The reservoir at Irishtown Nature Park in Moncton has been shut down for recreational use.

Blue-green algae was found in the reservoir during routine testing, city officials said Monday.

“Kayaking, canoeing, and other recreational activities are prohibited, and pet owners are asked to keep their dogs out of the water and not let them drink or swim in the water,” the city said in a news release.

Notices and signage have been posted, and the city said it will continue to monitor the situation.

Blue-green algae, also known as cyanobacteria, are naturally occurring bacteria found in many New Brunswick ponds, lakes, and rivers.

The bacteria are not normally visible, but under certain conditions, can increase in numbers to form surface blooms of benthic mats.

While not all blue-green algae are harmful, some can produce toxins that can cause skin, eye and throat irritation.

The algae are most commonly blue-green in colour as its name suggests, but surface blooms can also be green, red, brown, or yellow.

Blooms can also appear as mats that can look like clumps of vegetation that appear black, brown or dark green in the water.

On the shoreline, they may be brown or grey once they have dried and can sometimes be attached to rocks or aquatic vegetation found floating in the water.