MECHANISMS, MEASUREMENT AND IMPORTANCE OF SEDIMENT RESUSPENSION IN LAKES

The process of sediment resuspension in lakes influences lake metabolism by causing turbidity and cycling of particulate material. Wind, currents and morphometry of the lake basin are the most important causes of resuspension. So far, episodic resuspension events have been studied, rather than the impact on whole lakes. The bottom shear stress and the cohesion of sediments are the key mechanisms for sediment resuspension. Two zones of resuspension can be distinguished: the littoral zone, where wave action is significant; and the profundal zone, where seiche-induced currents are the most important factor governing resuspension. Repetitive sediment resuspension and redeposition over large areas are common in shallow lakes. Nearshore sediment resuspension, subsequent focusing and redeposition in the profundal zone are the main processes in large, deep lakes. The various methods of measuring sediment resuspension are reviewed, with special emphasis on the sediment trap method and the use of radionuclides.