Phosphorus partitioning in a shallow lake: implications for water quality management

This paper describes the seasonal partitioning of phosphorus (P) across the sediment–water interface in Loch Leven, Scotland, and discusses the implications for future lake management strategy with respect to recovery from eutrophication. In a 10-month survey, surface water total phosphorus (TP) concentrations were highest in late summer and lowest in early spring. In contrast, sediment TP concentrations were highest in mid-winter and lowest in late summer. Water discharge at the main outflow of the loch was highest when water-column TP was low and sediment TP high, and vice versa. Monthly sediment P uptake/release values showed significant cycling between the water-column and the sediment and showed seasonal variation in four release-sensitive P pools. Regulating the water level to increase flushing during sediment release periods and decrease flushing during uptake periods has the potential to significantly enhance the recovery of shallow lakes and reservoirs following historic nutrient loading.