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Blue Green Algae

The public should be aware of the dangers posed by poisonous plants and algae growing in the environment, but especially along riverbanks and in wet grassland or edges of lakes. In warmer weather conditions, there can be a rapid increase in the growth of algal blooms.

You can find out about Blue-Green Algae on the Department for Infrastructure's website

What is Blue-Green Algae?

Blue-green algae are microscopic, plant-like organisms that occur naturally in ponds, rivers, lakes and streams. Normally, blue-green algae are not visible in the water. However during periods of warm and sunny weather with little or no wind there can be a rapid increase in the numbers of algae and this is known as an algal bloom. 

Algal blooms can occur throughout the year but they are most common from May through to September when suitable weather conditions combine with a ready supply of nutrients.

What do algal blooms look like?

Algal blooms are often green, but can be other colours such as yellow-brown or red depending on the species of algae.

The duration of blooms may last for a few days to several weeks until conditions in the lake change and the algae die and decompose.

The behaviour of blooms is unpredictable and their location within a water body can change quickly throughout the day. 

Some, but not all blue-green algae produce toxins which can be released into the water.  

What Should I do about Blue-Green Algae?

  • Avoid all contact with the affected waters and ensure that children and pets are kept away.

  • Report suspected algal bloom to the Northern Ireland Environment Agency (NIEA)

How to I report a suspected algal bloom?

NIEA will investigate reports of algal blooms submitted through the incident hotline or Bloomin’ Algae App to confirm if blue green algae are present. The app will show the locations of confirmed cases. 

NIEA are encouraging everyone to get involved in citizen science and help monitor blooms of blue-green algae to help protect from public health risks and continue to enjoy our local water environment.

The Bloomin’ Algae App enables members of the public to submit a photo of the bloom taken on their phone and state what activity takes place at the location, so that the potential risks to people and animals can be gauged.

The submitted records are verified by trained environmental experts, enabling rapid feedback to the app user to verify if it may be blue-green algae, or something less harmful, and appropriate next steps they should take. Records will be used to alert authorities to provide early warnings of risks to other water users. The App is free to download directly from Google Play or App Store. 

Members of the public can also report suspected bloom through the NIEA incident hotline on 0800 80 70 60 or e-mail with a photo, if possible, and details on the location of the potential bloom.

If Council receive any notifications from NIEA confirming the presence of potentially toxic algal blooms in the Mid Ulster District area, Council can erect advisory signs to warn the public.