The swimming leg of the 70.3 Taupo half Ironman has been scrapped due to safety concerns over dense concentrations of algae in the town's famous lake.
A host of leading international triathletes have already registered for Saturday's race at Lake Taupo, which bills itself as the home of New Zealand ironman.
But after a Waikato Regional Council warning not to swim in the lake's water, they will now complete a modified course consisting of a 3km run, 90km bike ride and 21km run.
Race organisers say they were told at 8pm on Thursday that potentially toxic algal species, including phormidium, were present.
![Phormidium is one of the potentially toxic algal species under a microscope and found at areas within Five Mile Bay, Acacia Bay, the main lake front in Taupō, Whakaipo Bay and Kinloch Beach.](https://www.nzherald.co.nz/resizer/v2/FUCDMIGVRYYM2EOU6TRQOXWJPA.jpg?auth=f1abe1fb5e956f3fdffd62c87bd08a8b07d82b6b7ccffc280ea89f6012dca0e8&width=16&height=12&quality=70&smart=true)