Stramenopiles and Cercozoa dominate the heterotrophic protist community of biological soil crusts irrespective of edaphic factors

Abstract

Biological soil crusts (biocrusts) are terrestrial micro-habitats distributed in drylands and also in temperate coastal dunes. Biocrusts harbor phototrophic and heterotrophic microorganisms in the upper soil layer, which fulfil important ecological functions such as primary production and energy channelling via the microbial loop. Heterotrophic protists, although being an essential component of the microbial food web of biocrusts, have rarely been investigated. Therefore, in the present study, we used the liquid aliquot method (LAM) to assess the abundance and diversity of protists in biocrusts from coastal dunes at the Baltic Sea for the first time. The total abundance of protists ranged between 10 × 103 and 128 × 103 individuals g−1 dry weight. The community was dominated by naked amoebae (54 %) and flagellates (44 %). The most common taxa were Spumella-like flagellates (Stramenopiles), Paracercomonas-like amoeboflagellates, and Sandonidae-like glissomonads (both from the phylum Cercozoa) as well as heteroloboseans. Despite significant differences in the beta diversity of protist morphotypes, the measured environmental drivers, such as pH, total organic carbon, nitrogen, and phosphorus did not explain these differences. Also, the geographical distance could not predict the community dissimilarity, suggesting that the diversity of protists in biocrusts is controlled by biotic or other physicochemical parameters.