The Paradox of the Plankton: An Equilibrium Hypothesis

A model of nutrient-limited phytoplankton growth, based on Michaelis-Menten uptake kinetics, is offered as an explanation of the so-called paradox of the plankton. The model suggests that an assemblage of coexisting phytoplankton may be limited by several nutrients, each species principally limited by the availability of a different nutrient. The principal requirement of the model is that each species be less effective at obtaining at low concentration the nutrient of which it requires larger amounts for continued growth. The model offers an explanation for the continued coexistence of associated phytoplankters in a stable equilibrium. It also offers a possible explanation for the decreased diversity commonly observed in eutrophic lakes and is consistent with observations that a larger number of different nutrients are in short supply in oligotrophic waters.