|
|
 |
|
|
| |
Communication at the NABS Annual meeting, Keystone, 2000
(255) ENHANCED GROWTH OF BENTHIC DIATOMS IN AN ALPINE LAKE IN RESPONSE TO INCREASED ATMOSPHERIC NITROGEN DEPOSITION.
D.M. McKnight, S. Waters, and A. Wolfe. Institute of Alpine and Arctic Research, University of Colorado, Boulder, Colorado, USA 80303
The Green Lakes Valley in the Colorado Front Range is an important water supply for Boulder, CO and has been a protected watershed since the 1950’s. Nonetheless, the water quality in the valley has been influenced by increased nitrogen in atmospheric deposition associated with increased agriculture and population near the Front Range in recent decades. We determined the changes in diatoms in a sediment core taken from the deepest portion of Green Lake 4, one of the uppermost of the alpine lakes in the valley which has undergone no physical modifications. We found a significant shift in diatom species which began around 1949, with benthic diatoms of the genus Fragilaria increasing from about 25-30% of the total diatoms to about 60% of the total. There was a concomitant shift in the species of planktonic diatoms. We studied the seasonal changes in phytoplankton during 1998-1999 and found rapid changes in species distribution during the summer. PCA analysis showed that the diatom assemblages in the deeper sediments, prior to 1949, are much more similar to the diatom assemblage currently in the plankton than the diatom assemblages in the more recent sediments, which are dominated by benthic species.
Presented at 8:45 AM on Thursday, June 1, 2000 in Factors Affecting Algal and Macrophyte Growth I
|
|
|
|
|
|
|
