The frequency of highly-toxic algal blooms on Irish lakes is set to increase significantly over the next 15 to 30 years because of the stress on these waters caused by phosphate pollution, an Environmental Protection Agency seminar has been told.
Even if phosphate wastes, mainly arising from agricultural sources, were switched off in the morning, such is the phosphorus loading already in lake sediments that the blooms would persist for years, according to Dr Andrew Petersen, of Cork Institute of Technology.
Blooms are caused by cyanobacteria (blue-green algae), which release toxins when conditions allow for a bloom to occur on a water surface.
Speaking at the seminar in Co Wexford to outline the findings of a series of studies of Irish lakes, Dr Petersen said the Government and local authorities needed to urgently introduce more monitoring of the bacteria and their toxins.
"Consideration should be given to intensively monitoring bloomsusceptible water bodies, especially those having potable and recreational utility, in view of the tumour-promoting and carcinogenic activities of cyantoxins."
Following the deaths of some animals attributed to ingestion of toxins from lakes, Dr Petersen was asked to head an international study team to examine the incidence of cyanobacteria and their control. Of 55 Irish lakes surveyed, 42 per cent were experiencing "potential or actual nuisance from the organisms".
Dr Marie Sherwood, of the EPA, said it was easy to shout "stop polluting lakes" but extremely difficulty to arrest the polluter.
The EPA introduced the preliminary outcome of work carried out by researchers who surveyed 1,000 Irish lakes in a £1.3 million EU-supported programme. An EPA scientist, Mr Martin Garrigle, said it had resulted in technological advances in the monitoring of lake waters and would lead to better catchment management and pollution control.
An anglers' representative, Mr Tony Waldron, of the Connaught Angling Council, said: "The argument is over. Our wells and groundwater are polluted, our lakes and rivers over-enriched. Let us now focus on agreeing an effective solution." While many State bodies were unhappy that anglers concerned about water had chosen to bring their case to the EU in an attempt to force national policy changes, they had acted in the best interests of Irish water resources.
Dr Ken Irvine, of Trinity College, said the main threat to Irish lakes was enrichment by pollution from diffuse sources, but "pointsource pollution" was a problem in some areas due to sewage treatment discharges.
"Our study shows that although the majority of lakes are of high ecological standard, water quality is often poor in intensively-farmed catchments where modern practices have led to increased storage and land-spreading of animal waste [slurry]."
An EPA lake specialist Dr Jim Bowman, said the research would be used in formulating a national lake-monitoring programme, to be implemented by local authorities working with the EPA and fisheries boards.
