SPATIAL VARIABILITY IN SEDIMENT COMPOSITION AND EVIDENCE FOR RESUSPENSION IN A LARGE, DEEP LAKE

Spatial variability in the composition of sediments in Pyramid Lake, N evada, was assessed in June 1992 by collecting surficial samples at 32 sites. For those sites, organic fractions were highest in the centre of the lake and low near the single inflow to the system. The spatial patterns for organic C, N, and P in lake sediments indicated that smal l organic-rich particles are preferentially deposited in the centre of the lake. This sorting of particles by water depth was supported by a corresponding decrease in the particle size distribution of sediments with station depth and by limited sediment-trap data. Further, a comp arison of sediment-trap particle flux rates with the net sediment accu mulation rate for the centre of the lake based on Pb-210 decay indicat ed that the resuspension of bottom sediments in Pyramid Lake (z(max.) = 102 m) must occur throughout the lake.