Static chamber gas fluxes and carbon and nitrogen isotope content of age-dated sediment cores from a Phragmites wetland in Sage Lot Pond, Massachusetts, 2013-2015

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What does this data set describe?

Title:
Static chamber gas fluxes and carbon and nitrogen isotope content of age-dated sediment cores from a Phragmites wetland in Sage Lot Pond, Massachusetts, 2013-2015
Abstract:
Coastal wetlands are major global carbon sinks; however, quantification of carbon flux can be difficult in these heterogeneous and dynamic ecosystems. To characterize spatial and temporal variability in a New England salt marsh, static chamber measurements of greenhouse gas (GHG) fluxes were compared among major plant-defined zones (high marsh dominated by Distichlis spicata and a zone of invasive Phragmites australis) during 2013 and 2014 growing seasons. Two sediment cores were collected in 2015 from the Phragmites zone to support previously reported core collections from the high marsh sites (Gonneea and others 2018). Collected cores were up to 70 cm in length with dry bulk density ranges from 0.04 to 0.33 grams per cubic centimeter and carbon content 22.4 to 46.6 percent. Gamma counting results for excess lead-210 were used to construct Constant Rate of Supply (CRS) age models to age-date individual depth intervals in the cores. Additionally, gamma counting results for other radionuclides, particularly cesium-137 gave further insight to evaluate how vertical accretion and carbon burial rates have changed during the past century.
Gonneea, M.E., O'Keefe Suttles, J.A., and Kroeger, K.D., 2018, Collection, analysis, and age-dating of sediment cores from salt marshes on the south shore of Cape Cod, Massachusetts, from 2013 through 2014: U.S. Geological Survey data release, https://doi.org/10.5066/F7H41QPP.
Supplemental_Information:
For more information, see the following field activity: https://cmgds.marine.usgs.gov/fan_info.php?fan=2015-038-FA
  1. How might this data set be cited?
    Jennifer A. O'Keefe Suttles, Eagle, Meagan J., Martin, Rose M., Moseman-Valtierra, Serena, and Kroeger, Kevin D., 20220526, Static chamber gas fluxes and carbon and nitrogen isotope content of age-dated sediment cores from a Phragmites wetland in Sage Lot Pond, Massachusetts, 2013-2015: data release DOI:10.5066/P9JM751N, U.S. Geological Survey, Reston, VA.

    Online Links:

    Other_Citation_Details:
    Suggested citation: O'Keefe Suttles, J.A., Eagle, M.J., Martin, R.M., Moseman-Valtierra, S., and Kroeger, K.D., 2022, Static chamber gas fluxes and carbon and nitrogen isotope content of age-dated sediment cores from a Phragmites wetland in Sage Lot Pond, Massachusetts, 2013-2015: U.S. Geological Survey data release, https://doi.org/10.5066/P9JM751N.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -70.50481
    East_Bounding_Coordinate: -70.50478
    North_Bounding_Coordinate: 41.55656
    South_Bounding_Coordinate: 41.55651
  3. What does it look like?
    https://www.sciencebase.gov/catalog/file/get/624b1752d34e21f827635bdf?name=SLP_Phrag_SplitCore_2015.jpg (JPEG)
    Browse graphic is a photograph of a Phragmites sediment core, collected from Sage Lot Pond, after splitting in the laboratory.
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 19-Jul-2013
    Currentness_Reference:
    Ground Condition. These are the dates when the measurements were made and samples were collected. Exact dates for 2014 gas flux measurements were not recorded; they are reported as "Early", "Mid", and "Late" 2014 in reference to the approximate time of year of sample collection.
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: tabular digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference:
      Geographic Names Information System (GNIS) placenames are included as keywords to give the general location of core collections. The entity contains attributes with specific latitude and longitude of each core collection; several attributes are also included to describe the locations of core collections and gas flux measurement (nearest body of water and vegetation type). Refer to the entity and attribute definitions for "site_name", "veg_type", and "core_ID" for details.
      This is a Point data set. It contains the following vector data types (SDTS terminology):
      • Point
    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 1.0E-5. Longitudes are given to the nearest 1.0E-5. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Attribute values
  7. How does the data set describe geographic features?
    Data_SLP_Phrag_Cores.csv
    Comma separated text file with soil core data collected from Phragmites vegetated sites within Sage Lot Pond, a tidal wetland within the Waquoit Bay National Estuarine Research Reserve. The file includes latitude and longitude of core collection, calculated values of soil dry bulk density, mass accumulation rates, vertical accretion rates, and carbon burial rates. Also included are the data required for those calculations: radionuclide data, soil carbon and nitrogen content. The dataset includes 92 records. (Source: Producer-defined)
    site_name
    A text identifier for the general location of the study site. (Source: Producer-defined)
    ValueDefinition
    Sage Lot PondA data point from a sediment core collected from Sage Lot Pond, a tidal wetland within the Waquoit Bay National Estuarine Research Reserve, Mashpee, MA.
    veg_type
    A text identifier indicating the vegetation type that dominates the sediment core collection site. (Source: Producer-defined)
    ValueDefinition
    PhragmitesData point collected from a study site that is dominated by Phragmites australis.
    core_ID
    Abbreviated alphabetical identification code of each core to indicate: 1) the study site from which it was collected using a three-letter abbreviation, 2) a numeric qualifier to indicate the order of core collection over time/replicate core number (either 1 or 2), and 3) the vegetation type for the core collection site indicated by an abbreviation of the scientific name. (Source: Producer-defined)
    ValueDefinition
    SLP1PhragSage Lot Pond, core 1, Phragmites
    SLP2PhragSage Lot Pond, core 2, Phragmites
    date_collected
    A numeric identifier of the date the core was collected in the format of month/day/year. (Source: Producer defined)
    Range of values
    Minimum:05/21/15
    Maximum:05/21/15
    Units:mm/dd/yyyy
    latitude
    Latitude decimal degrees north, NAD83 (Source: Producer-defined)
    Range of values
    Minimum:41.55651
    Maximum:41.55656
    Units:decimal degrees
    longitude
    Longitude decimal degrees west, NAD83. The negative value indicates a location in the western hemisphere. (Source: Producer-defined)
    Range of values
    Minimum:-70.50481
    Maximum:-70.50478
    Units:decimal degrees
    depth_mid
    A numeric identifier of the interval mid-point depth below the sediment interface in centimeters. Note that depth = 0 cm is given as a reference point in order to include the land surface elevation within the dataset. Sediment core analyses are not reported for this sample depth because it is not a sampled horizon within a collected core. The minimum interval mid-point for each core is 0.5 cm. (Source: Producer-defined)
    Range of values
    Minimum:0
    Maximum:69.5
    Units:centimeters
    elevation
    A numeric identifier of interval mid-point elevation relative to NAVD88 datum in centimeters. Calculated by subtracting the mid-interval sample depth from the NAVD88 elevation of the core location reported as depth = 0 cm within the dataset for each core. (Source: Producer-defined)
    Range of values
    Minimum:-47.3
    Maximum:23.1
    Units:centimeters
    DBD
    Dry Bulk Density: A numeric identifier of the sediment dry bulk density in grams per cubic centimeter (g/cm3). Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0.0406
    Maximum:0.3368
    Units:grams per cubic centimeter
    210Pb
    A numeric identifier of the sediment total lead-210 activity in decays per minute per gram (dpm/g). Measured at 46.5 kiloelectron volts (KeV) on a planar gamma counter. Blank/empty cells indicate the measurement was not done. Minimum detection limit 0.244 (Source: Producer-defined)
    Range of values
    Minimum:0.2443
    Maximum:32.0775
    Units:decays per minute per gram
    210Pb_e
    A numeric identifier of the measurement error in sediment total lead-210 activity in decays per minute per gram (dpm/g). Blank/empty cells indicate the measurement was not done. The value 0.00 is given to analyzed samples found to be below detection. (Source: Producer-defined)
    Range of values
    Minimum:0.1084
    Maximum:1.6266
    Units:decays per minute per gram
    226Ra
    A numeric identifier of the sediment total radium-226 activity in decays per minute per gram (dpm/g). Measured at 352 kiloelectron volts (KeV) on a planar gamma counter. Blank/empty cells indicate the measurement was not done. The value 0.00 is given to analyzed samples found to be below detection (0.116 dmp/g). (Source: Producer-defined)
    Range of values
    Minimum:0.1168
    Maximum:8.7832
    Units:decays per minute per gram
    226Ra_e
    A numeric identifier of the measurement error in sediment total radium-226 activity in decays per minute per gram (dpm/g). Blank/empty cells indicate the measurement was not done. The value 0.00 is given to analyzed samples found to be below detection. (Source: Producer-defined)
    Range of values
    Minimum:0.0319
    Maximum:0.5850
    Units:decays per minute per gram
    210Pbex
    A numeric identifier of the sediment excess lead-210 activity in decays per minute per gram (dpm/g), decay-corrected to date of core collection. Calculated as the difference between total lead-210 and total radium-226 activities. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:-0.7255
    Maximum:31.7495
    Units:decays per minute per gram
    210Pbex_e
    A numeric identifier of the propagated measurement error in sediment excess lead-210 activity in decays per minute per gram (dpm/g), decay-corrected to date of core collection. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0.1155
    Maximum:1.6720
    Units:decays per minute per gram
    137Cs
    A numeric identifier of the sediment total cesium-137 activity in decays per minute per gram (dpm/g), decay-corrected to date of core collection. Measured at 662 kiloelectron volts (KeV) on a planar gamma counter. Blank/empty cells indicate the measurement was not done. The value 0.00 is given to analyzed samples found to be below detection (0.145 dpm/g). (Source: Producer-defined)
    Range of values
    Minimum:0.1451
    Maximum:1.0691
    Units:decays per minute per gram
    137Cs_e
    A numeric identifier of the measurement error in sediment total cesium-137 activity in decays per minute per gram (dpm/g), decay-corrected to date of core collection. Blank/empty cells indicate the measurement was not done. The value 0.00 is given to analyzed samples found to be below detection. (Source: Producer-defined)
    Range of values
    Minimum:0.0356
    Maximum:0.1438
    Units:decays per minute per gram
    7Be
    A numeric identifier of the measurement error in sediment total beryllium-7 activity in decays per minute per gram (dpm/g), decay-corrected to date of core collection. Measured at 477 kiloelectron volts (KeV) on a planar gamma counter. Blank/empty cells indicate the measurement was not done. The value 0.00 is given to analyzed samples found to be below detection (3.79 dpm/g). (Source: Producer-defined)
    Range of values
    Minimum:3.7955
    Maximum:5.9081
    Units:decays per minute per gram
    7Be_e
    A numeric identifier of the measurement error in sediment total beryllium-7 activity in decays per minute per gram (dpm/g), decay-corrected to date of core collection. Blank/empty cells indicate the measurement was not done. The value 0.00 is given to analyzed samples found to be below detection. (Source: Producer-defined)
    Range of values
    Minimum:0.9429
    Maximum:1.4248
    Units:decays per minute per gram
    wtC
    Total amount of carbon by weight percent in soil. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:22.4
    Maximum:46.58
    Units:unitless
    wtN
    Total amount of nitrogen by weight percent in soil. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0.98
    Maximum:2.19
    Units:unitless
    13C
    The carbon isotopic signature of the soil sample relative to Pee Dee Belemnite (PDB) standard. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:-28.75
    Maximum:-21.55
    Units:parts per thousand OR per mil
    15N
    The nitrogen isotopic signature of the soil sample relative to air. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0.04
    Maximum:2.99
    Units:parts per thousand OR per mil
    Age
    A numeric identifier for the age in years from the collection date of the core interval based on the Constant Rate of Supply excess lead-210 age model. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0
    Maximum:133.5
    Units:years
    Age_e
    A numeric identifier for the age model uncertainty in years of the core interval based on the Constant Rate of Supply excess lead-210 age model. Error is propagated through the model. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0
    Maximum:42.2
    Units:years
    VAR
    Vertical Accretion Rate: A numeric identifier for the vertical accretion rate of the sediment in millimeters per year (mm/y). Calculated as the difference in interval midpoint divided by the difference in ages of those adjacent sediment intervals. (Source: Producer-defined)
    Range of values
    Minimum:1.4
    Maximum:10.8
    Units:millimeters per year
    MAR
    Mass Accumulation Rate: A numeric identifier for the mass accumulation rate of the sediment in grams per square meter per year (g/m2/y). Calculated by multiplying dry bulk density times vertical accretion rate. (Source: Producer-defined)
    Range of values
    Minimum:256
    Maximum:1377
    Units:grams sediment per square meter per year
    CAR
    Carbon Accumulation Rate: A numeric identifier for the carbon mass accumulation rate of the sediment in grams of carbon per square meter per year (gC/m2/y). Calculated by multiplying the average mass accumulations rate for the combined depth interval of the elemental sample times weight percent carbon. (Source: Producer-defined)
    Range of values
    Minimum:65
    Maximum:213
    Units:grams carbon per square meter per year
    Year
    The year corresponding to the soil horizon based on the Constant Rate of Supply excess lead-210 age model. Calculated as collection date minus age of sediment at each depth interval. (Source: Producer-defined.)
    Range of values
    Minimum:1882
    Maximum:2015.5
    Units:calendar year
    SLP_Phragmities_GHGFluxes.csv
    Comma separated text file with measurements of carbon fluxes (carbon dioxide and methane) collected using static chambers at sites dominated by 2 different salt marsh vegetation types across a seasonal time scale at Sage Lot Pond in Mashpee, MA from July 2013 through November 2014. Environmental and biologic metrics that could inform carbon exchange, (including stem density, plant height, and porewater pH/ORP, salinity, sulfide, methane, and soil moisture) were also collected to support data interpretation. The dataset contains 36 records. (Source: Producer-defined)
    site_name
    A text identifier for the general location of the study site. (Source: Producer-defined)
    ValueDefinition
    Sage Lot PondA data point from a site location in Sage Lot Pond, a tidal wetland within the Waquoit Bay National Estuarine Research Reserve, Mashpee, MA.
    date
    An identifier of the date the GHG fluxes were measured and porewater samples were collected. (Source: Producer defined)
    Range of values
    Minimum:07/19/2013
    Maximum:09/20/2013
    Units:month/day/year
    In 2014, exact dates of field measurements were not recorded. Measurements were made to capture a seasonal time period. Approximate time of year is reported as "Early 2014", "Mid 2014", or "Late 2014".
    veg_type
    A text identifier indicating the vegetation type that dominates the location of the GHG measurement and porewater collection site. (Source: Producer-defined)
    ValueDefinition
    Phragmites australisData point collected from a location within the study site that is dominated by Phragmites australis.
    Distichlis spicataData point collected from a location within the study site that is dominated by Distichlis spicata.
    chamber_rep
    Identifier of the chamber replicate at each sampling location. (Source: Producer-defined)
    Range of values
    Minimum:1
    Maximum:3
    Units:numerical order
    stem_height
    Mean height in centimeters of 10 randomly selected shoots within the quadrat; see process step for measurement description. (Source: Producer-defined)
    Range of values
    Minimum:24
    Maximum:169
    Units:cm
    stem_density
    Number of individual plants per square meter; see process step for measurement description. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:9
    Maximum:133
    Units:stems per square meter
    sal_porewater
    A numeric data value of measured porewater salinity in practical salinity units (PSU); see process steps for measurement description. Blank/empty cells indicate the measurement was not done (Source: Producer-defined)
    Range of values
    Minimum:20
    Maximum:30
    Units:PSU
    soil_moisture
    Mean of three soil moisture measurements; see process steps for measurement description. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:55.9
    Maximum:69.7
    Units:percent
    pH_porewater
    A numeric data value of measured porewater pH; see process steps for measurement description. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:6.79
    Maximum:7.66
    Units:pH units
    ORP_porewater
    A numeric data value measured porewater Oxidation Reduction Potential; see process steps for measurement description. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:-352.5
    Maximum:148
    Units:mV
    sulfide_porewater
    A numeric data value of measured porewater sulfide; see process steps for field collection and laboratory analysis descriptions. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0
    Maximum:1334.79
    Units:micromol per liter
    CH4_porewater
    A numeric data value of measured porewater methane; see process steps for field collection and laboratory analysis descriptions. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0
    Maximum:33.40
    Units:micromol per liter
    CO2_flux
    Flux of carbon dioxide calculated from the slope of CO2 concentration change in micromoles of CO2 per square meter per second. Positive values indicate a flux of CO2 out of the ecosystem into the atmosphere and negative values indicate a flux out of the atmosphere into the ecosystem. See process steps for measurement description. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:-18.02
    Maximum:6.73
    Units:micromol CO2 per square meter per second
    CH4_flux
    Flux of methane calculated from the slope of CH4 concentration change in nanomoles of CH4 per square meter per second. Positive values indicate a flux of methane out of the ecosystem into the atmosphere and negative values indicate a flux out of the atmosphere into the ecosystem. See process steps for measurement description. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:0.00
    Maximum:33.40
    Units:nanomol CH4 per square meter per second
    N2O_flux
    Flux of nitrous oxide calculated from the slope of N2O concentration change in nanomoles of CH4 per square meter per second. Positive values indicate a flux of methane out of the ecosystem into the atmosphere and negative values indicate a flux out of the atmosphere into the ecosystem. See process steps for measurement description. Blank/empty cells indicate the measurement was not done. (Source: Producer-defined)
    Range of values
    Minimum:-1.42
    Maximum:0.36
    Units:nanomol N2O per square meter per second

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Jennifer A. O'Keefe Suttles
    • Meagan J. Eagle
    • Rose M. Martin
    • Serena Moseman-Valtierra
    • Kevin D. Kroeger
  2. Who also contributed to the data set?
    Dr. Elizabeth Watson and Dr. Cathleen Wigand performed pore water sulfide analyses at the Atlantic Ecology Division of the Environmental Protection Agency in Narragansett, RI.
  3. To whom should users address questions about the data?
    Meagan J Eagle
    Northeast Region: WOODS HOLE COASTAL AND MARINE SCIENCE
    Research Physical Scientist
    384 Woods Hole Road
    Woods Hole, MA
    US

    508-548-8700 x2280 (voice)
    meagle@usgs.gov

Why was the data set created?

The purpose of this study was to measure greenhouse gas fluxes across a seasonal time-scale and to determine sediment carbon content and sediment accumulation rates across contrasting plant-defined zones in order to model controls on GHG fluxes in a New England salt marsh. These data support research focused on understanding controls and scaling of carbon exchange in order to inform possible Blue Carbon management interventions in these vulnerable ecosystems.

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: 2014 (process 1 of 5)
    Gas Flux Measurements and Calculations in 2013 and 2014: Three plots were established in both the high marsh and Phragmites australis-invaded zones. Square steel collars (56 cm × 56 cm) sealed the base of the chambers and were preinstalled (at least 1 month prior to first measurements) to a depth of approximately 20 cm. Gas flux measurements were taken within 3 hours of low tide to minimize variability in data brought on by tidal cycling. Gas fluxes were measured during daytime with a transparent chamber to reflect the net result of photosynthesis and respiration in the marsh plots. Carbon dioxide (CO2) and methane (CH4) fluxes were measured by connecting a cavity ring-down spectrometer (Model G2301; Picarro Inc., Santa Clara, California, USA) to a transparent acrylic chamber (60 cm × 60 cm × 60 cm) in a closed loop. nitrous oxide (N2O) fluxes were measured by also connecting a nitrous oxide/carbon monoxide (N2O/CO) gas analyzer (Los Gatos Research, Mountain View, California, USA) to the same chamber. The chamber contained two battery-powered fans to homogenize the air inside, pigtails to prevent pressure accumulation (inner diameter of 0.71 mm), and four ports to connect to inlets and outlets of both analyzers in a closed loop system. All gas fluxes were calculated from linear rates of change in gas concentrations in each chamber over time using the ideal gas law (as detailed in Martin and Moseman-Valtierra 2015). Changes in gas concentrations over time (dC/dt) were analyzed with linear regressions. We define positive fluxes as those in which gas concentrations increased over time within a chamber (representing vertical emission from the marsh surface to the atmosphere), and negative fluxes as those in which concentrations decreased (representing net uptake from the atmosphere to the marsh). Significant fluxes were defined based on R2 values of 0.90 or greater and P-values of 0.05 or less. In cases in which both CH4 and CO2 fluxes showed insignificant R2 and P-values, the data were discarded.
    Stem Density and Plant Height 2013 and 2014: Native plant community composition and stem density were determined by identifying and counting plants in small quadrats (10 cm × 10 cm for the high marsh) within 1 m of each gas flux collar. Because marsh plant communities are uniform and homogenous within zones, it was not necessary to include flux collars in plant community composition surveys. Heights were measured from 10 randomly selected shoots; the average is reported.
    Porewater sampling 2013 and 2014: Water was sampled within 1 hour of gas flux measurements from 0 to 10 cm depths using Rhizon samplers (Soil Moisture Co., Goleta, California, USA) and preserved in equal volumes of 1 M zinc acetate and stored frozen (−17 degrees Celsius) for pore water sulfide analyses (following Cline 1969). Soil moisture content was measured (three times per plot in random locations between plant culms) by inserting an EC-5 soil sensor to a depth of 5 cm (Decagon Devices, Pullman, Washington, USA). Soil pH was measured by collecting a surface plug of soil (approximately 5 mL), adding to 10 mL of distilled water in a sterile centrifuge tube, and immediately measuring the pH of the resulting slurry (Orion Star A326 Multiparameter Meter; Thermo Scientific, Pittsburgh, Pennsylvania, USA). In all 2014 dates, soil pH methods were switched (for expediency) to the use of a surface probe pH meter (Ex Stick Instruments, Nashua, New Hampshire, USA). Measurement of pH in a slurry and directly in the sediment were comparable (data not shown). Salinity of water (filtered and squeezed) from surface (0-2 cm) sediments was measured with a handheld refractometer. Dr. Elizabeth Watson and Dr. Cathleen Wigand performed pore water sulfide analyses at the Atlantic Ecology Division of the Environmental Protection Agency in Narragansett, RI following the method of Cline (1969).
    Martin, R. M., and S. M. Moseman-Valtierra, 2015, Greenhouse gas fluxes vary between Phragmites australis and native vegetation zones in coastal wetlands along a salinity gradient: Wetlands, v. 35, p. 1021–1031, https://doi.org/10.1007/s13157-015-0690-y.
    Cline, J. D., 1969, Spectrophotometric determination of hydrogen sulfide in natural waters: Limnology and Oceanography,v. 14 p. 454–458, https://doi.org/10.4319/lo.1969.14.3.0454.
    These processes occurred during 2013 and 2014 with the process date being the most recent occurrence.
    Date: 21-May-2015 (process 2 of 5)
    A piston coring system was used to collect sediment cores from coastal wetlands on 05/21/2015. The PVC core liner (diameter 11 cm, 1 m in length) was fitted with a gasketed piston that was placed on the sediment surface. The clear, sharpened core liner was pushed down into the marsh subsurface, while the piston was maintained at the marsh surface via tension on the piston. We visually observed the sediment surface to ensure that the soil column did not compact during collection. Once the core reached the desired depth, the core liner and piston were removed from the marsh with a pulley system.
    Date: 2018 (process 3 of 5)
    Sediment cores were immediately returned to the USGS Woods Hole Coastal and Marine Science Center after collection. They were placed in a refrigerator for 1 to 3 days, then split vertically, sectioned at 1 or 2 cm intervals, frozen, and then freeze dried for 7 days until sediment weights did not change further. Dry bulk density was determined as the dry weight of a known volume of sample. Approximately 5 grams of dried sediment sample was blended and homogenized prior to sealing in a jar for a minimum of three weeks and then placed on a planar-type gamma counter for 24 to 48 hours to measure 7Be, 137Cs, 210Pb, and 226Ra at 477, 662, 46.5 and 352 kiloelectronvolts (KeV) energies respectively (Canberra Inc., USA). Detector efficiency was determined from EPA standard pitchblende ore in the same geometry as the samples. Excess 210Pb was calculated as the decay-corrected difference between total 210Pb and supported 210Pb (considered to be equal to 226Ra). Activities of 7Be, 137Cs, and excess 210Pb were decay corrected to time of collection, using their respective half-lives. Suppression of low energy peaks by self-absorption was corrected for according to Cutshall and others, 1983. Gamma spectroscopy detection limits were determined in APTEC software for each sample; refer to the attribute accuracy section of this metadata for further details. Values reported are above this limit, while values below are reported as 0. Core sections not analyzed are reported as blank cells. Sediment ages and accretion rates were calculated with the Constant Rate of Supply (CRS) excess 210Pb age model, a variant on the advection-decay equation (Appleby and Oldfield, 1978; Goldberg, 1963). This model assumes that 210Pb supply to the sediment surface is constant through time, but allows for changing sedimentation rates, in addition to decay, to control the down-core activity of excess 210Pb. The common form of the CRS model, as derived by Appleby and Oldfield (1978), solves for age based on the distribution of excess 210Pb in the sediment record. Prior to application of the age model, excess 210Pb profiles were evaluated to ensure they were sufficiently resolved to apply the CRS model without bias towards ages that are too old or accretion rates that are too low at depth (Binford, 1990). Negative values of excess 210P occur where 226Ra is greater than 210Pb-total. These sections are not included in the age-model calculations. All gamma analyses were ongoing from 2015 and completed in 2018.
    Appleby, P.G., and Oldfield, F., 1978, The calculation of lead-210 dates assuming a constant rate of supply of unsupported 210Pb to the sediment: Catena, v. 5, issue 1, p. 1–8, https://doi.org/10.1016/S0341-8162(78)80002-2.
    Binford, M.W., 1990, Calculation and uncertainty analysis of 210 Pb dates for PIRLA project lake sediment cores: Journal of Paleolimnology, v. 3, issue 3, p. 253-267, https://doi.org/10.1007/BF00219461.
    Cutshall, N.H., Larsen, I.L., and Olsen, C.R., 1983, Direct analysis of 210 Pb in sediment samples—Self-absorption corrections: Nuclear Instruments and Methods in Physics Research, v. 206, issues 1–2, p. 309–312, https://doi.org/10.1016/0167-5087(83)91273-5.
    Goldberg, E.D., 1963, Geochronology with 210 Pb, in Miller, J.A., convener, Radioactive dating: International Atomic Energy Agency Symposium on Radioactive Dating, Athens, Greece, November 19-23, 1962, [Proceedings], p. 121-131.
    Date: 2016 (process 4 of 5)
    A subsample of freeze dried sediment (0.5 g) was ball-milled to a fine powder and analyzed for weight percent carbon and nitrogen and the isotopic signature of carbon and nitrogen in organic matter at the University Rhode Island. During analysis, samples are interspersed with several replicates of laboratory reference material and blanks.
    Date: 2022 (process 5 of 5)
    Raw data were entered into an Excel spreadsheet where all calculations were completed. The Excel spreadsheet was exported as a CSV file from Excel for Mac version 15.33. The CSV file was processed in MATLAB to round calculated values to appropriate place values and again exported as a comma separated comma separated text file (*.csv). Note that all calculations were performed prior to rounding and truncating values reported in this data release. Person who carried out this activity:
    Meagan J Eagle
    Northeast Region: WOODS HOLE COASTAL AND MARINE SCIENCE CENTER
    Research Physical Scientist
    384 Woods Hole Road
    Woods Hole, MA
    US

    508-548-8700 x2280 (voice)
    meagle@usgs.gov
  3. What similar or related data should the user be aware of?
    Moseman-Valtierra, Serena, Abdul-Aziz, Omar I., Tang, Jianwu, Ishtiaq, Khandker S., Morkeski, Kate, Mora, Jordan, Quinn, Ryan K., Martin, Rose M., Egan, Katherine, Brannon, Elizabeth Q., Carey, Joanna, and Kroeger, Kevin D., 2016, Carbon dioxide fluxes reflect plant zonation and belowground biomass in a coastal marsh: Ecosphere 7(11), e01560, Ecological Society of America, Washington, D.C..

    Online Links:

    Other_Citation_Details:
    Data reported in this data release are an extension of data collections in this journal.
    Gonneea, Meagan E., O'Keefe Suttles, Jennifer A., and Kroeger, Kevin D., 2018, Collection, analysis, and age-dating of sediment cores from salt marshes on the south shore of Cape Cod, Massachusetts, from 2013 through 2014: data release DOI:10.5066/F7H41QPP, U.S. Geological Survey, Reston, VA.

    Online Links:


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

  1. How well have the observations been checked?
    Radionuclide detection limits are specific to an individual sample and are a function of: 1) the detector efficiency at the energy level of the peak being measured; 2) the branching ratio (expected fraction of decay events at the energy level); 3) the background activity within the sample. Detector efficiency was determined from EPA standard pitchblende ore in the same geometry as the samples. Activities of 7Be, 137Cs, and excess 210Pb (i.e. unsupported) were decay-corrected to time of collection. Suppression of low energy peaks by self-absorption was corrected for according to Cutshall and others, 1983. Peak detection, with respect to background activity, is calculated for each radionuclide in the APTEC peak integration spectroscopy software during sample analysis. Generally, measured radionuclide activity greater than or equal to 0.244 (210Pb), 0.116 (226Ra), 3.79 (7Be), and 0.145 (137Cs) disintegrations per minute per gram were accepted as above detection limit for this dataset.
    Samples were analyzed for weight percent carbon and nitrogen and the isotopic signature of carbon and nitrogen in organic matter at the University Rhode Island. During analysis, samples were interspersed with several replicates of laboratory reference materials. Any analysis value below detection is given the numerical value of 0. Any attribute that was not measured for a specific sample is left as a blank cell.
    Cutshall, N.H., Larsen, I.L., and Olsen, C.R., 1983, Direct analysis of 210 Pb in sediment samples—Self-absorption corrections: Nuclear Instruments and Methods in Physics Research, v. 206, issues 1–2, p. 309–312, https://doi.org/10.1016/0167-5087(83)91273-5.
  2. How accurate are the geographic locations?
    Latitude and longitude of core collection locations with a handheld Garmin GPSMAP 76Cx unit in the field at time of sediment core collection. The GPS unit indicated accuracy was within 3 meters. Exact coordinates of the gas flux measurements are not reported; however they are similar in location to those cited in Moseman-Valtierra and others (2016). No formal positional accuracy tests were conducted.
  3. How accurate are the heights or depths?
    Land surface elevation of the core collection sites were measured by SpectraPrecision (SP80) Real-Time Kinematic (RTK) GPS after core collection. An average elevation for clustered points around the core collection location is reported for the core depth at 0 centimeters. Average vertical accuracy of this method is +/- 5 centimeters. No formal positional accuracy tests were conducted.
  4. Where are the gaps in the data? What is missing?
    Gas fluxes were not measured 9/20/2013 due to instrument problems, these cells are left blank. In 2014 nitrous oxide was not measured and cells are left blank. In cases in which both methane and carbon dioxide fluxes showed insignificant R2 and P-values, the data were discarded from Data_SLP_Phrag_GHGFluxes.csv, as described in the first process step. Significant fluxes were defined based on R2 values of 0.90 or greater and P-values of 0.05 or less.
  5. How consistent are the relationships among the observations, including topology?
    Dataset was queried for maximum and minimum values to be sure sample analyses were within expected ranges for the environmental conditions. Data were plotted to look for any obvious outliers that may have been indicative of analytical error. Detection limits are defined in the attribute accuracy section of the metadata. Any analysis value below detection is given the numerical value of 0. Any attribute that was not measured for a specific sample is listed as an empty or blank cell. Each sample was treated in the same manner for each analysis.

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 none
  1. Who distributes the data set? (Distributor 1 of 1)
    ScienceBase
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO
    US

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? The dataset contains two CSV files containing the data (Data_SLP_Phrag_Cores.csv; Data_SLP_Phrag_GHGFluxes.csv), the browse graphic (SLP_Phrag_SplitCore_2015.jpg), and the FGDC CSDGM metadata in XML format.
  3. What legal disclaimers am I supposed to read?
    Neither the U.S. Government, the Department of the Interior, nor the USGS, nor any of their employees, contractors, or subcontractors, make any warranty, express or implied, nor assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, nor represent that its use would not infringe on privately owned rights. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Any use of trade, product, or firm 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?
  5. What hardware or software do I need in order to use the data set?
    The zip file resulting from the first network resource link contains data in CSV format. The user must have software capable of uncompressing the zip file and reading the data formats.

Who wrote the metadata?

Dates:
Last modified: 26-May-2022
Metadata author:
Jennifer A. O'Keefe Suttles
Northeast Region: WOODS HOLE COASTAL AND MARINE SCIENCE CENTER
Chemist
384 Woods Hole Road
Woods Hole, MA
United States

508-548-8700 x2385 (voice)
whsc_data_contact@usgs.gov
Contact_Instructions:
The metadata contact email address is a generic address in the event the person is not longer with USGS.
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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