On Thursday night in a social media post, the Otago Regional Council issued a water quality red alert, advising people not to swim in Macandrew Bay.
Results from water quality monitoring showed elevated levels of Enterococci bacteria, indicating higher levels of faecal material in the water.
Macandrew Bay School principal Nic Brown said the school was unaware of the closure until staff saw an article in yesterday’s Otago Daily Times.
"[I will] be sending some comms out to our whānau to obviously let them know, if they hadn’t seen the article, we’re advising people not to swim in Macandrew Bay," Ms Brown said.
The school held a beach day at Macandrew Bay Beach on Monday and while there had been no reports of illness, she would be asking parents to monitor their children.
"There was no indication that anything was not right.
"It’ll good to be able to get a little more information about how long it might be closed for, or just even perhaps some signage down there."
Regional council water quality scientist Helen Trotter said it was likely heavy rainfall before the sample was taken had caused runoff to be washed into waterways.
"Enterococci are a faecal indicator bacteria used to assess faecal contamination at coastal swimming sites.
"Faecal contamination can cause gastroenteritis or infections of ears, eyes, nasal cavity, skin and the upper respiratory tract."
She did not expect any negative effects on wildlife or seafood in the area from one elevated result.
"The long-term grade for this site is ‘good’. Monitoring results from the past five summers show 96% of samples met national water quality guidelines."
Regional council environmental monitoring manager Eve Bruhns said the high bacteria levels were detected during testing of Otago waterways which was conducted weekly, December to March.
The alert would be lifted when bacteria levels decline.
Otago Peninsula Community Board chairman Paul Pope said it was a timely warning about waterway health in the harbour area.
"There have been previous warnings from time to time in that area.
"So it’s not a new thing, but any time it comes up, there’s always a worry."
Macandrew Bay was a "hugely" popular recreation spot, known as a safe beach for families and prolonged closure would negatively affect local businesses, he said.
"We’re into summer now, people are wanting to swim, they’re wanting to fish, they’re wanting to boat.
"A healthy environment is good for business and good for the community."
A Dunedin City Council spokesperson said there was no sign of leakage from the wastewater network in the area.
