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Phytoplankton natural community competition experiments: A reinterpretation
Author(s) -
Sommer Ulrich,
Kilham Susan Soltau
Publication year - 1985
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1985.30.2.0436
Subject(s) - reinterpretation , limnology , competition (biology) , art history , history , art , ecology , biology , aesthetics
Smith and Kalff (1982, 1983) recently published two articles on phosphorus competition among freshwater phytoplankton whose main conclusions were that among competing phytoplankton there is no partitioning of the gradient of phosphorus availability and that competition for phosphorus occurs to the advantage of small algae. We acknowledge the value of the experiments presented in those papers, but feel that the conclusions are not fully supported by their own data or by recently published observations based on similar experimental techniques (Tilman et al. 1982; Sommer 1983; Tilman et al. in prep.). Using natural community competition experiments, Smith and Kalff ( 1983) concluded that there was no partitioning of a gradient of phosphorus availability among competing phytoplankton species. They derived this conclusion from the fact that in parallel chemostat competition experiments at different dilution rates the same alga, Synedra acus, usually was the most successful competitor. Partitioning (sensu Smith and Kalff 1983) means that one species is a better competitor at high supply rates of a resource and another species at low supply rates. We feel that their experiments actually demonstrate three different possibilities. We have abstracted data from their tables 1, 2, and 3 into a single table (Table 1) containing information only on the species that coexisted at the ends of the experiments. enough phosphorus (through a combination of processes, including uptake and storage) to maintain growth rate equal to dilution rate and can reduce the phosphorus concentration to a level below that needed by other species to maintain their growth rates equal to the dilution rate. Those are the conditions necessary for competitive exclusion with no resource partitioning, and Table 1 A seems to represent just such a set of cases. Synedra has also been reported to be the most successful genus in phosphorus competition by Tilman (198 1: Synedra jilzjkmis), Sommer ( 1983: S. acus), and Kilham (1984: Synedra sp.).