Coalition of Haliburton Property Owners' Associations

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Home » Lake Health » Algae & Algal Blooms

Algae & Algal Blooms

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How Can I Identify a Blue-Green Algae Bloom?

There has been a dramatic increase in blue green algae blooms in Ontario in recent years. As a result many lakefront property owners are very concerned when they see blooms or floating masses which they think could be a bloom. To alleviate unnecessary concerns and to share important information The Coalition of Haliburton Property Owners Associations is providing this fact sheet on how to identify blue green algae blooms and what to do if you do suspect one.

What is it? Info from MOECP

  • Blue-green algae are microscopic, plant-like organisms that occur naturally in ponds, rivers, lakes and streams.
  • Although often blue-green, they can also be olive-green or red.

How to recognize it

  • Blue-green algae are not normally visible in the water, but populations can rapidly increase to form a large mass or scum called a bloom when conditions are favourable.
  • Blooms most commonly occur in late summer and early fall. They thrive in areas where the water is shallow, slow moving and warm, but they may be present in deeper, cooler water.
  • Dense blue-green algae blooms may make the water look bluish-green, or like green pea soup or turquoise paint. Very dense blooms may form solid-looking clumps.
  • Fresh blooms often smell like newly mown grass, while older blooms may smell like rotting garbage.

Pic and table below from HKPR

What To Do If You Suspect a Blue Green Algae Bloom

  1. Take pictures
  2. Notify MOECP Spills Action Line at 1-866-663-8477 (line operates 24/7)
  3. Notify your Lake Association so that your Association can let all the members on the lake know
  4. Notify your municipal government
  5. Tell your neighbours
  6. Do Not
    1. Swim in the lake
    2. Let pets or any animals swim or drink from the lake
  7. Do Not allow water from the lake to enter your house/cottage
    1. Most water treatment systems will not safely treat water with a blue green algae bloom
    2. Boiling or chlorinating the water can release toxins into the air
    3. Even UV filters will not safely treat water which contains a blue green algae bloom
  8. Stop using the water and seek medical attention if symptoms such as skin, eye or throat irritation, allergic reactions or breathing difficulties occur while in contact with untreated surface waters.
  9. Do not eat fish caught in the water body.

Where to get more information: