SPELEOGENETIC EFFECTS OF MICROBIAL COMMUNITIES IN CARBONATE SYSTEMS

Of all the microorganisms that may inhabit caves, a subset of those present may be actively interacting with the geology and mineralogy of the cave system. Organisms can actively assist in the dissolution of bedrock thus enhancing cavity size. In some cases, microbial activity can contribute significantly to acid speleogenesis. On the deposition side of the geobiological equation, other microorganisms busily facilitate the precipitation of a wide variety of mineral types ranging from carbonates, silicates, iron and manganese minerals, sulfur minerals, and copper minerals. Microbes work with the prevailing geochemistries of the subsurface but they can greatly influence the nature, extent, and pace of processes in caves, particularly of secondary cave mineral deposits. The degree to which microorganisms can contribute to cave formation is still poorly quantified, but fundamental calculations of plausible mass balances for caves can be made using volume of rock removed, assumptions about microbial efficiency, evidence of byproducts of microbial activity like the production of unique cave-derived soils (speleosols) and other indicators including age dates of major speleogenetic epochs as revealed by dating techniques. We present approximations of microbial contribution to the formation of an idealized cave and consider the real cases of Lechuguilla Cave and Carlsbad Cavern in New Mexico, and Cueva de Villa Luz, Tabasco, Mexico.

The biochemistry and geochemistry of microbial communities may differ greatly in caves, but the communities exhibit sets of similar ecological, trophic, and chemical properties in common. This similarity can provide us with a tool to predict the likely effects of geomicrobial activities on caves. Such a predictive capability may help us understand caves on Earth, and may also provide analytical tools in the future to help unravel the geochemistry, hydrology, and geology of such systems on other planets in the Solar System.