Ecological Competition Between Algae: Experimental Confirmation of Resource-Based Competition Theory

All possible outcomes of ecological competition, including stable coexistence, were observed in laboratory studies of two species of freshwater diatoms potentially limited by phosphate and silicate. The relative abundance of these nutrients determined the outcome of competition. The observed conditions of coexistence and competitive displacement agree with those predicted solely from the abilities of each species to acquire and utilize limiting nutrients. Coexistence occurred only when the growth rate of each species was limited by a different resource. These results may help explain the regional coexistence in nature of an otherwise paradoxically high number of algal species.