Results are presented for a two-phytoplankton model of an unstable frontal
ecosystem. Vertical transport results in both an increased flux of nitrate
to surface waters and to a transport of phytoplankton communities at a rate
too rapid to track equilibrium. The former leads to an increase in primary
production within the region by similar to 10%. The latter is responsible
for transient heterogeneity in distributions, especially of phytoplankton r
atios. Although the inclusion of two size classes of phytoplankton does not
appear to change significantly the total primary production compared to a
single phytoplankton model, it does allow for a dynamic partitioning of phy
toplankton biomass and production between the classes. This partitioning is
controlled by biological responses to transport, dictated here by inter-cl
ass differences in nutrient limitation and mortality. Biological responses
to upwelling are also shown to be dependent on the background nitrate profi
le. (C) 2001 Elsevier Science B.V. All rights reserved.