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Algae warning at Wales' largest natural lake

Matt Lloyd
BBC News
Getty Images Llyn Tegid in Bala with mountains in the backgroundGetty Images
Llyn Tegid in Bala is Wales’ largest natural lake and popular for water sports 

Visitors are being warned to take extra care when visiting a popular north Wales lake after harmful algae was found in the water.

Eryri National Park said the blue-green algae was present in parts of Llyn Tegid in Bala, Gwynedd.

The authority has urged people to be careful around the lake and avoid direct contact with the algae.

Blue-green algae is a collection of microscopic organisms that are naturally present in lakes and streams which can become harmful.

Eryri National Park Lines of blue-green algae in the lake close to the shoreEryri National Park
Blue-green algae can be extremely dangerous to animals

The lake is popular with water sports enthusiasts.

Visitors are being asked to familiarise themselves with the safety notices on the foreshore, and not to enter the water when algal bloom is present.

A graphic with the image in the background of algae on a lake. The headline in white font reads: "What is blue-green algae?" There are six bullet points underneath. The first reads made up of tiny organisms naturally present in lakes and streams, the word tiny organisms is in a light blue font, and the rest is in a white font. The second reads it can form toxic blooms, with the word toxic blooms in a light blue font and the rest in a white font. The third says thee can cause diarrhoea, nausea, vomiting, irritation and breathing difficulties in us and our pets. The words diarrhoea, nausea, vomiting, irritation, breathing difficulties are in a light blue font and the rest is in a white font. The fourth says you can't see a toxic bloom, so take care near warm, shallow, undisturbed water, the words warm, shallow, undisturbed water is in a light, blue font with the rest in white. The fifth point reads, if you think your dog has been exposed, see the vet immediately, see the vet immediately is in a light blue font and the rest is in a white font. The last bulletin reads pay attention to warning signs, the words warning signs are in a light blue font, and the rest is in white.

Blue-green algae - cyanobacteria - can become abundant in warm, shallow, undisturbed, nutrient-rich surface waters that receive a lot of sunlight, leading to floating mats or scums on the water's surface.

Some algae produce toxins which can cause skin rashes, nausea, eye irritation, vomiting, fever, diarrhoea and muscular or joint pain if swallowed.

However, it is not possible to tell if a bloom is toxic simply by looking at it.

The algae can be extremely dangerous to pets, livestock and wildlife.