Extreme weather event results in the removal of invertebrates from cryoconite holes on an Arctic valley glacier (Longyearbreen, Svalbard)

Abstract

The question why aquatic communities are often absent in suitable pools still remains a topic of debate and is often explained by dispersal limitation or biological barriers. Cryoconite holes (water‐filled depressions on glaciers) as natural, simple and dynamic habitats in a glacial biome seem to be a good model for addressing this question. The main aim of our research was to investigate links between changes in weather conditions and short temporal changes in invertebrate densities on glaciers. For this study, we selected cryoconite holes on the valley Longyear Glacier and collected samples at two‐day intervals from the same holes in August 2016. During the sampling campaigns, we detected freezing, shrinking and ablation of cryoconite holes. In the samples, we found only two groups of invertebrates, Tardigrada and Rotifera. We observed invertebrates in cryoconite holes until calm weather patterns were interrupted by wind and rainstorm, after which no individuals were detected. Before the storm event, densities in the samples reached up to 149 tardigrades/cm3 and 119 rotifers/cm3 of cryoconite. In addition, we found a strong erosion of cryoconite granules, redistribution into sediments (mud‐like forms), and the migration of granules after rain, which confirmed the mechanical removal of invertebrates by streaming water. Water depth, pH or electrical conductivity did not seem to shape invertebrates communities. Their frequency and densities on valley glaciers depend on stochastic events, for example, weather breakdown (rainstorms). Furthermore, such events may form new niches for tardigrades and rotifers on polar glaciers and influence their coexistence within cryoconite holes.

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

“…Apart from cryoconite holes, tardigrades were highly abundant in wet supraglacial debris mixed with cryoconite material. A high concentration of cryoconite granules in supraglacial debris is probably connected mostly with the collapsing of cryoconite holes and the redistribution of material on ice surface (Zawierucha et al 2019b). In supraglacial debris, we found many small, most probably newly born tardigrades, which suggests that, as long as the supraglacial debris is wet, it forms a suitable habitat for tardigrades.…”

“…In a supraglacial zone, passive dispersal of tardigrades is less problematic. They are most probably transported by streams and melting water as was shown for tardigrades in the Arctic (Zawierucha et al 2019b) and in the Alps (Dastych et al 2003).…”

“…These specific reservoirs constitute glacial biodiversity hot spots and bioreactors responsible for organic matter production and also 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 2018aZawierucha et al , 2019a. Cryoconite holes are one of the most extreme freshwater ecosystems on Earth characterised by permanently low temperatures, frequent disturbance due to rain and flushing of melting water and periodic freezing (Mueller et al 2001;Zawierucha et al 2019b). However, despite harsh conditions, the diversity of biota is relatively high, and trophic relations form simple, truncated webs, where invertebrates function as apex consumers (Hodson et al 2008;Zawierucha et al 2018aZawierucha et al , 2019a.…”

“…Their species richness in extreme glacial habitats is known to be low in comparison with that of tundra or high mountain invertebrate communities, potentially as a consequence of a strong selection pressure of the cryosphere (e.g. Zawierucha et al 2016Zawierucha et al , 2019b.…”

A nematode in the mist: Scottnema lindsayae is the only soil metazoan in remote Antarctic deserts, at greater densities with altitude

“…Local climatic regimes of the environment (e.g., rainfall, humidity, temperature) seem to be responsible for the development and maintenance of invertebrates at a small scale (e.g., Andrew et al 2003;Guil et al 2009;Chown & Klok 2013;Convey et al 2014;Zawierucha et al 2019). However, the most important factors influencing densities of Antarctic soil fauna in deserts seems to be related to the soil geochemistry, and the differences at the meso-scale between the Bartrum Basin and Diamond Hill mirror this effect.…”