Abstract
Crangonyx islandicus is a groundwater amphipod endemic to Iceland, considered to have survived the Ice Ages in subglacial refugia. Currently the species is found in spring sources in lava fields along the tectonic plate boundary of the country. The discovery of a groundwater species in this inaccessible habitat indicates a hidden ecosystem possibly based on chemoautotrophic microorganisms as primary producers. To explore this spring ecosystem, we assessed its microbial diversity and analysed whether and how the diversity varied between the amphipods and the spring water, and if was dependent on environmental factors and geological settings. Isolated DNA from spring water and from amphipods was analysed using metabarcoding methods, targeting the 16S rRNA gene. Two genera of bacteria, Halomonas and Shewanella were dominating in the amphipod samples in terms of relative abundance, but not in the groundwater samples where Flavobacterium, Pseudomonas and Alkanindiges among others were dominating. The richness of the bacteria taxa in the microbial community of the groundwater spring sources was shaped by pH level and the beta diversity was shaped by geographic locations.
Highlights
Crangonyx islandicus, Svavarsson and Kristjansson 2006, is one of two endemic groundwater amphipod species in Iceland [1, 2]
The bacteria associated with the groundwater amphipods reveal groups which differ from the environmental samples, indicating a special microbiome associated with the amphipods independent of geographical location
Using environmental DNA metabarcoding targeting bacterial diversity in cold springs in lava fields within the volcanic active zone in Iceland we found that dominating taxa in terms of relative abundance are Flavobacterium, Alkanindiges and Pseudomonas
Summary
Svavarsson and Kristjansson 2006, is one of two endemic groundwater amphipod species in Iceland [1, 2]. The Icelandic groundwater amphipods are considered to have become geographically isolated when the groundwater in pre-Iceland got disconnected from Greenland during the submergence of the land bridge between the two islands around 15 million years ago [2]. Genetic variation and distinct mitochondrial DNA lineages of the species within Iceland supports this scenario [3]. As Iceland was repeatedly covered by an ice sheet during the Ice ages for the last 2.7 Myrs [4], it is likely that C. islandicus survived in subglacial refugia, most likely along the tectonic plate boundary [3]. The flora and fauna in Iceland are mostly considered to have colonized the island after the last glacial.
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