Increased risk from toxic algae in Hutt River

River users should avoid parts of the Hutt River due to widespread growth of potentially toxic cyanobacteria, Greater Wellington and Regional Public Health say.

Monitoring by Greater Wellington shows that the amount of cyanobacteria is now high in the Hutt River from Birchville downstream. Clumps of the algae, which is brown or black in colour, are also present on the river’s edge. River users, particularly those with dogs, should avoid contact with these parts of the river.

Local councils have posted warning signs at key access points along the river. Current warnings.

There is also moderate risk from cyanobacteria mats in the Waikanae and Waipoua rivers. River users should keep an eye out for cyanobacteria mats in these rivers and avoid contact with them if present.

Cyanobacteria are naturally present in many New Zealand waters, and grow in dark brown or black coloured mats on rocks in the river bed. Some produce toxins that can be fatal to livestock and to dogs. Dogs are particularly susceptible to exposure because they like to scavenge near water. Contact with algae toxins may also cause vomiting, diarrhoea and skin irritations in humans

“It’s now been almost three weeks since the Hutt River was flushed by high rainfall and this combined with warm weather has resulted in rapid cyanobacteria growth. This is typical of what has happened in the Hutt River during past dry summer periods,” Greater Wellington Senior Environmental Scientist Summer Greenfield says.

Find general information about toxic algae, including pictures and what to do if you are worried about possible contact.