A ten-year time series from Monterey Bay, California: Seasonal, interannual and long-term patterns

METHODS AND MATERIALS

Data collected from Shipboard CTD:

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). 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.

NUTRIENTS

Nutrient samples were drawn from the Mooring 1 site 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.

• Acoustic-Doppler Current Profiler (ADCP) data were collected from MBARI's M1 buoy near the mouth of Monterey Bay. MBARI’s ADCP separates the current measurements into 8-m depth bins and returns an average value for each bin. The first bin measures currents between 5 and 13 m, while the deeper bins extend past 230 m. Data were averaged to produce a daily mean for each bin.

• Wind velocities were obtained from USGS mooring 46012 near Half-Moon Bay.
• Upwelling indices were calculated by the Pacific Fisheries Environmental Laboratories for 36^oN 122^oW.

Data collected by satellite remote sensing

• Data collected by SeaWiFS are composite monthly images for 1998.

• Daily averages for the shipboard data were calculated from the major stations C1, C7, H1, H3, Mooring1, and Mooring2.

• Interpolation, using the Stineman algorithm, gridded the daily averaged shipboard data into 14-day intervals.
• Moving averages were calculated for the shipboard data using a 9-point running mean on the interpolated data.

• Along-shore and cross-shore components of wind and current velocities were derived by rotating the U and V axes to 330-150^o and 240-60^o respectively.
• Wind and current velocities, as well as upwelling indices, were low-pass filtered using a 128-day cutoff period.
• The data were then decimated by taking every 14^th day from the start of the record to match the shipboard data.

• Annual means were calculated for the 14 day data (~2 averages per month) which resulted in a total of 26 means per year.

• Anomalies were calculated by subtracting the binned mean for the period from the moving average.
• Trends were calculated using a linear regression on the daily averaged data.

Next: Results

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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