Former Northern Ireland farm minister Edwin Poots MLA has claimed that agricultural effluents are not to blame for the blue-green algal blooms now impacting on Lough Neagh.

By way of verification, he points to the fact that Northern Ireland is a nitrates vulnerable zone.

“As a consequence, the spreading of slurry on to land is not allowed at all from the end of October until the beginning of February,” he said.

“These measures have been in place for a number of years.”

Meanwhile, SDLP politician, Patsy McGlone, is claiming that a combination of human sewage run-off, agricultural wastes and the introduction of invasive mussel species to Lough Neagh are now impacting on the quality of the water in the lake.

McGlone also points out that the swarming of flies, which used to be such a feature of the entire Lough Neagh catchment area, has been relegated to the history books.

“It was the flies that fed the fish in the lake. I am deeply concerned about the overall quality of the water in Lough Neagh at the present time,” McGlone said.

His sentiment is matched by that of the Department of Agriculture, Environment and Rural Affairs (DAERA), which has previously said that the “key reason behind the algae is “excess nutrients are entering our water bodies, primarily from agricultural land use activities and from waste water pressures”.

Blue-green algae on Lough Neagh

According to the Agri-Food and Biosciences’ Institute, the green layer on Lough Neagh is an algal bloom, caused by the rapid growth and accumulation of blue-green algae.

Algal blooms can produce toxins and can also remove oxygen from the water as they decompose.

The current condition in the Lough is unusual in that these blue-green algae have not been abundant here since the mid-1970s. 

The Agri-Food and Biosciences Institute (AFBI) routinely monitors temperature and oxygen levels throughout the Lough and observed water temperatures steadily rising during the early summer period.

“We recorded surface temperatures of 21o, while average June surface temperatures in recent years have typically been around 15o,” an AFBI spokesperson said.

“Observers of Lough Neagh will also have noticed that the water is currently clearer than usual.

“The clearer waters are likely due to the activity of zebra mussels, an invasive non-native species, first seen in Lough Neagh in 2005.

“Zebra mussels feed by filtering particles from the water, and as a result remove food normally available to other species such as swan mussels.

“The resulting increased water clarity allows sunlight to penetrate deeper into the water, which can lead to increased nuisance plant and algal growth and allows prey species usually concealed by murky waters to become visible to their predators.”

Sonar surveys, conducted by AFBI, have shown that for now at least, most fish are remaining in their normal habitat near the bottom of the Lough.