Our water monitoring team has found black mat algae (Phormidium) in large quantities in the Esk River at Waipunga Bridge. It’s on the gravel bed upstream and downstream of the bridge.
Algal mats are also at Esk Park although there is less of it.
Please stay clear of these sites for recreation, especially walking dogs or riding horses as this algae can be toxic. Please take notice of the warning signs DHB has put up at the site.
More information on what to look out for and animal safety here: https://www.hbrc.govt.nz/assets/Document-Library/Fact-Sheets/Dog-owners-guide-to-algae-in-rivers.pdf