A Northland iwi is appealing to people to stop using a tiny lake as a car wash.
Lake Waiporohita on the Karikari Peninsula is one of just 12 rare dune lakes in the north with outstanding ecological ratings.
But Ngati Kahu, and the Department of Conservation and the Northland Regional Council say it is at growing risk from motorists who use it to wash down their vehicles.
Ngati Kahu runanga chief executive Anahera Herbert-Graves says people are driving straight into the lake to wash sea water off their cars and boats.
"By doing that they're introducing all sorts of aquatic weeds and putting the ecology of the lake under stress."
She also told Morning Report people are releasing pet fish, like guppies, into the lake which then "breed like maggots."