A predictive model for estimating rates of primary production in the subtropical North Pacific Ocean

A primary production model, specific to the subtropical North Pacific, was developed using productivity and chlorophyll data collected at Station ALOH A (22.75 degreesN, 158.00 degreesW) and measured phytoplankton physiologica l parameters. The production algorithm is a mechanistic, full spectral mode l that provides depth-dependent photosynthesis rates. Six years of phytopla nkton pigment data were analyzed to derive seasonal cycles and to parameter ize chlorophyll a (Chl; monovinyl and divinyl chlorophyll a) versus depth p rofiles. The Chi profiles fit a Gaussian-type distribution with depth over a constant background concentration equal to mixed-layer values. Maximum Ch i concentrations were always found below the surface, and the parameters di splayed distinct monthly and seasonal patterns. Photosynthesis versus irrad iance experiments were conducted at a number of locations and seasons in th e vicinity of Station ALOHA to calculate phytoplankton physiological parame ters needed for the computation of primary production rates. Relationships were explored between environmental conditions and the physiological and pr ofile parameters in order to develop algorithms based on remotely sensed se a-surface variables and time of year. These relationships were used to mode l primary production rates using data collected during the Hawaii Ocean Tim e-series (HOT) program. The performance of the model and model parameters w ere tested by comparing modeled results to those measured directly at Stati on ALOHA by trace metal-clean, in situ C-14 incubation techniques. Monthly averaged chlorophyll profile parameters and a constant maximum quantum yiel d (0.026 mol C (molquanta)(-1)) generates an annual production estimate of 168 g Cm-2, which closely resembles that measured at Station ALOHA (181g C m(-2)) during the same period. The measured and modeled primary production rates for the subtropical North Pacific are twice as high as values derived from Coastal Zone Color Scanner (CZCS) data (60-90gCm(-2)) during the peri od 1978-1986. If the study area near Station ALOHA is representative of mos t oligotrophic waters, current global estimates of primary production rates have been significantly underestimated. (C) 2001 Elsevier Science Ltd. All rights reserved.