Dataset: Water Column Nitrate d15N Cocos Ridge Upper 1000m

Name: Average nitrate d15N values from the upper 1000 meters of the water column at four stations sampled in the Eastern Tropical North Pacific on R/V Sally Ride cruise SR2113 in December 2021
Published: 2024-07-18
Keywords: isotopes, denitrification, equatorial Pacific, oxygen deficient zones, oceans

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Spatial Extent: N:6.7849 E:-86.5999 S:5.3501 W:-88.261

Cocos Ridge, Eastern Equatorial Pacific

Temporal Extent: 2021-12-02 - 2021-12-14

Project:

Collaborative Research: New approaches to study calcium carbonate dissolution on the sea floor and its impact on paleo-proxy interpretations (CDISP 2021)

Principal Investigator:

Xingchen Wang (Boston College, BC)

Student:

Kameko Landry (Boston College, BC)

BCO-DMO Data Manager:

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

Version:

Version Date:

2024-07-18

Restricted:

Validated:

Current State:

Data not available

Average nitrate d15N values from the upper 1000 meters of the water column at four stations sampled in the Eastern Tropical North Pacific on R/V Sally Ride cruise SR2113 in December 2021

Abstract:

These data are average nitrate d15N values (permille vs air) and d15N 1sd for the upper 1000 meters (m) of the water column at four stations (CR01, CR02, CR03, and CR05) in the Eastern Tropical North Pacific (ETNP). The cruise (R/V Sally Ride SR2113) occupied the four stations near the Cocos Ridge between 6.8 to 5.3 degrees North latitude and 86.6 to 88.26 degrees West longitude. Sampling occurred between December 2-14, 2021. A 24-bottle Niskin rosette and CTD were used to collect 30-milliliter (mL) water samples that were later analyzed using the denitrifier method and N gas bench coupled to a Thermo IV isotope ratio mass spectrometer (IRMS). The d15N of nitrate in the upper 1000 m of the water column has shown a dramatic increase in the d15N of nitrate in the thermocline, indicating active in-situ water column denitrification. The new denitrification signal detected at the southern extent of the ETNP oxygen deficient zone (ODZ) provides further insight into the movement and development of the ODZ. The data were collected by Kameko Landry of Xingchen (Tony) Wang's Stable Isotope Biogeochemistry Laboratory at Boston College.

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Description

Data were collected on the NSF-funded 2021 "CDISP" cruise on R/V Sally Ride (SR2113). Analyses of the samples presented in this dataset were funded through Boston College.

Methods & Sampling

Water samples were collected directly from the CTD Niskin bottles and filtered through 0.2-micrometer (um) PVDF syringe filters. Samples were collected from approximately 24 depths throughout the water column ranging from 7 to 2900 meters (m), with the shallowest depths being sampled first to avoid nitrate contamination from deeper, higher nitrate samples. The samples were collected in pre-cleaned acid-washed 30-milliliter (mL) HDPE bottles. The bottles and caps were rinsed three times with the sample water. The syringe was rinsed three times before attaching the PVDF syringe filter& and, once attached to the syringe, 10 mL of sample water was used to rinse the filter before filling the sample bottles. Once filled, sample bottles were labeled and parafilmed. Samples were immediately frozen on the ship and continued to be frozen until analysis.

For isotopic analysis using the denitrifier method, bacteria are grown in aerobic environments starting the seed of the bacteria Pseudomonas aurofaciens. Once all nitrate is fully consumed, the bacteria are harvested from a growth media and placed in clean pre-combusted vials. The vials are then sealed and purged with N2 gas for three hours to completely remove the N2O background. Approximately 200-500 mL of nitrate samples are then injected into a purged vial. After overnight complete conversion of nitrate to N2O in the sealed vials, the δ15N of N2O is analyzed using a customized gas bench isotope ratio mass spectrometer.

Problems/Issues

Did not collect water samples at CR04. Did not run duplicates on samples from CR03.

Data Processing Description

The data are processed and corrected based on amino acid standards (USGS64 and USGS65) and nitrate isotope standard (USGS34 and USGS35).

BCO-DMO Processing

- Imported original file "CCR_d15N_1000m_data.xlsx" into the BCO-DMO system.
- Marked "N/A" and "nd" as missing data values (missing data are empty/blank in the final CSV file).
- Converted the date column to YYYY-MM-DD format.
- Renamed fields to comply with BCO-DMO naming conventions.
- Saved the final file as "933292_v1_water_column_nitrate_d15n_cocos_ridge.csv".

More Information about this dataset

Funding Sources

Funding Source	Award Number
Boston College	BC internal award

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
SR2113	CDISP	2021-11-20	R/V Sally Ride	Jess F. Adkins (Co-Chief Scientist) William M. Berelson (Co-Chief Scientist)	data info

Instruments

Isotope-ratio Mass Spectrometer

Supplied Name: Thermo IV Isotope Ratio Mass Spectrometer

Supplied Description:

Instrument Type

Generic Name: Isotope-ratio Mass Spectrometer

Acronym: IR Mass Spec; IRMS

Community Identifier: http://vocab.nerc.ac.uk/collection/L05/current/LAB16/

Generic Description:

The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer).

Niskin bottle

Supplied Name: 24-bottle Niskin CTD rosette

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 Gas Bench II

Supplied Name: N2O Gas Bench

Supplied Description:

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.

Parameters

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

Supplied Name	Supplied description	Supplied Units	Standard Name
Station_ID	Cocos Ridge station number + cast number + Niskin bottle number	unitless	sample
Depth_m	Sample depth	meters (m)	depth
WC_d15N_avg	Averaged d15N in permille vs N2. Blank/empty values in this column mean water was not collected from this specific bottle.	permille vs N2	d15N
WC_d15N_1sd	Standard deviation of measurements for samples analyzed with more than one run	permille vs N2	d15N
Latitude	Latitude of sample collection	decimal degrees	lon
Longitude	Longitude of sample collection; negative values = West	decimal degrees	lon
Date	Date of sample collection Format: %Y-%m-%d	unitless	date

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Dataset: Water Column Nitrate d15N Cocos Ridge Upper 1000m