Effects of wind on a shallow lake ecosystem: Resuspension of particles in the Loosdrecht Lakes

Abstract

Horizontal variation of seston concentration in the shallow, eutrophic Loosdrecht Lakes (A=9.8 km²;$\overline z$=1.9 m) was studied in relation to windspeed and effective fetch. Simple wave theory was applied in order to predict resuspension using wind data from a nearby meteorological station. Most results were consistent with the theory, but a clear limit for the occurrence of resuspension could not be established. Generally, changes in epipelon—the particles at the sediment-water interface — were not directly related to computed frequency of resuspension at the sampling station. The frequency was estimated for 37 grid points over the entire lake. Resuspension was computed to affect high percentages of the lake area in winter. In summer the frequency was much lower, but in June and July 1984 there were days with nearly 50% of the lake area subject to resuspension. The resulting input of particulate organic carbon into the water column during these days was estimated to equal 12–25 times the daytime phytoplankton carbon fixation. Most of the resuspended matter appeared to be redeposited rapidly. The computed frequency of resuspension for the 37 locations of the lake varied between 7 and 48 days in 1984.