2008 Grant Recipients

Meghan A. Rector ($1500)
Ph.D. Student
Department of Evolution, Ecology, and Organismal Biology
The Ohio State University

Living in an Extreme Environment: Effects on Web Properties and Species Interactions in the Cave Spider Meta ovalis (Tetragnathidae, Araneae)

Abstract - Cave ecosystems are often underrepresented in scientific research. Cave systems are a particularly harsh environment for most organisms since there is little light, low food availability, high relative humidity, and constant cold temperatures. These ecological stressors are increased within caves in comparison to surface environments, often resulting in behaviors and traits that are quite different than those of related surface species. Pigment loss and decreased metabolism are widely recognized as adaptive characteristics in cave-dwelling organisms. However, there are other traits that are less apparent. In the proposed project using the cave orb-weaver Meta ovalis, web architecture and silk material properties will be examined as potential adaptations to subterranean life. Preliminary investigations suggest that the spiders are utilizing silk with unique material properties, especially in response of fibers to relative humidity. Their silk behavior contrasts with that of all other known spiders, a possible adaptation to their subterranean lifestyle. This project investigates a new and unexplored adaptation to cave dwelling with implications for comparative silk biomechanics and conservation efforts of these habitats.

Amy Renee Smith ($1500)
M.S. Student
Department of Biology
Portland State University

Mineral Weathering of Lava Tubes: Iron-Oxidizing Bacteria and the Search for Life on Mars

Abstract - Iron oxidizers in cave environments are assumed to play an important role in mineral precipitation and the evolution of cave features, yet the underlying processes of microbial mineral weathering are poorly understood. Iron oxidizers may have the ability to accelerate the natural weathering of volcanic rocks due to their ability to alter the chemistry and solubility of iron-containing minerals. Furthermore, iron oxidizers may produce changes in the internal crystalline environment that are dissimilar to natural abiotic weathering patterns, which can be detected microscopically. Biogenic weathering features may represent trace fossils (or biosignatures) that are applicable to the search for life on Mars and the study of life on early Earth. Various weathering features such as etched pits, tunnels, microchannels, and galleries have been described in volcanic rocks of ancient and modern origin, although it is unknown whether certain features such as microchannels are indeed biogenic. Therefo re, I propose to study the weathering patterns of isolated iron oxidizers that are produced on olivine crystals in the laboratory. Although cryophilic iron oxidizers have not yet been described, I am particularly interested in isolating this type of microorganism from lava tubes with permanent ice deposits. Ice-bearing lava tubes may host cryophilic iron-oxidizing communities that would be excellent analogs for life on Mars.

Mark Tracy ($1000)
M.S. Student
Department of Geography and Geology
Western Kentucky University

Impact of in-Cave Carbon Sources on the Evolution of the South Central Kentucky Karst Aquifer

Abstract - Previous observations done by Anthony (1998) and Vaughan (1998) propose that a significant source of carbon dioxide may exist within interstitial fluids in sediment beneath active cave streams. The purpose of this research is to better understand the distribution of organic carbon in cave streams sediment, the degree that these form a source of CO2, and the overall degree to which this may influence karst aquifer evolution. This will be achieved by systematic geochemical analyses of interstitial fluids in cave stream sediments in different karst environments across the south central Kentucky karst aquifer. Special attention will be paid to the relationship between soil CO2, levels and CO2, levels within the interstitial fluids during the transition from the warmer summer months to the cooler winter months. If an in-cave source of CO2, truly exists that is independent of soil CO2, then in-cave CO2, levels should remain relatively constant during the transition in seasons while soil CO2, level should be high in the summer and low in the winter. This research will be an important step in better understanding carbon dynamics and aquifer evolution in warm, humid karst environments like those found throughout south central Kentucky and many parts of the world.

Jack Wood ($3000)
M.S. Student
Department of Earth and Environmental Sciences
University of Illinois at Chicago

New Evidence for Speleogenesis ca. 50 to 18 ka from Porter Cave, Central Indiana: Potential Glacial Hydrologic and Dynamic Controls

Abstract- Questions remain on the role of hydrologic changes during Quaternary interglacial and glacial cycles on speleogenesis in mid-continent North America. There is limited evidence for direct glacial influence on karst development and speleogenesis, and if speleogenesis continues in ice proximal karst regions. The Northern Mitchell Plain, a karst plateau in central Indiana was subjected to glaciation during the Quaternary and hosted proglacial lakes. This study seeks to provide insight on hydrologic and glacier dynamic controls on karst development for the past 50 ka in central Indiana. Glaciallacustrine sedimentary sequences within Porter Cave and in the adjacent watershed indicate at least two significant rises in hydrologic base level at ca. 40 and 27 ka. Preliminary data suggests speleogenesis in the northern Mitchell Plain appears to be retarded during glacials, with higher and unstable base levels timed with the development of proglacial lake systems. Recent field studies support the hypo thesis that the glacial conditions destabilize baselevel and inhibit speleogenesis. Large and rapid changes in baselevel and discharge resulting from ice-marginal oscillations, such as deglaciation, are associated with enhanced speleogenesis. Lake highstand outlets during the last deglaciation intersect karst conduits to form hanging springs. Subsequently, nick-point migration at the waterfalls is the principle mechanism for lowering of the cave floor since the last deglaciation. Millennial-scale resolution from proglacial lake sediments from recently identified cave and surface sections provides new data to further assess the role of the interglacial/glacial cycle on speleogenesis and cave development.