Water bears dominated cryoconite hole ecosystems: densities, habitat preferences and physiological adaptations of Tardigrada on an alpine glacier

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.

A hole in the nematosphere: tardigrades and rotifers dominate the cryoconite hole environment, whereas nematodes are missing

“…(2016) for Svalbard, Zawierucha et al . (2019 a ) for the Alps, Takeuchi et al . (2000) for Himalaya, Buda et al .…”

“…Although 10% of that is covered by glaciers and ice sheets, our knowledge about microinvertebrate diversity in these parts of the cryosphere is very incomplete. While polar terrestrial habitats have been the subject of many microinvertebrate diversity studies (Wu et al ., 2011; Coulson et al ., 2014; Iakovenko et al ., 2015), glacial habitats have not been well characterized (Zawierucha et al ., 2015; Zawierucha et al ., 2019 a ). During the melt season, warm temperatures and solar radiation transform glacial snow into liquid water, thereby providing a suitable environment for psychrophilic organisms (Hodson et al ., 2008; Cook et al ., 2016).…”

“…Taken together, these studies suggest that although cryoconite holes may be seeded from environments containing nematodes, they do not thrive there. Moreover, in Norway and the Alps, remnants of various arthropods in cryoconite holes were detected with microscopy, but nematodes were not (Dastych, 2019; Zawierucha et al ., 2019 a ).…”

Physical, chemical, and biological characteristics of supraglacial pools on a debris-covered glacier in Mt. Gongga, Tibetan Plateau

“…Our results also represent the first documentation of Collembola from meltwater habitats (i.e., cryoconite holes and supraglacial pools) on glaciers in Asia. Previously, Collembola have been documented from cryoconite holes on the Tyndall Glacier in Patagonia, Chile (Takeuchi and Kohshima 2004;Zawierucha et al 2015), the Forni Glacier in Italy (Zawierucha, Buda, Azzoni et al 2019), and the Adishi Glacier in Georgia (Makowska et al 2016). Additionally, Collembola were found within meltwater ponds in Alaska and British Columbia (Fjellberg 2010).…”

“…Isotomidae are semi-aquatic macroinvertebrates found in a range of glacier habitat types from glacial ice fields to meltwater pools to glacier streams (Fjellberg 2010). Collembola within glacial meltwater habitats have been observed on the water surface and underwater on the benthic sediment (Takeuchi and Kohshima 2004;Zawierucha, Buda, Azzoni et al 2019). Semi-aquatic Collembola typically live on the water surface and on vegetation at the edges of aquatic habitats, but some species have been documented to survive up to forty days underwater (Deharveng, D'Haese, and Bedos 2008).…”