The MOOS Upper-Water-Column Science Experiment (MUSE)
MUSE Field Experiment, August 2000, Monterey Bay, CA 

Biogeochemical Response to Coastal Upwelling
Francisco Chavez

Methods

CLEAN WATER FOR PRODUCTIVITY 

Water for the productivity experiments was collected at six fixed depths,
representing 100, 50, 30, 15, 5,1 and 0.1% of the light penetration depths
(LPD's), which were estimated by secchi disk. 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 particulate carbon and nitrogen were made on samples collected in the upper 200m 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, 1, and 0.1% 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). 

NUTRIENTS

Nutrient samples were drawn from stations for all depths into seasoned polyethylene
scintillation vials and frozen aboard ship for later processing with an AlpChem
autoanalyzer. Surface samples were collected at all other sites. The samples
were analyzed for NO3, NO2, PO4 and SiO4 concentrations. 


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. 

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

Venrick, E. L., and T. L. Hayward. 1984. Determining chlorophyll on the
1984 CalCOFI surveys. California Coop. Oceanic Fish. Invest. Report 25:
74-79.

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      Last Updated: 07 June, 2002