Blue-green algae has been discovered at Pennington Flash, Leigh, for the first time this year following the recent spell of warm weather.
Notices are in place around the popular beauty spot warning members of the public not to swim in the water.
Blue-green algae is found naturally in many inland waterways, while in lakes and ponds the warmer summer weather is ideal for its growth.
The algae rises to the surface of the water as a scum and looks like blue-green paint.
Illnesses — including eye irritation, vomiting, diarrhoea, skin rashes, muscular pains and fever — have occurred in people who have swallowed or been swimming in infected water. The algae can be particularly harmful to animals.
Environmental health chiefs say levels of the algae fluctuate. It can appear one day, disperse in the wind the next, but come back at any time.
This pattern is peculiar to the weather conditions and the time of year, but the algae will disperse naturally when cooler weather sets in.
Peter Alker is the parks officer for Wigan Leisure and Culture Trust – who manage the site on behalf of Wigan Council.
He said: “Pennington Flash is a very popular beauty spot and people shouldn't be put off visiting by the presence of algae in the lake.
“People should avoid contact with the algae affected water and not allow children to paddle no matter how tempting on a hot day. It is particularly important to keep pets out of the water and not allow them to drink it.”
Other flashes and ponds in the borough may be affected as the summer progresses so people should always take care when near any areas of open water.
