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General Information

Algae are naturally occurring aquatic organisms, similar to plants, which contain chlorophyll and produce their own food through photosynthesis. Algae are present naturally in all lakes; however, they are often found at low enough concentrations that they are not noticeable to most people. These organisms form a significant component of the base of the aquatic food chain.

Algae blooms are caused by a number of environmental factors aligning to create ideal growing conditions.  These factors include calm water, warm sunny conditions, shallow warm water and, usually, high nutrient levels (although in some cases this does not seem to be necessary).  Conditions ideal for a bloom usually occur in late summer and early fall; however, due to the effects of climate change this window may be shifting.

Blue-Green Algae

Blue-green algae (scientifically referred to as Cyanobacteria) is actually a type of bacteria that contains chlorophyll.  Blue-green algae may produce a variety of toxins called microsystins, two of which are neurotoxins, and this is why blooms need to be reported and assessed.

A blue-green algae bloom can typically be identified because the water looks bluish-green, like green pea soup, or turquoise paint. When the blooms are very dense, they may form solid-looking clumps. Fresh blooms often smell like newly mowed grass; older blooms may smell like rotting garbage (Ontario Ministry of the Environment and Climate Change website, 2014).

Report a suspected blue-green algae bloom to the Ministry of Environment and Climate Change:

The Ministry of the Environment and Climate Change (MOECC) is responsible for sampling blooms to identify if it is a blue-green algae bloom and if it contains amounts of the toxin microsystins. They share their results with the local health unit who is responsible for determining if there should be a drinking water advisory or not.

How You Can Help

While we cannot control many of these conditions, we can influence one of the factors that affect their growth; that is the nutrients available to them. Property owners living on or near lakes and rivers can help by reducing or eliminating the use of fertilizers heavy with phosphorous, increasing the width and extent of vegetated buffer strips along shorelines and ensuring septic systems are fully functioning.

Algae blooms are a sign that the nutrient levels in the water are higher than normal. By tracking the occurrence of algae blooms it will help us to monitor changes in the health of our waterways.
You can help. If you see an algae bloom on your lake, please document it with our Algae Reporting Tool.