RT Journal Article
SR Electronic
T1 Rolling stones gather moss: Movement and longevity of moss balls on an Alaskan glacier
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 687665
DO 10.1101/687665
A1 Scott Hotaling
A1 Timothy C. Bartholomaus
A1 Sophie L. Gilbert
YR 2019
UL http://biorxiv.org/content/early/2019/07/02/687665.abstract
AB Glaciers support diverse ecosystems that are largely comprised of microbial life. However, at larger, macroscopic scales, glacier moss balls (sometimes called “glacier mice”) develop from impurities in the ice and represent a relatively rare biological phenomenon. These ovoid-shaped conglomerations of dirt and moss are only found on some glacier surfaces and provide key habitats for invertebrate colonization. Yet, despite their development and presence being widely reported, no targeted studies of their movement and longevity have been conducted. This knowledge gap is particularly important when considering the degree to which glacier moss balls may represent viable, long-term biotic habitats on glaciers, perhaps complete with their own ecological succession dynamics. Here, we describe the movement and longevity of glacier moss balls on the Root Glacier in southcentral Alaska, USA. We show that glacier moss balls move an average of 2.5 cm per day in herd-like fashion, and their movements are positively correlated with glacier ablation. Surprisingly, the dominant moss ball movement direction does not align with the prevailing wind nor downslope directions; instead, we propose that it depends on the dominant direction of solar radiation. We also show that glacier moss balls are relatively long-lived, with a lifespan in excess of 6 years and annual survival rates similar to large vertebrates. Finally, we observed moss ball formation on the Root Glacier to occur within a narrow, low albedo stripe downwind of a nunatuk, a potential key source of moss spores and/or fine-grained sediment that interact to promote their formation.