Abstract
We investigated the Forni Glacier and the surrounding area in the Alps in terms of habitat preferences, densities, dispersal and desiccation tolerance of glacier tardigrades, which are one of the most common faunal representatives and top consumers in supraglacial ecosystems. To do so, we sampled supraglacial environments (cryoconite holes, debris from ice surface, dirt cones and moraine, mosses from supraglacial stones) and non-glacial habitats (mosses, freshwater sediments and algae), and we installed air traps on the glacier and the nearby area. We found that cryoconite holes on the Forni Glacier are exclusively dominated by one metazoan group of tardigrades, representing one species, Hypsibius klebelsbergi (identified by morphological and molecular approaches). Tardigrades were found in 100% of cryoconite holes and wet supraglacial sediment samples and reached up to 172 ind./ml. Additionally, we found glacier tardigrades in debris from dirt cones and sparsely in supraglacial mosses. Glacier tardigrades were absent from freshwater and terrestrial samples collected from non-glacial habitats. Despite the fact that H. klebelsbergi is a typical aquatic species, we showed it withstands desiccation in sediments, but in low temperatures only. Treatments conducted in higher temperatures and water only showed low or no recovery. We suspect successful dispersal with wind might have taken place only when tardigrades desiccated in sediments and were passively transported by cold wind. Limited ability to withstand high temperatures and desiccation may be potential barriers preventing glacier tardigrades inhabiting new, even apparently suitable high mountain water bodies like temporary rock pools.
Highlights
Glaciers and ice sheets are considered to be a peculiar biome characterised by permanently low temperatures and unique cold-adapted organisms (Hodson et al 2008; Anesio and Laybourn-Parry 2012)
Hypsibius klebelsbergi was found in 100% of cryoconite samples from cryoconite holes and the mixture of cryoconite and gravel on a glacier’s surface (Fig. 4, Tables S1, S3)
We found that cryoconite holes on the Forni Glacier are exclusively dominated by one metazoan group of tardigrades, representing one aquatic species, H. klebelsbergi originally described and known from other glaciers in the Alps (Mihelcic 1959; Dastych et al 2003; Greven et al 2005; Dabert et al 2015)
Summary
Glaciers and ice sheets are considered to be a peculiar biome characterised by permanently low temperatures and unique cold-adapted organisms (Hodson et al 2008; Anesio and Laybourn-Parry 2012). Cryoconite holes host unique assemblages mostly of bacteria, algae and microfauna different from the ones found in ice-free areas (Stibal et al 2015; Franzetti et al 2017; Ambrosini et al 2017; Liu et al 2017; Zawierucha et al 2018a, b) These specific reservoirs constitute glacial biodiversity hot spots and bioreactors responsible for organic matter production and play an important role in glacier mass balance, glacial geochemistry, carbon cycling and as a storage of various pollutants (Mueller et al 2001; Fountain et al 2004; Bagshaw et al 2007; Stibal et al 2010; Pittino et al 2018; Łokas et al 2018; Zawierucha et al 2018a, 2019a). One of the common invertebrate taxa known to inhabit glacier surfaces in the Arctic, Antarctic, Central Asia and the Alps are tardigrades (Dastych et al 2003; Porazinska et al 2004; Zawierucha et al 2016, 2019a)
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