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Harmful invasive plants could be damaging Bear Lake

Posted at 10:57 PM, Jul 08, 2024

GARDEN CITY, Utah — It’s one of the clearest, most popular lakes in Utah — but that clarity is under threat from invasive plants.

The Utah Department of Natural Resources is going out on Bear Lake with a weed expert from Utah State University on board. They’re looking for Eurasian watermilfoil, which has been in Bear Lake for about four years but doesn’t come to the surface to flower.

"That means that the plant is not happy, it’s not thriving, and we don’t understand why," said Mirella Ortiz, a weed scientist at USU.

And the problem with an unhappy invasive plant?

"A plant that’s stressed cannot absorb the herbicide and be controlled by it," Ortiz said.

So they’re out on the water, checking equipment that measures sunlight and temperature at various depths. They’re also dragging the bottom in small marinas, looking for curly-leaf pondweed.

"It produces a lot of these turions, and each of these turions will sprout about 3-4 times and start new plants," Ortiz explained.

These invasive plants displace the food and hiding sources for fish, and more.

"They can also change the nutrient cycle of the water, and by that, they can cause harmful algal blooms at Bear Lake," Ortiz said.

They also pose a threat to humans' lives and property.

"If your boat prop gets stuck in these invasive plants, it gets all tangled up and then it can’t move," explained Jessie Danninger, the DNR Bear Lake program manager. "And obviously worst-case scenario, in some of these marinas, if a kid were to fall in, they could get tangled up and they could drown."

The DNR shut down the motorized craft in a small marina due to curly-leaf pondweed.

"Because the props will stir up all that vegetation, chop it up, and those fragments can establish new populations across the lake," Danninger said.

Ortiz and Danninger recognize that the in-season timing for this closure is lousy for business, but the growth cycle of the weeds and getting someone there to spray is controlling the schedule.

Ortiz says that while Utah has a plan to stop invasive mussels, with boats being inspected for them, that's not as much the case for plants. Ortiz says it was probably a traveling boat that brought the weeds to the lake.

"There are studies showing that plants that [stay] in the moist areas of boats during transportation, they can stay alive for up to 90 days," Ortiz said.

"It’s a big, beautiful lake, and we want to make sure we preserve that blue, clear color," Danninger said.