NOAA Long Line Cruises : N95F
Methods and Materials

CLEAN WATER FOR PRODUCTIVITY

Water for the productivity and grazing experiments was collected at six fixed depths, representing 100, 50, 30, 15, 5 and 1% of the surface irradiance (as determined with a secchi disk), with dedicated, Teflon-coated Go-Flo bottles lowered on a Kevlar cable and closed with Teflon messengers. The type of sampling system and cleaning of components, as well as bottle handling and filtration, was modeled after the recommendations of FITZWATER et al. (1982). Measurements of chlorophyll and carbon and nitrogen were made on samples collected in the upper 115m with the Kevlar cable and on samples collected from 115m to 300m with the rosette sampler on the CTD.

PRIMARY PRODUCTIVITY

The radioactive isotope, 14C, was used to measure primary production. Samples were drawn into 280ml polycarbonate bottles which had been washed using the FITZWATER et al. (1982) technique for cleaning Go-Flo bottles. The bottles were then encased in nickel-cadmium screens (Perforated Products) that acted as neutral density filters to reduce the light intensity to the same level as that occurring at the depth from which the sample was collected. The screens were calibrated using a Biospherical QLS-100 to 100, 50, 30, 15, 5, and 1% light levels. Approximately 10µCi of 14C were added to each sample bottle. An initial sample was inoculated with the tracer and filtered immediately, with no incubation, to determine abiotic particulate incorporation. The remaining samples were incubated for 24 hours in on-deck, seawater-cooled, Plexiglas incubators utilizing the natural sunlight as the light source. For determination of particulate carbon fixation, the samples were filtered onto Whatman GF/F filters at <200 mm mercury and the filters were soaked overnight with 0.5 N HCl to purge the filters of inorganic carbon isotope. The 14C filters were placed in 10 ml of Cytoscint ES scintillation cocktail and counted in a Beckman LS-3801 liquid scintillation counter.

CHLOROPHYLL

Chlorophyll a and phaeopigments were determined by the fluorometric technique using a Turner Designs Model 10-005 R fluorometer that was calibrated with commercial chlorophyll a (Sigma). Samples for determination of plant pigments were filtered onto 25-mm Whatman GF/F glass fiber filters and extracted in 90% acetone in a freezer for between 24 and 30 hours (VENRICK and HAYWARD, 1984). Other than the modification of the extraction procedure, the method used is the conventional fluorometric procedure of HOLM-HANSEN et al. (1965) and LORENZEN (1966). Additional samples were also filtered onto 1.0 and 5.0 micron pore size Nuclepore membrane filters.

PROTISTAN BIOMASS

Phytoplankton and small heterotrophs were sized and counted with epifluorescence microscopy (CHAVEZ et al. 1990, 1991). In addition to enumerating organisms on 0.2mm pore size filters, larger and rarer organisms were enumerated on 5.0mm pore size filters through which 200 ml was filtered.

UNDERWAY MEASUREMENTS

A mapping system for continuous measurement of fluorescence using a Turner Designs 10-005 and a SeaTech fluorometer, photosynthetically available radiation sensors (PAR), using two sensors: a LiCor 192-SA and a Biospherical QSR-240, location using a Magellan GPS board, and nitrate using a prototype nitrate analyzer based on a Kloehn syringe that was developed at MBARI (SAKAMOTO et al. 1995) and was used throughout the NOAA survey cruises. For more information regarding the underway system.

Next: Results

Last Updated: 28 April, 2004

References

Fitzwater, S. E., G. A. Knauer and J. H. Martin. 1982. Metal contamination and its effects on primary production. Limnology and Oceanography, 27: 544-551.

Holm-Hansen, O., C. J. Lorenzen, R. W. Holmes and J. D. Strickland. 1965. Fluorometric determination of chlorophyll. Journal Cons. Perm. Int. Explor. Mer, 30: 3-15.

Lorenzen, C. J. 1966. A method for the continuous measurement of in vivo chlorophyll concentration. Deep-Sea Research, 13: 223-227.

Sakamoto, C. M., Friederich, G. E., Codispoti, L. A. 1995. MBARI Procedure for Automated Nutrient Analyses Using a Modified Alpkem Series 300 Rapid Flow Analyzer. MBARI Technical Report No. 90-2