Complex Trophic Interactions in an Acidophilic Microbial Community.

Extreme habitats often harbor specific communities that differ substantially from non-extreme habitats. In many cases, these communities are characterized by archaea, bacteria and protists, whereas the number of species of metazoa and higher plants is relatively low. In extremely acidic habitats, mostly prokaryotes and protists thrive, and only very few metazoa thrive, for example, rotifers. Since many studies have investigated the physiology and ecology of individual species, there is still a gap in research on direct, trophic interactions among extremophiles. To fill this gap, we experimentally studied the trophic interactions between a predatory protist (, Heliozoa) and its prey, the rotifers and sp., the ciliate sp. and the mixotrophic protist (a green phytoflagellate, Chlorophyta). We found substantial predation pressure on all animal prey. High densities of reduced the predation impact on the rotifers by interfering with the feeding behaviour of . These trophic relations represent a natural case of intraguild predation, with being the common prey and the rotifers/ciliate and being the intraguild prey and predator, respectively. We further studied this intraguild predation along a resource gradient using sp. as the intraguild prey. The interactions among the three species led to an increase in relative rotifer abundance with increasing resource () densities. By applying a series of laboratory experiments, we revealed the complexity of trophic interactions within a natural extremophilic community.