Carbon assimilation was measured from the uptake 14C into particulate matter as an estimate of primary production (see Barber et al., 2001). Two replicate samples (in polysulfone tissue culture flasks or polycarbonate bottles) retrieved from eight depths in the euphotic zone were suspended from a spar buoy, floating free of the ship, from dawn until dusk. See Barber et al. (2001).
Phytoplankton absorption procedure followed that described in Mueller and Austin (1995). Two liters of water were collected onto GF/F filters and scanned over 400-700 nm in a Perkin-Elmer Lambda-3 spectrophotometer. The detrital spectrum was similarly scanned after an extraction in hot methanol and the phytoplankton pigment spectrum (aph, aphw) found by difference. The pathlength amplification (beta-correction) factors were determined for the Lambda-3, prior to the cruises, based on a composite of 12 different cultures of phytoplankton. See Marra et al. (2000).
HPLC methods for pigments varied over time. References are Trees et al. (2000), Bidigare et al. (1990), Latasa and Bidigare (1998), and Goericke and Repeta (1993).
PAR sensors (model QSP-200, Biospherical Instruments San Diego, CA), were used in a self- contained PAR-sensing and data-logging unit. Spectral irradiance (“irradiance” in the dataset) was measured using a Marine Environmental Recorder (MER) model 2040 (Biospherical Instruments) from which PAR was calculated. See Marra et al. (2000).
Methods for nutrient concentrations followed JGOFS protocols (see Barber et al., 2001).
Sampling and analytical procedures: The samples were subsequently filtered through GF/F filters, and the filters assayed for their radioactivity by liquid scintillation counting aboard ship. In the database,the primary production values are presented as the mean of the two replicate samples.
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