Ciliate diversity in cold water spring sources in Iceland

Cold groundwater springs at the edges of lava fields along the volcanic active zone in Iceland are an interesting habitat, presenting an ecotone between groundwater, surface water and the terrestrial ecosystems. They are categorized as fennoscandian mineral-rich springs according to the European Nature Information System (EUNIS) classification (C2.111 European Environmental Agency) and have a high conservation value. They are also an island-like phenomena in the landscape and, together with the stable chemical and physical properties of the groundwater, make excellent study sites for testing questions regarding community assembly theory. To explore the biota of these systems, we applied environmental metabarcoding to assess ciliate diversity in this habitat. DNA was extracted and metabarcoding based on the 18S rRNA gene was conducted for (1) water samples and (2) glass beads as support for biomass development. Alpha diversity for ciliate communities in the spring sources increased with temperature, and limnocrene springs had fewer, more abundant taxa than rheocrene springs. Differences were observed between the water samples and the glass bead samples, mainly in terms of abundance. When considering only the water samples, no variation was found among spring source communities, indicating that stochastic processes such as dispersal and ecological drift might be important in shaping the community composition.