μThis study of phosphorus (P) cycling in eutrophic Upper Klamath Lake (UKL), Oregon, was conducted by the U.S. Geological Survey in cooperation with the U.S. Bureau of Reclamation. Lakebed sediments from the upper 30 centimeters (cm) of cores collected from 26 sites were characterized. Cores were sampled at 0.5, 1.5, 2.5, 3.5, 4.5, 10, 15, 20, 25, and 30 cm. Prior to freezing, water content and sediment pH were determined. After being freeze-dried, all samples were separated into greater than 63-micron (μm) particle-size (coarse) and less than 63-μm particle-size (fine) fractions. In the surface samples (0.5 to 4.5 cm below the sediment water interface), approximately three-fourths of the particles were larger than 63-μm. The ratios [...]