Evidence for Geomicrobiological Interactions in Guadalupe Caves

The caves of the Guadalupe Mountains are located in southeastern New Mexico, U.S.A., near the city of Carlsbad (Fig. 1). Over 300 known caves exist in these mountains, the most famous being Carlsbad Cavern and Lechuguilla Cave. These caves are filled with secondary mineral deposits (speleothems), which have been described and classified by Hill (1987) and Hill & Forti (1997). Microorganisms have been found in association with carbonate and silicate speleothems, sulfur compounds, iron and manganese oxides, and saltpeter (Northup et al. 1997). As in surface environments, cave microorganisms participate in precipitation of minerals either passively by acting as nucleation sites (Went 1969), or actively through the production of enzymes or substances that lead to precipitation by changing the microenvironment (Danielli & Edington 1983). Microorganisms can also cause the dissolution of cave features through acidic metabolic by-products. While geomicrobiological interaction studies in the outside world are rather common (Ehrlich 1996), such studies in caves are just beginning. Studies of geomicrobiological interactions in caves can shed light on basic mechanisms of dissolution and precipitation by microorganisms, and, thus on the origin of specific types of speleothems. Guadalupe Mountain caves contain a number of examples of possible interactions between microorganisms and speleothems. In particular, Lechuguilla and Cottonwood caves contain speleothems that have been referred to as “biothems” by Cunningham et al. (1995)–features such as webulites and uloops that appear to be calcified filamentous microorganisms. The discovery of “snottites” in Cueva de Villa Luz (Hose & Pisarowicz 1999; Hose et al. 2000), a cave with active hydrogen sulfide vents, allows researchers to speculate that such EVIDENCE FOR GEOMICROBIOLOGICAL INTERACTIONS IN GUADALUPE CAVES