Resuspension in regulating sedimentation dynamics in Lake Vesijarvi

The role of resuspension in sedimentation dynamics and internal phosphorus (P) loading was investigated in the Enonselka basin of Lake Vesijarvi, sout hern Finland. The gross sedimentation rate was measured at three sampling s ites, where sedimentation traps were placed 2 m above the bottom (the depth of 28 m, 18 m and 7 m) and at the two deepest sites also in the metalimnio n (11 m depth). The total settling flux did not follow either the phytoplan kton biomass development in the lake or the bacterial mineralization rate i n the settled material. The gross sedimentation rate was much higher in the hypolimnion than in the metalimnion, indicating that resuspension increase d the settling flux. This conclusion is supported by the fact that when the gross sedimentation rate increased, the C and N concentrations of settled material resembled those of bottom sediment. The proportion of resuspended material, estimated by three different methods, averaged 56-99% of the gros s sedimentation rate during the study periods. Contrary to the common assum ption, the Enonselka basin provides an example of successful restoration by biomanipulation in lakes with high resuspension.