Environment Bay of Plenty monitoring of Rotorua's lakes for cyanobacteria (blue-green algae) has resulted in health warnings for Lake Rotoehu and for the Rangitaiki River upstream from Lake Aniwhenua.
Cyanobacteria are capable of producing toxins that are harmful to humans and animals if swallowed or if exposed to skin, such as may occur when swimming, skiing or kayaking.

Cyanobacteria bloom as a result of a combination of excess nutrients in the lakes and climatic factors.
Environmental Scientist Paul Scholes said that today's Toi Te Ora - Public Health warning would remain in place until further notice, however, all other Rotorua lakes currently remain safe for swimming.
'Our weekly monitoring shows that all of the other lakes we monitor for cyanobacteria are well under the safe threshold and there are currently no toxic algae levels that would warrant health warnings being put in place but with blue-green algae you just never know when it might flourish given the right climatic conditions,” says Paul.