A batch of marine diatoms
, just some of the many organisms to gain energy from the Sun
In aquatic biology, the paradox of the plankton describes the situation in which a limited range of resources (light, nutrients) supports a much wider range of planktonic organisms. The paradox results from the competitive exclusion principle (sometimes referred to as Gause's Law), which suggests that when two species compete for the same resource, ultimately only one will persist and the other will be driven to extinction. Phytoplankton life is diverse at all phylogenetic levels despite the limited range of resources (e.g. light, nitrate, phosphate, silicic acid, iron) for which they compete amongst themselves.
The paradox was originally described in 1961 by limnologist G. Evelyn Hutchinson, who proposed that the paradox could be resolved by factors such as vertical gradients of light or turbulence, symbiosis or commensalism, differential predation, or constantly changing environmental conditions. More recent work has proposed that the paradox can be resolved by factors such as: size-selective grazing; spatio-temporal heterogeneity; and environmental fluctuations. More generally, some researchers suggest that ecological and environmental factors continually interact such that the planktonic habitat never reaches an equilibrium for which a single species is favoured.