Mesoscale vortices and the paradox of the plankton

Coexistence of competitive species is severely limited by the availability of resources and the characteristics of the environment. In particular, the so-called 'competitive exclusion principle' states that, at equilibrium, t he number of coexisting species cannot be larger than the number of resourc es for which they compete. However, many in situ observations have revealed prolonged coexistence of a large number of competitive plankton species, a phenomenon known as 'the paradox of the plankton'. Here we investigate thi s problem and show that ocean mesoscale vortices generate transport barrier s and incomplete horizontal mixing, allowing for a prolonged survival of th e less-fit species, even for fully homogeneous resource distributions. In s uch a situation, the temporarily less-fit plankton species are protected fr om competition by the action of the vortices.