Rabalais, N., Unknown, Louisiana Coastal Hypoxia Shelfwide Survey, July 1997.
This is a Vector data set. It contains the following vector data types (SDTS terminology):
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.
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 30.3 |
| Units: | Meters |
| Range of values | |
|---|---|
| Minimum: | 3.928 |
| Maximum: | 35.119 |
| Units: | psu |
Character field
| Range of values | |
|---|---|
| Minimum: | 4 |
| Maximum: | 89 |
| Units: | Integer |
| Range of values | |
|---|---|
| Minimum: | -4.51 |
| Maximum: | 25.35 |
| Units: | Density sigma-t |
| Range of values | |
|---|---|
| Minimum: | 0.0 |
| Maximum: | 53.2 |
| Units: | Meters |
| Range of values | |
|---|---|
| Minimum: | 0.05 |
| Maximum: | 16.84 |
| Units: | mg/L |
| Range of values | |
|---|---|
| Minimum: | 0.8 |
| Maximum: | 236 |
| Units: | Percent |
| Range of values | |
|---|---|
| Minimum: | 7.5 |
| Maximum: | 8.87 |
| Units: | pH units |
| Range of values | |
|---|---|
| Minimum: | 0.4 |
| Maximum: | 36.4 |
| Units: | psu |
| Range of values | |
|---|---|
| Minimum: | 0.8 |
| Maximum: | 54.9 |
| Units: | mS/cm |
Character field
| Range of values | |
|---|---|
| Minimum: | 8 |
| Maximum: | 90 |
| Units: | Integer |
| Range of values | |
|---|---|
| Minimum: | 18.84 |
| Maximum: | 33.71 |
| Units: | Degrees centigrade |
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 53.2 |
| Units: | Meters |
| Range of values | |
|---|---|
| Minimum: | 0.2 |
| Maximum: | 5.5 |
| Units: | µg-at/L |
| Range of values | |
|---|---|
| Minimum: | 0.1 |
| Maximum: | 2.5 |
| Units: | µg-at/L |
| Range of values | |
|---|---|
| Minimum: | 0.1 |
| Maximum: | 100.5 |
| Units: | µg-at/L |
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 100.1 |
| Units: | µg-at/L |
| Range of values | |
|---|---|
| Minimum: | 0.1 |
| Maximum: | 2.9 |
| Units: | µg-at/L |
| Range of values | |
|---|---|
| Minimum: | 0.6 |
| Maximum: | 99.4 |
| Units: | µg-at/L |
Character field
| Range of values | |
|---|---|
| Minimum: | 4 |
| Maximum: | 89 |
| Units: | Integer |
| Range of values | |
|---|---|
| Minimum: | 0.13 |
| Maximum: | 301.39 |
| Units: | µg/L |
| Range of values | |
|---|---|
| Minimum: | 1.47 |
| Maximum: | 5.44 |
| Units: | FoFa ratio |
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 13.07 |
| Units: | µg/L |
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 53.2 |
| Units: | Meters |
Character field
| Range of values | |
|---|---|
| Minimum: | 4 |
| Maximum: | 90 |
| Units: | Integer |
| Range of values | |
|---|---|
| Minimum: | 0.17 |
| Maximum: | 310.06 |
| Units: | µg/L |
| Range of values | |
|---|---|
| Minimum: | 3.046271 |
| Maximum: | 5.640157 |
| Units: | S/m |
| Range of values | |
|---|---|
| Minimum: | 8.2957 |
| Maximum: | 26.1003 |
| Units: | sigma-t |
| Range of values | |
|---|---|
| Minimum: | 1.244 |
| Maximum: | 52.345 |
| Units: | Meters |
| Range of values | |
|---|---|
| Minimum: | 1.65277 |
| Maximum: | 195.18154 |
| Units: | Percent |
| Range of values | |
|---|---|
| Minimum: | 0.7619 |
| Maximum: | 17.74 |
| Units: | Voltage |
| Range of values | |
|---|---|
| Minimum: | 0.1114 |
| Maximum: | 12.88994 |
| Units: | mg/L |
| Range of values | |
|---|---|
| Minimum: | 16.9964 |
| Maximum: | 36.9588 |
| Units: | psu |
Character field
| Range of values | |
|---|---|
| Minimum: | 8 |
| Maximum: | 91 |
| Units: | Integer |
| Range of values | |
|---|---|
| Minimum: | 18.5978 |
| Maximum: | 32.207 |
| Units: | Degrees centigrade |
| Range of values | |
|---|---|
| Minimum: | 39.72 |
| Maximum: | 97.41 |
| Units: | Percent |
| Range of values | |
|---|---|
| Minimum: | 19970723 |
| Maximum: | 19970729 |
| Range of values | |
|---|---|
| Minimum: | 6 |
| Maximum: | 53.1 |
| Units: | Meters |
| Range of values | |
|---|---|
| Minimum: | 28.4987 |
| Maximum: | 29.706 |
| Units: | Decimal degrees |
| Range of values | |
|---|---|
| Minimum: | -93.6547 |
| Maximum: | -89.4347 |
| Units: | Decimal degrees |
Character field. #.# = no sample. Shallowest measured sample was 0.9 meters. Deepest measured sample was greater than 16 meters.
Character field
| Range of values | |
|---|---|
| Minimum: | 1 |
| Maximum: | 91 |
| Units: | Integer |
| Range of values | |
|---|---|
| Minimum: | 00:04:21 |
| Maximum: | 23:39:43 |
| Units: | HH:mm:ss |
| Range of values | |
|---|---|
| Minimum: | 00:15:00 |
| Maximum: | 23:58:00 |
| Units: | HH:mm:ss |
| Range of values | |
|---|---|
| Minimum: | 00:11:00 |
| Maximum: | 23:53:00 |
| Units: | HH:mm:ss |
Character field
| Range of values | |
|---|---|
| Minimum: | 1 |
| Maximum: | 90 |
| Units: | Integer |
| Range of values | |
|---|---|
| Minimum: | 3.1 |
| Maximum: | 50.22 |
| Units: | mg/L |
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Rabalais, N.N., Turner, R.E. and Wiseman Jr, W.J. Funding: Funds for the research were provided by the National Oceanographic and Atmospheric Administration, National Ocean Service, the Louisiana Sea Grant Program, and Louisiana Universities Marine Consortium.
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
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.
The Sea-Bird CTD number of scans to average in the deck unit is set to one. At the beginning of each hydrocast the entire CTD/Rosette package was soaked while submerged 0.5m to 1.0m below the surface until pump flow and oxygen values observed via the Sea-Bird deck unit indicated the system was operating correctly.
In order to minimize the effect of delays in oxygen sensor response time caused by temperature, sensor condition and plumbing configuration, the CTD package was lowered as close to dead slow as possible. The sensor packages were located below the Niskin bottles and rosette.
At stations where the watch chief deemed the structure of the oxygen profile contained features useful in post-processing the oxygen data (AlignCTD), the CTD package was raised at the same speed it was lowered. At all other stations, the upcast is rapid in order to save time.
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, a data record of all the sensor values was stored electronically. The sonde was raised in approximately 0.5-meter increments, after D.O. sensor stabilization, data records were stored. After storing data for the few meters closest to the bottom, the Hydrolab was raised to two to three meters from the surface and a data record was saved. The sonde was raised, and records stored, in approximately 0.5-meter increments until finally a record was stored with the sonde submerged but as close as possible to the surface.
Water for chlorophyll analysis (30 - 100 ml) was filtered on board ship through GF/F (0.7 micron) filters, which are then fixed in 5 ml of DMSO/90% acetone (40/60) solution, allowed to extract for at least one hour in the dark, then measured pre- and post-acidification on a Turner Model 10 fluorometer.
PortaSal Field: Water were collected in a triple-rinsed 500ml Nalgene jar from a twice-rinsed bucket of surface water. The jar lid was secured tightly to minimize evaporation.
Field station locations: Stations were occupied along 13 generally North-South transects across the Louisiana coastal shelf. Station depths ranged from 6.0 to 53.1 meters. The objective was to delimit and describe the area of midsummer bottom dissolved oxygen less than 2 (mg/L). Due to limitations of equipment, time and funding, this was not always possible. Northern end stations of transects were chosen based on the survey vessel's minimum depth limits for each longitude. The Northern extent of hypoxia was not reached on thirteen transects. Optimally, one or two stations South of the Southern most station with bottom dissolved oxygen less than 2 (mg/L) were sampled. The limit of hypoxia on the Southern end of all transect was reached. The limit of hypoxia was not reached at stations M1 and M3 on the Western end of the survey.
Care was taken that the collector's hands were clean and avoided touching the water. Gloves were worn when 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.
Water (approximately 300 to 1000 ml) was filtered on board ship through pre-weighed GF/F filters, rinsed with distilled water. The filters were placed in Petri dishes and frozen for later analysis.
Suspended sediment filters were dried at 40 - 60 degrees centigrade for 24 hours. Filters were weighed. Total suspended sediments was derived from volume filtered, pre-weight and post weight values.
Nitrogen and phosphorus are analyzed according to methods described in EPA publication EPA 600/4-79-020 (1979), method 350.1 for ammonia-N, method 353.2 for nitrate/nitrite-N, and method 365.1 for phosphate-P. Silicate is analyzed according to Technicon Industrial method 186-72 W/B (1977).
Water for chlorophyll, nutrient analyses, Portasal salinity and suspended sediments was collected from the surface by twice-rinsed bucket, from mid-water in 5-l Niskin bottles on the Seabird CTD/rosette system and from bottom in a 5-l bottom tripping Niskin bottle secured in a frame with the Hydrolab Surveyor 3.
Depth values of 0 indicate a bucket sample collected from the surface of the water. Deepest depths of water samples were from the bottom-tripping Niskin and correspond to the deepest depth recorded from the Hydrolab. Other depths indicate the p-sensor reading for 5-l Niskin bottles on the Seabird rosette. The Seabird p-sensor was located approx. 1 meter below the mid-point of the 5-l Niskin.
Sea-Bird CTD data were acquired and post processed using Seasoft version 4.225. All scans were processed without averaging or interpolation with a bin size of one scan. In order to improve alignment between oxygen sensor values and other CTD sensor values, the Seasoft module ALIGNCTD was used to determine which advance best compensated for the delay in oxygen sensor response time. When Seabird data were processed, dissolved oxygen was advanced relative to temperature and conductivity values: + 6.47 seconds.
Data values reported are from downcasts. Downcast scans selected for each CTD station were chosen to illustrate: 1) data values as near to the surface as possible, 2) data values at whole meter increments, and 3) data values as close to the bottom as the CTD was lowered. In certain cases where data values of a parameter changed significantly between whole meter increments, 0.1- or 0.2-meter scans were selected.
S797HydroLab: The Hydrolab Surveyor 3 Conductivity, pH and Oxygen sensors were serviced and calibrated before deployment and maintained in accordance with Hydrolab recommended procedures. The Sonde and Logger are returned to the factory at least annually for inspection and service. Percent oxygen saturation for Hydrolab values above 175% saturation were derived from the figure given in Green and Carritt, 1967, J. Mar. Res., 25(2):140-147.
S797Nutrient: Nutrient analyses were conducted by Tom Oswald under the supervision of R. E. Turner.
S797Pigment: 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. Pigment measurements were supervised and quality controlled by Nancy Rabalais.
S797SeaBird: Sea-Bird SBE 13-01 dissolved oxygen sensors, the Paroscientific Digiquartz® pressure sensor, the SBE 3-01/F temperature sensors , SBE 5-01 pumps, and the SBE 4-01/0 Conductivity sensors were factory tested and calibrated at Sea-Bird recommended intervals and maintained and serviced by RV Pelican Electronic Technical support staff in accordance with Sea-Bird procedures. The Sea Tech 5.0 cm Transmissometer was factory tested and calibrated at Sea Tech recommended intervals and maintained and serviced by RV Pelican Electronic Technical support staff in accordance with Sea Tech procedures. The Chelsea AQUATRAKA III Fluorometer was factory tested and calibrated at Chelsea Instruments recommended intervals and maintained and serviced by RV Pelican Electronic Technical support staff in accordance with Chelsea procedures.
Oxygen sensors were calibrated using the procedures described in Seabird APPLICATION NOTE NO. 13-1, Rev. D. The Winkler Titration (OXFITW) oxygen value was determined chemically from replicate samples processed using a Mettler DL21 Titrator. Shipboard Winkler titrations during the cruise were used to develop a regression against CTD data, which were corrected if necessary. A correction was not needed for the July 1997 CTD oxygen data because there was good agreement of SeaBird CTD values with Winkler values and bottom values obtained from the HydroLab CTD.
Winkler titrations were conducted under the supervision of Nancy Rabalais. Data reductions from the SeaBird were generated by Ben Cole and quality controlled by Nancy Rabalais.
S797-Stn: Times and locations of operations were acquired from RV Pelican's Multiple Instrument Data Acquisition System (MIDAS) which was maintained by the ship's electronic staff. Navigational data were acquired from a Starlink differential GPS or a Trimble GPS with a Micronet Receiver Station with sub 5-meter accuracy. Station depths were logged from the ship’s Odom Echotrac II fathometer. The Secchi disk depths were measured by hand using standard protocol.
S797PortaSal: The samples were analyzed in the lab by Guildline Instruments PortaSal, using Guildine methods. Salinity analyses were conducted by Jim Lee under the supervision of R. E. Turner.
S797SuspSed: Suspended sediment concentrations were supervised and quality controlled by Nancy Rabalais.
N.B. There may have been a problem with samples collected with the bottom tripping Niskin. Surface PortaSal samples were collected at each station in order to get precise salinity values for the bucket samples. On transect C in addition to surface salinity samples; bottom salinity samples were collected from the Niskin. The salinity samples were read after the cruise in the laboratory using both the HydroLab and the PortaSal.
PortaSal salinity readings matched those taken in the lab with the Hydrolab. Surface salinity data recorded in the field also corresponded well with the PortaSal data. Bottom salinities recorded in the field with the Hydrolab and CTD, however, were an average of 4 ppt higher than those recorded in the lab with the Hydrolab and PortaSal using water taken from the horizontally mounted bottom-tripping Niskin. Lab values ranged between 1.0 and 6.7 ppt lower than field samples.
Since the proper functioning of the Hydrolab was supported by the PortaSal and the CTD, the water from the horizontal Niskin does not appear to have been collected at the bottom. Smaller discrepancies (< 1 ppt) could be expected due to the Niskin not sampling at exactly the same location as the other instruments. Differences of
3 ppt, however, are highly unlikely. Water column data suggestthat the horizontally mounted Niskin sample salinities would have been encountered above the bottom.
The horizontal Niskin was used to collect bottom water samples at all stations, but bottom salinity samples were collected only for transect C. The possibility exists that other bottom samples also had salinities that differed from those recorded by the Hydrolab or CTD. The "bottom" samples may not represent bottom water.
N. Rabalais performed an additional procedure in quality-control/quality-assurance by evaluating relationships between the data in S797PortaSal, S797HydroLab, S797Nutrient, S797Pigment, S797-Stn and S797SuspSed.
Station positions are logged from the ship's differential GPS at the beginning of sampling operations. GPS manufacturer's accuracy claim is 1-5 meters 95% of the time. Wind, currents and tidal forces may move the ship from the beginning position.
Unknown.
At stations A'4, A'5, A7 and B6 maximum HydroLab p-sensor depth is greater than station depth reported by ship's Fathometer. This may be attributable to drift during sampling operations. Two density sigma-t values are negative.
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.
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
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.
| Data format: | MDB (version 9) Size: 0.816 |
|---|---|
| Media you can order: |
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Ben Cole
Louisiana Universities Marine Consortium
LUMCON 8124 Hwy 24
Chauvin, LA 70344
USA
985 851 2800 (voice)
985 851 2874 (FAX)
Unknown