H00Nutrients: Nutrient analyses were conducted using a Technicon (<http://www.techniconinstruments.com/>) autoanalyzer by Tom Oswald under the supervision of R. E. Turner.
H00Pigments: The Turner Designs model 10 AU fluorometer was calibrated for chlorophyll a against a chemical supply house chlorophyll a standard measured on a spectrophotometer. Each time the fluorometer was moved, it was tested with a Turner 10-AU solid standard. During cruises, the fluorometer was blanked and calibrated daily in accordance with Turner Designs recommended procedures. Pigment measurements were supervised by Ben Cole or Nancy Rabalais and quality controlled by Nancy Rabalais.
H00PortaSal: Salinity samples were analyzed in the lab by Guildline Instruments PortaSal, using Guildline methods (<http://www.guildline.ca/>). Salinity analyses were conducted by Jim Lee under the supervision of R. E. Turner.
H00Refract: The refractometer was checked with distilled water before each cruise and re-zeroed when necessary.
H00SeaBird: Sea-Bird SBE 13-01 dissolved oxygen sensors, the Paroscientific Digiquartz(r) 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 (<http://www.seabird.com/>) recommended intervals and maintained and serviced by RV Pelican Electronic Technical support staff in accordance with Sea-Bird procedures. The Sea Tech 500m Fluorometer and Sea Tech 5.0 cm Transmissometer were 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. Note: WET Labs acquired SEA Tech June 1, 1998, (<http://www.wetlabs.com/>).
At the beginning of the July shelfwide cruise, 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 (<http://www.mt.com/> ). Shipboard Winkler titrations during the cruise were used to develop a regression against CTD data.
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.
H00SPM: Suspended sediment concentrations were supervised by Ben Cole or Nancy Rabalais and quality controlled by Nancy Rabalais.
H00Stn: Station time and location and depth were logged from RV Acadiana's Garmin GPSMAP 168 Sounder except during the July shelfwide cruise.
On the July cruise, Times and locations of operations were logged 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 (<http://www.starlinkdgps.com/>) differential GPS or a Trimble (<http://www.trimble.com/>)GPS with a Micronet Receiver Station with sub 5-meter accuracy. Station depths were logged from the ship's Odom Echotrac II (<http://www.odomhydrographic.com/>) fathometer. The Secchi disk depths were measured by hand using standard protocol.
Hydrolab cast position data on a few dates were acquired using a Garmin 12XL. See Horizontal_Positional_Accuracy_Report for further details.
N. Rabalais performed an additional procedure in quality-control/quality-assurance by evaluating relationships between the data in H00Hydrolab, H00Nutrients, H00Pigments, H00PortaSal, H00Refract, H00SeaBird, H00SPM and H00Stn.
The fluorometer in the SeaBird CTD package had maximum value of 15. Fluorometer values of 15 were observed at nine stations. See FlS entity Detailed_Description for details.
The maximum fathometer depth (Fath) reported in table H00Stn is 53.3 meters. The maximum depth pressure sensor depth (DepS) reported in table H00SeaBird is 53.467 meters.
A pin connector in the Hydrolab CTD cable broke at station C4 on the date 20001115. Hydrolab data were only collected at Stations C1 and C3 on 20001115.
Station positions acquired during the other months on RV Acadiana were logged from the ship's Garmin GBR 21 DGPS receiver. The manufacturer describes the accuracy to be between 1 - 5 meters 95% of the time. Wind, currents and tidal forces may have moved the ship from the beginning position.
Hydrocasts were made from Whiskey Pass, a small boat, on the following dates: 20000302, 20000406, 20000427, 20000508, 20000602, 20000705, 20000710, 20000818, 20001128. The boat tied up to the oilfield platform at station C6B, but other positions were logged from a Garmin 12XL handheld GPS. The manufacturer describes the accuracy to be approximately 15 meters 95% of the time. Wind, currents and tidal forces may have moved the boat from the beginning position.
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 sonde 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.
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 was rapid in order to save time.
During the July shelfwide cruise, stations were occupied along 13 generally North-South transects across the Louisiana coastal shelf. Station depths ranged from 4 to 53.3 meters. The objective was to delimit and describe the area of midsummer bottom dissolved oxygen less than 2 (mg/L). 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 reached on all transects except D. The limit of hypoxia on the southern ends of all transects was reached. The limit of hypoxia was reached at all stations on the western end of the survey. The limit of hypoxia was reached at station A'4 on the eastern end of the survey.
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 pressure sensor reading for 5-l Niskin bottles on the SeaBird rosette. The SeaBird pressure sensor was located approx. 1 meter below the mid-point of the 5-l Niskin.
Beginning with the July cruise, in addition to pre-weighing, filters were also pre-combusted. When the filters were returned to the lab after the cruises, they were dried overnight at 60°C and weighed. The filters were then combusted at 400°C for 12 hours and weighed. The weights of the total suspended, organic and inorganic materials were derived.
In order to improve alignment between oxygen sensor values and other CTD sensor values, the Seasoft module ALIGNCTD was used, when possible, 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 by 3.5875 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.