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Communication at the NABS Annual meeting, Keystone, 2000
(256) NUTRIENT LIMITATION EXPERIMENTS IN SUBALPINE LAKES OF THE LOCH VALE
WATERSHED,
ROCKY MOUNTAIN NATIONAL PARK.
K. Nydick1, B. Moraska2, J. Baron1,3, and B.M. Johnson2. 1Natural Resource Ecology Laboratory, Colorado State University, 2Department of Fishery & Wildlife Biology, Colorado State University, 3U.S. Geological Survey
In order to understand how nutrients limit phytoplankton growth in high
elevation lakes that are influenced by atmospheric nitrogen deposition, we
conducted monitoring and nutrient experiments in 3 subalpine lakes located
within 2 km of each other. We monitored dissolved inorganic nitrogen (DIN)
and phytoplankton biomass (as chlorophyll a) weekly during the ice-free
season and conducted in situ nutrient bioassay experiments 3 times during
this period. Previous researchers found that nitrogen limitation is common
in Colorado Front Range lakes and that nutrient limitation status can
fluctuate throughout the season. We hypothesized that N limitation would
occur only in late summer when DIN concentrations reached their minimum.
Our experiments revealed that N alone never limited phytoplankton growth,
although co-limitation by N and P occurred 50% of the time. The largest
lake was P limited, the smallest lake progressed from N&P co-limitation to
P limitation, and the intermediate lake was either N&P co-limited or showed
no nutrient limitations. Future increases in N deposition are not likely
to increase phytoplankton biomass without commensurate enhancement of P
loading.
Presented at 9:00 AM on Thursday, June 1, 2000 in Factors Affecting Algal and Macrophyte Growth I
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