Increased risk from blue-green algae in Hutt River

Greater Wellington and Regional Public Health want people to take care around the Hutt River due to the risk from potentially toxic blue-green algae (also known as cyanobacteria).

Moderate growth of blue-green algal mats has been recorded in the Hutt River at Poets Park and Silverstream this week and mats are starting to detach and wash up on the rivers edge. In other parts of the Hutt River the amount of algae remains low but could increase quickly if warm, dry weather continues.

Hutt River users, particularly those with dogs, should keep a look out for blue-green algal mats and avoid contact with them if present.

Blue-green algae, which are naturally present in many New Zealand waters, 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.

“Despite the wet summer we’ve had so far it’s now warm and dry enough for rapid algae growth to occur. This is typically the time of year when there’s increased growth of blue-green algae because river flows and levels are usually lower and there’s less frequent rain to flush the algae away,” Greater Wellington Senior Environmental Scientist Summer Greenfield says.

Local councils have posted signs at key access points along these rivers to warn people of the risk. Up-to-date information on blue-green algae growth across the region is at www.gw.govt.nz/current-warnings.

General information about toxic algae, including pictures and what to do if you are worried about possible contact with toxic algae can be found at www.gw.govt.nz/toxic-algae.