Autonomous Flow-Thru (AFT) pH data of the West Florida Shelf: USGS Cruise 11BHM04

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Frequently anticipated questions:

What does this data set describe?

Autonomous Flow-Thru (AFT) pH data of the West Florida Shelf: USGS Cruise 11BHM04
The United States Geological Survey (USGS) is conducting a study on the effects of climate change on ocean acidification within the Gulf of Mexico; dealing specifically with the effect of ocean acidification on marine organisms and habitats. To investigate this, the USGS participated in two cruises in the West Florida Shelf and northern Gulf of Mexico regions aboard the R/V Weatherbird II, a ship of opportunity lead by Dr. Kendra Daly, of the University of South Florida (USF). The cruises occurred September 20 - 28 and November 2 -4, 2011. Both left from and returned to Saint Petersburg, Florida, but followed different routes (see Trackline). On both cruises the USGS collected data pertaining to pH, dissolved inorganic carbon (DIC), and total alkalinity in discrete samples. Discrete surface samples were taken during transit approximatly hourly on both cruises, 95 in September were collected over a span of 2127 km, and 7 over a trackline of 732 km line on the November cruise. Along with the surface samples, another set of samples were taken at various depths at stations; 27 in September at four stations and 15 in November at five stations. In addition to the discrete samples flow-through data was also collected on both cruises in a variety of forms. Surface CTD data was collected every five minutes which includes temperature, salinity, and pH. In addition, two more flow-through instruments were setup on both cruises that recorded pH and CO2 every 15 minutes. Corroborating the USGS data is the vertical CTD profiles collected by USF, using the following sensors: CTD, oxygen, chlorophyll fluorescence, optical backscatter, and transmissometer. Additionally, discrete depth samples for nutrients, chlorophyll, and particulate organic carbon/nitrogen were collected.
The USGS Saint Petersburg Coastal and Marine Science Center (SPCMSC) - St. Petersburg, FL, assigns a unique identifier to each cruise or field activity. For example, 11BHM04 tells us the data were collected in 2011 for Benthic Habitat Mapping and the data were collected during the fourth field activity for that project in that calendar year. Refer to for a detailed description of the method used to assign the cruise ID.
  1. How might this data set be cited?
    Robbins, Lisa L., Knorr, Paul O., Barrera, Kira E., and Daly, Kendra L., 2013, Autonomous Flow-Thru (AFT) pH data of the West Florida Shelf: USGS Cruise 11BHM04: Data Series 822, U.S. Geological Survey - St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -85.325780
    East_Bounding_Coordinate: -82.658480
    North_Bounding_Coordinate: 27.619100
    South_Bounding_Coordinate: 27.047430
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 2011
    data collection
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: vector digital data
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a Vector data set. It contains the following vector data types (SDTS terminology):
      • Entity point (191)
    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 8.9831528411952133e-009. Longitudes are given to the nearest 8.9831528411952133e-009. 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 6378137.0.
      The flattening of the ellipsoid used is 1/298.257223563.
  7. How does the data set describe geographic features?
    Autonomous Flow Through (AFT) system continuous measurements of chemical and physical parameters of seawater (Source: USGS)
    Internal feature number. (Source: ESRI) Sequential unique whole numbers that are automatically generated.
    Feature geometry. (Source: ESRI) Coordinates defining the features.
    Cruise name according to the USGS Field Activity Collection (Source: USGS) 11BHM04
    Date in UTC time zone; MM/DD/YYYY (Source: USGS) Date of sample collection in MM/DD/YYYY format
    Time of data collection in HH:MM UTC, 24 hour format (Source: USGS) Time of data collection in HH:MM UTC
    Date in EDT time zone; MM/DD/YYYY (Source: USGS) Date of sample collection in MM/DD/YYYY format
    Time of data collection in HH:MM EDT, 24 hour format (Source: USGS) Time of data collection in HH:MM EDT
    Latitude in decimal degrees (Source: WGS 1984)
    Range of values
    Longitude in decimal degrees (Source: WGS 1984)
    Range of values
    a measure of acidity and alkalinity of a solution (Source: USGS)
    Range of values
    water temperature (Source: USGS)
    Range of values
    measurement of salt within a body of water (PSU) (Source: USGS)
    Range of values
    All attributes are common between the three data formats provided (.csv, .xls, .shp), except for the attributes FID and SHAPE (indicated by *), which are found only within the shapefile (.shp) because they are unique to that data type. Additionally, the GPS data was taken from the Weatherbird II's navigation logs and was matched with the time logs on the sonde. These data have not been QA/QC yet, and as such could have data errors due to tubes clogging, or flowthrough shutdown for inclement weather.
    Robbins, L.L., Knorr, P.O., Barrera, K. E., Daly, K.L., 2012, USGS Field Activities 11BHM03 and 11BHM04 on the West Florida Shelf, Gulf of Mexico, in September and November 2011: U.S. Geological Survey Data Series 822, available online at

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • Lisa L. Robbins
    • Paul O. Knorr
    • Kira E. Barrera
    • Kendra L. Daly
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
    United States Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Lisa Robbins
    Research Oceanographer
    600 4th Street South
    St. Petersburg, Florida

    727-502-8005 (voice)
    727-502-8181 (FAX)
    Hours_of_Service: 8am to 5pm M-F EST

Why was the data set created?

Discrete water samples were collected underway to corroborate the continuous pCO2 measurements. Water samples were analyzed for salinity, pH, and total alkalinity at the USGS geochemistry laboratory in St. Petersburg, Florida. This continuous flow through data is used to corroborate the discrete sample data using CO2SYS.

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: 02-Nov-2011 (process 1 of 5)
    Flow-through data was collected using a Sunburst AFT pH, which measures pH on the total hydrogen ion scale, was attached to the flow-through system. This system sampled the seawater approximately every three minutes and has a precision and accuracy of 0.001 and ±0.003, respectively. The Sunburst AFT-CO2 system was used to measure the partial pressure of CO2 in water (pCO2) and was attached to the shipboard flow-through system. The instrument sampled approximately every five minutes and had a precision and accuracy of about 1 ppm and ± 3 ppm, respectively.
    Date: 16-Aug-2012 (process 2 of 5)
    Data entered into a spreadsheet and merged with other data sources: GPS from the ship, as well as the lab results of total alkalinity and disolved inorganic carbon from the USGS St. Petersburg Carbon Analytical Laboratory. Data sources produced in this process:
    • 2011_November_AFT_pH.csv
    • 2011_November_AFT_pH.xls
    Date: 16-Aug-2012 (process 3 of 5)
    The spreadsheet was imported into ArcGIS 10 and converted into a shapefile. Data sources used in this process:
    • 2011_November_AFT_pH.xls
    Date: 13-Mar-2017 (process 4 of 5)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    Date: 13-Oct-2020 (process 5 of 5)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
  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?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
    These data are collected along tracklines (2-D) and therefore inherently incomplete geologic details between lines must be inferred.
  5. How consistent are the relationships among the observations, including topology?
    The QA/QC process looked for internal consistencies in the data by calculating the results using CO2SYS and back checking with the collected data.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
USGS and USF requests to be acknowledged as originator of the data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey St. Petersburg Coastal and Marine Science Center
    Attn: Lisa Robbins
    600 4th Street South
    St. Petersburg, Florida

    727-502-8005 (voice)
  2. What's the catalog number I need to order this data set?
  3. What legal disclaimers am I supposed to read?
    This digital publication was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Although all data published in this report have been used by the USGS, no warranty, expressed or implied, is made by the U.S. Geological Survey as to the accuracy of the data and related materials and/or the functioning of the software. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of this data, software, or related materials. Graphical map depictions are intended to be used within the map scale limits applicable to the source data. Although software enables the user to view data at various scales, the user is cautioned to refer to the source documentation for the appropriate map scale limitations.
  4. How can I download or order the data?

Who wrote the metadata?

Last modified: 09-Nov-2021
Metadata author:
United States Geological Survey, St. Petersburg Coastal and Marine Science Center
Attn: SPCMSC Data Management Group
600 4th Street South
St. Petersburg, Florida

727-502-8000 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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