HR: 15:00h
AN: B23C-06    [Abstracts]
TI: Microbial activity and nutrient concentrations from a North American rock glacier: An Antarctic analogue.
AU: * Knauf, M
EM: knauf@colorado.edu
AF: Department of Geography, University of Colorado, Boulder, Co 80309
AU: * Knauf, M
EM: knauf@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th Street, Boulder, Co 80309
AU: Williams, M
EM: markw@snobear.colorado.edu
AF: Department of Geography, University of Colorado, Boulder, Co 80309
AU: Williams, M
EM: markw@snobear.colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th Street, Boulder, Co 80309
AU: Lui, F
EM: fengjing.lui@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th Street, Boulder, Co 80309
AU: Cory, R M
EM: rose.m.cory@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th Street, Boulder, Co 80309
AU: Cory, R M
EM: rose.m.cory@colorado.edu
AF: CVEN, University of Colorado, Boulder, Co 80309
AU: Caine, N
EM: cainen@colorado.edu
AF: Department of Geography, University of Colorado, Boulder, Co 80309
AU: Caine, N
EM: cainen@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th Street, Boulder, Co 80309
AB: Here we provide the first report on microbial activity in a previously un-investigated icy system thought to be devoid of life: rock glaciers. Water draining from the Green Lake 5 rock glacier (RG5) in the Colorado Front Range has been sampled for water chemistry since 1998 as part of the Niwot Ridge LTER program. Maximum nitrate concentrations from the outflow of RG5 of 136 umoles/L are an order of magnitude greater than most alpine streams in the western US. Both lab and field incubations showed that microbial activity on the surface of RG5 was similar to that of well-developed tundra soils. Source waters and flowpaths of RG5 outflow were determined using end-member mixing analysis (EMMA) with isotopic and geochemical tracers. EMMA showed that nitrate flux was conservative with respect to flowpaths. Interestingly, the highest nitrate concentrations in RG outflow were from the baseflow component, which we believe was internal ice melt. DOC concentrations in RG5 outflow were similar to nearby streams at 1-2 mg/L. Fluoresence index values for the DOC increased from about 1.4 early in the season to 1.6 late in the season, suggesting a switch from terrestrial DOC production to aquatic microbial precurser DOC material similar to Anarctic streams. More sophisticated PARAFAC analysis of DOC showed that loadings of aquatic microbial components, which are similar to components found in Antarctic streams, increased by a factor of 2-4 from early to late season. Unexpectedly, nitrate concentrations were found to be significantly correlated with these aquatic microbial components (R2 = 0.70). These results indicate a strong microbial presence within the rock glacier itself, which is similar to aquatic microbial activity and not terrestrial microbial activity. A synoptic sampling of the outflow of 11 additional rock glaciers in the Rocky Mountains of Colorado and Wyoming showed similar results, suggesting that our results may be applicable to many other rock glaciers in the Rocky Mountain region.
DE: 1806 Chemistry of fresh water
DE: 1871 Surface water quality
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting