Water Clarity, Total Phosphorus and Calcium Results 2018

Eagle Lake water samples have been collected and tested since 1978. In the early years, the Ministry of the Environment ran a “Self Help Program” and volunteers from the Eagle Lake Conservation Association collected water samples that were analyzed for chlorophyll a concentrations (the green photosynthetic pigment in algae–microscopic plants suspended in lakes). This information, along with Secchi disc visibility data, was used to estimate the nutrient enrichment of the lake.

Secchi depths averaged between 4 and 5.5m and chlorophyll concentrations between 2-5 ug/L. Eagle Lake was classified as at ‘level 2’—good water quality with moderate water clarity and low to moderate chlorophyll a concentration.

Starting in 1996, the Ministry of the Environment initiated the ‘Lake Partner Program’ (LPP). Lake association volunteers from across Ontario, including the ELCA, continued to collect water clarity data using the Secchi disc, but water samples were now tested for total phosphorus as this element is a major factor contributing to algae growth. Starting in 2008, water samples were also tested for calcium concentration.

Board member Deb leads water quality testing.

Eagle Lake Water Clarity
The data shows that water transparency has declined over the last 20 years. In 1998, the Secchi disc disappeared at 5m in the north basin and 5.7m in the south basin. In 2018, this depth was 3.0m (north basin) and 3.3m (south basin). According to FOCA, water clarity is impacted by fluctuations in algae, detritus, dissolved organic carbon, and other suspended solids in a lake (eg. tree pollen).

Phosphorus
Increases in phosphorus can decrease water clarity by stimulating algal growth. Average total phosphorus concentration (µg/L) has increased. In 2003, the average TP concentration was 5.5µg/L in the north basin and 4.6µg/L in the south. Last year, the average was 10.2 µg/L (north) and 8.4 µg/L (south).

If we want to stop the further deterioration of the water quality in Eagle Lake, we must decrease the amount of nutrients that enter our lake!

• Fertilizers should not be used as rain and irrigation carry these fertilizers into the water and encourage the growth of algae.
• Pumping out your septic tank on a regular basis is critical to reducing nutrient flows into lakes.
• Use phosphate-free soaps (dishwashing, laundry), shampoos and other cleaning products
• Maintaining a vegetative barrier of native plants on the shoreline to absorb some phosphorous before it can enter the Lake

Calcium
Calcium concentrations have remained fairly consistent since 2008. Results for 2018: 2.1 mg/L (north end) and 1.9 mg/L (south end). However, Ca concentration measurements collected between 1982 and 1993 show there has been a decline from an average of 3.1 mg/L. Calcium is necessary for the development of the outer covering (and survival!) for many organisms (eg. mollusks, clams, crayfish). Daphnia, a type of lake plankton, is an important food source for fish. The reproduction of most Daphnia species is jeopardized at lake calcium concentrations below 1.5 mg/L. Unfortunately, today’s low levels of calcium are a result of past human influence—-acid rain and logging.

Debra Lamb, April 2019