Distribution of parasitic chytrids of glacier algae in Alaska; Cryoconite holes as a hotspot of chytrid infection

Glacier algae, which are photosynthetic microbes growing on ice, considerably reduce the surface albedo of glaciers and accelerate their melting rate. The growth of glacier algae can be suppressed by parasitic chytrids, yet their impacts on algal population are still largely unknown. In this study, we described the morphology of chytrid infecting glacier alga, Ancylonema nordenskioldii, and quantified their prevalence of infection in different habitats on a mountain glacier in Alaska. Microscopic observation revealed three different morphological types of chytrids with distinct rhizoid shapes. The size of the sporangia varied probably because of the different stages of their growth, indicating that they actively propagated on the glacier. The prevalence of infection did not vary among sites with different elevations but was significantly higher in cryoconite holes (20 %) than on ice surface (4%) at all sites. This indicates that cryoconite holes are hot spots for chytrid infection of glacier algae, and the dynamics of cryoconite holes might affect the host–parasite interactions between chytrids and glacier algae, which may in turn alter surface albedo and ice melting.