Abstract
Diverse microbes have been revealed to live in glaciers worldwide, but only a few biological studies were dedicated to glaciers in tropical Africa. These glaciers are shrinking rapidly and are expected to disappear shortly. In this study, we carried out biological and glaciological field observations on Stanley Glacier, the largest remaining glacier in the Rwenzori Mountains, Uganda, Africa. Microbial aggregates ranging from micrometer to centimeter in size were found on the glacier surface and contained moss and various types of Chlorophyta, among which a new endemic species of green alga. Concentrations of total impurities on the glacier surface, including microbial aggregates, varied spatially and decreased as altitude increased. The large microbial aggregates (larger than 4 cm in diameter) were found only at the glacier surface near the terminus and side margins, where the surface was less frequently covered with snow. It is also shown that the total organic matter on the glacier surface is determined by the timing of snow cover, which affects the quantity of solar radiation reaching the glacier ice surface. Furthermore, the total impurity content was negatively correlated with surface reflectivity, revealing their potential role in albedo reduction at the glacier surface through positive feedback between enhanced meltwater and increased biological growth.
Highlights
Glaciers and ice sheets are biological habitats hosting various forms of life (Boetius et al, 2015)
Our measurements of total impurity concentration at the surface of Stanley Glacier point to exceptionally high organic content compared to other regions of the world
An inverse relationship was found between the surface reflectivity and the total impurity content
Summary
Glaciers and ice sheets are biological habitats hosting various forms of life (Boetius et al, 2015). Submillimeter to millimeter-sized biological aggregates known as “cryoconite granules” have similar effects, thereby reducing surface reflectivity (Cook et al, 2015). These granules are bound together through an extracellular polymeric substance produced by filamentous cyanobacteria (Langford et al, 2010; Uetake et al, 2019), forming a layered structure of microorganisms with complex biofilm (Smith et al, 2016; Takeuchi et al, 2010). The large-scale effect of these granules on water cycling in the Arctic has been reported (Musilova et al, 2016)
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