Invertebrate communities on seasonal snow patches in the European lowlands are shaped by tree canopy-derived organic inputs

Abstract. The cryosphere encompasses a wide range of habitats that support cold-adapted communities. Seasonal snow patches (SSPs) in lowlands are underexplored cryohabitats, characterised by a short persistence period (late winter–early spring) and the presence of trees around, in contrast to large vegetation-free high-mountain and polar ecosystems. To provide the first assessment of organisms from SSPs, we focused on invertebrate diversity and densities from 40 sites in the Baltic States in relation to physicochemical parameters (i.e., suspended solids, chlorophyll a, nutrients), microalgae, and surrounding landscape features (i.e., tree canopy cover). SSPs appeared to be an important spot for bdelloid rotifers (Bdelloidea), tardigrades (Tardigrada), and nematodes (Nematoda), which together accounted for 60 %–100 % of all invertebrates, reaching densities >7000 ind m−2. Acari and Insecta were less abundant, whereas other invertebrates occurred only sporadically. The community was strongly determined by surroundings (trees), which supply snow ecosystems with organic and inorganic matter. Chlorophyll a, particulate phosphorus, total suspended solids and organic debris were strongest predictors of invertebrate distribution. The canopy cover also influenced invertebrate communities, highlighting the importance of the organic deposition from trees and also suggesting that trees may be a source of microscopic invertebrates to the snow. Results demonstrate the importance of SSPs as overlooked ephemeral habitats and can be used as a baseline for future changes in snow communities in temperate regions.