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Nutrient imbalance keeps Flathead Lake clean and clear, researchers say

A research boat at the Flathead Lake Biological Station.
Corin Cates-Carney
Montana Public Radio
A research boat at the Flathead Lake Biological Station.

A recent study has discovered that there’s a natural nutrient imbalance in Flathead Lake, and that's a good thing for water quality.

There are low levels of phosphorus compared to nitrogen relative to other bodies of water, researchers found.

“We think most of the processes that are driving it are internal to the lake,” said Jim Elser. “That’s how the lake is processing phosphorus and nitrogen.”

Elser is the director of the Flathead Lake Biological Station of the University of Montana and was the lead author on the study, which examined nutrient levels in Flathead Lake over the past 40 years.

Elser says this imbalance, particularly the low levels of phosphorus, is in a way starving phytoplankton — also known as algae — and the zooplankton that feed on them. But the stunted growth of those microorganisms has another byproduct.

“It’s why many of the lakes around here are quite clear and quite low productivity.”

Elser says that’s good news for water quality and notes that long-standing regulations around agriculture and development near the lake have kept this natural imbalance of nutrients intact. The research indicates Flathead Lake should remain clean, clear and blue for years to come.

Aaron graduated from the University of Minnesota School of Journalism in 2015 after interning at Minnesota Public Radio. He landed his first reporting gig in Wrangell, Alaska where he enjoyed the remote Alaskan lifestyle and eventually moved back to the road system as the KBBI News Director in Homer, Alaska. He joined the MTPR team in 2019. Aaron now reports on all things in northwest Montana and statewide health care.
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