Physical ecology of hypolithic communities in the central Namib Desert: The role of fog, rain, rock habitat, and light

Hypolithic microbial communities thrive in desert environments, but their ecology remains poorly understood. This study reveals that fog plays a pivotal role in sustaining these communities in the Namib Sand Sea. Fog effectively replaces rainfall in the western zone, enabling high hypolithic abundance (≥95%) at landscape scales and promoting colonization of smaller rock size classes (mean 6.3 ± 1.2 cm) compared to hyperarid deserts. Despite rainfall events supplying more liquid water than fog, fog provides nearly twice as much annual moisture to hypolithic zones. Hypolithic abundance reaches 100% at a mean annual precipitation (MAP) of approximately 40–60 mm, but this threshold drops significantly (to ~25 mm) when fog is present. The study also identifies light as a limiting factor for colonization on unexposed rock surfaces, with hypolithic growth occurring at just 0.1% of incident sunlight.

Warren‐Rhodes, K. A., McKay, C. P., Boyle, L. N., Wing, M. R., Kiekebusch, E. M., Cowan, D. A., Stomeo, F., Pointing, S. B., Kaseke, K. F., Eckardt, F., Henschel, J. R., Anisfeld, A., Seely, M., & Rhodes, K. L. (2013). Physical ecology of hypolithic communities in the central Namib Desert: The role of fog, rain, rock habitat, and light. Journal of Geophysical Research: Biogeosciences, 118(4), 1451–1460. Portico. https://doi.org/10.1002/jgrg.20117