Pervasive speleogenetic modification of cave passages by nitrification of biogenic ammonia

Research in Gunung Mulu National Park, Sarawak, reveals a previously undocumented process of cave passage modification driven by microbial nitrification of biogenic ammonia. This study demonstrates that ammonia gas released from bat and swiftlet guano is oxidized on moist cave surfaces, producing aggressive nitric acid solutions that accelerate limestone dissolution. The resulting geomorphological features overwrite original passage morphologies, challenging traditional interpretations of speleogenesis in tropical environments. Geomorphological and geochemical evidence suggests this biogenic overprint is more widespread than previously recognized, with profound implications for understanding post-speleogenetic modification and secondary cave enlargement.

Farrant, A. R., Koether, J. M., Barton, H. A., Lauritzen, S.-E., Pennos, C., Smith, A. C., White, J., McLeod, A., & Eavis, A. J. (2025). Pervasive speleogenetic modification of cave passages by nitrification of biogenic ammonia. Geomorphology, 483, 109822. https://doi.org/10.1016/j.geomorph.2025.109822