On advection in phytoplankton models

Scale analysis is used to deduce a new non-dimensional number, $\text{S =}\text{C}\text{[(A}{}_{\mathrm{H}}\text{τ)}\text{1}\text{2}\text{V}{}_{\mathrm{<mtext>m</mtext>}}\text{]}$ which defines the importance of advection of phytoplankton by organized fluid motion in spatial models of marine food chains. When S ? 1, advection greatly affects biological productivity; when S ? I, advection may be neglected. When S is order one, advection and biological productivity play competing roles in determining the spatial configuration of the plankton biomass.