Diversity and connectivity of microbial eukaryotes in High Arctic terrestrial and aquatic ecosystems

High Arctic ecosystems are being rapidly altered by climate change. Increased permafrost thaw and rainfall are making terrestrial landscapes more hydrologically active, increasing the input of organic and inorganic material into freshwater systems and freshening coastal marine ecosystems. Understanding the ecological implications of this environmental change requires an improved taxonomic and ecological resolution for less-studied microbial eukaryote communities. Microbial communities were investigated from freshwater, terrestrial, and coastal marine ecosystems on Ward Hunt Island, Ward Hunt Ice Shelf and Ellesmere Island along the coastal margin of the Last Ice Area, Canadian High Arctic. For the first time, Arctic microbial eukaryotic diversity was assessed using full-length 18S rRNA gene metabarcoding sequencing. Terrestrial microbial eukaryotic richness correlated with soil moisture, extending biogeographical patterns observed in lower latitudes. A greater connectivity between terrestrial and freshwater, than to coastal communities was identified, with a predicted input of terrestrial microbial eukaryotes into the Ward Hunt Lake microplankton. As Arctic catchments become more hydrologically active, increased transport of microbial eukaryotes may strengthen connectivity and homogenisation between terrestrial and freshwater ecosystems, while greater freshwater inputs may alter microbial diversity in adjacent coastal waters.