Summary Hot springs integrate hydrologic and geologic processes that vary over short‐ and long‐term time scales. However, the influence of temporal hydrologic and geologic change on hot spring biodiversity is unknown. Here, we coordinated near‐weekly, cross‐seasonal (~140 days) geochemical and microbial community analyses of three widely studied hot springs with local precipitation data in Yellowstone National Park. One spring...

Summary Hydrogen (H 2 ) is enriched in hot springs and can support microbial primary production. Using a series of geochemical proxies, a model to describe variable H 2 concentrations in Yellowstone National Park (YNP) hot springs is presented. Interaction between water and crustal iron minerals yields H 2 that partition into the vapour phase during decompressional boiling of ascending hydrothermal fluids. Variable vapour inpu...