How to prevent algal blooms at your lake

Published: May 10, 2018

algal-blooms-in-lake Photo by C N Elliott/Shutterstock

An oxygen-starved area of almost 165,000 square kilometres in the Gulf of Oman is now the world’s largest marine “dead zone.” Incapable of supporting life, dead zones can occur naturally in deep water but are becoming more common in coastal waters because of algal blooms that use up the water’s oxygen when they die and decompose. Algal blooms, meanwhile, are increasing as agricultural runoff, containing chemical fertilizers like phosphorus, contaminates water sources.

Algal blooms aren’t just an ocean problem. At one point in the 1960s, Lake Erie was thought to be dying because of extensive blooms, which led to 1972’s Great Lakes Water Quality Agreement between the U.S. and Canada. And while phosphorus levels dropped in Lake Erie and the other Great Lakes in the 1980s, rising lake temperatures caused by climate change mean algae growth is now a problem in the Great Lakes once again.

Dead zones aren’t the only problem with algal blooms. Some species of algae are toxic to animals and humans, affecting fish and bird populations as well as making swimming and fishing dangerous. Cyanobacteria, which is called blue-green algae but is actually a photosynthesizing bacteria, can contaminate water supplies and cause headaches, fever, nausea, vomiting and, in serious cases, severe liver damage.

Algae doesn’t necessarily mean poor water quality, but it can be a problem. So what’s the key to reducing algae on your lake? The most effective thing to do is reduce the number of algae-feeding nutrients, especially phosphorus, that make it into the water. Here are some tips to keep your lake in tip-top shape.

Be careful with fertilizer

Sure, you want a nice green lawn and healthy plants — but that fertilizer you spread in your garden also encourages algae to bloom. It’s best to avoid fertilizer altogether if you’re close to a water source — plant native plants instead, which are well-adapted to the environment and don’t require special maintenance. If you must fertilize, try and find a phosphorus-free product, and reduce run-off by applying it when there’s no rain in the forecast.

And don’t think natural fertilizer like manure or compost is any better than a chemical version, anything that’s going to make your garden plants grow is going to make algae grow as well.It’s best to avoid fertilizers generally.

Check your septic system

Just as manure encourages algae to grow, so does human sewage. (Plus, gross.) A leaky septic system can easily contaminate water sources, so make sure you keep your septic tank well maintained and be on the lookout for cracks and fissures.

It also goes without saying that you shouldn’t, ahem, go number 2 anywhere close to a water source, and don’t allow your pets to poop close to the water either. Even if you didn’t run the risk of making people sick, you don’t want to give algae any extra nutrients.

Don’t use a garburator

Compost is great for gardens — which means it’s great for algae, too. Garburators, or in-sink garbage disposals, deposit food waste into the water system, which can lead to “nutrient loading” into lakes through water treatment plants. Land composting is a much better option for kitchen waste.

Combat shoreline erosion

An eroded shoreline, meaning few plants or trees, means more run-off from the land into your lake. Make sure your shoreline is planted with native species to help keep its integrity intact and run-off out of the lake, and don’t cut down vegetation that’s already there.

Don’t lather up near water sources

Even if you’re using biodegradable or organic soap, it’s best to keep it far from water sources. Use a bucket or other container for your wash water, then bury your rinse water so bacteria in the soil can break down any contaminants. It sounds like a pain, but it’s better than washing in slimy, smelly algae.

Be careful with your detergents

Canada banned phosphates in household cleaning products in 2010, but if you’re using an old bottle of dish detergent, you could still be dumping algae-feeding nutrients into your lake. Make sure you’re using phosphate-free cleaners and soaps.

Minimize impervious surfaces close to the water where possible

The goal in preventing nutrient-rich runoff from making it into lakes and other water sources is making sure it’s absorbed by the earth, which is a lot harder to do if you’ve paved right up to the edge of your shoreline. Ideally, you’ll have a nice, natural shoreline, complete with plenty of native plants, around your lake to make sure run-off stays on land.

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