Biodiversity of plankton by species oscillations and chaos

Abstract

Biodiversity has both fascinated and puzzled biologists1. In aquatic ecosystems, the biodiversity puzzle is particularly troublesome, and known as the ‘paradox of the plankton’2. Competition theory predicts that, at equilibrium, the number of coexisting species cannot exceed the number of limiting resources3,4,5,6. For phytoplankton, only a few resources are potentially limiting: nitrogen, phosphorus, silicon, iron, light, inorganic carbon, and sometimes a few trace metals or vitamins. However, in natural waters dozens of phytoplankton species coexist2. Here we offer a solution to the plankton paradox. First, we show that resource competition models6,7,8,9,10 can generate oscillations and chaos when species compete for three or more resources. Second, we show that these oscillations and chaotic fluctuations in species abundances allow the coexistence of many species on a handful of resources. This model of planktonic biodiversity may be broadly applicable to the biodiversity of many ecosystems.