Water Quality Research

Trout Lake boasts clear, clean, cold water. As such it is relatively unproductive and is classified as an oligotrophic lake. Typically these kinds of lakes boast many species within their waters, but not very many individuals of each species. This is in contrast to warm water lakes (usually referred to as eutrophic lakes) which have fewer species, and often incredible numbers of individuals of these few species.

Water quality is directly tied to productivity, which itself is a reflection of the amount of microscopic plant life in a given volume of water. In the summer, marsh water turns green . . . an indication of the tremendous concentration of microscopic plant life. This we associate with poor water quality. It turns out that in most lakes, in our area at least, the chemical element "phosphorus" is in short supply and is readily absorbed by the microscopic plants. Once it is all gone, the plants can no longer thrive and their concentrations reach an equilibrium value. These systems are referred to as phosphorus limited systems.

Thus, a measure of the total phosphorus in the water provides a good indication of the expected water quality. A reading of less than ten micrograms of total phosphorus per litre of water, gives the lake an "excellent water quality" classification. The Trout Lake Conservation Association, in conjunction with the Ontario Ministry of Environment and Energy, Ecole Secondaire Algonquin, and the City of North Bay, operates a water quality monitoring program on TroutLake.

Some of the data gathered to date is presented in graphical format. From the total phosphorus graph (open water summer sampling program) you can see that all the basins in Trout Lake still enjoy excellent water quality as all the curves lie well below 10 micrograms per litre. The main concern is the long term trend in phosphorus concentration. Is the lake accumulated disturbance, as caused by ongoing development in the watershed, increasing this phosphorus concentration and, hence, deteriorating the water quality?

Lake phosphorus - sampling dilemna

Above are two data sets that represent two different sampling methods to determine the phosphorus content of Trout Lake. On the left is the phosphorus concentration calculated as the average of weekly samples taken during the summer of each year. On the right is the phosphorus concentration as measured by a single sample taken each year in the spring, soon after ice-out. The Ontario Ministry of the Environment models suggest that the spring sampling is all that you require to characterize the lake's water quality because it is thought that maximum phosphorus concentrations are to found in early spring (technically referred to as spring turnover). The summer data set, which involves much more sampling, should improve the precision of the same measurement. Unfortunately, in Trout Lake, this is not happening. The two methodologies are producing contradictory trends.

Statistical analysis of the data shows that, for the summer sampling method, there is an increase in phosphorus over the years that is statistically significant. No such trend is evident in the spring sampling data. Why? Scientific evidence suggests that in Trout Lake, phosphorus concentrations do not peak early in May but rather peak sometime in late June. Consequently, for Trout Lake, sampling in the early spring is not coinciding with peak phosphorus concentrations. This points to the spring data set being less useful for planning lake development in Trout Lake.

Water transparency

Another measure of water quality is the clarity or water transparency. This is measured using a black and white disk called a "secchi" disk which is lowered into the water until it just disappears. Twice this depth is called the euphotic zone - the zone in which plant photosynthesis is thought to occur. Secchi depths greater than 5 m give the lake an "excellent water clarity" rating - not to be confused with water quality (see above).

From the graph you can see that Four Mile Bay is running the risk of losing its excellent water clarity rating. We encourage you to download the Trout Lake Status Report for a more comprehensive look at water quality issues as they pertain to ecosystem interactions and development priorities.