Public notice

Please keep out of Tomahawk Lagoon - potentially toxic algae is present

Thursday 11 February 2021

Results from the weekly samples taken at Tomahawk Lagoon have shown high levels of potentially toxic cyanobacteria (blue-green algae). Cyanobacteria can produce toxins which may cause serious illness in people and animals.

Otago Regional Council Scientist – Lakes, Hugo Borges, said it’s important for everyone to keep out of the water, and for dog owners to do the same with their pets. 

Potentially toxic algae are naturally occurring and blooms are more common during summer, when low rainfall, warm temperatures, the right level of nutrients and more sunlight create an environment where it can thrive.

“It’s not uncommon for potentially toxic algae to bloom in the upper lagoon during summer, and it’s not possible to predict how long it will take to recede,” said Mr Borges. “However, the most important thing is to keep out of the water until the warning is removed.”

ORC has installed warning signs at the entrance to the upper lagoon and at the creek that enters Tomahawk Beach as a precaution in case the wind sweeps the algae down the creek. 

All warning signs will remain in place until monitoring showed the algal bloom had reduced and weekly samples were consistently below levels posing any threat to health.

More information on potentially toxic algae is available on the LAWA factsheet: