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

已知高强度的野火会造成地表植被的破坏、土壤的杀菌和土壤化学和水力特性的改变；而它们对地下环境的影响则相对未知。最近加利福尼亚北部的考德威尔和羚羊野火烧毁了数百英亩的土地，其中包括97%的熔岩床国家纪念碑（熔岩床），保护火山（熔岩）洞穴。火山洞穴为细菌和古细菌提供了一个独特的栖息地，并且在存在水的情况下，形成了形态多样的次生矿物特征（洞穴）。本文通过对火山洞穴水和微生物垫的采样，研究了强烈野火对火山洞穴生态系统的影响，并对其进行了详细的无机和有机化学、微生物多样性和活性分析。这些来自受火灾影响的洞穴的数据将与早期研究的火灾前数据以及来自未燃烧地区的对照洞穴的数据进行比较，以量化由于野火而在洞穴内发生的变化。该RAPID项目支持德克萨斯大学圣安东尼奥分校的一名少数族裔研究生、一家领先的西班牙裔服务机构（HSI）和几名本科生（西班牙裔、少数族裔、女性和第一代）。在与国家公园管理局的合作下，这项研究的结果将有助于为保护熔岩床国家纪念碑的敏感自然遗产提供信息，重要的科学发现将向公园的游客提供。高强度野火对地表环境的影响有充分的文献记载，如植被的完全破坏、土壤的灭菌以及土壤物理、化学和水力性质的改变。然而，它们对地下环境的影响，如渗透带、浅层含水层和洞穴的研究相对较少。2020年的考德威尔大火和2021年加州北部的羚羊大火影响了97%的熔岩床国家纪念碑（美国加利福尼亚州）景观，那里有许多火山（熔岩）洞穴。火山（熔岩）洞穴是营养贫乏、无光的环境，但它们却拥有丰富多样的细菌和古细菌，这些细菌和古细菌经常利用宿主岩石和洞穴内矿床中可用的减少的能量来源（例如，减少的铁、硫、锰或氮化合物）。洞穴中营养物质的可用性在很大程度上取决于寄主岩石（玄武岩）和大气水之间的相互作用，大气水通过表层土壤通过破碎的洞穴壁渗透到洞穴中。这项RAPID研究将在火灾后的水文响应时间内，从熔岩床受野火影响和未受影响地区的火山洞穴中获取水和微生物样本，并将其与样品中的化学和分子特征相关联。火灾后洞穴水化学的变化将通过测量阳离子、阴离子、微量金属和溶解有机物的浓度来量化，并与早期研究和对照洞穴的火灾前数据进行比较。16S rRNA基因测序和ATP分析将用于追踪火灾后洞穴内微生物多样性和活性的变化。来自德克萨斯大学圣安东尼奥分校和新墨西哥大学的一名研究生和几名本科生将进行样本收集和随后的实验室分析。这些结果将为地表野火对地下生态系统的影响提供关键信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.