Porewater dissolved organic carbon and associated geochemical data for methane seeps in the Cascadia Margin: Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent

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Frequently anticipated questions:

What does this data set describe?

Title:
Porewater dissolved organic carbon and associated geochemical data for methane seeps in the Cascadia Margin: Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent
Abstract:
These data include vertical profiles of concentrations and stable carbon isotope values of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), total organic carbon (TOC) from sediment cores collected at methane seeps and reference sites. Sediment porosity and dissolved sulfate and methane concentrations are also presented. Methane seeps in Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent, along the Cascadia Margin, were sampled. These data were collected over two decades and across four cruises: PGC02-08 (CCGS John P. Tully, 2002), Hydrates 2004 Sea Trial (CCGS John P. Tully, 2004), AT50-14 (R/V Atlantis, 2023), and AT50-29B (R/V Atlantis, 2024).
Supplemental_Information:
This Microsoft Excel workbook contains data in a single tab. The cruises involved in this work are: R/V Atlantis - AT50-14, AT50-29B; Canadian Coast Guard Ship (CCGS) John P. Tully - PGC02-08 and Hydrates2024.
  1. How might this data set be cited?
    Lalk, Ellen, Pohlman, John W., Lapham, Laura L., Casso, Michael, Glenna, Madeline, Hildebrand, Anna, Lloyd, Karen, Ma, Kun, Seewald, Jeffrey, Stock, Lennart, Strauss, Maureen A., Sylva, Sean, Traver, Lily, Wilson, Rachel, and Williams, Leketha, 20250521, Porewater dissolved organic carbon and associated geochemical data for methane seeps in the Cascadia Margin: Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent: data release DOI:10.26008/1912/bco-dmo.959765.1, Biological and Chemical Oceanography Data Management Office (BCO-DMO), Woods Hole Coastal and Marine Science Center, Woods Hole, Massachusetts, USA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: Lalk, E., Pohlman, J.W., Lapham, L.L., Casso, M., Glenna, M., Hildebrand, A., Lloyd, K., Ma, K., Seewald, J., Stock, L., Strauss, M.A., Sylva, S., Traver, L., Wilson, R., Williams, L., 2025, Porewater dissolved organic carbon and associated geochemical data for methane seeps in the Cascadia Margin—Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent : Biological and Chemical Oceanography Data Management Office (BCO-DMO), https://doi.org/10.26008/1912/bco-dmo.959765.1 .
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -126.849944
    East_Bounding_Coordinate: -124.6027
    North_Bounding_Coordinate: 48.671875
    South_Bounding_Coordinate: 44.568359
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 2002
    Ending_Date: 2024
    Currentness_Reference:
    Ground condition. Cores were collected in 2002 using a piston corer, in 2004 using an ROV, and in 2023 and 2024 using a submersible. Pore waters were extracted from these cores during the cruise on which they were acquired. The measurements presented here were completed within 1 year post core collection for each cruise. Initial sample collection dates are listed as the parameter 'SamplingDate'.
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point (126)
    2. What coordinate system is used to represent geographic features?
      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0001. Longitudes are given to the nearest 0.0001. Latitude and longitude values are specified in decimal degrees. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
      Vertical_Coordinate_System_Definition:
      Depth_System_Definition:
      Depth_Datum_Name: local surface - depth below sea floor
      Depth_Resolution: 0.5
      Depth_Distance_Units: centimeters
      Depth_Encoding_Method: attribute values
  7. How does the data set describe geographic features?
    "Discrete_GeochemicalData_CascadiaMarginSeeps"
    Microsoft Excel workbook that contains tabulated location and property data for specimens collected and published as part of this Cascadia Margin methane seep study. (Source: producer defined)
    Region
    General sampling location within the Cascadia Margin (Astoria Canyon, Barkley Canyon, Hydrate Ridge, Bullseye Vent). (Source: U.S. Geological Survey) user defined text field
    Cruise
    Cruise ID for sample collection with the following values: PGC02-08 (CCGS John P. Tully, 2002), Hydrates2004 (CCGS John P. Tully, 2004, Hydrates 2004 Sea Trial), AT50-14 (R/V Atlantis, 2023), and AT50-29B (R/V Atlantis, 2024) (Source: U.S. Geological Survey) user defined text field
    CoreID
    Core IDs are specific letter and number combinations given to cores when collected, and are specific to each individual cruise. (Source: U.S. Geological Survey) user defined text field
    SampleID
    Sample IDs are numbers given to each sediment sub-sample when collected, and are specific to each individual cruise. (Source: U.S. Geological Survey) user defined text field
    CoreType
    Core type specifies the environment of the core collection (seep = collected in a methane seep, reference = collected outside a methane seep). (Source: U.S. Geological Survey) user defined
    Latitude
    Sample latitude, south is negative (decimal degrees). (Source: U.S. Geological Survey)
    Range of values
    Minimum:44.568359
    Maximum:48.671875
    Units:decimal degrees
    Longitude
    Sample longitude, west is negative (decimal degrees). (Source: U.S. Geological Survey)
    Range of values
    Minimum:-126.849944
    Maximum:-124.6027
    Units:decimal degrees
    WaterDepth_m
    Depth of the sea floor relative to the sea surface at the sample location (meters, m). Based on shipboard tidally corrected values. (Source: U.S. Geological Survey)
    Range of values
    Minimum:787
    Maximum:1282
    Units:meters
    MidDepth_cmbsf
    Mid-depth of core sub-section relative to the sediment water interface (centimeters below sea floor, cmbsf). (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.75
    Maximum:818
    Units:centimeters below sea floor (cmbsf)
    Porosity
    Sediment water volume relative to total specimen volume (unitless). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.64
    Maximum:0.9
    Units:unitless
    SO4_mM
    Pore water dissolved sulfate (millimolar, mM). NaN = “Not a Number (no data value).” BDL = “Below Detection Level.” (Source: U.S. Geological Survey)
    Range of values
    Minimum:0
    Maximum:31.07346
    Units:millimolar (mM)
    CH4_uM
    Pore water dissolved methane (micromolar, uM). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.001346
    Maximum:26907.1
    Units:micromolar (uM)
    DOC_uM
    Pore water dissolved organic carbon (micromolar, uM). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:283.3
    Maximum:3600
    Units:micromolar (uM)
    DOC_d13C_permil
    Bulk stable carbon isotope value of pore water dissolved organic carbon (per mille) relative to Vienna Pee Dee Belemnite (VPDB). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:-60.44
    Maximum:-7.46
    DIC_mM
    Pore water dissolved inorganic carbon (millimolar, mM). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:1.3
    Maximum:27.49
    Units:millimolar (mM)
    DIC_d13C_permil
    Bulk stable carbon isotope value of pore water dissolved inorganic carbon (per mille) relative to Vienna Pee Dee Belemnite (VPDB). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:-52.62
    Maximum:11.89
    Units:per mille
    TOC_wt.%
    Sediment total organic carbon content (weight percent, wt.%). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:2.54
    Maximum:3.18
    Units:weight percent (wt.%)
    TOC_d13C_permil
    Bulk stable carbon isotope value of pediment total organic carbon content (per mille) relative to Vienna Pee Dee Belemnite (VPDB). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:-26.05
    Maximum:-22.91
    Units:per mille
    H2S_mM
    Pore water dissolved sulfide (millimolar, mM). NaN = “Not a Number (no data value).” (Source: U.S. Geological Survey)
    Range of values
    Minimum:0.00096
    Maximum:21.1
    Units:millimolar (mM)
    Entity_and_Attribute_Overview:
    The workbook Discrete_GeochemicalData_CascadiaMarginSeeps.xlsx contains one tab. The first row in the XLSX file is a header row. The remaining rows contain all data included in this data release, with non-measurements and undetected quantities given by “NaN,” and “BDL” as indicated in the attribute definitions in this xml file. Additionally, a CSV file “parameters_CascadiaMarginSeeps.csv” provides definitions for the attributes in the Discrete_GeochemicalData_CascadiaMarginSeeps.xlsx file. Definitions in the CSV file follow an initial header row. These files are part of a data release posted to the BCO-DMO data repository (Biological and Chemical Oceanography Data Management Office, BCO-DMO)
    Entity_and_Attribute_Detail_Citation:
    Lalk, E., Pohlman, J. W., Lapham, L. L., Casso, M., Glenna, M., Hildebrand, A., Lloyd, K., Ma, K., Seewald, J., Stock, L., Strauss, M. A., Sylva, S., Traver, L., Wilson, R., Williams, L., 2025, Porewater dissolved organic carbon and associated geochemical data for methane seeps in the Cascadia Margin—Astoria Canyon, Barkley Canyon, Hydrate Ridge, and Bullseye Vent: Biological and Chemical Oceanography Data Management Office (BCO-DMO). https://doi.org/10.26008/1912/bco-dmo.959765.1 .

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Lalk, Ellen
    • Pohlman, John W.
    • Lapham, Laura L.
    • Casso, Michael
    • Glenna, Madeline
    • Hildebrand, Anna
    • Lloyd, Karen
    • Ma, Kun
    • Seewald, Jeffrey
    • Stock, Lennart
    • Strauss, Maureen A.
    • Sylva, Sean
    • Traver, Lily
    • Wilson, Rachel
    • Williams, Leketha
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov

Why was the data set created?

These data are used to assess the prevalence of methane-derived DOC at methane seeps in the ocean, which may contribute ‘old’ carbon to the deep ocean or serve as a source of reduced carbon for the deep ocean microbial loop.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 2024 (process 1 of 8)
    Sediment and porewater handling; PCG02-08- Core material was sectioned and pressure-squeezed with a modified Reeburgh squeezer (Reeburgh, 1967) into acid-washed all-plastic syringes. Porewater was then filtered through 0.45 um polyethersulphone syringe filters. Hydrates2004- Core material was sectioned and pressure-squeezed with a modified Reeburgh squeezer (Reeburgh, 1967) into acid-washed all-plastic syringes. Porewater was then filtered through 0.2 um arodisc polyethersulphone syringe filters. AT50-14- Core material was sectioned and pressure-squeezed with a modified Reeburgh squeezer (Reeburgh, 1967) into acid-washed all-plastic syringes. Porewater was then filtered through pre-combusted 0.4 um glass fiber filters. AT50-29B- Core material was sectioned into acid-washed falcon tubes and refrigerated. Porewater was extracted using Rhizons with a 0.2 um filter size. The process step took place over a time period of 2002 to 2024. The cores were collected and porewater was squeezed during field expeditions in 2002, 2004, 2023, and 2024. The process date represents the most recent completion of the work.
    Reference:
    Reeburgh, W.S., 1967, An improved interstitial water sampler: Limnology and Oceanography, 846 12(1), 163–165, https://doi.org/10.4319/lo.1967.12.1.0163 Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
    Date: 2024 (process 2 of 8)
    Porosity; Fresh sediment was placed in pre-weighed petri-dishes, sealed, and refrigerated until measurement in lab. Petri dishes were weighed upon return to shore, then were played in a drying oven (45 degress Celsius, 1 week). Petri dishes with dried sediment were weighed again. The difference between the wet and dry measurements is the water weight, and the difference between the dry weight and the petri dish is the sediment weight. Assuming a constant water density of 1.025 g/cc and a constant sediment grain density of 2.5 g/cc, the water and sediment masses are converted to volumes. The ratio of the water volume to the total volume is the porosity. The process step took place over a time period of 2002 to 2024 where the analyses were run in the 1 year post core collection for each field expedition. The process date represents the most recent completion of the work. Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
    Date: 2024 (process 3 of 8)
    SO4_mM (Pore water dissolved sulfate); 0.5 mL porewater was sub-sampled into 2 mL microcentrifuge tubes and dosed with 50 uL 0.1M phosphoric acid. Samples were measured using ion chromatography. IAPSO certified seawater was used for standardization, and precision is ±1.5%. The process step took place over a time period of 2002 to 2024 where the analyses were run in the 1 year post core collection for each field expedition. The process date represents the most recent completion of the work. Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
    Date: 2024 (process 4 of 8)
    CH4_uM (Pore water dissolved methane); Sediment plugs (volume = 3-6 cm3) were sampled and stored in serum bottles sealed with 1-cm-thick butyl rubber septa. 5mL of saturated brine was added to the serum bottles and shaken to equilibrate the headspace. The samples were refrigerated until analysis. For cruises PCG02-08, Hydrates2004, and AT50-14, methane concentrations of serum bottle headspaces were determined by gas chromatography flame ionization detection. These headspace concentrations were processed into dissolved concentrations of methane in porewater. For samples measured by GC, dissolved concentrations were calculated following Hoehler et al. (2000). For cruise AT50-29B, methane concentrations were determined using cavity ringdown spectroscopy. Check standards for concentration were run approximately every 5 samples and corrected as described by Pohlman and Casso (2021). For samples measured by cavity ring-down spectroscopy, dissolved concentrations were calculated using the following equation: ((pCH4 * 10^-6 * Vg) / (R * T_extraction) + (Vw * pCH4 * 10^-6 * Sol_CH4)) / Vw * 10^6 = [CH4] Where pCH4 is the headspace concentration of methane in ppm, Vg is the volume of gas sample in mL, R is the gas constant in L-atm/mol-K, T_extraction is the extraction temperature in Kelvin, Vw is the volume of water sample that was extracted in mL, Sol_CH4 is the solubility of methane in mol/L-atm (Wiesenburg & Guinasso, 1979), and [CH4] is the dissolved concentration of methane in the original natural water sample, in micromoles per liter. The process step took place over a time period of 2002 to 2024 where the analyses were run in the 1 year post core collection for each field expedition. The process date represents the most recent completion of the work.
    References:
    Hoehler, T., Borowski, W., Alperin, M., Rodriguez, N., and Paull, C., 2000, Model, stable isotope, and 727 radiotracer characterization of anaerobic methane oxidation in gas hydrate-bearing sediments 728 of the Blake Ridge: Scientific Results, 164, https://doi.org/10.2973/odp.proc.sr.164.242.2000.
    Pohlman, J.W., and Casso, M., 2021, Comparison of methane concentration and stable carbon isotope data for natural samples analyzed by discrete sample introduction module - cavity ring down spectroscopy (DSIM-CRDS) and traditional methods: U.S. Geological Survey data release, https://doi.org/10.5066/P99B34V1.
    Wiesenburg, D. A., and Guinasso Jr, N.L., 1979, Equilibrium solubilities of methane, carbon monoxide, and hydrogen in water and sea water: Journal of Chemical and Engineering Data, 24(4), 356-360, https://doi.org/10.1021/je60083a006. Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
    Date: 2024 (process 5 of 8)
    DOC_uM (Pore water dissolved organic carbon) and DOC_d13C_permille (Bulk stable carbon isotope value of pore water dissolved organic carbon); Samples (2-4 mL) were stored in combusted borosilicate glass vials with acid-cleaned teflon-lined septa caps. Vials were pretreated with 20 percent hydrochloric acid (12 microliters per milliliter of sample) to decrease the pH of the sample to 2 or less, and samples were stored at 4 degrees Celsius until analysis. Concentrations were determined with a TOC Analyzer using wet chemical oxidation (cruises PGC02-08 and Hydrates2004) (Heuer et al., 2009; Pohlman et al., 2011) and high temperature catalytic oxidation (cruises AT50-14 and AT50-29B) to convert DOC to CO2. For all cruises, nondispersive infrared detection was used to quantify this CO2. Potassium hydrogen phthalate (KHP) calibration standards were run to quantify DOC concentration. Stable carbon isotopes (d13C-DOC) were measured by isotope ratio mass spectrometry. Stable carbon isotope ratios are reported in standard d notation relative to Vienna Pee Dee Belemnite (VPDB). Quality assurance included replicate analysis of natural reference materials, field samples and calibration standards. Uncertainty in DOC concentration was 5 percent or less, and uncertainty in d13C was 0.2 permille or less, based on replicate measurements. The process step took place over a time period of 2002 to 2024 where the analyses were run in the 1 year post core collection for each field expedition. The process date represents the most recent completion of the work.
    References:
    Heuer, V.B., Pohlman, J.W., Torres, M.E., Elvert, M., and Hinrichs, K.U., 2009, The stable carbon isotope biogeochemistry of acetate and other dissolved carbon species in deep subseafloor sediments at the northern Cascadia Margin: Geochimica et Cosmochimica Acta, 73(11), 3323-3336, https://doi.org/10.1016/j.gca.2009.03.001.
    Pohlman, J.W., Bauer, J.E., Waite, W.F., Osburn, C.L., and Chapman, N.R., 2011, Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans: Nature Geoscience, 4(1), 37-41, https://doi.org/10.1038/ngeo1016. Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
    Date: 2024 (process 6 of 8)
    DIC_mM (Porewater dissolved inorganic carbon) and DIC_d13C_permille (Bulk stable carbon isotope value of porewater dissolved inorganic carbon); Samples for DIC concentration for cruises PCG02-08 and Hydrates2004 were collected as 2 ml aliquots in 5 ml serum vials, sealed with butyl rubber septa, and quantified by coulometry. Samples for stable carbon isotopes (d13C-DIC) for cruises PGC02-08 and Hydrates2004 were collected as 1 ml aliquots in 2 ml serum vials, sealed with butyl rubber septa and analyzed as CO2 by isotope ratio mass spectrometry following acidification of the sample (Pohlman et al., 2013). Samples for DIC concentration and stable carbon isotopes for DIC for cruises AT-50-14 and AT50-29B were collected by injecting 1mL porewater into a helium-filled 12 mL exetainer vial pre-filled with 1mL 85% phosphoric acid. The stable carbon isotope ratios and concentrations were determined from CO2 by isotope ratio mass spectrometry. Measurements are standardized with lithium carbonate reference material, and isotope ratios are reported in the standard delta notation relative to VPDB. The process step took place over a time period of 2002 to 2024 where the analyses were run in the 1 year post core collection for each field expedition. The process date represents the most recent completion of the work.
    Reference:
    Pohlman, J.W., Riedel, M., Bauer, J.E., Canuel, E.A., Paull, C.K., Lapham, L., Grabowski, K.S., Coffin, R.B., and Spence, G.D., 2013, Anaerobic methane oxidation in low-organic content methane seep sediments: Geochimica et Cosmochimica Acta, 108, 184-201, https://doi.org/10.1016/j.gca.2013.01.022. Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
    Date: 2024 (process 7 of 8)
    TOC_wt.% (Sediment total organic carbon content) and TOC_d13C_permille (Bulk stable carbon isotope value of pediment total organic carbon content); Sediment samples from all cruises were freeze-dried and ground with a mortar and pestle. Homogenized sediment was weighed into silver capsules for acid fumigation. Samples were acid fumigated to remove carbonate and dried at 45 degrees C for 24 hours, then wrapped into tin capsules. Samples were run on an elemental analyzer interfaced with an isotope ratio mass spectrometer. Samples from PGC02-08 were normalized to an acetanilide standard and samples from AT50-14 were run with a peptone reference material, as well as standards USGS 40 226 and USGS 41. Stable carbon isotope values are reported in d notation relative to VPDB. The process step took place over a time period of 2004 to 2024 where the analyses were run in the 1 year post core collection for each field expedition. The process date represents the most recent completion of the work. Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
    Date: 2024 (process 8 of 8)
    H2S_mM (Pore water dissolved sulfide); Porewater sulfide (ΣH2S) was determined by sparging the sample aliquot after acidification with 25 % phosphoric acid, and trapping evolved H2S in sulfide antioxidant buffer (SAOB) solution for measurement with a sulfide specific electrode. Standards were prepared from a sodium bisulfide stock solution that was titrated with lead nitrate to determine its concentration, daily. Also on a daily basis, the stock solution was serially diluted to produce a five-level calibration. The process step took place over a time period of 2023 to 2024 with the analyses for a particular cruise run onboard the ship during the cruise. The process date represents the most recent completion of the work. Person who carried out this activity:
    Ellen Lalk
    U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
    Research Chemist
    384 Woods Hole Rd.
    Woods Hole, MA

    508-548-8700 (voice)
    elalk@usgs.gov
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
    For the 2002 cruise, horizontal positioning information for cores was achieved with an acoustic bottom transponder constellation, which provided an accuracy of 1-2 meters.
    For the 2004 cruise, positioning information for the underwater vehicle ROPOS (Remotely Operated Platform for Ocean Science) relied on Long Baseline (LBL) transponder technology. Ideally, this system provides sub-meter location accuracy (as noted by a commercial producer of the technology: https://www.hydro-international.com/content/article/lbl-underwater-positioning). ROPOS cruise reports from the early 2000s (https://www.pmel.noaa.gov/eoi/nemo2006/nemo06-crrpt-final.pdf) note the positional accuracy degraded on several occasions, with the worst reported accuracy (50 - 100 m) providing an upper bound on the positional accuracy for the 2004 samples.
    Samples collected in 2023 and 2024 for this study utilized underwater vehicles launched from the R/V Atlantis. The R/V Atlantis vehicles use a Sonardyne Ranger 2 ultra-short baseline (USBL) positioning system. Horizontal position for this system was found to be ~1% of the depth, meaning the horizontal position accuracy for this study is 7-13 meters. USBL accuracy study found on slide 17 at https://www.unols.org/sites/default/files/201910rvt_breakout03_shipboard_USBL_systems.pdf
  3. How accurate are the heights or depths?
    Material collected for this study was subsampled from shallow cores (within 9 meters of the sediment surface). Core locations were determined based on standard tape-measure core layouts, with 0.25 cm accuracy.
    Water depth is available via tidally-corrected shipboard bathymetric measurements with an accuracy of 0.3% of water depth (https://mac.unols.org/wp-content/uploads/2021/10/Atlantis_2021_EM124_SAT_report_v1p0.pdf). The seafloor sediment collection platforms are also equipped with pressure-based depth sensors accuracy to 0.1% of water depth (https://www.researchgate.net/publication/275271368). An upper bound on the water depth accuracy is taken here as the less accurate shipboard measurement of 0.3% of water depth.
    For the spatial reference information, the seabed surface reference is used because the sediment-water interface is the most relevant physical boundary associated with these data.
  4. Where are the gaps in the data? What is missing?
    This Microsoft Excel workbook represents the complete collected and calculated data in support of the Cascadia Margin dissolved organic carbon study.
  5. How consistent are the relationships among the observations, including topology?
    For each of the chemical and isotopic property measurements described in the Process Steps below, standards relevant to the particular property were entrained in the measurement sequence to ensure fidelity within each Process Step. The standards are noted in the Process Steps as well as the citations for those references.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints None
Use_Constraints Public domain (CC0-1.0) data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information.
  1. Who distributes the data set? (Distributor 1 of 1)
    Biological and Chemical Oceanography Data Management Office (BCO-DMO)
    Biological and Chemical Oceanography Data Management Office BCO-DMO, Woods Hole Oceanographic Institution, Shiverick House, MS #36
    Woods Hole, Massachusetts
    USA

    +1 508 289 2772 (voice)
    info@bco-dmo.org
  2. What's the catalog number I need to order this data set? The Biological and Chemical Oceanography Data Management Office (BCO-DMO) is a trustworthy, publicly-accessible, domain science data repository created to curate, publish, and archive digital data and information from biological, chemical, and biogeochemical research conducted in coastal, marine, Great Lakes, and laboratory environments. The office provides services that span the full data life cycle, from data management planning support and DOI creation, to archive with appropriate long-term facilities. Repository staff work closely with investigators to help them prepare, publish, and share their data and related information for reuse. Views and opinions expressed by BCO-DMO belong solely to the project PIs and its team members, and do not necessarily reflect those of project funders.
  3. What legal disclaimers am I supposed to read?
    Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 22-May-2025
Metadata author:
Brian J. Buczkowski
U.S. Geological Survey, Northeast Region, Woods Hole Coastal and Marine Science Center
Supervisory Physical Scientist
U.S. Geological Survey
Woods Hole, MA

508-548-8700 x2361 (voice)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is no longer with USGS.
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/approved_repository/bco-dmo_959765_1/Lalk_meta_DiscreteGeochemicalData_CascadiaMarginSeeps.faq.html>
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