  The paradox of the plankton highlights the apparent contradiction between
Gause's law of competitive exclusion and the observed diversity of
phytoplankton. It is well known that phytoplankton dynamics depend heavily on
two main resources: light and nutrients. Here we treat light as a continuum of
resources rather than a single resource by considering the visible light
spectrum. We propose a spatially explicit reaction-diffusion-advection model to
explore under what circumstance coexistence is possible from mathematical and
biological perspectives. Furthermore, we provide biological context as to when
coexistence is expected based on the degree of niche differentiation within the
light spectrum and overall turbidity of the water.
