Blue-green algae may to be blame for swan deaths

The deaths of a swan and her four cygnets on Bailieborough’s Castle Lake this summer has mobilised locals to do what they can to ensure such a terrible outcome doesn’t happen again.

Ben Malone, a Community Water Officer working within the local authority water programme covering counties Cavan, Monaghan, and Louth met with a large group of close to 20 people at the popular amenity spot in early September.

The group had gathered to hear from Ben who has a remit of engaging with communities about the health of catchments, rivers and streams, and in turn support individuals and groups with projects focused on improving the quality of water sources.

The deaths of the swans in early August had caused consternation in the locality, and raised concern over what might have killed the birds.

The Department of Agriculture was contacted, who sent vets to take samples and tested the dead birds for possible traces of Avian Influenza. Those tests came back negative.

“So if we know that it wasn’t Avian Influenza that caused their deaths, well then what is it? Really that’s going to be a question mark that will remain,” says Ben, when speaking to The Anglo-Celt.

With further toxicological testing unlikely at this stage, he says that people like himself can only make informed guesses.

“We can’t be very certain of what killed them, but what we do know is that there was a significant algal bloom in Castle Lake, and there is evidence of blue-green algae present.”

Blue-green algae, he says, if ingested can cause severe neurological or liver damage to some animals, especially dogs if they drink from, or even simply swim in, contaminated waters. It can prove toxic to wild fowl also.

“It can be quite dangerous, and so that’s where we’re at. Did the swans die by ingesting toxins produced by the blue-green algae? That’s the only obvious thing we can think of.”

Ben acknowledges that Castle Lake holds a special place in the hearts of many in the locality, and that people from Bailieborough had grown attached to seeing swans return each year to raise their young.

Seeing locals take such a “keen interest” is heartening, says the community water officer, and encourages people to join a water trust, or set up one.

Ben is currently working on the draft River Basin Management Plan for Ireland 2022 – 2027, which he hopes to see published before the year is out.

They include the Annalee, Laragh and East Cavan river and lake catchments in the Bailieborough – Cootehill area; the Oughter and West Cavan’s River and Lake Catchments in Cavan-Belturbet; and the Upper Erne and South Cavan’s River and Lake Catchments in Ballyjamesduff.

He believes that publication will be very important for the future of Castle Lake.

“What was designated in the second cycle was this network of priority areas for action, so they actually get a concentrated effort to identify significant pressures. What’s interesting in the third cycle is that Castle Lake falls within one of these priority areas for action, so there’ll be a dedicated effort going forward to work with other agencies and stakeholders to mitigate those pressures on water quality. We know the river flowing into Castle Lake is poor quality, and coming out of Castle Lake it is moderate quality, so it is basically unsatisfactory from a water framework perspective. All rivers and streams need to be of good status by 2027, that’s what we need to get to.”