The northern tip of the southern alps near St Arnaud in the Nelson Lakes National Park in late June. Photo: Tracy Neal / RNZ
The Department of Conservation (DOC) is asking visitors to Nelson Lakes National Park this summer to stay out of some of its lakes, to help protect the lakes from an algae that causes a mucus-like substance.
It said the microscopic algae lindavia that caused the sticky mucus-like substance known as 'lake snow' was in the park's Lake Rotoiti and Lake Rotoroa.
DOC said it wanted to prevent the algae being spread to Rotomairewhenua/Blue Lake, Rotomaninitua/Lake Angelus and Rotopōhueroa/Lake Constance.
DOC community ranger Sandra Wotherspoon said hut wardens were stationed at Blue Lake Hut over the summer peak visitor season to advise trampers about protecting the lakes.
She said visitors were being asked to not swim in or touch Blue Lake and Lake Constance, to protect their water quality from being ruined by the 'lake snow'.
Visitors are being asked to not swim in or touch Blue Lake and Lake Constance. Photo: Supplied/DOC
DOC said NIWA testing found the water clarity at Blue Lake was among the highest in the world, with 63m visibility.
Wotherspoon said the algae lindavia could be spread to a new area in just one drop of water.
"Clothing, boots, drink bottles and swimming, tramping and fishing gear could harbour lindavia. It could then be washed out when entering a different lake or river," she said.
DOC said although lindavia was not toxic to humans, it was not known how it would affect the ecology and health of the lakes.