Paper No. 6
Presentation Time: 9:20 AM

MICROBIAL MN(II) OXIDATION AS AN INDICATOR OF ANTHROPOGENIC IMPACT IN CAVES: A CASE STUDY IN CARTER SALT PETER CAVE, CARTER COUNTY, TN


CARMICHAEL, Sarah K.1, CARMICHAEL, Mary Jane2, JOHNSON, Krissy W.3, ROBLE, Leigh Anne4, STROM, Amanda C.3, SANTELLI, Cara5 and BRAUER, Suzanna L.3, (1)Geology, Appalachian State University, 572 Rivers St, Boone, NC 28608, (2)Biology, Wake Forest University, Winston-Salem, NC 27109, (3)Biology, Appalachian State University, ASU P.O. Box 32027, Boone, NC 28608, (4)Geology, University of Maryland, College Park, MD 20742, (5)National Museum of Natural History, Smithsonian Institute, Washington D.C, 20560, carmichaelsk@appstate.edu

Anthropogenic impact and eutrophication is a pervasive problem Carter Salt Peter Cave (CSPC) in Carter County, Tennessee, a heavily visited epigenetic cave in the southern Appalachians. Although it is difficult to visually assess changes in microbial diversity in response to eutrophication or other disturbances directly in the field, changes in function among Mn and Fe oxidizing microbial communities are easily seen as a significant alteration in the abundance of metal oxide produced.

CSPC exhibits Mn(III/IV) oxide formation in biofilms associated with several groundwater seeps as well as on cave litter. Culturing and molecular data indicates that Mn(III/IV) oxide production in groundwater seeps is primarily associated with Mn(II) oxidizing bacteria, but culturing results reveal that Mn(III/IV) oxide production (predominantly poorly crystalline buserite, birnessite, or todorokite) on cave litter is also associated with Mn(II) oxidizing fungi. In 2008, one of the Mn oxide-rich seeps bloomed in a massive Mn(II) oxidizing biofilm, anecdotally related to a release of sewage in a nearby sinkhole. Molecular methods (16S rRNA) confirmed the presence of Bacteroides-Prevotella human fecal indicators in this seep, and most probable number (MPN) assays and ion chromatography of the associated seep water confirmed nutrient loading at the site. Phylogenetic analysis from clone sequences suggested a strong initial human-specific fecal signature (50% of the sequences clustering with human feces sequences) in July 2009, and a weaker human signature (20% clustering) by July 2011. From 2009-2011, the seep exhibited a dramatic visual reduction in Mn(IV) oxide production, which was hypothesized to correlate with a decrease in nutrient input. MPN analyses suggested that Mn(II) oxidation at the seep was correlated with heterotrophic activity (most likely due to reactive oxygen species production), in this case due to point source exogenous nutrient loading.

Preliminary phylogenetic analysis (using SSU, LSU, and ITS rRNA) to identify Mn(II) oxidizing fungi associated with cave litter revealed the presence of Plectosphaerellaceae sp. DCIF (growing on battery), and two Genus incertae sedis (Fungal sp. YECT1, and Fungal sp. YECT 3, growing on electrical tape) that are are not closely related to any known Mn oxidizing species.