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How do algae affect water quality?

Updated: Aug 5, 2021

Algae on a rock

This looks gross, eh?

What are algae?

Algae are the basis of the aquatic life food chain. Like plants, they produce their own food. Algae contain chlorophyll, which is the substance that makes plants green and allows them to turn sunlight into sugars (photosynthesis).

When algae are living, they produce oxygen and are food for many water-dwelling organisms. But when algae die, decomposing bacteria suck the oxygen out of the water.

Low oxygen levels can harm or kill fish and other aquatic life. As algae blooms increase in size, more and more bacteria are needed to decompose all the dead algae.

In the Lake Winnipeg watershed, the green algal blooms we sometimes see are evidence of eutrophication, which occurs when excess nutrients overfeed a lake or waterbody.

The Eutrophication Cycle

What are excess nutrients?

All living things require nutrients (like phosphorus and nitrogen) to grow, function and live. Nutrients come from many sources, including pets, detergents, fertilizers, and industrial by-products.

Like most things, nutrients are good in moderation, but excess nutrients runoff into our waterways and create a situation where algae take over.

Person submerged in algae water

Why should you care?

Human actions contribute nutrients to our lakes. The detergents and fertilizers we use run off into our waterways, where they act as fertilizer for algae, eventually choking Manitoba’s fish and destroying our beaches.

Algal blooms cause fish to die and cause our beautiful beaches to be unusable. Fishing and beaches are important for Manitoba’s economy, tourism and our environment.

To reduce your nutrient runoff:

  • Use the Right Source of fertilizer at the Right Rate, the Right Time and the Right Place

  • Choose detergents and cleaners that have eco-friendly certification, like Green Seal or EcoLogo

  • Wash your car at a car wash that recycles water and uses nutrient-free washing products

  • Minimize rainwater runoff from your yard. Collect it in rain barrels and use it to water your garden. Do not overwater your lawn and garden

Visit the Lake Friendly website to learn how to do what matters.

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