The dense concentrat~ons of blomass colnmonly seen at fronts are often explalned by a phys~olog~cal response of the oiganlsms to the frontal environment However, some fractlon of the enhanced b~o m a s s may be explalned through purely phys~cal processes the interaction of floating sinking or swlmmlng w~t h the flows at a front To explore this hypothesis, I present a model of steady, 2-dlmenslonal cross-frontal circulat~ons, whlch I combine ~1 1 t h a vanety of swlrnming behaviors The models show how patchmess may arise at fronts through retention and accumulat~on zones, and the patterns which evolve glven vanous flow and swimmlng characterlst~cs The ecological slgnlficance of the results 1s discussed

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ABSTRACT. We present a simple new formulation of photoresponse in the diatom Laudena borealis. This formulation assumes time-dependence in the value of P,,,,,, the maximal photosynthetic rate. The rate of change of P,,, is nonhearly dependent on the present irradiance, giving a photosynthetic rate that depends on the weighted light history of the cell. The 2 new parameters introduced in this formulation were found to be robust, i.e. they did not change for a variety of data sets. The photoresponse model was incorporated into a simple Lagrangian model of wind-driven vertical mixing. It was found that the modelled photoresponse can lead to enhanced vertically integrated photosynthesis under certain conditions of light extinction and wind mixing. In particular, phytoplankton in wind-mixed coastal regions may experience an increase in integrated photosynthesis per cell under strong incident irradiance.

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