Biogeochemical and sediment characteristics of the Cinder Cones Methane seep site in the Ross Sea from November 2016

Data Type: Other Field Results
Version: 1
Version Date: 2019-06-21

» EAGER: Elucidating the Antarctic Methane Cycle at the Cinder Cones Reducing Habitat (Cinder Cone Seep)
Thurber, AndrewOregon State University (OSU)Principal Investigator
Biddle, MathewWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

These data are samples of pore water collected from a methane seep on Ross Island. This seep had been active for 5 years at the time of sampling and were collected from 10m water depth.


Spatial Extent: Lat:-77.8 Lon:-166.666
Temporal Extent: 2016-11-07 - 2016-11-15

Dataset Description

Biogeochemical and sediment characteristics of the Cinder Cones Methane seep site

Methods & Sampling

Sediment samples: Sediment cores were collected from the Cinder Cones site including a methane seep habitat and vertically sectioned into identified intervals at either 3cm or 1cm intervals depending on the analysis. To quantify methane from sediment plugs, subcores were taken vertically via a syringe with the end cut off to sample 3 cm3 of sediment.  The subcores were preserved in 2ml of 5M NaOH in a serum bottle and caped with a butyl stopper for later analysis. It was stored and shipped upside down. Large grain size led to rapid dewatering of the cores making the concentrations likely conservative estimates of the methane (i.e. the is a chance some of the porewater was lost during sampling).  For 0-1 cm sediment plugs, a core was vertically sectioned and frozen at -80oC until later analysis.

Porewater samples:  Pore water was sampled in situ by placing a vertical barrier in the sediment, excavating one side and inserting a Rhyzon filter (0.2 um) into the intact sediment on the opposite side of the excavation. 1 ml of porewater was discarded as a rinse and then 5ml of pore water was extracted. These were taken at 2 cm intervals starting at 1 cm below the sediment surface to 5cm.  3ml were preserved in serum bottles with 2ml of 5M NaOH for later methane analysis. 1 ml was filtered to remove particles >0.2 um and frozen for ion analysis and 1ml was preserved with 0.25ml of 0.05 M Zinc acetate for hydrogen sulfide concentration for Spectrophotometric analysis following Cline (1969).  

Sampling and analytical procedures:  
Methane: Samples were kept stored cold and inverted for both porewater and sediment plug sampling approaches for methane.  Headspace from each of the serum vials was injected into a Gas Chromatograph with Flame Ionization Detector (GC-FID) after a standard curve was generated based on known standards increasing from 10 to 1000 ppm and the same injection volume (between 50 and 100 ul) as the headspace of the samples.  Adjusted r2 of the calibration curve was  1.0.  Response area was measured using “Peak Simple” software.

Methane Flux: Methane flux was measured in 2016 through the deployment of benthic flux chambers. Chambers were 10cm i.d. cores with a cap containing a septa sealed hole for sampling and an o-ring seal around the cap. The chambers were sealed with the caps after the cores were inserted into the sediment to ensure minimal disturbance to the system. Chambers were not continually stirred but were stirred by using magnetic propeller system that allowed gentle agitation prior to each sample collection. Samples were taken on 12-hour intervals to quantify that release of methane through syringe sampling through the septa; at no point were the chambers opened

Data Processing Description

Data processing was limited to using standard curves from and converting to water volume and surface area.

BCO-DMO Processing Notes:
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
- converted "Collection_Date" from Excel date integer to ISO yyyy-mm-dd representation and inserted into "Date" column.


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Data Files

(Comma Separated Values (.csv), 8.40 KB)
Primary data file for dataset ID 770638

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Related Publications

Cline, J. D. (1969). Spectrophotometric Determination of Hydrogen Sulfide in Natural Waters. Limnology and Oceanography, 14(3), 454–458. doi:10.4319/lo.1969.14.3.0454

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Site_nameName of dive location on Ross Island Antarctica unitless
HabitatWhether the sample was from an area of active methane seepage or sampled adjacent to this habitat. unitless
Collection_DateDate sample was collected as Excel integer representation unitless
DateCollection Date represented as yyyy-mm-dd unitless
geo_loc_latLatitude of the sample in degrees decimal degrees
geo_loc_longLongitude of the sample in degrees decimal degrees
Water_depthDepth in meter that the sample was collected from meters (m)
ReplicateIndividual identifier for the core (all letters indicate samples from a single core or sampling cluster). Pore water was taken adjacent to the core however within 10cm of the core and thus from the same geochemical environment. unitless
Sediment_Depthdepth or depth range from which the same was taken centimeters (cm)
sampling_approachsampling approach used for the observations (porewater; sediment; or flux chamber) unitless
FluorideFluoride millimole (mmol)
AcetateAcetate millimole (mmol)
FormateFormate millimole (mmol)
ChlorideChloride millimole (mmol)
NitriteNitrite millimole (mmol)
BromideBromide millimole (mmol)
SulfateSulfate millimole (mmol)
ThiosulfateThiosulfate millimole (mmol)
LithiumLithium millimole (mmol)
SodiumSodium millimole (mmol)
AmmoniumAmmonium millimole (mmol)
PotassiumPotassium millimole (mmol)
MagnesiumMagnesium millimole (mmol)
CalciumCalcium millimole (mmol)
SulfideSulfide millimole (mmol)
Methane_porewaterMethane in porewater nanomole per milliliter of porewater (nmol ml-1 porewater)
Methane_sedimentMethane in sediment nanomole per cubic centimeter of sediment (nmol cm^-3 sediment)
d2HVSMOWstable isotopic composition of hydrogen in comparison to the reference "Vienna-Standard Mean Ocean Water" per mil
d13CVPDBstable isotopic composition of carbon in comparison to the reference "Vienna PeeDee Belemnite" per mil
Methane_FluxMethane_Flux millimole per meter squared per day (mmol m-2 d-1)

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Dataset-specific Instrument Name
Thermo Delta V Plus isotope ratio mass spectrometer
Generic Instrument Name
Isotope-ratio Mass Spectrometer
Dataset-specific Description
The δ13C and δ2H of methane were analyzed at the University of California, Davis on a Thermo Scientific GasBench-Precon interfaced to a Thermo Delta V Plus isotope ratio mass spectrometer.
Generic Instrument 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).

Dataset-specific Instrument Name
HP 5890 Gas Chromatograph
Generic Instrument Name
Gas Chromatograph
Dataset-specific Description
Methane concentration was measured with a HP 5890 Gas Chromatograph with an AllTech Porapak N8/100 column and a Flame ionization detector.
Generic Instrument Description
Instrument separating gases, volatile substances, or substances dissolved in a volatile solvent by transporting an inert gas through a column packed with a sorbent to a detector for assay. (from SeaDataNet, BODC)

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Project Information

EAGER: Elucidating the Antarctic Methane Cycle at the Cinder Cones Reducing Habitat (Cinder Cone Seep)

Coverage: Ross Sea, Antarctica (78 S, 166 E)

NSF abstract:

Methane is a potent greenhouse gas that is naturally emitted into the oceans by geologic seeps and microbial production. Based on studies of persistent deep-sea seeps at mid- and northern latitudes, researchers have learned that bacteria and archaea can create a "sediment filter" that oxidizes methane prior to its release. Antarctica is thought to contain large reservoirs of organic carbon buried beneath its ice which could a quantity of methane equivalent to all of the permafrost in the Arctic and yet we know almost nothing about the methane oxidizing microbes in this region. How these microbial communities develop and potentially respond to fluctuations in methane levels is an under-explored avenue of research. A bacterial mat was recently discovered at 78 degrees south, suggesting the possible presence of a methane seep, and associated microbial communities. This project will explore this environment in detail to assess the levels and origin of methane, and the nature of the microbial ecosystem present.

An expansive bacterial mat appeared and/or was discovered at 78 degrees south in 2011. This site, near McMurdo Station Antarctica, has been visited since the mid-1960s, but this mat was not observed until 2011. The finding of this site provides an unusual opportunity to study an Antarctic marine benthic habitat with active methane cycling and to examine the dynamics of recruitment and community succession of seep fauna including bacteria, archaea, protists and metazoans. This project will collect the necessary baseline data to facilitate further studies of Antarctic methane cycling. The concentration and source of methane will be determined at this site and at potentially analogous sites in McMurdo Sound. In addition to biogeochemical characterization of the sites, molecular analysis of the microbial community will quantify the time scales on which bacteria and archaea respond to methane input and provide information on rates of community development and succession in the Southern Ocean. Project activities will facilitate the training of at least one graduate student and results will be shared at both local and international levels. A female graduate student will be mentored as part of this project and data collected will form part of her dissertation. Lectures will be given in K-12 classrooms in Oregon to excite students about polar science. National and international audiences will be reached through blogs and presentations at a scientific conference. The PI's previous blogs have been used by K-12 classrooms as part of their lesson plans and followed in over 65 countries.

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Funding SourceAward
NSF Office of Polar Programs (formerly NSF PLR) (NSF OPP)

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