Bio-optical characteristics of phytoplankton and carbon assimilation were measured in the NW Atlantic Ocean near the continental shelf break South of New England (40 degrees N/70 degrees W) in August 2002. Discrete samples included: chlorophyll a (Chl a), phytoplankton absorption (a(ph)), the photosynthetic versus irradiance (P versus E) response using carbon fixation, the maximum quantum yield for charge separation at Photosystem II (PSII) (F-v/F-m) and its recovery kinetics and the functional absorption cross-section (sigma(PSII)). In this study, we present a robust empirical relationship that illustrates the possibility of estimating photosynthetic carbon uptake using independent measures of absorption and variable fluorescence. Covariations between the initial slope of the photosynthesis-irradiance curve normalized per Chl a, the a(ph) index of the ratio of photoprotective to total photosynthetic carotenoids and the dark recovery of the maximum quantum yield efficiency of PSII suggest a new pathway to estimate primary production in the marine environment, including the effect of the recent light history. Recovery kinetics in laboratory culture confirmed the effects of light history in the derived parameter from the dark incubations from natural populations.
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