Toxic algae found in Hawke's Bay's Tukituki River

Thursday, 29 March 2018

Toxic algae has been found in the Tukituki River again. 

The Hawke's Bay Regional Council has found potentially toxic algae levels on the river at Black Bridge near Haumoana.

Parts of the Tukituki River are prone to algal growth in summer, due to lower water flows, higher water temperatures and nutrients in the water. Green strand algae is harmless but black Phormidium bacteria growth on the rocks is potentially toxic for humans and dogs. It can detach from the rocks and dry as mats on the sides of the rivers, and these can also be toxic.

'Our advice is to always treat the black growth on rocks in the water and the drying mats as toxic, stay out of the water if you see it, and swim or walk your dog elsewhere,' the council's senior environmental scientist Anna Madarasz-Smith said.

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Contact with Phormidium bacteria can make people sick, with flu-like symptoms. Dogs are more vulnerable. They are particularly attracted to the odour of the mats and being smaller, the toxins can be more dangerous. Dogs should be under control in river beds and not allowed to scavenge. Clinical signs are vomiting, diarrhoea and lethargy, and heat stroke- like symptoms such as muscle tremors, breathing difficulties, paralysis and convulsions.

Warning signs will be erected at affected areas by HB District Health Board staff.

Cyanobacteria are single celled creatures that live in water environments. Cyanobacteria have characteristics in common with both bacteria and algae. In warm nutrient rich conditions free-floating cyanobacteria cells can multiply quickly to form what are known as algal blooms. Large numbers of Cyanobacteria can also grow as mats on river and lake beds and these mats can sometimes detach and float to the surface. Some cyanobacteria species produce toxins (cyanotoxins), which pose a risk to humans and animals when consumed in drinking water or by direct contact during recreational activities.