Protozoa of biological soil crusts of a cool desert in Utah

In arid and semiarid lands throughout the world, many of the open spaces between higher plants are covered by biological soil crusts, communities of cyanobacteria: algae, lichens, and bryophytes associated with bacteria and fungi. These crusts are miniature ecosystems between the atmosphere and soil, furnishing a habitat where microorganisms conduct nutrient recycles, especially nitrogen fixation, and contribute nutrients to the soils underneath. Photosynthetic components and ecosystem metabolism have been extensively studied, but the microfauna contributing to crust bacterial functioning have received little attention. This study of five crusts in southeastern Utah describes diversity and abundance of the protozoa, which constitute most of the microfauna. Amoebae numbered 680–2500, ciliates 20–460, and testate amoebae 2400–4800 g dry weight of crust material, and increased in numbers in the succession from Microcoleus to lichen to bryophyte crusts. Twenty-eight species of amoebae, 45 of ciliates, and 19 of testate amoebae were found. Acanthamoeba, Hartmanella, Vahlkampfidae, two species of Colpoda, 4–5 other colpodids, a species of Polyhymenophora, and species of the tiny testate genera Cryptodifflugia and Difflugiella furnish most of the protozoa in biological soil crusts communities.