title: The species composition of Antarctic phytoplankton interpreted in terms of Tilman's competition theory.
abstract: An attempt was made, to test for the impact of resource competition on Antarctic marine phytoplankton. According to theory, species composition near competitive equilibrium should be determined by the ratios of limiting resources. Enrichment bioassays identified silicon and nitrogen as limiting nutrients for some of the most important phytoplankton species during early austral summer in the region near the Antarctic Peninsula. Together with the generally acknowledged limiting resource light, this gave three meaningful ratios of essential resources (Si:N, Si:light, N:light) and one ratio of substitutable resources (NO3:NH4). Phytoplankton species assemblages were found to be well separated by the ratios of the essential resources and by mixing depth. Nine out of 12 individual species were found to be separated along at least one of the gradients of resource ratios. Where comparison with competition experiments was available, predicted and realized distributions of species were compatible.
authors.affiliation: Max-Planck-Institut für Limnologie, Postfach 165, D-2320, Plön, Federal Republic of Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Sommer
keywords: Antarctic phytoplankton; Competition; Nutrients; Resource ratios