As holidaymakers flock to Rotorua, health authorities have warned people to stay away from two of the district’s lakes due to the presence of potentially toxic blue-green algae or cyanobacteria.

The warning was based on water test results and visual observations provided by the Bay of Plenty Regional Council that indicate blue-green algal blooms were affecting significant parts of Lake Rotorua and the western end of Lake Rotoiti.

Today’s warning extends the current health warnings in place for Okawa Bay and Te Weta Bay at Lake Rotoiti issued last week.

While not all parts of the lakes were affected, Toi Te Ora Public Health medical officer of health Dr Phil Shoemack said in a statement that experience with similar blooms in the past indicated they could move quickly from one area to another.

“These blooms have the capacity to release toxins into the water which can cause significant ill-health to anyone who has contact with the water.

“The toxins can affect the nervous system causing numbness and difficulty with breathing, and also sparking asthma attacks. Contact with the water can also cause skin rashes, stomach upsets and visual problems.”

Shoemack said it was likely the algae bloom would be present for several kilometres along the Kaituna River as water from both lakes flowed into it.

He urged people to keep an eye out for blooms while using lakes and rivers in the Bay of Plenty and Lakes districts over summer.

“Algal blooms can develop rapidly and unpredictably. If the water looks discoloured, has an unusual smell, or has green or brown particles floating in it then it is best to avoid contact with it.”