Toxic algae: deadly and delicious
It’s not just the heat that’s been worrying Dr Mark Heath of late.
The black, velvety mats of algae on the sides of the Hutt River, near Wellington, are what is preying on the scientist’s mind.
More toxic than cobra venom, it takes only a coin-sized piece to kill a 20kg dog, Heath said. ‘‘And if we talk about a 20kg dog we could just as easily be talking about a 20kg child.’’
Cyanobacteria – or toxic algae – has been the scourge of the capital’s summer with Greater Wellington Regional Council twice urging swimmers and their pets to stay away from the river.
Heath, the council’s freshwater scientist, is disappointed that despite the warnings, at least two dogs have already died after eating the algae. Nationwide, about 150 dogs have been killed in the past 15 years.
It’s an agonising death and, although he said it was unlikely, he feared what would happen to a child who ‘‘got some on their hands’’ or ate some of the algae.
‘‘This scares me just about every night when we have big algal blooms.’’
For now, scientists don’t know exactly what the algae could do to humans, but Heath said one thing was certain should a person swallow a piece of the floating bloom: ‘‘There’s a really big risk that someone could become very ill or sick.’’
The algae was a neuro-toxin and killed by blocking nerves from communicating to each other. In extreme cases, dogs die within 30 minutes of eating the algae.
Toxic algae occurs everywhere but it’s during hot weather and low water that the problems start.
When it comes loose from the river bed and brown or black mats wash up on the banks or form floating rafts is when it becomes dangerous, Heath said.
‘‘As the mats start to die, the cells break open and release these odour compounds, which actually seem to attract dogs for some unknown reason.’’
The council tested the district’s water weekly but people needed to recognise what the algae looked like so they could keep themselves safe.
‘‘Sometimes you can smell it when you open your car door down at the river.’’
He said the council did everything it could to alert people to the algae’s presence by using traditional and social media, interactive maps, signs and website information, but the public had to do their part too. ‘‘Do your research so you can identify it.’’
Dogs die from seizures, severe vomiting and diarrhoea after they eat toxic algae, Pet Doctors New Zealand clinical director Dr Callum Irvine said.
‘‘People perceive that the dog actually has to get into the water but it isn’t the case, they will eat it from the banks.
‘‘The bottom line is quite simply to stay away. If you know it’s there, then don’t take the risk.’’