Algal bloom

During the warmer months lakes, rivers and coastal bays can be affected by blooms of algae. Most of these blooms are harmless even if we can see them, but some can be toxic.

Blooms may develop rapidly. When they decompose they may cause a bad smell and affect other lifeforms in the water. Some blooms can be harmful to humans and animals, such as dogs, especially when they break down.

It is best to avoid contact with the water if:

  • it looks discoloured
  • has an unusual smell
  • has green or brown particles suspended in it, or
  • if you can see unusual scum or leathery mats of algae on the surface or on the bottom of the waterway

If you feel unwell as a result of contact with algal bloom, you should contact your doctor, or call Healthline on 0800 611 116.

Last updated 19.12.2023

For health advice call Healthline for free anytime on 0800 611 116
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