Warning signs on the banks of the Waipoua River in Masterton. PHOTO/MARCUS ANSELM
A swimming ban has been extended to the entire Waipoua River.
Greater Wellington Regional Council announced on Wednesday that 80 per cent of the riverbed was covered with algae and there was a constant stream of floating and detached mats.
People and their pets have been urged to avoid the river and its banks until conditions improved.
Sections of the river were closed earlier this month.
Red flags were also raised over parts of the river in February.
Exposure to high levels of algae and toxins can cause diarrhoea, nausea or vomiting, skin, eye or throat irritation, and allergic reactions or breathing difficulties.
“This is as bad as it gets and represents a very real risk to human and animal health,” the regional council’s senior environmental scientist Mark Heath said.
“People are warned to stay away from the river.”
Wherever toxic algae was present it was important to keep an eye on babies and toddlers who may put objects in their mouths.
Seek emergency medical attention immediately if you or anyone in your group swallowed toxic algae.
Dogs in particular were attracted to the aroma of toxic algae, which could be fatal for them if eaten.
See your doctor if you have been swimming in a river or lake and have any of these symptoms: nausea, vomiting, numbness, tingling, muscle twitches, shaking, or weakness.
Seek immediate medical attention for more serious symptoms such as breathing difficulties, convulsions, or loss of consciousness.
Before you swim, keep yourself safe by finding out about toxic algae at http://www.gw.govt.nz/safeswim/