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Blue Green Algae

Blue Green Algae

To report an algal bloom, please email: or call the Ranger service on 01259 450000

Blue green algae are primative bacteria that occur naturally in inland waters, on the coast and at sea. They have been around for millions of years and are an important part of aquatic ecosystems.

If the water conditions are right, the numbers of blue-green algae can rapidly increase to excessive levels and form visible 'blooms'. This often happens during periods of calm, warm weather.

Blue green algae blooms can vary in appearance depending on which species are present, but common things to look out for are:

  • green, blue-green or greenish-brown cloudy water;
  • clumps of greenish flakes, greenish bundles or brown dots; and
  • foaming on the shoreline.

Why are they a problem?

Some species of blue green algae can produce toxins. When the algae bloom, the toxins can be produced in potentially dangerous quantities. This means that blue-green algae can cause environmental problems, disrupt drinking water supplies, recreational activities, and pose a risk to livestock, wildlife and human health.

While the toxins have the potential to kill animals, in humans the effects tend to be less severe but the toxins can cause skin rashes, eye rashes, vomiting, diarrhoea, fever, and joint and muscle pain if ingested or if they come into contact with skin.

Not all algal blooms or scum are toxic, but since you can't tell just by looking at the bloom, it is safest to assume they are toxic and avoid contact.


The ranger service will put up warning signs when algal blooms are likely, or if they have been seen.

If you see the signs or, if you spot an algal bloom:

  • keep yourself, your children, and pets out of the water;
  • if you do need to go into the water, shower thoroughly once you get home;
  • if you need to seek medical assistance for yourself, children, or pets inform them of the circumstances; and
  • if there are no signs about, please report it to us so we can ensure warning signs are put up.

For Further Information Contact

Countryside Rangers
Kilncraigs, Greenside Street, Alloa, FK10 1EB
Tel: 01259 450000