In last week’s sweltering heat, many of us turned on our air conditioning and fans, visited cooling centres or went for a swim.
Like humans, many fish in the Nottawasaga River watershed prefer cooler temperatures less than 22 degrees Celsius. As water temperatures rise, the fish will seek out cooler areas with shade or a cold-water source, such as a groundwater spring, to stay out of the heat.
Unfortunately, there are other organisms that live in the river that thrive in the heat, like algae. Algae are important to life in our rivers as they are a food source for many insects and small animals. However, too much algae can have devastating impacts to the river and on human health.
For algae to thrive, there must be three components: sunlight, heat and nutrients such as phosphorus. Areas without shade or cold-water sources, and with excess nutrients, can create the perfect conditions for rapid algae growth, causing algae blooms.
Not only can algae blooms be gross to look at; some algae species, such as blue-green algae, can cause serious harm to humans and pets. Also known as cyanobacteria, blue-green algae occur naturally in many of our favourite swimming areas such as lakes, ponds, rivers and streams. Swimming in blue-green algae can cause itchy, irritated eyes and skin, and swallowing it can cause headache, fever, diarrhea, abdominal pain, nausea and vomiting.
Local public health units regularly test select beaches for blue-green algae, Escherichia coli (E. coli) and other factors that are not safe for humans. It’s always a disappointment when trips are cancelled because the water is not safe for swimming, but a cancelled trip is better than a trip to the hospital.
There are many opportunities to reduce the sunlight, heat and nutrients that contribute to algae blooms. For more than 60 years, the Nottawasaga Valley Conservation Authority (NVCA) has monitored our rivers and streams and has determined some ‘hotspots’ where algae blooms can occur, and devised ways to reduce their impact.
For example, ponds are relatively slow moving, 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.
The NVCA provides funding and technical support to landowners looking to restore and enhance water quality and wildlife habitats on their land. These include community tree-planting events, manure storage projects and planting vegetation along rivers and streams.
The NVCA also works with many partners and landowners to stabilize stream banks to reduce the amount of phosphorus that goes into the rivers.
For more information about landowner grants and restoration projects, visit the NVCA’s website at nvca.on.ca.
Information about blue-green algae can be found on the Government of Ontario’s website.
Contact your local health unit for more information about beach water testing.
Maria Leung is the senior communications specialist at the Nottawasaga Valley Conservation Authority.
