FLATHEAD LAKE MATTERS: A scientist works to untangle the intricate web of Flathead Lake

By DAVID REESE

Bigfork Eagle

Bonnie Ellis had already put in a full day at the Yellow Bay Biological Station when it was time to grab a nap before she was to board a boat and head out onto Flathead Lake.

She’d be spending the night on the dark waters of the lake, trapping mysis shrimp.

The tiny shrimp, less than an inch long, have captivated her in the 33 years she’s been a scientist at the research station on the east shore of Flathead Lake. In that time, the tiny shrimp have completely changed the food web of the lake, affecting not only native species like bull trout and cutthroat trout, but also algae and even bald eagles in Glacier National Park.

Mysis shrimp have now become a keystone species — an organism that has a far greater effect on the food web than its size or numbers would suggest.

It’s called a trophic cascade — how the alteration of a major predator alters the other species. Adding an element like mysis shrimp to the food web, as state fisheries managers did several decades ago, had dramatic effects. Ellis is fascinated at how this continues to play out. Not just in fisheries, but in other elements of water quality, such as algae.

Zooplankton were reduced by 50 percent after the arrival of mysis shrimp. Some of those species recovered, some did not, and others have taken their place.

The alteration of the food web led to a dramatic spike around 1987 in the lake’s ability to grow algae. Since then the trend has dropped, but it’s on a gradual process back up. “You can see the trend but it will take a few more years to see if that trend is statistically significant,” Ellis said.

And in Flathead Lake, that change from the mysis being a food base to a keystone species has occurred fast — and there’s more coming.

Ellis is now studying how mysis are changing. Lake trout have eradicated kokanee salmon in Flathead Lake and prey on mysis shrimp (which were intended to be a prey base for kokanee). The shrimp are reacting. The shrimp spend most of their days at the bottom of Flathead Lake, then come to the dark surface to feed on other zooplankton at night. They may be learning to avoid predation by lake trout, and in doing so are continuing to alter the intricate food web of the lake.

“It’s a very complex web,” she said. “We’re working on a very detailed food web model.” Ellis had her findings published in the Proceedings of the National Academy of Sciences.

Flathead Lake is classified in Montana law as an A-1 water body. That means its level of protection is the highest under Montana law, and under Montana law the requirement called total maximum daily load (TMDL) is the guideline that says how much nutrient load the lake can — and should — take. Nutrients like nitrogen and phosphorous are the real culprits of water quality, leading to algae blooms that dirty the shorelines and impair water clarity.

The biological station, formed in 1899 by Dr. Morton Elrod, is the champion of Flathead Lake. It’s the largest single research organization that has compiled data not only on Flathead Lake, but also on the surrounding basins that impact the lake. Elrod was the first biology professor at the University of Montana, and he performed the first gill net study on Flathead Lake. That study revealed a much different lake than today. Westslope cutthroat trout were dominant, the 14 other nonnative species, while present, lived in the background.  “It was a complete, native fishery,” Ellis said. That has changed. Nonnative species like lake trout, lake whitefish and mysis shrimp dominate the lake biology.

The “U.S. Fish Commisssion” hauled nonnative fish to Flathead Lake starting in 1903. Kokanee were introduced in 1916. By the 1920s, anglers began catching kokanee and lake whitefish. There were 12 fish hatcheries established in Montana by 1924. “It was a big business and a big effort” to increase angling in Montana, Ellis said. Those efforts continued into the 1960s, Ellis said. Nineteen nonnative species have been introduced in the lake.

“The next step that makes this so complex is how mysis caused a fairly rapid change in the fishery from the 1980s to now,” Ellis said.

The biological station, too, comes under threats just like the water quality it seeks to protect. After 25 years of helping the biological station, the Montana Department of Environmental Quality in 2006 cut funding to the station that resulted in the station not being able to perform some critical monitoring in the Whitefish and Stillwater rivers, and Ashley Lake, which carries effluent from the Kalispell wastewater treatment plant into the Flathead River — and ultimately Flathead Lake.

While it was only about $30,000 a year, “It was consistent,” Ellis said. “That loss was enough for us to have to drop monitoring sites.”

The station now relies on private donations and a $1 million challenge grant to finance its monitoring operations. The station received a $1 million donation from an anonymous person about two years ago and the station is working to match those funds. Ellis said she’s still curious why the state, which is charged with monitoring total maximum daily loads in Flathead Lake is not stepping up financially to help the lake’s largest research operation.

“I believe they should be interested in water quality monitoring,” Ellis said.

Losing those monitoring sites creates a gap in the data that is being collected — and used in political policy, fisheries policy and more. “Without that data it becomes very difficult to assess trends,” Ellis said. “The only way to assure water quality protection is monitoring.”

When Elrod was beginning his research on Flathead Lake in 1899, westslope cutthroat trout were the dominant fish species in the lake.

 If he were alive today, “I think he’d be very surprised to see that westslope cutthroat trout are not the dominant angler catch, and a large shrimp is now a keystone species in the lake,” Ellis said.

The game seems to always keep changing in Flathead Lake; from political parameters of research, to social and biological constraints. protected wilderness and national park lands. After 33 years Ellis is still intrigued at studying the big lake. She’s the longest-tenured employee at the Yellow Bay Biological Station aside from Jack Stanford, who has been director since 1980.

“I just keep my focus on what is impacting water quality and construct research around that,” she said, “so we know the variations and can tease out the human factors.”

Along with Mark Lorang, a physical limnologist, Yellow Bay scientists have installed an acoustic Doppler current profiler. This equipment, set deep in Flathead Lake, allows the scientists to sample mysis and zooplankton as the organisms move  throughout the water column. This helps the scientists determine if mysis are resting higher in the water column to avoid predation. Mysis prefer water temperatures that stay within 15 degrees centigrade variation. That might be changing, and the new equipment will help them track the tiny critters in the dark.

“If they are able to adapt, will the numbers of lake trout and lake whitefish fluctuate?” Ellis said. “It’s all connected.”

Even if it means getting on a boat at 11 p.m. after a long day in the office, Ellis loves the challenge of studying Flathead Lake. “As a scientist, you’re interested in what’s intriguing,” she said. “You make discoveries along the way and right now it’s how mysis are adapting to predators and the change in their prey.

“It’s an exciting place to work. I feel like I’m working on a different lake than when I started.”

On the Web: umt.edu/flbs