Water film fauna of microbiotic crusts of a warm desert

Twenty-eight microbiotic crusts containing cyanobacteria, lichens and bryophytes, collected from desert soils of the Grand Canyon in northern Arizona, between Lees Ferry and Whitmore Wash in May 2000, were examined for water film fauna. Fifty-one species of ciliates, 28 of amoebae, 17 of testacea, four metazoan taxa, and a number of flagellate morphotypes were found. In the non-flagellated protozoan groups, r-selected bactivores, responding rapidly to wetting, quickly exploiting resources, and possessing efficient encysting abilities, predominated. The few nematodes were principally stylet-bearing tylenchids, feeding on fungal hyphae and moss rhizoids.