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Public urged to stay out of water at Portstewart Strand after toxic blue green algae concerns

Red flag on beach

The National Trust has warned the public that bathing is currently unsafe after concerns over the presence of blue green algae potentially detected at both Castlerock and Portstewart Strand.

It comes after the Northern Ireland Environment Agency (NIEA), part of the Department of Agriculture, Environment and Rural Affairs (DAERA) discovered blue green algae blooms in the Lower Bann River. The river mouth of the Bann can be found dividing Castlerock beach and Portstewart Strand.

In a short statement, a spokesperson for the National Trust said:

"Beach has been red-flagged by RNLI - unsafe for bathing due to blue green algae detected.

"DAERA sampling today (Wednesday 6 July) has confirmed potentially toxic blue green algae at Castlerock, with suspected blue green algae noted at Portstewart.

"These are freshwater species and the source is likely to be the River Bann. DAERA Emergency Pollution are aware of the situation.


"Please stay out of the water!"

Blue-green algae (cyanobacteria) is a type of algae that can occur naturally in lakes, ponds, canals, rivers and reservoirs. Unlike other types of algae, if it becomes too abundant it can pose a health risk to people, pets and wild animals who come into contact or ingest it. It can cause skin rashes, eye irritations, vomiting, diarrhoea, fever and muscle and joint pain.

Blue-green algae has also been attributed to the death of dogs, birds, fish and livestock in parts of the UK.

People are advised not to swallow, swim or allow pets in the water. Avoid all contact with the algae.

The algae has been attributed recently as the cause of death for a number of dogs in the area of Rea's Wood, Lough Neagh in Antrim.

Blue green algae app graphic

Swimmers, boaters, dog owners, anglers and anyone else spending time this summer in, or around, fresh water can now record the presence of harmful algal blooms with an app called “Bloomin’ Algae”, developed by the UK Centre for Ecology & Hydrology (UKCEH).

Bloomin’ Algae App helps make reporting of blue-green algae easier and quicker, allowing environmental experts to respond faster and issue public warnings more efficiently.

Bloomin’ Algae App is free to download directly from Google Play or App Store. It enables users to submit a photo of an algae bloom on their mobile device, along with the location and activities taking place in the associated waters.

The submitted records are verified by trained environmental experts, enabling 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.

NIEA fully support the use of the App and working with UKCEH in reporting blue-green algae blooms, and supporting local authorities to provide appropriate warnings to water users.

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


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