Cooper, M. R.. Eastern Washington University, mcooper2@ewu.edu
Barlow, G. R.. Eastern Washington University,
Black, A. R.. Eastern Washington University, rblack@ewu.edu

 
USING ENCLOSURES TO ESTIMATE PLANKTONIC SECONDARY PRODUCTIVITY IN LAKE ROOSEVELT OF THE COLUMBIA RIVER
 
We used 9700 liter, in-situ enclosures to make weekly estimates of planktonic secondary production in the Lake Roosevelt reservoir of the Columbia River. The enclosures allowed repeated, short-term observations of closed plankton populations in an environment that did not differ from the epilimnetic conditions of the lake. Additionally, the enclosures ensured advection effects did not complicate demographic observations. Four 200 m mesh enclosures were placed at each of three study sites representing upper, middle, and lower portions of the reservoir. The enclosures were supported by a plastic frame and suspended from a dock anchored at each study site. Weekly production estimates were conducted by filling each enclosure with Lake Roosevelt zooplankton at ambient densities, allowing the plankton to acclimate for 24-48 hours, then collecting an initial sample, followed by a final sample (96 hours later). Change in biomass was calculated per each species of crustacean zooplankton for each 96 hour production period. Additionally, birth, death, and population growth rates were calculated for the branchiopod zooplankton present during each production period. Productivity and demographic estimates from the enclosure samples were compared to productivity and demographic estimates calculated from samples collected from the lake proper during the study period.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: SS51TH1513S