The Role of Predators in the Stable Coexistence
of Several Alga Species

P. P. Umorin

Papanin Institute of Biology of Inland Water, Russian Academy of Sciences,
Borok, Nekouz Raion, Yaroslavl Oblast, 152742 Russia;

e-mail: upp@ibiw.yaroslavl.ru

Received July 24, 2007

Abstract—Experiments were conducted on growing mixed cultures of green Ankistrodesmus arcuatus Korsch
and diatom Diatoma elongatum (Lyngb.) algae with and without ciliates Cyclidium glaucoma Ehrenberg and
Paramecium caudatum Ehrenberg in accumulative and perfusion cultures. Both alga species successfully
developed in the presence of ciliates despite their grazing on both alga species; however, in their absence, Anki-
strodesmus arcuatus were suppressed and did not develop. It is supposed that ciliates contribute to the stabilization
of the community not only as predators but also by excreting dissolved reduced nitrogen into the environment as
a result of their vital functions.

Key words: competition, coexistence, algae.

DOI:10.1134/S1995082909010015

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