‘Unsafe for swimming’: Ironman Leeds is latest casualty of heat-fuelled toxic algae

Athletes faced last-minute cancelling of 2.4-mile swim, as experts say pollution and extreme heat are causing blooms

As far as athletic accomplishments go, few are held in higher regard than completing an Ironman triathlon.

The amount of training required to tackle the 2.4-mile swim, 112-mile bike ride and 26-mile run that make up the course, as well as the expensive equipment required to train in the first place, means that only about 50,000 people in the world complete a full race and earn the title of Ironman every year.

For some, however, such as Jack Chamberlain, that title has an asterisk next to it.

Chamberlain was one of about 2,000 people who competed in Ironman Leeds on 16 August, an annual triathlon event whose swimming section was cancelled because of a bloom of toxic blue-green algae. Algae blooms aren’t particularly unusual this time of year, but the successive heatwaves that have hit Britain this summer have caused more problems than usual for freshwater swimming.

“My life, for the past four or five months, has been completely consumed by this,” said Chamberlain, who estimates he trained for about 15 hours a week to prepare for the event. While Chamberlain has completed triathlons in the past, Sunday’s event would have been his first full Ironman.

“When you cross the finish line you hear those famous words, ‘you are an Ironman’, and that comes from finishing a triathlon, not a duathlon. So I’m proud of myself, but it felt off,” he said.

According to British Triathlon, the governing body for triathlons, aquathlons and duathlons in the UK, Sunday’s event was the fourth event to be cancelled due to algae blooms so far this year.

Chamberlain, like many others, felt that more notice would have lessened the blow and given athletes more time to find an alternative. Even though it didn’t go towards his official time, Chamberlain said that he swam the nearly two and a half miles in a nearby lake the day before, with other athletes asking to do their laps in a local leisure centre before it opened.

“It’s something they should have been checking weeks in advance,” said Chamberlain. “There were something like 58 countries represented in the race, so people came from all over the world. I think with people putting in time and effort and, you know, thousands of pounds into such events, things should be put in place.”

Marina Angela Andresen, a committed marathoner who has set herself the goal of completing 10 Ironman events in 12 months, was one of the few who saw the silver lining in the swimming leg being cancelled.

“This was the first time in my life I’ve had a full swim cancellation. I’ve had swims shortened before because of temperatures, but not this. Honestly though, I was very happy with it. Because I know Ironman looks out for the athletes and I would not want to swim with blue-green algae, it’s dangerous,” Andresen said.

“I’m very happy to not be forced to swim under such conditions and I can still make the best out of the day. I had a fantastic race with the people of Yorkshire. The mood was great. I really loved it.”

Triathlons haven’t been the only events hit by algae in the past week, with several public swimming spots, including the first official bathing site on the Thames in London, warning potential swimmers to avoid the water until the blooms clear up.

Daniel Start, an avid wild swimmer who has written numerous books on the subject, said increasing pollution was as big a cause of the blooms as the heat.

“It’s not a problem that is going away any time soon,” said Start. “It’s getting worse with more intensive farming and more fertiliser being put on fields that trickle down into lakes and rivers.”

A spokesperson for the Ironman Group, which organised Sunday’s event as well as similar events around the world, said: “Ironman was devastated to have to cancel the swim portion of this year’s Ironman Leeds. We know how hard our athletes train across all three disciplines (swim, bike, run) and how disappointing it was to forgo the swim segment due to water quality issues.

“Continuous hot weather and the absence of rain contributed to a bloom of blue-green algae, which can be hazardous to humans and made the lake unsafe for swimming. The decision to cancel the swim was made in conjunction with Leeds city council, who has jurisdiction over Waterloo Lake. 2026 was the second edition of Ironman Leeds; the swim was successfully conducted the previous year.”