Algal Bloom At Castlewellan Lake Still Halts Water Activities

Blue/Green Algae count on Castlewellan Lake breaches limits for water safety quality.

Blue/Green Algae count on Castlewellan Lake breaches limits for water safety quality.

Slieve Croob Alliance Councillor Andrew McMurray has expressed his concern about the algal bloom at Castlewellan Lake which appeared over two weeks ago.

The lake is a popular angling and canoeing venue and all water sports have been halted.

Cllr McMurray said: “I have been informed that blue/green algae have reached levels in Castlewellan Lake which breach water quality standards.

“As a result, activities are not allowed on the lake and anglers are asked not to consume any fish caught from the lake.

Cllr Andrew McMurray at Castlewellan Lake.

“This is obviously disappointing given the lakes popularity amongst locals and visitors alike for recreational purposes.

“It is concerning given that this is the second time this year which such a bloom has occurred.

“Castlewellan Lake is an Area of Special Scientific Interest. As this is occurring more frequently, then it needs to be monitored, and investigations need to be carried out as to the causes.

“From this, actions need be taken by the agencies responsible to prevent this becoming something which permanently damages the lake.”

Algae blooms can be caused buy a number of complex environmental factors such as nutrients in the water often as a result of phosphates and nitrates washed off agricultural land in feeder streams to the lake.

Also, the recent warm temperature with strong summer sunlight can be significant. But a key factor is probably low turbity. This means that the particles suspended in the water are at a low which allows the sunlight to penetrate and cause algae growth which in turn creates high turbidity. Also the lake levels and water chemistry such as acidity levels can also be a factor.

An algal bloom can reduce oxygen levels in the water and this in turn could result to a significant fish kill if uncorrected.

A spokesperson for DAERA said: “The NIEA received a call, via the NIEA Incident Hotline, on 16 September 2020 from Newry and Mourne District Council reporting an algal bloom at Castlewellan Forest Park Lake.

“NIEA tasked an officer to investigate the incident and a sample was taken for analysis. The analysis indicated the presence of toxin forming algal species.

“In warmer weather conditions, there can be a rapid increase in the growth of microscopic algae in the aquatic environment and this is known as an algal bloom.

“This can cause a discolouration of the water resulting from the high density of pigmented cells. Algal blooms are often green or blue-green in colour, but may also be other colours such as dark brown or red depending on the species of algae.

“Freshwater algal blooms tend to be the result of an excess of nutrient input to waterways, particularly phosphorus, related to medium or longer term land usage.

NIEA take samples in order to identify whether the blooms are a potentially toxic algal species. These algal species are potentially toxic to humans and other mammals e.g. livestock and pets and, this being the case, NIEA inform the owner/operator of the waterway so that they may make an informed decision as to whether access to the waterway should be restricted.

“Toxins, associated with algal blooms, are generally released when the algal cells die off. The volume of toxins produced by these algal species and their toxicity vary.”

The Department acted swiftly to protect local users of the lake. The spokesperson added: “Following confirmation that water in Castlewellan lake contained blue/green algae, Forest Service and Inland Fisheries liaised closely with NIEA and Newry Mourne and Down DC in agreeing appropriate safety advisory precautions.

“This includes informing the main users of the lake such as Outdoor Recreation providers as well as individual visitors with safety notices erected at key locations around the lake advising visitors to take the following precautions”

• Avoid skin contact with water and the algae

• Do not drink the water

• Do not catch or consume fish from the lake

• Keep animals away from the water

“Safety notices have been erected at key locations around Castlewellan Lake.

“It is not possible to say how long this current algal bloom episode will last for, however, a sample taken on Wednesday 23 September 2020 indicated that toxin forming algal species were still present in Castlewellan Forest Park Lake.”