RAPID: Impacts of high magnitude wildfire on volcanic (lava tube) cave water chemistry, nutrient transport, activity and diversity of cave microbiome

University Of Texas At San Antonio, San Antonio TX

Investigators

Abstract

Wildfires of high magnitude are known to cause destruction of surface vegetation, soil sterilization, and alteration of soil chemical and hydraulic properties; whereas their effects on subsurface environments are relatively unknown. Recent Caldwell and Antelope wildfires in northern California burnt over hundreds of acres of landscape which included 97% of the area in Lava Beds National Monument (Lava Beds) that protects volcanic (lava) caves. The volcanic caves provide a unique habitat for bacteria and archaea, and morphologically diverse secondary mineral features (speleothems) in the presence of water. This study investigates the impacts of intense wildfires on volcanic cave ecosystems by sampling cave water and microbial mats, and analyzing them for detailed inorganic and organic chemistry, microbial diversity and activity. This data from fire-affected caves will be compared with pre-fire data from earlier studies, and the control caves from the unburnt areas, to quantify the changes occurred within the caves due to wildfires. This RAPID project supports one minority graduate student at the University of Texas at San Antonio, a leading Hispanic Serving Institution (HSI) and several undergraduate students (Hispanic, minorities, women and first generation). In collaboration with the National Park Service, the findings of this study will help inform protection of the sensitive natural heritage at Lava Beds National Monument, and important scientific findings will be made available to the visitors of the park. Impacts of high magnitude wildfires on surface environments are well documented such as complete destruction of vegetation, soil sterilization, and alteration of physical, chemical and hydraulic soil properties. However, their effects on subsurface environments like vadose zones, shallow aquifers, and caves are relatively understudied. The Caldwell Fire in 2020 and Antelope Fire in 2021 in northern California have affected 97% of Lava Beds National Monument (California, USA) landscape that hosts numerous volcanic (lava) caves. Volcanic (lava) caves are nutrient-poor, aphotic environments, and yet they host a rich diversity of bacteria and archaea which often utilize reduced energy sources (e.g., reduced iron, sulfur, manganese, or nitrogen compounds) available within the host rock and mineral deposits within the caves. Availability of nutrients in caves greatly depends upon the interactions between host rock (basalt) and meteoric water that infiltrates through surface soils into caves through fractured cave walls. This RAPID study will obtain water and microbial samples from volcanic caves in wildfire affected and unaffected areas at Lava Beds, during a post-fire hydrologic response time, and correlate it with chemical and molecular signatures in the samples. Post-fire changes in cave water chemistry will be quantified by measuring concentrations of cations, anions, trace metals, and dissolved organic matter, and comparing with pre-fire data from earlier studies, and from control caves. Analysis of 16S rRNA gene sequencing and ATP will be used to track changes in microbial diversity and activity within the caves during the post-fire period. One graduate student and several undergraduate students from the University of Texas at San Antonio and University of New Mexico will perform samples collection and subsequent laboratory analyses. These results will provide a key information regarding impacts of surface wildfires on subsurface ecosystems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.