EqPac New Production by N

James J. McCarthy and Patricia A. Wheeler
  1. Sampling

    Six to eight depths will be sampled, including some below the photic zone, with the Kevlar cable/rosette system. Samples to be used for determination of nutrient uptake rates will be transferred immediately to acid cleaned polycarbonate bottles.

  2. Nutrient Chemistry

    Standard autoanalyzer techniques will be relied upon when N concentrations are above ~100 nM. The low level techniques will be used when N concentrations are <100 nM, i.e., chemiluminescent technique (Garside, 1982) for NO¯ and the solvent extraction technique (Brzezinski, 1987) for NH.

  3. Tracer Additions

    Additions of 10 % ambient substrate concentration will be used when substrate concentrations are above the analytical limit of detection. When substrate concentrations are at or below the limit of detection (whether by conventional methods or the new low level methods), tracer additions will be at the detection level.

  4. Incubation

    Rates of nitrogen uptake will be determined during the course of 3--4 hour simulated in situ incubations. Subsurface light will be approximated with a combination of neutral density and colored filters. Temperature will be maintained ± a few C of the depth from which samples were collected. For each station uptake rates will be determined twice during the day and once at night.

  5. Intercalibration

    Preparations of enriched and unenriched plankton nitrogen will be prepared by each lab group and exchanged for intercalibration.

Literature Cited

Garside, C. (1982).
A chemiluminescent technique for the determination of nanomolar concentrations of nitrate, nitrite, or nitrite alone in seawater. Marine Chemistry, 11: 159--167.
Brzezinski, M. A. (1987).
Colorimetric determination of nanomolar concentrations of ammonium in seawater using solvent extraction. Marine Chemistry, 20: 277--288.