Tipperary County Council, in consultation with the Health Service Executive (HSE) has advised the public about the presence of algal bloom on Lough Derg in recent days.

The blue green algae bloom can produce harmful toxins and is most easily recognisable when it forms a bright pea green paint-like scum on or close to the shoreline.

The local authority has advised the public to exercise caution adding that contact with the bloom should be avoided as it may cause skin irritation.

The public is also advised to keep all animals, especially dogs, away from the affected area and ensure that animals have an alternative source of drinking water.

According to the US Centers for Disease Control and Prevention (CDC), algae are a group of plants usually found in water.

Algae can grow in all types of water, including salt water, fresh water, and brackish water. Brackish water is a mix of salt and fresh water.

Algae that live in water can be grouped into two categories, seaweed and phytoplankton.

Seaweed are large plants made up of many cells;
Phytoplankton are small, single-celled organisms (living things like plants or bacteria).

Both seaweed and phytoplankton sometimes grow quickly, or bloom. Some of these algal blooms harm people, animals, or the environment.

Most harmful algal blooms that make people and animals sick are caused by phytoplankton.

Many types of phytoplankton can cause harmful algal blooms. However, three types of phytoplankton cause most blooms that make people and animals sick:

Cyanobacteria (sometimes called blue-green algae);
Dinoflagellates (sometimes called microalgae or red tide);
Diatoms (sometimes called microalgae).

Algal bloom has been a feature of Lough Neagh in Northern Ireland for some time with NI Water stating: "Blue-green algae is caused by the presence of high levels of nutrients in the Lough. Sunlight and increased temperatures can then trigger blooms."

It added that high levels of nutrients in NI waterways stem from several sources:

Artificial fertilisers and slurry/manure derived from livestock that runs-off the land when it rains;
The resulting water recycled to the lake when wastewater is collected from local communities and processed to standards set by NIEA within our wastewater treatment works;
Sewage that is heavily diluted with rainwater that, by design and with approval of NIEA, will spill from storm overflows during periods of heavy rain to prevent the wastewater system becoming overwhelmed and cause properties to flood;
Discharges from privately-owned septic tanks and industrial treatment processes.