New Mexico Geological Society Annual Spring Meeting — Abstracts

Volcanic landscapes on Earth are valuable planetary analogs for the moon and Mars, and the lava tubes and other caves associated with these terrains are targets in the search for extraterrestrial life. Volcanic caves provide shelter from harsh surface environments and contain nutrients and energy resources such as iron (Fe) that could support microbial growth. Capulin Volcano National Monument (CAVO) is a well-preserved cinder cone in northeastern New Mexico, with trachybasalt lava flows and volcanic caves. The goal of this project was twofold: to begin to create a cave and microbial inventory for conservation purposes, and to evaluate CAVO as a Mars analog site. We described several small primary and secondary volcanic caves within the Monument, and mapped two primary caves that are likely tumulus or blister features. While we did not find extensive lava tubes within Monument boundaries, there are secondary caves and possibly substantial subsurface habitat within the lava flows. To perform a reconnaissance geobiology survey, we combined culture independent and dependent analyses to describe microbial communities in CAVO caves and evaluate if microorganisms from this site could live on reduced compounds in basalt. High-throughput 16S rRNA gene sequencing from small primary and secondary caves showed that the most abundant taxa on the walls were members of the Actinobacteria and Alphaproteobacteria, and that many samples include abundant phototrophs and some potential iron- and sulfur-oxidizing taxa. Multivariate analyses show that different caves have distinct communities, and that CAVO microbial communities are different from those in well-studied lava tubes. Several isolates were obtained on low nutrient organoheterotrophic media, including strains of Bacillus, Arthrobacter, Pontibacter, Curtobacterium, and Dietzia. Long-term enrichments on olivine showed growth over time, including ammonia oxidizers and nitrate reducers in secondary enrichments, although we did not find evidence that microbes were having an impact on olivine dissolution rates. Ongoing analyses will continue to explore whether microorganisms from these communities can obtain energy from olivine and other Fe-bearing minerals in basalt, and evaluate microbial communities and activity in situ with additional rRNA gene and transcript libraries.