Blue-Green Algae
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Blue-green algal blooms have been recorded at a number of locations in rivers, lakes and coastlines this year. DAERA continue to respond to reports of blue-green algae within Northern Ireland waters and have put in place some emergency planning measures to deal with the situation. Impacts have primarily been seen in Lough Neagh and the Lower Bann but other sites have also been impacted including north coast bathing waters and the Fermanagh lakes.
The occurrence of blue green algae can impact recreational water users and fisheries (both Commercial and pleasure). Food Standards Agency (FSA) confirmed it is safe to eat fish from Lough Neagh if it is properly gutted and the fillets are rinsed with clean water to remove any contamination from the gutting process. The guidance from FSA can be found in their news article FSA confirms fish caught from Lough Neagh is safe to eat.
Click here for all Blue-Green Algae News Stories
Monitoring, assessment and emergency pollution response activities are being carried out and an urgent review of existing policies has been commissioned. Meetings have been held with the Department for Infrastructure, Public Health Agency, Food Standards Agency, Councils and AFBI to discuss current trends and to ascertain whether more can be done to address these.
The underpinning drivers of the increase in blue-green algae blooms include the excess nutrients from agricultural and waste water systems within the Lough Neagh catchment, combined with climate change and the associated weather patterns, with the very warm June, followed by the wet July and August to date. This has been exacerbated by factors such as zebra mussels, which are upsetting the ecological balance in the Lough.
Local councils or water operators are responsible for managing and assessing risks associated with blue-green algae. The public are reminded that blue-green algae can be harmful to humans and is highly toxic to animals. The public should therefore follow signage erected by local authorities. Members of the public can report suspected blue green algal blooms in several ways - via the Bloomin Algae App which can be downloaded at: https://www.ceh.ac.uk/our-science/projects/bloomin-algae or e-mail emergency-pollution@daera-ni.gov.uk or phone 0800 80 70 60.
More information can be found on the following webpages:
- Be Blue-Green Algae aware this summer
- About bathing water quality
- Blue-Green Algae - Confirmed Locations
What is Blue-Green Algae
Blue-green algae is not actually an alga but rather a type of bacteria called cyanobacteria. Cyanobacteria naturally inhabit our freshwater, coastal and marine waters and, like plants, require sunlight, nutrients and carbon dioxide to grow and reproduce.
Cyanobacteria can increase greatly in numbers and form visible ‘algal blooms’ which can lead to poor water quality and potential toxicity. Suitable conditions for ‘blooms’ to occur include abundant sunlight, still or slow-flowing water and sufficient levels of nutrients (nitrogen and phosphorus). 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 particularly phosphorus.
Nitrogen and phosphorus are naturally present in waterways but they can also come in excessively from external sources such as agricultural fertilisers, sewage effluent, household products and storm water runoff.
What does Blue-Green Algae look like?
During a bloom, the water becomes less clear and may look green, blue-green or greenish-brown. Scums can form during calm weather when several bloom forming species rise to the surface. This can look like paint, mousse or small clumps. The duration of blooms may last for a few days to several weeks until conditions in the water body change and the algae die and decompose.
Examples:

Why should you be aware of Blue-Green Algae
The excessive toxins produced during a bloom can potentially be harmful to public health.
Blue-green algae can harm people, producing rashes after skin contact and illnesses if swallowed, or can potentially kill wild animals, livestock and pets if ingested.
Algal blooms also block sunlight from reaching other plants in the water, use up oxygen in the water at night and when decaying and hence can suffocate fish and other creatures.
What to do if you think you see Blue-green algae
If you are at a river, lake or the sea and suspect there is blue-green algae, follow these steps:
Report it: Bloomin Algae App
The 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. 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. Bloomin’ Algae App is free to download directly from Google Play or App Store.
Find out more at: Bloomin’ Algae | UK Centre for Ecology & Hydrology (ceh.ac.uk)
If you don’t have Bloomin Algae App – email photos to NIEA
Report the bloom to the Northern Ireland Environment Agency. You can report any suspected blooms either by emailing the location and photographs to emergency-pollution@daera-ni.gov.uk.
Follow advice provided by the landowner/operator of the river, lake or beach.
For more information please visit the About bathing water quality page.
Roles and responsibilities
Landowners/ Operators
You must consider how your water is used when assessing risk to people and animals from exposure to blue-green algae.
You are responsible for controlling discharges of water off-site, warning users, putting up signs and restricting access. You are also responsible for deciding when restrictions can be removed. The local council also has these responsibilities for water they own.
Blue-green algal blooms and scums are natural features of some waters. Increasing shade and reducing nutrients in the water can help reduce risk of algal blooms.
NIEA
NIEA provides a supporting role to landowners and operators, through verifying the presence of blue-green algae through photos submitted to the Bloomin’ Algae App or directly to the emergency-pollution@daera-ni.gov.uk, or in some cases through water samples.
It must be highlighted, that collecting and analysing a sample provides only a location specific indication of the presence or absence of algae at that point in time. NIEA will follow internal response procedures for blue-green algae.
Landowners or operators are responsible for managing and assessing risks associated with blue-green algae.
Identified and candidate Bathing Waters
Where there are concerns of risks to bathers’ health from a visual assessment of, for example, blue-green algae, further assessment is made by taking water samples to establish levels in relation to agreed health guidelines for safe bathing. In the case of blue-green algae, the World Health Organisation (WHO)’s guidelines are applied.
If levels of blue-green algae exceed the safe threshold from WHO, DAERA notifies the Bathing Water Operator to issue ‘advice against bathing’ notices. DAERA works closely with Bathing Water Operators to reduce and manage risks to bathers’ health from pollution incidents including blue-green algae. Depending on visual assessments of algal scum precautionary closures may be required until full sample results become available.
For more information please visit the About bathing water quality page.