HR: 1330h
AN: NB33R-06    [Abstracts]
TI: Lake Disruptions on Sediment Mobility and Effects on Benthic Chlorophyll
AU: * Myers, A K
EM: andrewkmyers@hotmail.com
AF: Aquatic, Watershed and Earth Resources and Ecology Center, Utah State University, Logan, UT 84322 United States
AU: Marcarelli, A M
EM: amym@cc.usu.edu
AF: Aquatic, Watershed and Earth Resources and Ecology Center, Utah State University, Logan, UT 84322 United States
AU: Arp, C D
EM: carp@biology.usu.edu
AF: Biology and Ecology Center, Utah State University, Logan, UT 84322 United States
AU: Wurtsbaugh, W
EM: wurts@cc.usu.edu
AF: Aquatic, Watershed and Earth Resources and Ecology Center, Utah State University, Logan, UT 84322 United States
AU: Baker, M A
EM: mbaker@biology.usu.edu
AF: Biology and Ecology Center, Utah State University, Logan, UT 84322 United States
AB: Watershed structure can have a profound effect on physical, chemical, and biological characteristics of streams. We investigated stream reaches above and below lakes in three watersheds that varied in the size and numbers of lakes in the Sawtooth Mountains to address how lakes affect sediment mobility and how this in turn affects algal biomass. During base flow, we gathered physical data such as pebble counts, stream geometry, and gradient to calculate sediment mobility. Chlorophyll a was measured as the biological response variable. We found that excess shear stress in lake outflows was <1, while excess shear stress was >1 in inflows, indicating that inflow sediments were mobile. Chlorophyll a concentrations were at least 10X greater at outflow sites compared to inflow sites. At one watershed where chlorophyll a was measured at a variety of sites on rocks of median sediment size (D50), there was a positive correlation between D50 and algal biomass (R² =0.31, p=0.02). Other experiments indicated that lower chlorophyll a at inflow sites was due to increased bed mobility and not due to abrasion by bedload. Together, these results support the hypothesis that sediment trapping by lakes leads to increased substrate stability, and in turn allows increased periphyton growth.
DE: 0400 Biogeosciences
DE: 1824 Geomorphology (1625)
DE: 9810 New fields (not classifiable under other headings)
DE: 9901 NABS Student Award - Basic Research
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly