale eddies in the North Pacific Subtropical Gyre from water samples collected on R/V Kilo Moana cruise KM1709 in June-July 2017
Published: 2025-01-13
Keywords: N stable isotopes, mesoscale eddies, North Pacific Subtropical Gyre, oceans

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Cite This Dataset

Spatial Extent: N:27.95 E:-157.28 S:24.47 W:-158.72

Temporal Extent: 2017-06-29 - 2017-07-01

Project:

CAREER: The biological nitrogen isotope systematics of ammonium consumption and production (Biological Nitrogen Isotope Fractionation)

Principal Investigator:

Julie Granger (University of Connecticut, UConn)

Scientist:

Benedetto Barone (University of Hawai'i, UH)

Angelicque E. White (University of Hawaiʻi at Mānoa, SOEST)

Student:

Mengyang Zhou (University of Connecticut, UConn)

BCO-DMO Data Manager:

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2025-01-13

Restricted:

Validated:

Current State:

Data not available

Nitrate 15N/14N measurements in two adjacent mesoscale eddies in the North Pacific Subtropical Gyre from water samples collected on R/V Kilo Moana cruise KM1709 in June-July 2017

Abstract:

Two adjacent mesoscale eddies of opposite polarity were surveyed during the MESO-SCOPE (Microbial Ecology of the Surface Ocean-Simons Collaboration on Ocean Processes and Ecology) expedition in June – July of 2017 aboard R/V Kilo Moana (cruise ID KM1709). The expedition aimed to understand the impact of mesoscale eddies on the ecosystem of the North Pacific Subtropical Gyre. Hydrographic water samples collected during the cruise were measured for nitrate 15N/14N isotope ratios using the denitrifier method. These measurements were performed by Mengyang Zhou at the University of Connecticut.

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Methods & Sampling

Water was collected during the MESO-SCOPE research cruise aboard R/V Kilo Moana (KM1709) during June-July 2017. Upper ocean biogeochemistry was characterized at 11 stations along the transect traversing the cyclonic and anticyclonic eddies, using a rosette mounted with 10-liter (L) Niskin® bottles. Water samples for nutrient and nitrate isotope analyses were collected at ~25-meter (m) intervals from 5 m to 500 m with higher vertical resolution (~5 m intervals) near the deep chlorophyll maximum (DCM). Samples were frozen at -20 degrees Celsius (°C) after collection pending analysis.

The N isotope ratios of nitrate (15N/14N) in water samples from stations 4 to 13 were measured with the denitrifier method (Casciotti et al., 2002; Sigman et al., 2001) for concentrations exceeding 0.5 micromoles per liter (µmol L-1). Nitrate was converted to nitrous oxide (N2O) by cell concentrates of the denitrifying bacterial strain Pseudomonas chlororaphis (ATCC 43928, Manassas, VA, USA), which lacks the terminal N2O reductase. The N2O gas was extracted and purified using a custom-modified Thermo Fisher Scientific Gas Bench II fronted by dual cold traps and a GC Pal autosampler, and analyzed with a Thermo Delta V Advantage continuous flow gas chromatograph isotope ratio mass spectrometer (Casciotti et al., 2002; McIlvin & Casciotti, 2011). Working solutions were diluted from primary stocks into nutrient-free seawater to concentrations bracketing sample concentrations to account for potential matrix effects (Weigand et al., 2016; Zhou et al., 2021). Individual samples were measured 3 to 9 times to achieve an analytical uncertainty to ≤ 0.3 ‰. The oxygen isotope ratios of nitrate (ẟ18ONO3) were not measured concurrently as we did not secure sufficient sample volumes to estimate these reliably (see Zhou et al., 2021).

Data Processing Description

The N isotope ratios are expressed in delta (ẟ) notation in units of per mil (‰) vs. a standard material (N2 gas in the air): ẟ15Nsample = [(15N/14N)sample/(15N/14N)standard – 1] × 1000. Nitrate isotopic analyses were calibrated to internationally recognized nitrate reference materials IAEA-NO3 (International Atomic Energy Agency, Vienna, Austria) and USGS-34 (National Institute of Standards and Technology, Gaithersburg, MD, USA), with reported δ15N values of 4.7 ‰ and −1.8 ‰ (vs. air). Individual samples were measured 3 - 9 times to achieve an analytical uncertainty to ≤ 0.3 ‰.

BCO-DMO Processing

- Imported original file "Zhou_etal-BCO-DMO.xlsx" into the BCO-DMO submission.
- Renamed fields to comply with BCO-DMO naming conventions.
- Created ISO-DateTime fields in local (HST) and UTC format.
- Removed the original, separate date and time columns.
- Converted longitude values from positive to negative to indicate the direction is West.
- Saved the final file as "948358_v1_nitrate_15n_14n_meso-scope.csv".

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-1554474
Simons Foundation	329104

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
KM1709	MESO-SCOPE	2017-06-26	R/V Kilo Moana	Benedetto Barone (Chief Scientist)	data info

Instruments

Laboratory Autosampler

Supplied Name: GC Pal autosampler

Supplied Description:

a custom-modified Thermo Fisher Scientific Gas Bench II fronted by dual cold traps and a GC Pal autosampler, and analyzed with a Thermo Delta V Advantage continuous flow gas chromatograph isotope ratio mass spectrometer

Instrument Type

Generic Name: Laboratory Autosampler

Generic Description:

Laboratory apparatus that automatically introduces one or more samples with a predetermined volume or mass into an analytical instrument.

Niskin bottle

Supplied Name: 10 L Niskins

Supplied Description:

Instrument Type

Generic Name: Niskin bottle

Community Identifier: http://vocab.nerc.ac.uk/collection/L22/current/TOOL0412/

Generic Description:

A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc.

Thermo Fisher Scientific DELTA V Advantage isotope ratio mass spectrometer

Supplied Name: Thermo Delta V Advantage continuous flow gas chromatograph isotope ratio mass spectrometer

Supplied Description:

Instrument Type

Generic Name: Thermo Fisher Scientific DELTA V Advantage isotope ratio mass spectrometer

Acronym: Delta V Advantage

Generic Description:

The Thermo Scientific DELTA V Advantage is an isotope ratio mass spectrometer designed to measure isotopic, elemental, and molecular ratios of organic and inorganic compounds. The DELTA V Advantage is the standard model of the DELTA V series of isotope ratio mass spectrometers, which can be upgraded to the DELTA V Plus. The DELTA V Advantage can be operated in Continuous Flow or Dual Inlet mode. The standard collector configuration is the Universal Triple Collector. H2 collectors with online hydrogen capability are optional. The DELTA V Advantage is controlled by an automated, integrated Isodat software suite. A magnet, whose pole faces determine the free flight space for the ions, eliminates the traditional flight tube. The magnet is designed for fast mass switching which is further supported by a fast jump control between consecutive measurements of multiple gases within one run. The sample gas is introduced at ground potential, eliminating the need for insulation of the flow path, ensuring 100 percent transfer into the ion source. The amplifiers register ion beams up to 50 V. The DELTA V Advantage has a sensitivity of 1200 molecules per ion (M/I) in Dual Inlet mode and 1500 M/I in Continuous Flow mode. It has a system stability of < 10 ppm and an effective magnetic detection radius of 191 nm. It has a mass range of 1 - 80 Dalton at 3 kV.

Thermo-Fisher Scientific Gas Bench II

Supplied Name: Thermo Fisher Scientific Gas Bench II

Supplied Description:

custom-modified Thermo Fisher Scientific Gas Bench II fronted by dual cold traps and a GC Pal autosampler, and analyzed with a Thermo Delta V Advantage continuous flow gas chromatograph isotope ratio mass spectrometer

Instrument Type

Generic Name: Thermo-Fisher Scientific Gas Bench II

Acronym: GasBench II

Generic Description:

An on-line gas preparation and introduction system for isotope ratio mass spectrometry that is designed for high precision isotope and molecular ratio determination of headspace samples, including water equilibration, carbonates and atmospheric gases. The instrument allows for the use of a dual viscous flow inlet system of repetitive measurements of sample and standard gas on a continuous flow isotope ratio mass spectrometer (CF-IRMS) system. The sample volume is the sample vial (instead of a metal bellows), and the reference gas volume is a pressurized gas tank. The instrument consists of a user programmable autosampler, a gas sampling system, a maintenance-free water removal system, a loop injection system, an isothermal gas chromatograph (GC), an active open split interface, a reference gas injection system with three reference ports, and one or two optional LN2 traps for cryofocusing. The gas sampling system includes a two port needle which adds a gentle flow of He into the sample vial, diluting and displacing sample gas. Water is removed from the sample gas through diffusion traps. The loop injector aliquots the sample gas onto the GC column, which separates the molecular species. The reference gas injection system allows accurate referencing of each sample aliquot to isotopic standards. The system can be used with several options including a carbonate reaction kit that allows injection of anhydrous phospohric acid into sample vials.

Note "Finnigan GasBench-II" is the previous brand name of this instrument.

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
ISO_DateTime_Local_HST	Date and time of sample collection in the local time zone (HST); in ISO 8601 format Format: %Y-%m-%dT%H:%M	unitless	ISO_DateTime_Local
ISO_DateTime_UTC	Date and time (UTC) of sample collection; in ISO 8601 format Format: %Y-%m-%dT%H:%MZ	unitless	ISO_DateTime_UTC
Latitude	Latitude of sample collection	decimal degrees	lat
Longitude	Longitude of sample collection; negative values = West	decimal degrees	lon
Station	Station number	unitless	station
Depth	Sample depth	meters (m)	depth
Mean_d15NNO3	Mean of the ?15NNO3 measurements for each sample	‰ vs. air	dN15_NO3
Stdev_d15NNO3	Standard deviation of the ?15NNO3 measurements for each sample	‰ vs. air	dN15_NO3

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Dataset: Nitrate 15N/14N measurements in two adjacent mesoscale eddies in the North Pacific Subtropical Gyre