We have applied a mixed layer model and a simple biological model to examine spring phytoplankton increase observed during the North Atlantic Bloom Experiment of the Joint Global Ocean Flux Study. Despite spatial variability in water column conditions, the one-dimensional mixed-layer model (PRICE et al., Journal of Geophysical Research, 91, 8411-8427, 1986) reproduced satisfactorily the increasing stratification during the 2-week observation period. Likewise, the gradient and extent of nutrient removal (exemplified by nitrate) and the timing of the increase in phytoplankton biomass (represented by chlorophyll a) compared reasonably well between the model and observations. The cell-quota formulation for phytoplankton growth, and an adaptive feeding model for zooplankton appear to be necessary to accord with the observations. On the other hand, adaptive feeding by zooplankton makes the model sensitive to the choice of a maximum growth rate in phytoplankton. Zooplankton were probably not a factor early in the simulation, but according to the model, exerted significant grazing pressure by the end of the observational period.
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