Parts of Lake Waihola, one of four "areas of concern" identified by the Otago Regional Council in recent weeks, were covered in dank-smelling, vivid-green algae.
Yesterday, Lake Waihola Holiday Park owner Pete Michelle said the blooms were ephemeral.
"It comes and goes," he said. "Some days are worse than others."
The blooms seemed to blow on over to the side of the camping ground with a northwesterly wind.
And there did not seem to be a local consensus about their severity, he said.
Some locals took their dog to the lake for a swim every day and never had a problem, while others did complain about it.
Mr Michelle said he advised swimmers to shower after taking a swim.
"It’s a bit of a tricky one, really. I’m not there to see it today.
"It just comes around when it heats up a bit."
Council water quality scientist Helen Trotter said a sample collected on December 18 found toxic algae (cyanobacteria) present at the lake south of Dunedin.
She advised people to avoid contact with the water there and at Butchers Dam and connected bodies of water where toxic algae had been found earlier this month.
There had also been reports of potentially toxic algae at Waianakarua River, in North Otago, Ms Trotter said.
The deaths of three dogs near Alexandra last Friday had not yet been confirmed as linked to algae, but had raised concerns around the lower Manuherikia River, while upstream at Ophir there were already signs in place warning of a toxic algal bloom, she said.
Rivers which are known cyanobacteria hotspots around Otago are Silver Stream, Mosgiel, Cardrona River, Central Otago, Manuherikia River, Central Otago, Hāwea River, Central Otago, Waianakarua River, North Otago.
Lakes which are known cyanobacteria hotspots in Otago are Lake Waihola, Tomahawk Lagoon in Dunedin and Butchers Dam in Central Otago, she said.
- ORC pollution hotline: 0800 800 033
