2010 results are not yet available.  In 2009 the phosphorus reading for Dickey Lake was 4.5 and for Lake of Islands the reading was 5.6.  Both lakes were in the mid range of the oligotrophic category.

Phosphorus is an essential nutrient that is supplied to the aquatic systems from natural sources such as rainfall and overland runoff, as well as human resources.  Unlike most aquatic pollutants, phosphorus is not toxic to aquatic life.  High levels of phosphorus however, can set off a chain of events that can have serious repercussions on the aesthetics of recreational waters and the health of coldwater fisheries.

For Ontario’s inland lakes on the Precambrian Shield, trophic (nutrient) status is determined by the level of phosphorus in the water.  (Oligotrophic less than 10, Mesotropic between 10 & 20, Eutrophic more than 20).

Lakes do have a finite capacity for nutrient assimilation, beyond which water quality is impaired.  Excessive phosphorus loadings to a lake promote the growth of algae. The proliferation of algae reduces water clarity, which lessens a lake’s aesthetic appeal.  More serious effects may occur after the algae die and settle to the bottom.  When this takes place, bacteria levels increase to decompose the algae and collectively their respiration consumes more oxygen in the water column.  This means a loss of the cold, well oxygenated habitat that is critical to the survival of coldwater species such as lake trout.  The ultimate outcome can be extirpation (local extinction) of the species.

The main sources of phosphorus to many of Ontario’s recreational inland lakes are sewage systems from houses and cottages. Clearing the shoreline of native vegitation, use of fertilizers, storm water runoff and increased soil erosion also can contribute significant amounts of phosphorus to a lake.