NOAA Long Line
Cruises : N93S
Methods and Materials
CLEAN WATER FOR PRODUCTIVITY AND GRAZING EXPERIMENTS
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). In addition to samples from the Kevlar casts, measurements of chlorophyll
and particulate carbon and nitrogen were made on samples collected in the upper 200m with
the rosette sampler on the CTD.
Contour graph of Chlorophyll taken from both CTD and KEVLAR casts. To see chlorophyll,
phaeo, and productivity contours click here(33k).
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 0.2, 1.0 and
5.0 mm pore size Nuclepore filters.
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)
procedure that is used for cleaning the Go-Flo bottles. The bottles were encased in nickel
screens (Perforated Products) that act as neutral density filters reducing the light
intensity to the same level as that occurring at the depth from which the sample was
collected. Isotopes 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 samples were incubated in on-deck seawater-cooled Plexiglas
incubators for 24 hr with natural sunlight as the light source. For determination of
particulate carbon fixation, the water was filtered onto Whatman GF/F filters at <200
mm mercury and the filters were soaked with 0.5 N HCl to purge the filters of inorganic
carbon isotope. The 14C filters were placed in 10 ml of Cytoscint and counted in a liquid
scintillation counter aboard ship.
Temperature Contour. To see temperature, salinity
and nitrate contours (39k) click here.
TEMPERATURE, SALINITY, AND NUTRIENTS
During the CTD casts, temperature, conductivity, and pressure were measured by
personnel from NOAA/AOML. In addition samples for oxygen, nitrate, nitrite, phosphate, and
silicate were also collect by NOAA/AMOL. The biological, chemical, and physical data are
available through the internet from http://www.aoml.noaa.gov/ocd/oaces/
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.
Venrick, E. L., and T.L.Hayward. 1984. Determining chlorophyll on the 1984
CalCOFI surveys. California Coop. Oceanic Fish. Invest. Report 25: 74-79.