Visitors to Clatto Reservoir in Dundee are being been warned to stay away from the water due to potentially lethal algae in the water.
The blue-green algae poses a serious health hazard to people and animals and in some cases contact can prove fatal.
A spokesman for Dundee City Council says recent sampling has identified high levels of blue-green algae and until the all clear is given, people are being asked to avoid contact with the water and keep their pets away.
He said: “Blue-green algae are tiny organisms which develop naturally in lochs, ponds, reservoirs, rivers and in the sea.
“They are a common seasonal occurrence and waters which have been affected by agricultural, domestic or industrial discharges are most at risk of developing the algae.”
He explained that the algae can multiply during the summer months and discolour the water which then appears green, blue-green or greenish brown.
Effects of blue-green algae can be ‘severe’
Occasionally they clump together to form a scum on the surface of the water. At the shoreline, algal crusts may appear brown to almost black in colour.
The spokesman said: “Contact with algal scum or water close to it can cause skin rashes.
“More serious health effects can include stomach upsets, eye irritations and pain in muscles and joints. These symptoms are usually mild, but in some cases can be severe.”
He added: “The risk 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 keep an eye on their pets, especially if they come in to contact with water which could be affected.”
Dorothy McHugh of Friends of Clatto confirmed there was blue green algae at the reservoir.
She said: “Fortunately it is not as bad this year as it has been some other years.
“However, people ought to stay away at the moment.”
If anyone has been in contact with the water and experiences health problems they should contact their GP or NHS 24 on 111.
Notices are being been posted at the reservoir. Dundee City Council’s Neighbourhood Services can provide further information on the algae on 01382 433 710.
People were also warned to stay away from Loch Earn in Perthshire after blue green algae confirmed there at the weekend.