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Blue-green algae

What are blue-green algae?

There is a wide range of blue-green algae (cyanobacteria). In fresh waters, they are suspended within the water or attached to rocks and other surfaces. They include single-celled species and others whose cells are arranged in colonies and filaments. It is difficult to see individual cells, colonies and filaments, but you usually can when they’re concentrated into clumps. These clumps can look like green flakes, greenish bundles or brownish dots.

How can blue-green algae affect you?

Bloom and scum forming blue-green algae can produce toxins. Toxin-producing blooms are called Harmful Algal Blooms (HABs). These toxins can kill wild animals, farm livestock and domestic pets. In humans, they can cause rashes after skin contact and illnesses if swallowed.

Not all blue-green algae blooms and scums are toxic, but you can’t tell just by looking at them, so it’s best to assume they are. Read through our FAQs for more information or see the Environmental Protection Agency's information leaflet.

Local alerts: Monastery Dam and Sutton Mill Dam

Following notification from the Environment Agency, who have undertaken water sampling, the Council have put up notices around both dams to warn people to avoid all contact with the affected waters and ensure that children and pets are kept away. Contact with affected water can cause rashes, blisters, joint and muscle pain diarrhoea and vomiting in humans, and prove lethal to livestock and pet animals if ingested. 

Further information on this matter can be obtained by phoning the Environment Agency Incident hotline on 0800 807060 or the Council’s Environmental Health Section on 01744 676299, or by visiting the Environmental Agency website.