Toxic algae found in Hawke's Bay river

People are warned to take care around parts of the Tukituki river where potentially toxic algae levels have been found. PHOTO/FILE.

Potentially toxic algae levels have been identified in the Tukituki River near Black Bridge, Haumoana, through water quality monitoring by the Hawke's Bay Regional Council.

Parts of the 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.

HBRC's Senior Environmental Scientist Anna Madarasz-Smith said "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".

She said science had 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.

Warning signs would be put up at affected areas by the Hawke's Bay District Health Board, but people were urged to avoid contact with the Cyanobacteria mats and to keep animals away.

In January a no-swim warning was put in place for parts of the Tukituki River when Cyanobacteria mats became exposed.

- Check water quality and algae warnings at lawa.org.nz, or for more information go to lawa.org.nz/explore-data/hawkes-bay-region/river-quality/tukituki-river/tukituki-river-at-black-bridge-(haumoana)/