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Glacier surfaces are the most biologically productive parts of glaciers with a variety of organisms and habitats. However, distinctiveness of habitats and communities of dominant invertebrate consumers on the ice surface is poorly documented. We focused on dominant consumers in three supraglacial (on the glacier surface) habitats on the alpine glacier Forni – cryoconite holes (water-filled reservoirs with a thin layer of sediment at the bottom), supraglacial debris (layer of stones and gravel covering glacier surface), and surface ice of the weathering crust. We analyzed carbon and nitrogen contents and stable isotope ratios (δ13C, δ15N), organic matter (OM) content, biomass of consumers, and the community composition of consumers to investigate differences between supraglacial habitats. In cryoconite holes, tardigrades (Tardigrada) were dominant consumers. In supraglacial debris, only springtails (Collembola) occurred mainly between stones and ice. No active animals were found in the surface ice of the weathering crust. Carbon and nitrogen contents, δ13C, and δ15N of invertebrates and OM differed between habitats. Cryoconite was enriched in OM with high δ13C and low δ15N compared to supraglacial debris likely indicating differences in major components of OM serving as food of invertebrates. Also, the OM, and carbon and nitrogen contents differed between habitats with the highest concentration in cryoconite. The dry biomass of tardigrades was similar compared to springtails. We present the first observation of differences between supraglacial habitats in the Alps based on the community composition of invertebrates, OM and stable isotopes. This initial study highlights the importance of differences in habitats and its consumers in the functioning of supraglacial ecosystem.

Microplastic (MP) contamination is ubiquitous and widespread in terrestrial and aquatic ecosystems, including remote areas. However, information on the presence and distribution of MPs in high-mountain ecosystems, including glaciers, is still limited. The present study aimed at investigating presence, spatial distribution, and patterns of contamination of MPs on three glaciers of the Ortles-Cevedale massif (Central Alps, Northern Italy) with different anthropic pressures, i.e., the Forni, Cedec and Ebenferner-Vedretta Piana glaciers. Samples of supraglacial debris were randomly collected from the glaciers and MPs were isolated. The mean amount (±SE) of MPs measured in debris from Forni, Cedec and Ebenferner-Vedretta Piana glaciers was 0.033 ± 0.007, 0.025 ± 0.009, and 0.265 ± 0.027 MPs g−1 dry weight, respectively. The level and pattern of MP contamination from the Ebenferner-Vedretta Piana glacier were significantly different from those of the other glaciers. No significant spatial gradient in MP distribution along the ablation areas of the glaciers was observed, suggesting that MPs do not accumulate toward the glacier snout. Our results confirmed that local contamination can represent a relevant source of MPs in glacier ecosystems experiencing high anthropic pressure, while long-range transport can be the main source on other glaciers.

Contamination by plastic debris has been documented in most regions of the world, but their occurrence in high mountain areas has not been investigated to date. Here we present the first report of the occurrence and amount of microplastic in any terrestrial glacier environment. In the supraglacial debris of the Forni Glacier (Italian Alps), we observed the occurrence of (mean ± standard error) 74.4 ± 28.3 items kg−1 of sediment (dry weight). This amount is within the range of variability of microplastic contamination observed in marine and coastal sediments in Europe. Most plastic items were made by polyesters, followed by polyamide, polyethylene and polypropylene. We estimated that the whole ablation area of Forni Glacier should host 131–162 million plastic items. Microplastic can be released directly into high elevation areas by human activities in the mountain or be transported by wind to high altitude. The occurrence of microplastic on Forni Glacier may be due to the gathering of debris coming from the large accumulation area into the relatively smaller ablation area of the glacier, as a consequence of its flow and melting.