New Mexico Geological Society Annual Spring Meeting — Abstracts

Bacterial mats cover walls and ceilings of lava tubes around the world, yet little is known about what controls their species diversity. To address this issue, I and others in my lab group, are asking the following questions: 1) Does diversity vary with respect to the different ages and elemental composition of lava flows in which the lava tubes occur? 2) What is the amount of organic carbon and nitrogen present in the drip water entering the cave system that can fuel heterotrophic microbial growth? To address these questions, rock and water samples were collected from three lava tubes in El Malpais National Monument (ELMA) in New Mexico and from six lava tubes on the Big Island of Hawai’i. Dissolved organic carbon, total nitrogen, and ammonia were measured in infiltrating water. Carbon, nitrogen, phosphorus, manganese, sulfur, iron and other minor elements were analyzed from volcanic rock samples from each lava tube. These data are shedding light on how geological/geochemical parameters influence the diversity of the bacterial communities, which is poorly understood. Examining the different geologic constraints found at each site in New Mexico and Hawai’i will provide a better understanding of the effects these parameters have on bacterial communities found within lava tubes. In a general trend, the composition of the Hawaiian lava cave basalt shows significantly more of the following elements: calcium, magnesium, lead, phosphorus and zinc. Other elements such as cobalt, copper, iron, manganese and sulfur have similar values between Hawaiian and New Mexican lava caves. These results will help to elucidate the role of geology in shaping diversity within caves and the interplay between biology and geology.