Beutel, M. W. U.C. Berkeley, beutel@socrates.berkeley.edu
Horne, A. W. U.C. Berkeley, horne@ce.berkeley.edu

 
BENCH SCALE TESTING OF THE EFFECTS OF OXYGENATION ON RESERVOIR SEDIMENT NUTRIENT RELEASE RATES
 
Undisturbed superficial sediment cores were collected from a number of California reservoirs to examine the effects of proposed hypolimnetic oxygenation on nutrient release rates from pelagic sediments. Undisturbed sediment was initially collected using an eckman dredge. A sediment core (10 cm diameter, 5 cm deep) was then subsampled in a specially designed chamber (on display at poster presentation). Cores were incubated at in situ conditions with 1 L of bottom water overlaying sediments. Water was monitored for ammonia, nitrate and soluble reactive phosphate (SRP). In Upper San Leandro Reservoir, California, (A = 2.4 km2, Zavg = 15 m, Zmax = 40 m), a eutrophic drinking water reservoir with a history of taste and odor problems, SRP release rates ranged from 2 to 10 mg P m-2 d-1 in anoxic chambers. Aerated chambers showed no SRP release. Ammonia release rates ranged from 3 to 6 mg N m-2 d-1 in anoxic chambers and -2 to 10 mg N m-2 d-1 in aerated chambers. Data from ongoing studies on sediment collected from Lake Tahoe (A = 500 km2, Zavg = 248 m, Zmax = 501 m) will also presented. While still ultra-oligotrophic, researchers have documented a slow but steady decline in bottom water dissolved oxygen. Results from the Tahoe cores should show the dramatic effects that unmitigated declines in bottom water oxygen levels could ultimately have on the lake's trophic status.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: CS63TH0662S