New research into lake snow has found Wanaka boat users, fishermen, swimmers and anyone else who uses New Zealand's recreational lakes could be behind the spread of "lake snow" in the lake.
Sometimes referred to as lake snot, it has been persistently found in Lake Wanaka since it was first identified in 2002.
Lincoln Landcare researcher Phil Novis has been researching lake snow and said results so far showed humans were "very important vectors as the lakes with detectable Lindavia (or lake snow) are highly accessed recreational lakes".
All the remote lakes tests were negative, he said.
Lake snow has been found in more than a dozen lakes or lake outlets around New Zealand.
When present in high quantities, frothy white floccules appear on the surface, giving rise to a snow-like appearance.
Novis gave a presentation this week in Wanaka called "What is that brown slime on my fishing line/water filter/wet suit?", along with University of Otago freshwater scientist Marc Schallenberg and Ferrier Research Institute, Victoria University of Wellington, PhD candidate Cara Luiten.
They presented information about new tools developed to study lake snow, its causes and future prospects for control.
Novis said the talk was prompted by the serendipitous occasion of having the three researchers in Wanaka at the same time.
"Which may not happen again," he said.
On Monday, the Otago Regional Council advised people to keep out of Lake Hayes and to keep dogs well away from the edge after toxic cyanobacteria, blue-green algae (Anabaena lemmermannii) was found after lake water testing.
Cyanobacteria has the potential to produce toxins that are harmful to humans and pets if swallowed or through skin contact.
Warning signs were put up around the Lake Hayes recreational reserve on Saturday evening due to the green-coloured algae in the water.