Public health warning after possible blue-green algae spotted in Innisfil

Blue-green algae in this undated file image.

Blue-green algae spotted in several local lakes, including Lake Simcoe.

The Simcoe Muskoka District Health Unit says there is a blue-green algae bloom under investigation that is impacting Innisfil's southwest shoreline of Lake Simcoe and the southeast shoreline of Kempenfelt Bay between the Big Bay Point government dock and Maple Street in Innisfil.

Blue-green algae are microscopic organisms that are naturally present in lakes and streams. They are usually present in low numbers but can rapidly increase when the water is warm, slow moving and full of nutrients such as nitrogen and phosphorous. When this happens, they can form dense blooms, and some blooms can produce toxins.

How to spot a potential blue-green algae bloom:

Blooms are also present in Three Mile Lake, Bass Lake, Bonnie Lake and Lake Muskoka.

The health unit says people cannot tell if a bloom is harmful just by looking at it, so it's best to use caution and stay out of the water, as well as keep pets out of the water.

Symptoms and illness

Several types of blue-green algae are not harmful to human health, but some can produce toxins. Large amounts of these toxins, also called cyanotoxins, can be harmful.

People exposed to cyanotoxins by swallowing contaminated water may experience the following symptoms depending on the cyanotoxin involved:

People exposed to toxins through swimming or breathing in droplets of contaminated water may experience irritation to the:

Check out the Simcoe Muskoka District Health Unit's website for more information on blue-green algae.