URLhttps://www.bco-dmo.org/dataset/637919
Download URLhttps://www.bco-dmo.org/dataset/637919/data/download
Media Typetext/tab-separated-values
CreatedFebruary 4, 2016
ModifiedAugust 19, 2016
StatePreliminary and in progress
Brief DescriptionPorewater measurements of nitrate concentration and N and O isotopic ratios (d15N and d18O) from bore holes U1382B, U1383D, and U1384A at North Pond during IODP 336.

Acquisition Description

Sediment cores were collected using an advanced piston corer. Porewaters were extracted by Rhizon samplers either immediately shipboard or later on 10cm whole core rounds that were stored at -80 degrees C.

Nitrate from shipboard extracted samples were measured using ion chromatography, where samples collected later were measured using chemiluminescence after reduction in hot acidic vanadyl sulfate solution on a NOx analyzer (Braman and Hendrix, 1989) (detection limit <0.5 uM). Nitrite was measured using the Griess-Ilosvay method followed by measuring absorption at 540 nm or by chemiluminescence in a sodium iodide solution on a NOx analyzer.

Stable isotopes of nitrate were measured using the denitrifier method (Casciotti et al., 2002; Sigman et al., 2001). Where detected, nitrite was removed by sulfamic acid addition (Granger and Sigman, 2009) prior to isotopic analysis of the nitrate. Samples were run on either a Delta V Advantage (Thermo, Inc.) at the University of Basel or an IsoPrime100 (Elementar, Inc.)

Processing Description

For the stable isotope measurements, corrections for drift, size and fractionation of isotopes during the denitrifier method were carried out using nitrate standards USGS 32, USGS 34, and USGS 35 (Casciotti et al., 2002; McIlvin and Casciotti, 2011), with a typical reproducibility of 0.2 and 0.4 ‰ for δ15N and δ18O, respectively.

BCO-DMO Processing:
- modified parameter names to conform with BCO-DMO naming conventions;
- added cruise ID;
- replaced blanks (missing data) with "nd", meaning "no data".

Instruments

Advanced Piston Corer [Advanced Piston Corer]
Details
Instance Description (Advanced Piston Corer)

Sediment cores were collected using an advanced piston corer.

The JOIDES Resolution's Advanced Piston Corer (APC) is used in soft ooze and sediments. The APC is a hydraulically actuated piston corer designed to recover relatively undisturbed samples from very soft to firm sediments.

More information is available from IODP (PDF).

Ion Chromatography [Ion Chromatograph]
Details
Instance Description (Ion Chromatography)

Nitrate from shipboard extracted samples were measured using ion chromatography.

Ion chromatography is a form of liquid chromatography that measures concentrations of ionic species by separating them based on their interaction with a resin. Ionic species separate differently depending on species type and size. Ion chromatographs are able to measure concentrations of major anions, such as fluoride, chloride, nitrate, nitrite, and sulfate, as well as major cations such as lithium, sodium, ammonium, potassium, calcium, and magnesium in the parts-per-billion (ppb) range. (from http://serc.carleton.edu/microbelife/research_methods/biogeochemical/ic.html)

Details
Instance Description (NOx analyzer)

Nitrate from shipboard extracted samples were measured using ion chromatography, where samples collected later were measured using chemiluminescence after reduction in hot acidic vanadyl sulfate solution on a NOx analyzer (Braman and Hendrix, 1989) (detection limit <0.5 uM). Nitrite was measured using the Griess-Ilosvay method followed by measuring absorption at 540nm or by chemiluminescence in a sodium iodide solution on a NOx analyzer.  

The chemiluminescence method for gas analysis of oxides of nitrogen relies on the measurement of light produced by the gas-phase titration of nitric oxide and ozone. A chemiluminescence analyzer can measure the concentration of NO/NO2/NOX.

One example is the Teledyne Model T200: http://www.teledyne-api.com/products/T200.asp

Delta V Advantage or IsoPrime100 [Isotope-ratio Mass Spectrometer]
Details
Instance Description (Delta V Advantage or IsoPrime100)

Samples were run on either a Delta V Advantage (Thermo, Inc.) at the University of Basel or an IsoPrime100 (Elementar, Inc.)

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).

Parameters

core [unknown]
Details
core
Core identifier.
association with a community-wide standard parameter is not yet defined
lat [latitude]
Details
lat
Latitude.

latitude, in decimal degrees, North is positive, negative denotes South; Reported in some datasets as degrees, minutes

lon [longitude]
Details
lon
Longitude.

longitude, in decimal degrees, East is positive, negative denotes West; Reported in some datsets as degrees, minutes

bottom_water_depth [unknown]
Details
bottom_water_depth
Bottom water depth.
association with a community-wide standard parameter is not yet defined
cruise_id [cruise_id]
Details
cruise_id
Cruise identifier.
cruise designation; name
sample [sample]
Details
sample
Sample identifier.

unique sample identification or number; any combination of alpha numeric characters; precise definition is file dependent

section [unknown]
Details
section
Section identifier.
association with a community-wide standard parameter is not yet defined
depth_mbsf [unknown]
Details
depth_mbsf
Depth (top of section mbsf).
association with a community-wide standard parameter is not yet defined
nitrate [unknown]
Details
nitrate
Nitrate.
association with a community-wide standard parameter is not yet defined
nitrite [unknown]
Details
nitrite
Nitrite.
association with a community-wide standard parameter is not yet defined
d15N_nitrate [unknown]
Details
d15N_nitrate
d15N-Nitrate.
association with a community-wide standard parameter is not yet defined
d18O_nitrate [unknown]
Details
d18O_nitrate
d18O-Nitrate.
association with a community-wide standard parameter is not yet defined

Dataset Maintainers

NameAffiliationContact
Scott D. WankelWoods Hole Oceanographic Institution (WHOI)
Wiebke ZiebisUniversity of Southern California (USC)
Moritz F. LehmannUniversity of Basel (Universitat Basel)
Scott D. WankelWoods Hole Oceanographic Institution (WHOI)
Carolyn BuchwaldWoods Hole Oceanographic Institution (WHOI)
Shannon RauchWoods Hole Oceanographic Institution (WHOI BCO-DMO)

BCO-DMO Project Info

Project TitleIODP Expedition 336- Mid-Atlantic Ridge Microbiology
AcronymMid-Atl Ridge Microbio
URLhttps://www.bco-dmo.org/project/637905
CreatedFebruary 4, 2016
ModifiedOctober 3, 2018
Project Description

This project was funded by a C-DEBI small grant to SW and WZ, by a C-DEBI Postdoctoral Fellowship to CB, and by NSF award OCE-1131671 to WZ.

Project title (SW and WZ) "Autotrophy and heterotrophy supported by microbial nitrogen cycling in sediments underlying the oligotrophic ocean: A stable isotope study of North Pond porewaters"

Description from C-DEBI:
As a key element in fundamental biomolecules, the cycling and availability of nitrogen is a central factor governing the extent of ecosystems across the Earth. In the organic-lean sediment porewaters underlying the oligotrophic ocean, where low levels of microbial activity persist despite exceedingly energy-depleted conditions, the extent and modes of nitrogen transformations have not been widely investigated. We used the N and O isotopes of porewater nitrate from the North Pond site in the oligotrophic North Atlantic (North Pond) to provide constraints on the extent of both nitrate production (via nitrification) and consumption (via denitrification). Nitrate accumulates far above bottom seawater concentrations (~21 uM) throughout the sediment column (up to almost ~50 uM) and persists down to the oceanic basement as deep as 90 mbsf, indicating the predominance of aerobic nitrification and remineralization in these sediments. However, large changes in the δ15N and δ18O of nitrate also reveal variable influence of nitrate respiration across the three boreholes.

Combining the N and O isotopes and using an inverse porewater diffusion-reaction model, we estimate rates of nitrification and denitrification throughout the sediment column. Results indicate a range of rates across the three boreholes and are generally consistent with variations observed in profiles of dissolved oxygen at this site. The model also estimates values of the N isotopic composition of newly produced nitrate, which were generally lower than measurements of sinking particulate nitrogen in this region. We suggest that this must be the result of sedimentary-hosted nitrogen fixation supplementing the relatively small organic matter pool derived from the overlying euphotic zone. These findings indicate that the production of organic matter by in situ autotrophy (by both nitrification and nitrogen fixation) must supply a large fraction of the biomass and organic substrate for heterotrophy in these sediments. This work sheds new light on an active nitrogen cycle operating, despite exceedingly low carbon inputs, in the deep sedimentary biosphere.

Project title (CB) "Determining the rates of denitrification, nitrification, and nitrogen fixation using natural abundance isotope profiles in North Pond sediments"

Description from C-DEBI:
The sedimentary contribution to the global ocean fixed nitrogen budget is currently under debate. Early studies using the isotopic balance of 15N of nitrate, predicted a large nitrogen loss through sedimentary denitrification and yielding an enormous imbalance in the budget, with nitrogen loss far outweighing sources of nitrogen to the ocean. The major roadblock preventing our ability to estimate the rates of nitrogen metabolisms within the deep biosphere is the difficulty sampling and measuring rates while keeping in situ conditions. Even with the recent technological advances in collecting deep sediments, there is still perturbation of the microbial community when conducting bottle incubations and adding artificial isotope tracers. To overcome these issues, I plan to use natural abundance stable isotope profiles of multiple nitrogen species to more quantitatively constrain rates of microbial nitrogen metabolism. Stable isotope profiles have the potential to tease apart multiple processes that the concentration profiles alone cannot. In order to do this, however, we need a more in-depth understanding of the isotope systematics of each process under conditions that more closely approximate the low-energy systems manifested in sediments underlying the oligotrophic ocean. Here I plan to conduct multiple incubation experiments designed to measure the isotope systematics during a) coupled denitrification and nitrification and b) benthic nitrogen fixation, under conditions relevant to the deep biosphere.

Project Maintainers
NameAffiliationRoleContact
Scott D. WankelWoods Hole Oceanographic Institution (WHOI)Principal Investigator
Carolyn BuchwaldWoods Hole Oceanographic Institution (WHOI)Principal Investigator
Wiebke ZiebisUniversity of Southern California (USC)Co-Principal Investigator
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