34-4 Newly Formed Lava Cave in Hawai`i Reveals Early Microbial Colonizers That Utilize Nitrogen, Sulfur, and Methane

Session: Geobiology and Astrobiology in Modern and Ancient Environments: From Microbial Interactions to Planetary Exploration

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Abstract:

Wela Makani Cave (Cave of the Hot Winds), also known as Ana Polu (Blue Cave), was discovered by Andreas Pflitsch in May 2018, close to when it was first formed following the Puʻu ʻŌʻō eruption. He could still see the red glow inside the cave and the walls of the entrance area were still around 750 °C, with extremely hot winds emerging from that cave at high velocity from two openings. Pflitsch placed three temperature sensors at the entrance to measure the temperature to the outflowing air and documented the temperature falling to 254 °C in September 2018, and then 133 °C in April 2019. Peter Bosted and colleagues mapped the new cave in November 2022 and documented it to be 818 m in length. The cave was approximately five years old when we entered it in 2023 to conduct microbiological and climate surveys. Samples of potential microbial deposits on the walls and ceiling included a blue-green biofilm, an orange-red slime layer, a yellow-cream coating, and a white biofilm on the floor. DNA was extracted from the samples and sequenced with an Earth Microbiome primer.  The major bacterial players were Nitrospira, Gemmatimonas, Aridibacter, Methanomassiliicoccus, and Sulfuriferula. These five bacteria have different roles in the nitrogen, methane, and sulfur cycles. Nitrospira is a nitrogen oxidizer that often partners with Archaea in the nitrogen cycle. Gemmatimonas and Aridibacter are reducers of N₂O and NO₃^- respectively. The Methanomassiliicoccus are known to be methanogens, and Sulfuriferula oxidize sulfur. The four samples varied considerably in what bacteria dominated in each. For example, the blue-green samples were dominated by the Paraflavisolibacter, Aridibacter, Sulfuriferula, and Methanomassiliicoccus. Acquiring samples soon after a lava cave forms provides critical information about what organisms colonize early on, what their energy sources likely are, and how they modify their environment. Resampling these sites will provide critical information about how microbial communities change over time in lava caves.

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