Q and A: What’s the deal with algae blooms?

Photo of an algal bloom on a lagoon in North Carolina.

Algae blooms often look like ‘scum’ on the surface of the water. Photo credit: Ildar Sagdejev

Every year, we receive a lot of questions about the huge ‘blooms’ of algae that suddenly pop up on Alberta’s lakes – and it’s easy to understand the confusion. Sudden advisories can make it seem like affected lakes have been invaded by foreign creatures – but that’s actually not the case at all.

 Blue-green algae are naturally occurring in Alberta’s lakes – but they normally pop up in manageable quantities. When the population of blue-green algae in the water explodes – what we call an algal bloom – risk levels can rise for both humans and animals. When this happens, the government of Alberta’s water and beach monitoring programs kick in.

Why are algal blooms dangerous?

 Many types of blue-green algae produce substances that irritate the skin; some produce toxins that can make people and pets sick or fatally ill when swallowed. In small amounts, these substances are pretty harmless – but during blooms, they are present in much higher concentrations and pose a much greater risk.

Why do blooms only happen at certain times or in certain places?

 Blue-green algae can grow and reproduce extremely quickly. When conditions are ideal – meaning warm water temperatures, good water quality, and high phosphorous and nutrient levels – algae populations can explode, leading to blooms.

What makes blooms go away?

 Lakes are dynamic environments, where climate, nutrient, and water quality are constantly changing. When conditions become less favourable, blooms can stop growing and eventually disappear.

Can we do anything to get rid of blooms once they appear or minimize the risk they’ll occur?

Nutrient levels play a big role in determining rates of algae growth, and these nutrients come from lots of sources – including fertilizer, wastewater, and other products of human activity. Avoiding the use of fertilizer and keeping private sewer systems in good working order helps keep blooms from growing.

Photo of a dog swimming through a blue-green algae bloom

Toxins produced by blue-green algae blooms can harm animals as well as people – keep pets out of the water. Photo credit: Ildar Sagdejev

What’s the impact of algal blooms on animals? 

Toxins produced by blue-green algae can harm animals as well as humans. Until the advisory is lifted, pets should not swim in or drink affected water, and Albertans may want to limit consumption of fish caught in these waters.

I see a ‘scum’ on the surface of a lake – how do I know if it’s an algal bloom?

 Blue-green algae often look like scum floating on the surface of a lake. The algae might look blue, green, or brown, and may produce a musty earth or grassy odor. But sight and smell won’t necessarily tell you if algae is dangerous. The bottom line: treat all blooms with caution, check advisories often, and stay informed – better safe than sorry.

 What should I do if I see a bloom that hasn’t been reported yet?

Contact your regional health advisory – they can investigate whether the bloom is dangerous and issue an appropriate advisory.

2 thoughts on “Q and A: What’s the deal with algae blooms?

    • Hi Terry,

      Everyone has a role to play when it comes to reducing blue algae. While algae does occur naturally in Alberta, nutrient levels play a big role in determining rates of algae growth, and these nutrients come from lots of different sources – including fertilizer, wastewater, and other products of human activity. Avoiding the use of fertilizer and keeping private sewer systems in good working order helps keep blooms from growing. Thanks for the question.

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