COLUMN: Treating algae blooms is a balancing act

In last week’s sweltering heat, many of us turned on our air conditioners and fans, visited cooling centers or went swimming.

Like humans, many fish in the Nottawasaga River watershed prefer cooler temperatures below 22 C. As the water temperature rises, the fish will seek cooler areas with shade or a cold water source such as a underground water source, to stay away from the heat.

Unfortunately, there are other organisms that live in the river and thrive in the heat, such as algae. Algae are important to life in our rivers because they are a food source for many insects and small animals. However, too much algae can have devastating effects on the river and human health.

For algae to thrive, three components must be present: sunlight, heat, and nutrients such as phosphorus. Areas without shade or cold water sources and with excess nutrients can create the perfect conditions for algae to grow rapidly, causing algal blooms.

Not only can algal blooms be awful to look at; some species of algae, such as blue-green algae, can cause serious harm to people and pets. Also known as cyanobacteria, blue-green algae occur naturally in many of our favorite swimming areas, such as lakes, ponds, rivers and streams. Swimming in blue-green algae can cause itching, irritated eyes and skin, and swallowing it can cause headache, fever, diarrhea, abdominal pain, nausea and vomiting.

Local public health units regularly test selected beaches for blue-green algae, Escherichia coli (E. coli) and other factors that are not safe for humans. It’s always a bummer when trips are canceled because the water isn’t safe for swimming, but a canceled trip is better than a trip to the hospital.

There are many opportunities to reduce the sunlight, heat and nutrients that contribute to algal blooms. For more than 60 years, the Nottawasaga Valley Conservation Authority (NVCA) has monitored our rivers and streams and identified several “hot spots” where algal blooms can occur and devised ways to reduce their impact.

For example, ponds move relatively slowly, and when exposed to the sun, the water is an effective heat trap. By removing ponds that are connected to rivers and streams, we can greatly reduce the temperature of the water downstream.

Leaving trees, shrubs and other types of vegetation along rivers and streams provides shade to the river. These trees and shrubs also absorb a lot of nutrients that would otherwise flow into the river and feed the algae.

NVCA provides funding and technical support to landowners who want to restore and improve water quality and wildlife habitat on their land. These include community tree planting events, manure storage projects and planting vegetation along rivers and streams.

NVCA also works with many partners and landowners to stabilize riverbanks to reduce the amount of phosphorus entering rivers.

For more information on landowner grants and restoration projects, visit the NVCA website at nvca.on.ca.

Information on blue-green algae can be found on the Government of Ontario website.

Contact your local health authority for more information about beach water testing.

Maria Leung is the Senior Communications Specialist at the Nottawasaga Valley Conservation Authority.