Toxic algae is lethal to dogs - and it's in our rivers
Monday, 11 January 2021
Dog owners and swimmers in the Hutt Valley are being reminded to watch out for toxic algae.
Cyanobacteria – or toxic algae – has been the scourge of the capital's summers in recent years, with significant outbreaks in the Hutt Valley, Wairarapa and Kāpiti.
Blooms have been found in the Waipoua River in Wairarapa, and Te Awa Kairangi/Hutt River between Birchville and Silverstream, and the Pakuratahi River at Kaitoke campground, both in the Hutt Valley.
In the Hutt River, blooms have been spotted near Silverstream, Poets Park, Māoribank Corner and Birchville.
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In 2018, the regional council’s freshwater scientist Mark Heath said that nationwide about 150 dogs had been killed by algae in the previous 15 years.
It is not known how many dogs have died in the region but there have been regular deaths in the Hutt Valley.
The algae is a neuro-toxin and kills by blocking nerves from communicating to each other. Dogs die from seizures, severe vomiting and diarrhoea after they eat toxic algae. In extreme cases, dogs die within 30 minutes of eating the algae.
The algae is also considered a risk to humans, particularly young children, but there are no known cases of humans becoming sick.
Greater Wellington regularly tests for the algae and is advising everyone to check their website before swimming or taking their dog near a river.
In recent years there have been significant outbreaks of toxic algae in the Ōtaki, Waikanae, Hutt, Ruamahanga and Waingawa rivers. With the warmer weather since Christmas, the council is expecting more rivers to be impacted.
Toxic Facts
Toxic algal blooms occur in rivers and streams and don't cause any problems most of the time. During summer, with higher temperatures and long dry periods, cyanobacteria can form extensive blooms that can be toxic, particularly to dogs if they eat the algal mats.
Toxic algae can form brown, dark green or black mats that grow on rocks in the river bed. Mats can come loose from the riverbed and wash up on the banks or form floating “rafts” in shallow areas.
When exposed, the mats may dry out and turn light brown. The mats produce a strong musty odour. Dogs are attracted to the smell, and may eat any accessible mats that wash up on the river’s edge.
A small amount, the size of a 50 cent piece, can kill a dog.