Original paper

Phosphorus sedimentation during stratification in two small lakes

Hudson, J.J. Taylor


Sedimentation of phosphorus was measured with sediment traps during spring through fall at 3 depths in 2 small lakes that had initially different fish and zooplankton communities, but were subject to a manipulation of their fish communities. P sedimentation (P area-1 time-1) increased with depth in both lakes and all years, and more than accounted for the decline in total P through the stratified season. Sedimentation measured at the base of the epilimnion was sufficient to remove the epilimnetic total P only every 36 days on average, and sedimentation velocities were very low, about 10 to 15 cm d-1. P sedimentation did not vary significantly between lakes and among years, although it did demonstrate temporal variability. Sedimentation velocity also varied among depths, and was greater in the epilimnion than in the metalimnion. Sedimentation rates were not related to particulate phosphorus concentrations, or to particular size fractions, while sedimentation velocities were only weakly correlated to particle-size distribution. Mass balance calculations suggest that there was substantial input of P to the epilimnion of these small lakes during stratification. This and the resuspension and mineralization of P from the shallow sediments may account for the differences between these results with those for larger lakes and for limnocorrals, respectively.


phosphorussedimentation ratesedimentation velocityplankton size-distribution