Warning about toxic algae in Tukituki
Water quality monitoring by Hawke’s Bay Regional Council staff indicates that potentially toxic algae levels are present
on the Tukituki 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,” says HBRC’s Senior Environmental Scientist Anna
Madarasz-Smith.
She adds that science has not yet identified when Phormidium turns toxic or why, so to be safe it should always be
treated as harmful.
• 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.
People can check water quality and algae warnings here which displays data from LAWA (Land Air Water Aotearoa = www.lawa.org.nz).
Warning signs would be put up at affected areas by HB District Health Board staff, but people were urged to avoid
contact with the cyanobacteria mats and to keep animals away.
For information:
What are Cyanobacteria?
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.