Molecular and Morphological Snapshot Characterisation of the Protist Communities in Contrasting Alpine Glacier Forefields

Phagotrophic protist diversity in oligotrophic soils such as alpine glacier forefields is still poorly studied. Combining morphologic observations with molecular-based analyses, we assessed the diversity of major phagotrophic protist groups in two contrasting glacier forefields in the Swiss Alps (Tiefen glacier forefield, siliceous bedrock, and Wildstrubel glacier forefield, calcareous bedrock), at sites differing in soil development. Ciliates and heterotrophic flagellates could be detected with both approaches, while amoebae could be observed only microscopically. Soils from Tiefen and Wildstrubel glacier forefields harboured distinctly different ciliate, flagellate and amoebae communities. The ciliate clone libraries from the Tiefen glacier forefield were dominated by Oligohymenophorea-related sequences while those from the Wildstrubel glacier forefield were dominated by Spirotrichea-related sequences. Testate amoebae morphospecies of the genera Corythion, Cryptodifflugia, Euglypha and Tracheleuglypha were restricted to the Tiefen glacier forefield, while Centropyxis and Trinema to the Wildstrubel one. No ciliate sequences and only a few ciliate and testate amoebae morphospecies could be retrieved from unvegetated soils of both glacier forefields. The ciliate and testate amoebae community detected at unvegetated sites were a subset of the community developed at vegetated sites. Overall, our results suggest that alpine glacier forefields are colonised by a diverse community of phagotrophic protists which seems to be shaped by bedrock geology and vegetation cover.