The question of how species can coexist has long troubled ecologists. It is especially pressing for marine phytoplankton, where 1000s of species co-exist in areas the size of the North Sea. Hutchinson (1961) already described this paradox of the plankton by noting: “The problem that is presented by the phytoplankton is essentially how it is possible for a number of species to coexist in a relatively isotropic or unstructured environment all competing for the same sorts of materials.” The specific mechanisms making this possible remains unidentified (Record et al. 2014), and so the paradox remains unresolved. Recent analyses of plankton booms using rRNA to identify taxa (Needham et al. 2016) reveal a surprising differentiation in the times/places at which different taxa reach their abundance maxima. The aim of this project is to build a theory and a model for phytoplankton diversity on this observation. The idea is that competitive exclusion can be greatly reduced through localization in both space and time of phases where species populations are sufficiently large to actively drive density-dependent interactions, and so competition. At all other places/times the populations only change by passively responding to changes in the environment, but somehow must be “ready” to bloom when the right time has come. In the project, you will build models to test this mechanism, and identify the conditions that enable co-existence of 1000s of species that all compete for similar resources.