Physical, chemical, and biological characteristics of supraglacial pools on a debris-covered glacier in Mt. Gongga, Tibetan Plateau

Meltwater habitats are found on glacier surfaces worldwide, but much of the current understanding of these habitats comes from clean glaciers sprinkled with cryoconite. Cryoconite is windblown dust particles covered with biological material that form small meltwater holes due to difference in the albedo of cryoconite compared to clean ice. However, no information is available on the physical, chemical, and biological characteristics of supraglacial pools on debris-covered glaciers. We measured physical and chemical variables and sampled macroinvertebrates from forty-six supraglacial pools during the summers of 2018 and 2019 on the debris-covered Hailuogou Glacier in southeastern Tibet. Our physical and chemical results indicated that the sampled supraglacial pools exhibited a greater diversity of shapes, were larger, contained larger substrate sizes, and had greater substrate diversity than cryoconite holes. The sampled supraglacial pools frequently contained Chironomidae (Diptera) and Isotomidae (Collembola), which are macroinvertebrate taxa that are uncommon in cryoconite holes. Chironomidae occurrence and abundance was not correlated with any measured environmental variable. The best predictors of Isotomidae and macroinvertebrate occurrence and abundance were conductivity, ice to water surface depth, and number of supraglacial pools within 5 m. Our results highlight the uniqueness of supraglacial pools on a debris-covered glacier in southeastern Tibet.