Remember to watch out for blue-green algae on the water

Argyll and Bute Council and NHS Highland are issuing a reminder to people to be on the lookout for blooms of potentially hazardous blue-green algae (also known as Cyanobacteria) in the area’s lochs and rivers.

Blue-green algae occurs naturally in lochs, ponds, reservoirs, rivers and in the sea. Sometimes it forms blooms which can release toxins into the water. These are a common seasonal occurrence and blooms occur across Argyll and Bute  fairly regularly each year. However, during this current period of prolonged mild weather, the chance of blue-green algae affecting water courses increases significantly.

In still waters, the algae can multiply during the summer to such an extent that it discolours the water making it appear green, blue-green or greenish brown.  Shoreline mats of blue-green algae may appear and scum may form on the surface of the water. This scum can appear in different places at different times, but is most commonly found near the shoreline.

Contact with blue-green algae can have adverse health effects for humans and animals. The health effects on people coming into contact with toxic scums include skin rashes, eye irritation, vomiting and diarrhoea, fever and pains in muscles and joints. The toxins, which may be produced by the algae, are also poisonous to animals and can cause severe illness and death of livestock, dogs, waterbirds and fish.

Argyll and Bute Council is  advising the public, especially dog owners, to be alert to the blooms as temperatures rise. People are advised to avoid contact with the algal scum and the water close to it. The risk posed by blue-green algae to small animals like dogs is significant over the summer months as they tend to drink more water in the heat and may eat shoreline algal crusts. Dog owners should prevent their pets from coming into contact with water which could be affected. Fish caught in waters affected by blue-green algae should not be eaten and should not be fed to pets.  People visiting lochs and waterways in the area are asked to be vigilant and check whether there are signs of blue-green algae growth in the water or around the shoreline.

Where there is evidence of this, it would be sensible to avoid swimming or other water-based activities like canoeing or water skiing. Make sure that pets don’t drink or enter the water. Further information is available here.

The council’s environmental health team works closely with SEPA where there are reports of possible blue-green algae growth, and place warning notices for members of the public. However the transient nature of these blooms and the vast areas of waterways that could be affected, means users must also be aware of possible unmarked affected areas. By taking precautions and being vigilant, everyone can continue to enjoy Argyll and Bute’s lochs and waterways safely. If you are concerned, contact our environmental health team on 01546 605519 or via email at

You can also download the Bloomin’ Algae app and help monitor blooms across Scotland and the UK: