Thomas, S. A.. Idaho State University, thomstev@isu.edu
Minshall, G. A.. Idaho State University, minswayn@isu.edu
Newbold, J. D.. Stroud Water Research Center, newbold@stroudcenter.org
Cushing, C. E.. Colorado State University, cecushing@aol.com

 
BENTHIC - WATER COLUMN EXCHANGE OF FINE PARTICULATE ORGANIC MATTER IN LOTIC ECOSYSTEMS
 
Natural particulate organic matter (POM) was labeled with 14-C and released into first, second, and third order Idaho streams. The longitudinal loss of particles from the water column was used to determine mean transport distances and deposition velocities of two size fractions. Very-fine POM (15-52 um) deposited less rapidly than fine POM (53-106 um) but by a magnitude much less than expected by empirical estimates of fall velocity. Greater variation in particle deposition rates occurred within and among streams than between size classes. Variation was most strongly associated with transient storage characteristics. Long term sampling and a two compartment storage model were used to quantify particle residence time within the benthos and resuspension rates. The probability of entering long- vs short-term storage was similar (60% and 40%, respectively) and consistent between size classes. Fine POM turnover rates were 0.14 and 2.89 days for short- and long-term storage. Experimental results were combined with field estimates of transported and benthic POM to derive bulk deposition, resuspension, and transport rates. The resulting particle budgets indicate tight coupling of benthic and water column POM and validate an important assumption used in previous estimates of organic carbon spiraling in streams.
 
Day: Wednesday, Feb. 3
Time: 11:15 - 11:30am
Location: Eldorado Hotel
 
Code: SS03WE1115E