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Is this Algae Bloom Dangerous?

written by
Jake Britton


Harmful Algal Blooms (HABs), also known as blue-green algae or cyanobacteria, are a very serious issue impacting the safety of our waterways.  Exposure to HABs can be life-threatening for people and pets. However, the toxicity of an algal bloom cannot be confirmed with a visual inspection. Suspected HABs must be sampled and tested at a lab to confirm the species of algae present. Once the species is confirmed, a management plan can be implemented.

A lakeshore free of algae and HABs.

The late summer months often come with an increase in algal blooms in our waterways. Although not all algae are toxic, we must be mindful and diligent about limiting our exposure to algal blooms.

What does Harmful Algae look like?

According to the Illinois EPA, harmful algal blooms can look like blue or green paint spilled into the water, thick puffy blue or green foam on the surface of the water, or swirling colors beneath the surface of the water. Harmful algal blooms can also have distinct smells, and have been described as grassy, fishy, or septic.

A dock area contaminated with HABs.

What should I do if I suspect the presence of Harmful Algae?

Here are four things to do – or not do! – if you see anything that looks like blue-green algae in a water source:

  1. Call a pro immediately: It is impossible to tell from a visual inspection whether an algal bloom is toxic. It must be appropriately sampled and tested. Aquatic services companies like Clarke can help with this.
  2. Avoid it: Do not swim or wade through blue-green algal scums. Do not boat, water ski, jet ski, or fish where algal scum is present. And certainly, don’t source drinking water where algal blooms are present!
  3. Keep pets out: Do not let your pets swim in or drink from the water. Toxic algae blooms can be fatal to pets. Even short exposures to some HABs can be fatal.
  4. Take extra precautions: If you or your family members, including pets, have been in water with any algae present, always shower off with soap and clean water after swimming.

Learn more about waterbody management:

Want to speak to someone on the Aquatics team about our experience with managing Harmful Algal Blooms? Contact us here.