Phytoplankton Patchiness Generated by Long Internal Waves: A Model

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Abstract
A simple computer model is used to investigate the interaction between long internal waves (period .apprx. 13 days) and processes of primary productivity in the Baltic Sea [northern Europe]. The periodic vertical displacements in or near the photic zone affect the availability of light and nutrients to primary producers, resulting in integral vertical fluxes of nutrients and biomass. If the N flux is parameterized implicitly by a diffusive flux across the halocline, the apparent coefficients of eddy diffusivity are more often negative and exceed in absolute value by 2 orders of magnitude the experimentally determined values. Differences in the depth integrals of daily primary production between wave crests and troughs amount to .apprx. 50% and the vertical flux of the nitrate N may locally reach .apprx. 50 mg N m-2 per day. The outlined mechanism might be a significant additional source for the formation of mesoscale horizontal heterogeneities in phytoplankton biomass.