S796Nutrient: Nutrient analyses were conducted by Tom Oswald under the supervision of R. E. Turner.
S796Pigment: 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. Chlorophyll concentrations were supervised and quality controlled by Nancy Rabalais.
S796Seabird: Sea-Bird factory calibrated conductivity and temperature sensors were maintained and serviced in accordance with to Sea-Bird recommended procedures. The Sea Tech fluorometer and transmissometer were maintained and serviced in accordance with Sea Tech recommended procedures. Sea-Bird dissolved oxygen sensor was maintained and serviced in accordance with Sea-Bird recommended procedures.
Two oxygen sensors were used on the Sea-Bird CTD. In the early part of the cruise (stations A'1, A'2, A'3 and A7), D.O. sensor 1 was connected to a pump. Due to equipment problems, no data were collected at A'4 and A'5. Beginning with station A6 and continuing throughout the cruise, sensor 1 was removed from the pumped circuit and replaced with sensor 2. The station B4 data file was damaged and unusable. Oxygen data for stations A'1 and A7 were deleted because the values were unrealistic. Oxygen data for stations A'2 and A'3 were left in the data table but should be considered suspect. Oxygen data values reported in the Seabird table were acquired with sensor 2.
Oxygen concentration determinations, upper and lower end, were made prior to the cruise by the LUMCON CTD technician and entered into the SeaSoft configuration file. Winkler oxygen titrations on board ship were used to develop a regression against Sea-Bird oxygen data, which were corrected if necessary. A correction was not needed because there was good agreement of Sea-Bird oxygen values with Winkler values and bottom values obtained with the Hydrolab CTD.
Data reductions from the SeaBird were generated by Ben Cole and quality controlled by Nancy Rabalais.
S796Stns: Depths were logged from the RV Pelican’s fathometer.
S795SalSed: Suspended sediment concentrations were supervised and quality controlled by Nancy Rabalais. Salinity determinations were made with a Guildine Portasal maintained by the LSU Coastal Studies shop.
N. Rabalais performed an additional procedure in quality-control/quality-assurance by evaluating relationships between the data in S796Hydrolab, S796Nutrient, S796Pigment, S796SalSed, S796Seabird and S796Stns.
Data values reported are from downcasts. Downcast scans selected for each CTD station are 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.
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. Bottom 5-l Niskins on the rosette were used to collect “bottom” water samples at stations A7, A6, B1, B2, B6, B8, C7, C6B, C4, D1, E2, E2A and F3.
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 contains 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.