HR: 1330h
AN: NB33N-01    [Abstracts]
TI: Alpine Lake Phytoplankton Responses to the 2002 Drought in Colorado
AU: * Flanagan, C M
EM: colleen.flanagan@colorado.edu
AF: University of Colorado at Boulder, Institute of Arctic and Alpine Research (INSTAAR) 1560 30th St., 450 UCB, Boulder, CO 80309
AB: Because the hydrologic regime of alpine catchments is dominated by snow melt, their terrestrial and aquatic ecosystems are extremely sensitive to physical and climatic fluctuations in the amount of snow and timing of snowmelt. The drought of 2002 in Colorado was the most extreme drought of the past 100 years of record for the state. Measured at the outflow of Green Lake 4, an alpine lake in Green Lake Valley, located within the Niwot Ridge Long Term Ecological Research (LTER) site in the Front Range of Colorado, the 2002 drought resulted in snowmelt discharge that was just 60% of recent historical averages for stream discharge. We examined how the drought affected the phytoplankton population in this alpine lake. Algal biomass was quantified and samples for community composition analysis were collected during the summers of 2000, 2001 and 2002. The results of the statistical comparison indicate a significant increase in total density of algal cells, possibly caused by drought-induced factors such as earlier ice-out and hence higher irradiance, higher hydraulic residence time and lower wash-outs, plus higher surface water temperatures. Species in three divisions, Bacillariophyta, Chlorophyta and Cyanophyta, showed significant responses. A principal components analysis confirmed a shift in the community composition during the drought. Although based on only three seasons of monitoring data, these results may foreshadow climate change and implicate subsequent biological effects in high altitude watersheds.
DE: 1812 Drought
DE: 1845 Limnology
DE: 1851 Plant ecology
DE: 1860 Runoff and streamflow
DE: 4855 Plankton
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly