Water and algal chemistry measurements collected from the National Park Service's National Park of American Samoa (NPS-NPSA) Ofu Island unit

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Frequently anticipated questions:

What does this data set describe?

Title:
Water and algal chemistry measurements collected from the National Park Service's National Park of American Samoa (NPS-NPSA) Ofu Island unit
Abstract:
Geochemical analysis of coastal springs and possible source waters were conducted in the National Park Service's National Park of American Samoa (NPS-NPSA) Ofu Island unit. Water samples were analyzed for dissolved nutrients, nitrate isotopes (delta-18-O and delta-15-N). Algae samples were collected and analyzed for delta-15-N and delta-13-C values.
Supplemental_Information:
Additional information about the field activity or activities from which these data were derived is available online at: http://cmgds.marine.usgs.gov/fan_info.php?fan=2020-601-FA http://cmgds.marine.usgs.gov/fan_info.php?fan=2020-620-FA http://cmgds.marine.usgs.gov/fan_info.php?fan=2020-670-FA Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  1. How might this data set be cited?
    Prouty, Nancy G., 20250717, Water and algal chemistry measurements collected from the National Park Service's National Park of American Samoa (NPS-NPSA) Ofu Island unit: data release DOI: 10.5066/P1DVZPUV, U.S. Geological Survey, Pacific Coastal and Marine Science Center, Santa Cruz, California.

    Online Links:

    Other_Citation_Details:
    Suggested Citation: Prouty, N.G., 2025, Water and algal chemistry measurements collected from the National Park Service's National Park of American Samoa (NPS-NPSA) Ofu Island unit: U.S. Geological Survey data release, https://doi.org/10.5066/P1DVZPUV.
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -169.6767950
    East_Bounding_Coordinate: -169.6216050
    North_Bounding_Coordinate: -14.1850000
    South_Bounding_Coordinate: -14.1715070
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 05-Jul-2019
    Ending_Date: 09-Feb-2020
    Currentness_Reference:
    Ground condition at time data were collected.
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: comma-delimited text
  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 (112)
    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 0.00000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is D_WGS_1984.
      The ellipsoid used is D_WGS_1984.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257224.
  7. How does the data set describe geographic features?
    Ofu_water_algal_chemistry.csv
    Output from chemical analysis of water and algae samples (Source: Producer defined.)
    Sample ID
    Sample identification of sampled based on location (Ofu), site (CS=coastal spring, CP=cesspool, WL=well, MS=marsh, FR=forereef) or sample type (algae), sequential number and year of collection. (Source: Producer defined) List of station names
    Date
    Sample collection date (Source: Producer defined.)
    Range of values
    Minimum:2019-07-05
    Maximum:2020-02-09
    Units:YYYY-MM-DD
    Time
    Sample collection time (GMT-11). Values of -9999 indicate the parameter was not measured. (Source: Producer defined.)
    Range of values
    Minimum:7:26
    Maximum:19:15
    Units:Hour:minutes
    Latitude
    Latitude of sample location (Source: Producer defined.)
    Range of values
    Minimum:-14.18533201
    Maximum:-14.17150700
    Units:decimal degrees
    Resolution:0.00000001
    Longitude
    Longitude of sample location (Source: Producer defined.)
    Range of values
    Minimum:-169.6767950
    Maximum:-169.6216050
    Units:decimal degrees
    Resolution:0.000001
    Salinity
    Measured salinity of water sample. Values of -9999 indicate the parameter was not measured. (Source: Producer defined.)
    Range of values
    Minimum:0.1
    Maximum:35.0
    Units:parts per thousand
    Resolution:0.1
    Temperature
    Measured temperature of water sample. Values of -9999 indicate the parameter was not measured. (Source: Producer defined.)
    Range of values
    Minimum:25.5
    Maximum:29.4
    Units:degrees Celsius
    Resolution:0.1
    Phosphate
    Dissolved inorganic phosphate concentration. Values of -9999 indicate the parameter was not measured. (Source: standard reporting value in inorganic chemistry)
    Range of values
    Minimum:0.16
    Maximum:340.18
    Units:micromole per liter of seawater
    Resolution:0.01
    Silicate
    Dissolved inorganic silicate concentration. Values of -9999 indicate the parameter was not measured (Source: standard reporting value in inorganic chemistry)
    Range of values
    Minimum:0.91
    Maximum:1203.85
    Units:micromole per liter of seawater
    Resolution:0.01
    Nitrate and nitrite
    Dissolved inorganic nitrate and nitrite concentration. Values of -9999 indicate the parameter was not measured (Source: standard reporting value in inorganic chemistry)
    Range of values
    Minimum:0.37
    Maximum:52.83
    Units:micromole per liter of seawater
    Resolution:0.01
    Ammonium
    Dissolved inorganic Ammonium concentration. Values of -9999 indicate the parameter was not measured. Values of -8888 indicate that the compound was not detected. (Source: standard reporting value in inorganic chemistry.)
    Range of values
    Minimum:0.02
    Maximum:2783.34
    Units:micromole per liter of seawater
    Resolution:0.01
    delta-N-15
    delta-N-15 is a measure of the ratio of stable isotopes Nitrogen-15:Nitrogen-14, reported in parts per thousand (per mil). Values of -9999 indicate the parameter was not measured. (Source: standard reporting value in inorganic chemistry.)
    Range of values
    Minimum:-9.75
    Maximum:9.77
    Units:per mil
    Resolution:0.01
    delta-O-18
    delta-O-18 is a measure of the ratio of stable isotopes Oxygen-18:Oxygen-16 in water, reported in parts per thousand (per mil). Values of -9999 indicate the parameter was not measured. (Source: Producer defined.)
    Range of values
    Minimum:-1.79
    Maximum:4.84
    Units:per mil
    Percent organic nitrogen
    Percentage by weight (wt percent) of organic nitrogen; values of -9999 indicate the parameter was not measured. (Source: Producer defined)
    Range of values
    Minimum:0.68
    Maximum:2.77
    Units:percent weight
    Resolution:0.01
    delta-C-13
    delta-C-13 is a measure of the ratio of stable isotopes Carbon-13:Carbon-12 in water, reported in parts per thousand (per mil). Values of -9999 indicate the parameter was not measured. (Source: Producer defined.)
    Range of values
    Minimum:-20.95
    Maximum:-5.18
    Units:per mil
    Percent organic carbon
    Percentage by weight (wt percent) of organic carbon; values of -9999 indicate the parameter was not measured. (Source: Producer defined)
    Range of values
    Minimum:5.52
    Maximum:10.59
    Units:percent weight
    Resolution:0.01
    Entity_and_Attribute_Overview: The first line of the csv file is a header line.
    Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Nancy G. Prouty
  2. Who also contributed to the data set?
    Brendan Roark (Texas A&M) and Danielle Hull (University of Hawaii) completed the stable isotope analysis and nutrient analysis, respectively.
  3. To whom should users address questions about the data?
    U.S. Geological Survey, Pacific Coastal and Marine Science Center
    Attn: PCMSC Science Data Coordinator
    2885 Mission Street
    Santa Cruz, CA

    831-427-4747 (voice)
    pcmsc_data@usgs.gov

Why was the data set created?

These samples were collected and analyzed as part of an effort to characterize the spatiotemporal variability of nutrient-enriched submarine groundwater (SGD) in NPSA. This project focused on identifying and quantifying the composition and fluxes of submarine groundwater discharged onto the reef. These results will inform help NPS-NPSA staff and local government to direct remediation actions related to outbreak of Valonia fastigiata algae.

How was the data set created?

  1. From what previous works were the data drawn?
    Nitrate delta-N-15 and delta-O-18 (source 1 of 3)
    University of California, Davis Stable Isotope Facility, 2020, nitrate stable nitrogen isotope analysis.

    Type_of_Source_Media: seawater lab samples
    Source_Contribution:
    Denitrifier method of Sigman and others, (2001) using a Thermo Finnigan MAT 252 coupled with a GasBench II interface, isotope values are presented in per mil with respect to AIR for delta-N-15 and VSMO for delta-O-18
    nutrient analysis (source 2 of 3)
    University of Hawaii, School of Ocean and Earth Science and Technology (SOEST), 2020, nutrient analysis.

    Online Links:

    Type_of_Source_Media: water lab samples
    Source_Contribution:
    Nutrient autoanalyzer for analysis for dissolved nutrient (nitrate, ammonia, phosphate, and silicate) concentrations.
    Stable isotope analysis (source 3 of 3)
    University, Texas A&M, 2020, nutrient analysis.

    Online Links:

    Type_of_Source_Media: algae lab samples
    Source_Contribution:
    Nitrogen (delta-N-15) and Carbon (delta-C-13) analysis on algae samples.
  2. How were the data generated, processed, and modified?
    Date: 2020 (process 1 of 2)
    Discrete water sampling included pumping from coastal springs at low tide and a groundwater well, marsh, and cesspool using a peristaltic pump with an in-line 0.45-micron filter and grab samples from the nearshore and reef flat by filtering with a 0.20-mircron syringe filter and storing frozen until analysis. Water samples were analyzed by several different labs (see Sources) for different variables. Data from all lab analyses were combined into a single document. -9999 cell value indicates no data (for example, where water sample was not analyzed for a particular variable given sample volume limitations). Algae samples were collected by snorkel, stored frozen, freeze dried at the lab, and homogenized prior to lab analysis for delta-N-15 and delta-C-13. Data sources used in this process:
    • nutrient analysis
    • Nitrate delta-N-15 and delta-O-18
    • Stable isotope analysis
    Data sources produced in this process:
    • lab data
    Date: 2020 (process 2 of 2)
    Water and algae data were combined into a single document (Ofu_water_algal_chemistry.csv). Data sources used in this process:
    • lab data
  3. What similar or related data should the user be aware of?
    Sigman, D.M., Casciotti, K.L., Andreani, M., Barford, C., Galanter, M., and Bohlke, J.K., 2001, A bacterial method for the nitrogen isotopic analysis of nitrate in seawater and freshwater.

    Online Links:

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

  1. How well have the observations been checked?
    All geochemistry data were calibrated against known standards
  2. How accurate are the geographic locations?
    A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. The horizontal accuracy is based on hand-held Garmin GPS. Horizontal accuracy is approximately 3 meters.
  3. How accurate are the heights or depths?
    A formal accuracy assessment of the vertical positional information in the data set has not been conducted.
  4. Where are the gaps in the data? What is missing?
    Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the metadata for each part of this data release carefully for additional details. Dataset is considered complete for the information presented, as described in the abstract. Users are advised to read the metadata for each part of this data release carefully for additional details.
  5. How consistent are the relationships among the observations, including topology?
    No formal logical accuracy tests were conducted.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints No access constraints
Use_Constraints USGS-authored or produced data and information are in the public domain from the U.S. Government and are freely redistributable with proper metadata and source attribution. Please recognize and acknowledge the U.S. Geological Survey, and the National Park Service (NPS) as the originators of the dataset and in products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey - ScienceBase
    Denver Federal Center, Building 810, Mail Stop 302
    Denver, CO

    1-888-275-8747 (voice)
    sciencebase@usgs.gov
  2. What's the catalog number I need to order this data set? These data are available in a comma-delimited text file (Ofu_water_algal_chemistry.csv) which contains water and algae analysis.
  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 on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty.
  4. How can I download or order the data?
  5. What hardware or software do I need in order to use the data set?
    These data can be viewed with any text editor software.

Who wrote the metadata?

Dates:
Last modified: 17-Jul-2025
Metadata author:
U.S. Geological Survey, Pacific Coastal and Marine Science Center
Attn: PCMSC Science Data Coordinator
2885 Mission Street
Santa Cruz, CA

831-427-4747 (voice)
pcmsc_data@usgs.gov
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/pcmsc/DataReleases/ScienceBase/DR_P1DVZPUV/Ofu_water_algal_chemistry_metadata.faq.html>
Generated by mp version 2.9.51 on Fri Jul 18 11:07:49 2025