Toxic blooms of blue/green algae known as cyanobacteria have been found in the Bosherston Lakes in Broad Haven South.

Scientists are warning pet owners to be vigilant looking for this type of blue-green algae, which can be fatal for pets and harmful for peoples health.

As a result of the recent warm, dry weather more of this algae could appear in other water courses in south Wales.

To help isolate areas infected with the blue-green algae, professor Laurence Carvalho, a freshwater ecologist at UKCEH has developed an app where people can report sightings.

Mr. Carvalho said: "Blue-green algae tend to flourish in the UK from June to the autumn, during long spells of warm and dry weather. They are becoming more frequent due to climate change and the increasing amount of nutrients entering our waters, for example from sewage or fertilisers.

“By reporting blooms via the Bloomin’ Algae app, the public is providing a rapid, early warning about outbreaks and helping to give a comprehensive picture of these harmful blooms across Wales."

Experts will quickly verify submitted records, and inform the person who reported the sighting whether it is blue-green algae or not. They will provide advice on whether outbreaks need to be reported to the landowner, who is responsible for ensuring warning signs are put up at a site. App users can also set up notifications of confirmed blooms in their area.

In separate incidents in Scotland at the end of May, a dog died after coming into contact with suspected blue-green algae at Loch Awe, while another dog became seriously ill after taking a drink from the River Fillan near Crianlarich.

People who come into contact with the algae, such as open water swimmers and canoeists, could suffer skin rashes, vomiting, diarrhoea, fever or muscle and joint pain.

Professor Carvalho says blue-green algae can be confused with harmless blooms of blanketweed or duckweed [please see images in dropbox for comparisons]. Blue-green algae are often a vivid green colour, characteristically turning turquoise when they decay along the shoreline. Unlike blanketweed or duckweed, they do not look like clumps of hair or tiny leaves, and if you poke the blooms with a stick, they break up like a cloud of dust in the water.

Parents of young children are advised to keep them out of water where there is suspected blue-green algae, and dog walkers should keep their pets on a leash and wash their coats down as soon as possible if they go into contaminated water. Anyone concerned that they or their pets have been in contact with blue-green algae is advised to seek medical advice.

Dogs can become extremely ill within just a few minutes so owners should seek urgent veterinary assistance if their pets show symptoms such as diarrhoea, excessive drooling, muscle tremors and disorientation.

Visit Google Play and the App Store to download the Bloomin’ Algae app for free.