Deatched algal mats accumulated at river's edge Photo: Supplied / Greater Wellington Regional Council
Wellington authorities are warning the public to take care near two rivers in the region due to toxic algae blooms.
Red alert level warnings are in place for the Waipoua River at Columbo Road in Masterton and the Hutt River at Silverstream Bridge.
Greater Wellington Regional Council is urging people not to swim in these river areas.
It also wanted dog walkers to not let their animals in the water and avoid the river's edge where significant amounts of toxic algae had accumulated.
Toxic algae grows on rocks in the riverbed and forms leathery, dark green or black mats, which can break off and accumulate at the river's edge.
Greater Wellington's Darien Kissick monitoring toxic algae at Te Awa Kairangi Hutt River. Photo: Supplied / Greater Wellington Regional Council
The regional council's knowledge and insights manager, Dr Evan Harrison, said the algae could be harmful to humans and lethal for dogs if ingested.
"Even a small amount of toxic algae, the size of a 50-cent piece, can be enough to kill a dog."
Toxic algae on a rock at river's edge. Photo: Supplied / Greater Wellington Regional Council
Dog owners who think their animals have swallowed toxic algae, or shows signs of lethargy, muscle tremors, fast breathing, paralysis or convulsions, should go to the nearest vet immediately.
People who have been in contact with toxic algae and are feeling unwell should see a doctor, or ring Healthline on 0800 611 116.
The community is advised to check the LAWA website for toxic algae warnings and alerts before visiting rivers in the Wellington region this summer.