Snow microinvertebrates from lowlands, high mountains and the Arctic—implications for conservation efforts

The protection of cryospheric ecosystems and their biota cannot be properly defined without a detailed species inventory. Snow microinvertebrates are crucial for estimating cryophilic biodiversity, yet they are poorly described at broader spatial scales. To fill this knowledge gap, we collected samples from different snow surfaces in the Pyrenees, European Alps, Tatra Mts. (Poland), Baltic states (Latvia and Estonia), central Norway, Svalbard, and Alaska between 2021–2025. Snow was collected from glacier and glacieret surfaces and forefields, mountain valleys and slopes, and forest floors. Invertebrates were identified by morphological and DNA-based approaches. Collectively, we found representatives of Tardigrada, Rotifera, Nematoda, Acari and Collembola. Tardigrades were found in all sampling localities, and along with rotifers were the most abundant invertebrate groups. Tardigrades and rotifers reached the highest population densities with ~ 7,600 individuals per liter of melted snow in the Tatra Mts., Poland. In general, we found invertebrates typical for glacial ecosystems (e.g., certain species of Tardigrada) and those likely transported by wind to snow surfaces (e.g., Acari). Rotifers on non-glacial snow were different species from those in the snow on glaciers. The glacier tardigrade Fontourion glaciale was found on snow in Svalbard and the Tatra Mts., while dark-pigmented tardigrades represent the same species on snow in the Pyrenees and in the Tatra Mts. Some invertebrates found on snow represent new or putatively new species. We present here a first assessment of snow microfauna across latitudes, which identifies similarities and differences in faunal composition between glacial- and non-glacial snow, and consider the role of snow algae in sustaining invertebrates. Our data suggests that snowfields and glacierets may function as refugia during warm climatic periods for certain cryophiles (e.g., during summer in polar and high mountain regions, through interglacials) and therefore require conservation efforts.