The significance of recent glacial history for the limno-terrestrial microfauna in Trygghamna (Svalbard, High Arctic)

The diversity and spatial distribution of microscopic invertebrates in the Arctic have yet to be studied in detail. Knowledge of this is especially important in the context of glacier shrinking, one of the most visible environmental consequences of climate change. To understand how time since deglaciation shapes the communities of limno-terrestrial microfauna, we analysed samples of moss collected during the summer of 2021 in forefields of Trygghamna (Svalbard), where glaciers thought to have started to recede at the beginning of the twentieth century. We estimated the taxonomic and trophic composition and abundance of all microfauna groups (with a specific focus on little-known bdelloid rotifers) in two areas, which correspond to the different stages of the glacial retreat. The impact of 14 other environmental parameters (distance from the sea, moisture, moss structural complexity, soil nutrient, and isotopic composition) was considered. Thirty-seven microfauna taxa were found, wherein Dorylaimida nematodes (Dorylaimida, Nematoda) dominated both in frequency (present at all sites) and abundance (50 ± 21% from all individuals). Less prevalent bdelloid rotifers (Bdelloidea, Rotifera) were followed by tardigrades (Tardigrada), which, in contrast to others, were more abundant in the later deglaciated area. In general, environmental parameters explained 81.8% of the microfauna distribution. Time since deglaciation was the most significant factor (9.5%). Among the variables that act at a fine scale, the most important were moisture in the habitat (6%), presence of ground in the samples (4%), and δ 15 N (4%). The moss structural complexity did not have a significant effect, and neither did most of the variables characterising soil nutrient and isotopic composition. However, some variability was observed for different lower taxa.