Tardigrades and rotifers likely play an important role in supraglacial nutrient cycling through grazing and thus shaping the structure of primary producers in cryoconite holes. However, there is a considerable lack of knowledge of their feeding behaviour and, therefore, their significance in the supraglacial ecosystem remains unclear.
A new paper in Biogeosciences lead by PhD student Tereza Novotná Jaroměřská and co-authored by Jakub Žárský presents the first observation of carbon and nitrogen stable isotopic composition of cryoconite top consumers, tardigrades and rotifers. Samples of cryoconite collected in 2016 on three Svalbard glaciers (Ebbabreen, Svenbreen, and Nordenskiöldbreen) were analysed on carbon and nitrogen stable isotopes in cooperation with Jakub Trubač at Charles University’s Stable and Radiogenic Isotope Research Laboratory. The results revealed that rotifers differ from tardigrades in their nitrogen isotopic composition, which points to their different roles in the cryoconite trophic network. The carbon stable isotopic values showed differences in their distribution between taxa as well as between glaciers suggesting that the sources of carbon may differ between glaciers and affect the carbon isotopic composition in cryoconite and its top consumers. Nevertheless, this study did not reveal a mechanistic explanation of the observed variations and so the role of the consumers and their contribution to supraglacial nutrient cycling still awaits to be explored.
Novotná Jaroměřská T, Trubač J, Zawierucha K, Vondrovicová L, Devetter M, Žárský JD (2021) Stable isotopic composition of top consumers in Arctic cryoconite holes: revealing divergent roles in a supraglacial trophic network. Biogeosciences 18:1543–1557 doi:10.5194/bg-18-1543-2021