Calcium carbonate application at Puslinch Lake (Cambridge, Ontario) for phosphorus control: Theory versus practice

A summary and history of data collected at Puslinch Lake (near Cambridge, Ontario) are provided. Information pertaining to bacterial densities, phosphorus loading, hydrology, sediment chemistry, macrophytes, fish, plankton and water chemistry are summarized. The lake is a shallow, wind mixed, eutrophic, hard water system suffering from excessive phytoplankton blooms (over 70 ?g/L chlorophyll a) with Cyanophycean genera (Aphanothece, Chroococcus, Lyngbya and Oscillatoria) dominating in summer and fall. Zooplankton densities are relatively low with cyclopoid copepods and non-daphnid cladocerans predominating. Fish populations are poorly developed. Macrophytes can cover extensive portions of the lake with Potamogeton crispus dominating in the spring and Chara dominating during the remainder of the season. Beach closures due to high bacterial counts are common. Residents were surveyed regarding their opinions on lake water quality, recreational opportunities and lake rehabilitation. In September, 1988, 76.4 tonnes of calcium carbonate powder were applied in water slurry form over the surface of the lake in an attempt to precipitate phosphorus and improve water quality. The experiment was unsuccessful in improving water quality. Future rehabilitation of Puslinch Lake should include a program of phosphorus loading controls and partial or complete removal of flocculent, nutrient rich surficial sediments.