Lava caves, tubes, and fumaroles in Hawai‘i present a range of volcanic, oligotrophic environments from different lava flows and host unexpectedly high levels of bacterial diversity (see Prescott et al. 2022 in Frontiers). Lava caves and tubes, geological features in some volcanic landscapes, form when the surface of flowing molten lava cools, crust over, and the molten lava beneath continues to flow, leaving tube-like structures or pockets behind that to form caves. Lava caves are common in the US state of Hawai‘i and the Região Autónoma dos Açores (Autonomous Region of the Azores), Portugal, both areas with active volcanoes where the MISA lab does research. They are also structures on the Moon and Mars that we believe are lava tubes or caves. Study of the microbial communities in volcanic environments on Earth are potentially helpful to understand how life may have existed in caves on Mars in the ancient past, or possibly even today. In addition, lava caves and the volcanic environment in Hawai‘i have important cultural value that must be included and honored in study of them, and can help teach and understand different world views about biodiversity and the origins of life. Understanding how life survives in volcanic ecosystems helps us understand the interactions among Earth’s geologic, chemical, and biological history.
Fumaroles (terrestrial steam vent) produce volcanic gasses like CO2 and sulfur dioxide near the caldera of Kīlauea, on the Island of Hawai‘i, and are another feature of volcanic environments where microbial growth can be abundant.
Participants in the European Astrobiology Institute’s workshop on “Volcanism, Plate Tectonics, Hydrothermal Vents and Life” begin a lava cave walk with experts in October 2023, Terceira, Açores, Portugal.
Microbial community growing on the wall of a cave in the Açores creating different geologic features.
A purple and green biofilm grows on the wall of a geothermal cave near the caldera of Kīlauea, on the Island of Hawai‘i. The biofilm (surface attached microbial community encased in mucus) is predominantly Cyanobacteria and Chloroflexota, both bacterial phyla that have ancient representatives and metabolisms of microbes that might have lived early in Earth’s history. The purple color is likely from Gloeobacter kilaueensis, a genus of Cyanobacteria that is the sister group to all other cyanobacteria (See Saw et al. 2013: https://doi.org/10.1371/journal.pone.0076376).
A blue-green copper mineral is precipitated on a lava cave wall in Hawai‘i. Microbe-mineral interactions in volcanic ecosystems are not well studied, but many minerals and nutrients are formed through microbial metabolic activity.
Dr. Diana Northup in a lava cave in the Hawaiian Islands taking measurements. Roots from trees above hang down from the ceiling.
