Louisiana Coastal Hypoxia Shelfwide Survey, July 1986

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Frequently-anticipated questions:

What does this data set describe?
    Title: Louisiana Coastal Hypoxia Shelfwide Survey, July 1986
    Abstract:
    Hydrographic data were collected during a July, 1986 survey of the Louisiana continental shelf. The first part of the cruise was conducted on the R/V Acadiana between July 7 and July 10. Rough seas prevented continuation on the smaller ship. The remaining stations were sampled from on board the R/V Pelican between July 16 and July 17. While not synoptic in coverage, a few mid-depth stations were reoccupied during the second leg and hydrographic conditions were similar on the two dates. Nutrient, pigment and station information data were also acquired.

  1. How should this data set be cited?

    Rabalais, N., 1989, Louisiana Coastal Hypoxia Shelfwide Survey, July 1986.

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -93.6
    East_Bounding_Coordinate: -89.4
    North_Bounding_Coordinate: 29.7
    South_Bounding_Coordinate: 28.4
    Description_of_Geographic_Extent: Louisiana coastal waters, Northwestern Gulf of Mexico.

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 07-Jul-1986
    Beginning_Time: Unknown
    Ending_Date: 18-Jul-1986
    Ending_Time: Unknown
    Currentness_Reference: ground condition

  5. What is the general form of this data set?

    Geospatial_Data_Presentation_Form: Database

  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 (69)

    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 Degrees and decimal minutes.

      The horizontal datum used is WGS84.
      The ellipsoid used is WGS84.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257223563.

  7. How does the data set describe geographic features?

    S786HydroLab
    The table lists Hydrolab CTD station density, dissolved oxygen, percent oxygen saturation, pH, salinity, specific conductance and temperature values at depths. There are 755 records. (Source: None.)

    Density
    Density sigma-t (Source: Producer defined)

    Range of values
    Minimum:-2.61
    Maximum:25.54
    Units:Density sigma-t

    Depth
    Depth of HydroLab pressure sensor (Source: Producer Defined)

    Range of values
    Minimum:0.0
    Maximum:62.5
    Units:Meters

    DO
    Dissolved oxygen (Source: Producer defined)

    Range of values
    Minimum:0.13
    Maximum:13.20
    Units:mg/L

    DOPctSat
    Oxygen percent saturation (Source: Producer defined)

    Range of values
    Minimum:2.0
    Maximum:197.5
    Units:Percent

    pH
    pH (Source: Producer defined)

    Range of values
    Minimum:7.6
    Maximum:8.9
    Units:pH units

    Sal
    Salinity (Source: Producer defined)

    Range of values
    Minimum:2.13
    Maximum:36.28
    Units:ppt

    SpCond
    Specific conductance (Source: Producer defined)

    Range of values
    Minimum:4.4
    Maximum:57.58
    Units:mS/cm

    Sta
    Station name of location sampled (Source: Producer defined)

    Character field

    StnID
    Station identification number (Source: Producer defined)

    Range of values
    Minimum:455
    Maximum:523
    Units:Integer

    Temp
    Temperature (Source: Producer defined)

    Range of values
    Minimum:19.64
    Maximum:33.58
    Units:Degrees centigrade

    S786Nutrient
    The table lists station NH4, NO2, NO2+NO3, NO3, PO4 and SiO3 values at depths. There are 130 records. (Source: None.)

    Depth
    Depth of HydroLab p sensor, 0.0 depth = surface Niskin sample. (Source: Producer defined)

    Range of values
    Minimum:0
    Maximum:62.5
    Units:Meters

    NH4
    Ammonium (Source: Producer defined)

    Range of values
    Minimum:0.1
    Maximum:34.4
    Units:µg-at/L

    NO2
    Nitrite (Source: Producer defined)

    Range of values
    Minimum:0
    Maximum:9.3
    Units:µg-at/L

    NO3
    Nitrate (Source: Producer defined)

    Range of values
    Minimum:0
    Maximum:72.9
    Units:µg-at/L

    PO4
    Phosphate (Source: Producer defined)

    Range of values
    Minimum:0.2
    Maximum:5.3
    Units:µg-at/L

    SiO3
    Silicate (Source: Producer defined)

    Range of values
    Minimum:1.5
    Maximum:73.3
    Units:µg-at/L

    Sta
    Station name of location sampled (Source: Producer defined)

    Character field

    StnID
    Station identification number (Source: Producer defined)

    Range of values
    Minimum:455
    Maximum:521
    Units:Integer

    S786Pigment
    The table lists station mean chlorophyll a, Fo/Fa ratio, and mean phaeopigment values at depths. There are 130 records. (Source: None.)

    MeanC
    Mean Chlorophyll a (Source: Producer defined)

    Range of values
    Minimum:0.18
    Maximum:55.18
    Units:µg/L

    MeanF
    Mean Fo/Fa ratio (Source: Producer defined)

    Range of values
    Minimum:1.1
    Maximum:3.1
    Units:FoFa ratio

    MeanP
    Mean Phaeopigments (Source: Producer defined)

    Range of values
    Minimum:0
    Maximum:17.44
    Units:µg/L

    SampD
    Depth of HydroLab p sensor, 0.0 depth = Surface Niskin sample. (Source: Producer defined)

    Range of values
    Minimum:0
    Maximum:62.5
    Units:Meters

    Sta
    Station name of location sampled (Source: Producer defined)

    Character field

    StnID
    Station identification number (Source: Producer defined)

    Range of values
    Minimum:455
    Maximum:521
    Units:Integer

    S786Stns
    The table lists station, date, latitude, longitude, Secchi disk, time of HydroLab cast and station ID. There are 69 records. (Source: None.)

    Date
    Date station was sampled. (Source: Producer defined.)

    Range of values
    Minimum:19860707
    Maximum:19860718
    Units:YYYYMMDD

    Latitude
    Latitude of sampling station. (Source: Producer defined.)

    Range of values
    Minimum:28.4833
    Maximum:29.6417
    Units:Decimal degrees

    Longitude
    Longitude of sampling station. (Source: Producer defined.)

    Range of values
    Minimum:-93.558
    Maximum:-89.475
    Units:Decimal degrees

    Secc
    Secchi disk depth. (Source: Producer defined.)

    Range of values
    Minimum:0.5
    Maximum:16
    Units:meters

    Sta
    Station name of location sampled. (Source: Producer defined.)

    Character field

    StnID
    Station identification number. (Source: Producer defined.)

    Range of values
    Minimum:455
    Maximum:523
    Units:Integer

    Time
    Time of beginning of HydroLab CTD cast. (Source: Producer defined.)

    Range of values
    Minimum:0:08
    Maximum:23:40
    Units:HH:mm

    Entity_and_Attribute_Overview:
    The related data tables S786HydroLab, S786Nutrient, S786Pigment, and S786Stns contain spatial, temporal, physical and biological water quality data acquired during the July 1986 cruise. Each table contains a StnID field that can be used to key joins with the other tables.
    Entity_and_Attribute_Detail_Citation: For detailed attribute information contact Nancy Rabalais.

  8. What special analytical tools are available to help me understand this data set?

    Tool 0 of 3
    Autoanalyzer

    How to obtain this tool:

    How to access the tool:

    Tool_Access_Instructions: Unknown.

    Whom to contact for more information:

    Tom Oswald
    110 Coastal Studies Coastal Ecology Institute LSU
    Baton Rouge, LA 70803

    225 388-6700 (voice)
    Unknown

    Tool 0 of 3
    Fluorometer

    How to obtain this tool:

    How to access the tool:

    Tool_Access_Instructions: Contact Turner Designs.

    Whom to contact for more information:

    Turner Designs Inc.
    845 W. Maude Avenue
    Sunnyvale, CA 94085
    US

    877 316-8049 (voice)

    Tool 0 of 3
    CTD

    How to obtain this tool:

    How to access the tool:

    Tool_Access_Instructions: Contact Hydrolab Corporation.

    Whom to contact for more information:

    Hydrolab Corporation
    8700 Cameron Road
    Austin, TX 78754
    US

    800-949-3766 (voice)
    techsupport@hydrolab.com

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    Rabalais, N.N., Turner, R.E., Wiseman Jr, W.J. and Boesch, D.F. Funding: Funds for the research were provided by the National Oceanographic and Atmospheric Administration, Ocean Assessments Division, through Louisiana Sea Grant Program and by the Louisiana Universities Marine Consortium.

  3. To whom should users address questions about the data?

    Nancy N. Rabalais
    Louisiana Universities Marine Consortium
    Louisiana Universities Marine Consortium 8124 Hwy 56
    Chauvin, LA 70344
    USA

    985 851 2800 (voice)
    985 851 2874 (FAX)
    Unknown

Why was the data set created?
The physical, biological and chemical data collected are part of a long-term coastal Louisiana dataset. The goal is to understand physical and biological processes that contribute to the causes of hypoxia and use the data to support environmental models for use by resource managers.

How was the data set created?
  1. What methods were used to collect the data?

    Method 0 of 6
    Type: Field HydroLab

    Deployment: The HydroLab CTD was attached by chain to a lead weight. The weight was lowered to the bottom by hydrowire. With the weight on the bottom, the Hydrolab sonde was positioned just above the bottom. When the oxygen sensor stabilized, sensor values were logged. The sonde was raised in 1-, 2-, 3- or 5-m intervals through the water column.

    Method 0 of 6
    Type: Field Pigment

    Water for chlorophyll analyses was collected from surface and bottom waters in 5 liter Niskin bottles.

    Method 0 of 6
    Type: Field Station Locations

    Transects re-occupied stations sampled during a previous midsummer Louisiana coastal survey in 1985. Series of generally North-South transects from the mouth of the Mississippi River across the Louisiana coastal shelf and into Texas waters. Most station depths are less than 50 (m). The objective was to delimit and describe the area of midsummer bottom dissolved oxygen less than 2(mg/L). Biological, chemical and physical properties of the water are measured. Northern end stations of transects were chosen based on the survey vessel's minimum depth limits for each longitude. Optimally, one or two stations South of the Southern most station with bottom dissolved oxygen less than 2 (mg/L). Due to constraints of time and funding it was not possible to sample the southern limits of low oxygen for all transects or to reach the western limit of the hypoxic water mass.

    Method 0 of 6
    Type: Field Nutrient

    Water for nutrient analyses was collected from surface and bottom waters in 5-liter Niskin bottles. Care was taken that the collector's hands were clean and avoided touching the water. Three replicate sample vials and caps were triple rinsed with sample before vial filling and closing. Samples were not filtered. The sample vials were frozen for later analysis in the laboratory.

    Method 0 of 6
    Type: Lab Nutrient

    Nitrogen and phosphorus were analyzed according to methods described in EPA publication EPA 600/4-79-020 (1979), method 350.1 was used for ammonia-N, method was used for 353.2 for nitrate/nitrite-N, and method 365.1 for phosphate-P. Silicate was analyzed according to Technicon Industrial method 186-72 W/B (1977).

    Method 0 of 6
    Type: Lab Pigment

    Analysis for chlorophyll and phaeopigment concentrations followed the fluorometric methods outlined in Strickland and Parsons (1972). Known volume of seawater was filtered onto a GF/F (0.7 micron) filter. Filter was fixed in 90% acetone, stored in the dark for one hour and ground with a Teflon mortar. Filtrant was read on a Turner Designs model 10 fluorometer before and after acidification with 10% Hcl.

  2. From what previous works were the data drawn?

  3. How were the data generated, processed, and modified?

    Date: Unknown (process 1 of 1)
    Unknown

How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?

    S786HydroLab: Temperature, pH, dissolved oxygen, conductivity, salinity, and depth were measured with a Hydrolab Surveyor II Water Quality Data System at 1-, 2-, or 3-m intervals through the water column. Readings from a digital display unit were recorded on board ship. Conductivity in 25°C equivalents was converted to in situ conductivity and in situ salinity. Water samples were collected to check the conductivity sensor against water of a known salinity. A correction factor was applied as necessary for in situ salinity calculations. Selected samples for dissolved oxygen analysis were collected from surface and bottom waters and analyzed according to a modified Winkler procedure (Strickland and Parsons, 1972). Operation, maintenance, and calibration of the Hydrolab Surveyor II followed instructions provided by the Hydrolab manual (Hydrolab Corp., 1984). Yearly maintenance of the Surveyor II was performed by Hydrolab Corporation.

    S786Nutrient: Nutrient analyses were conducted by Tom Oswald under the supervision of R. E. Turner.

    S786Pigment: The Turner Designs model 10 fluorometer was calibrated for chlorophyll a against a chemical supply house chlorophyll a standard measured on a spectrophotometer yearly (or more frequently if needed). During the cruise, the Fluorometer was blanked and calibrated daily in accordance with Turner Designs recommended procedures. Analysis for chlorophyll and phaeopigment concentrations followed the fluorometric methods outlined in Strickland and Parsons (1972). Pigment measurements were supervised and quality controlled by Nancy Rabalais.

    N. Rabalais performed an additional procedure in quality-control/quality-assurance by evaluating relationships between the data in S786HydroLab, S786Nutrient, S786Pigment and S786Stns.

  2. How accurate are the geographic locations?

    Station positions were logged from RV Acadiana and RV Pelican's NorthStar LORAN C at the beginning of sampling operations. Manufacturer's accuracy claim is 30 meters 90% of the time. Wind, currents and tidal forces may have moved the ships from the beginning positions.

  3. How accurate are the heights or depths?

  4. Where are the gaps in the data? What is missing?

    Unknown.

  5. How consistent are the relationships among the observations, including topology?

    At stations A'01 two density sigma-t values are negative.

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:
1. Dataset credit required. 2. Experience with similar datasets has shown that when data are plotted or used in further analysis, outlying values may occasionally be discovered. Please report any possible problems with the data to N. Rabalais.

  1. Who distributes the data set? (Distributor 1 of 1)

    Nancy N. Rabalais
    Louisiana Universities Marine Consortium
    Louisiana Universities Marine Consortium 8124 Hwy 56
    Chauvin, LA 70344
    USA

    985 851 2800 (voice)
    985 851 2874 (FAX)
    Unknown

  2. What's the catalog number I need to order this data set?

  3. What legal disclaimers am I supposed to read?

    I, the data requestor, agree to credit the data originators in any publications, reports or presentations generated from this data. I also accept that although these data have been processed successfully on a computer system at the Louisiana Universities Marine Consortium, no warranty expressed or implied is made regarding the accuracy 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. I recognize that these data are best acquired from the originator and not from a secondary source. I recognize that careful attention must be paid to the contents of the metadata file associated with these data. I will not hold Louisiana Universities Marine Consortium liable for improper or incorrect use of the data described and/or contained herein. This disclaimer applies both to individual use of the data and aggregate use with other data.

  4. How can I download or order the data?

  5. Is there some other way to get the data?

    Contact distributor

Who wrote the metadata?
Dates:
Last modified: 26-Apr-2002
Last Reviewed: 27-Jun-2002
To be reviewed: 15-Jun-2012

Metadata author:
Ben Cole
Louisiana Universities Marine Consortium
LUMCON 8124 Hwy 24
Chauvin, LA 70344
USA

985 851 2800 (voice)
985 851 2874 (FAX)
Unknown

Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

Generated by mp version 2.6.2 on Mon Sep 09 15:37:32 2002
Created using the Automated Cast-net Metadata Entry Tool