Parks Canada says Whirlpool Lake and its campground area will remain closed for the 2018 season, as a precautionary measure to protect it from invasive zebra mussels.
Whirlpool Lake is in Riding Mountain National Park.
The east portion of the Cowan Lake trail from the Cowan Lake campsite to Whirlpool Lake is also temporarily closing.
Parks Canada says there are no zebra mussels in the lake, but water samples taken last summer and fall from Whirlpool Lake tested positive for Environmental DNA of zebra mussels.
Environmental DNA are microscopic genetic traces that an organism leaves behind as it moves through an environment.