PEOPLE are being advised not to enter a lake after testing found blue-green marine algae was present.

The result comes after a cyclist, who asked not to be named, told the Journal of his concerns after spying Marine Lake had turned 'green'.

Precautionary signs have been placed around the lake in Rhyl advising people not to enter the water.

Blue-Green algae (cyanobacteria) are natural inhabitants of many inland waters, estuaries and the sea. Blue-Green algal blooms produce toxins that can adversely affect human and animal health.

The algae is normally reported during the summer months.

Denbighshire County Council is working with Natural Resources Wales (NRW) to identify steps to clear the algae.

Cllr Mark Young, cabinet lead member for Planning, Public Protection and Safer Communities, said: “Regular testing takes place at Marine Lake to monitor the quality of water and tests have now shown the presence of blue-green algae in the lake.

“Algae of this nature is quite a common occurrence in areas of water, especially during the summer months and after periods of warm weather.

“In the interest of public health, we have places signs around the lake, asking people to stay away from the water for the time being. We are also asking people to make sure their animals do not enter the water.

“We are working closely with Natural Resources Wales to identify what needs to be done to remove the algae and to re-open the lake as soon as it is safe to do so”.

Tom Lewis, NRW Senior Environment Officer said: “Marine Lake, and other lakes, can suffer from a population explosion of algae, known as algal blooms, at this time of year in dry, warm, calm weather

“We are working closely with Denbighshire County Council to monitor Rhyl’s Marine Lake, working within the Government’s Covid 19 social distancing guidelines."

There’s a wide range of blue-green algae.

In fresh waters, they are suspended within the water or attached to rocks and other surfaces. They include single-celled species and others whose cells are arranged in colonies and filaments. It is difficult to see individual cells, colonies and filaments, but they can usually be seen when they are concentrated into clumps.

These clumps can look like green flakes, greenish bundles or brownish dots.

Bloom and scum-forming blue-green algae can produce toxins.

Toxin-producing blooms are called Harmful Algal Blooms (HABs). These toxins can kill wild animals, farm livestock and domestic pets.

In humans, they can cause rashes after skin contact and illnesses if swallowed.

Not all blue-green algae blooms and scums are toxic, but as it is not easy to tell just by looking at them, it is best to assume they are.

For further information on blue-green algae, click here.