Comparison between steady state and non‐steady state competition: Experiments with natural phytoplankton

Abstract

Chemostat competition experiments with natural phytoplankton communities are compared to experiments in which either one (phosphorus) or two (phosphorus and silicon) key nutrients were added discontinuously at 1‐week intervals. In all types of experiments wide ranges of Si:P ratios were tested. Deviation from steady state was found not only to increase the number of coexisting species, but also to shift the regions of dominance of species and of higher taxa along the gradient of Si:P ratios. Pulsed nutrient addition was mainly to the advantage of green algae and to the disadvantage of diatoms.