Researchers say, "Our lakes are changing" | www.WDIO.com

Researchers say, "Our lakes are changing"

Brandon Weathers
Updated: July 26, 2021 11:50 PM
Created: July 26, 2021 10:43 AM

Our lakes are reflecting the exceptionally dry and hot summer we’ve had. Boat launches have struggled with low water levels, swimmers have enjoyed warmer waters earlier in the season, and sensitive ecosystems have been affected.

Minnesota DNR fisheries research scientist Casey Schoenebeck tracks the changes reflected in our lakes. “One of the things we’ve seen this year with decreases in precipitation,” Schoenebeck said, “We saw decreases in the algae in that particular lake and the fish community also responded to that change.”

While a single year like this one can have dramatic changes, the Minnesota DNR Sentinel Lakes Program is more interested in the changes observed by long-term averages. They monitor 25 carefully selected lakes across the state. WDIO Meteorologist Brandon Weathers met Schoenebeck at Hill Lake which is one of the sentinel lakes representing northern Minnesota.

“Because we can’t monitor all of Minnesota’s lakes, we’re monitoring a subset of lakes to learn as much as we can about those changing conditions,” Schoenebeck said.

Each sentinel lake has continuous water temperature loggers in them. There are differences from one lake to another, but the data has revealed a consistent warming trend.

Schoenebeck said, “Ice cover has been, on average, declining over time, water temperatures are increasing, and the differences that we’re seeing are both regional with the greatest increases in north central Minnesota, and seasonally with the greatest increases in June.”

The DNR is very interested in where and when the changes are occurring in order to monitor how they are influencing the fish communities.

“Some of the increases that we’re seeing are in largemouth bass, blue gill, black crappie. And other fish, like white sucker, yellow perch, different bullhead species, we’re seeing declines over time,” Schoenebeck said.

White sucker in particular has been declining statewide. Schoenebeck says this is significant because anglers don’t target them.
Schoenebeck said, “So when you see declines in certain species not attributed to angler harvest, it can be attributed to changing environmental conditions over time.”

An evolving fish community directly affects anglers and the overall ecosystem of a given lake.

“This information is important for DNR so as we can understand these changes over the course of time, that’s going to factor into the management of Minnesota’s lakes as well,” Schoenebeck said.

Beyond the Sentinel Lakes, the DNR also has programs monitoring our shallow and wild rice lakes. WDIO meteorologist Brandon Weathers met biologist Melissa Thompson at Big Rice Lake north of Virginia. Thompson says changes in the wild rice harvest over time have been evident.

Thompson said, “I’ve heard stories of people from 30 years ago talk about pulling hundreds of pounds of rice off of lakes, and you see pictures, here at Big Rice, there were hundreds of vehicles parked at the access waiting for that opening day of ricing, and we’re not seeing that as much nowadays.”

A number of factors may be contributing to the decline of wild rice. Warmer water temperatures in the winter can cause problems with germination.

“Rice needs a pretty long dormancy season over the winter,” Thompson said, “It germinates at about 42 degrees or so, so sometimes it’s already germinating when there’s still ice on the lake.”

Warmer water earlier in season allows competing vegetation, like pickerelweed, to take over

Thompson said, “As the years went on and we tried different management things, we tried to set it back, we tried different water levels, we tried all of this stuff, and the pickerelweed has continued to spread across the lake.”

Pests are another cause of problems.

“When it’s really hot, and more so when it’s humid, these rice worms can decimate a stand of rice because they just go through and eat the little kernel,” Thompson said.

Wild rice is also very sensitive to water levels. Thompson says most of what they do to maintain water levels is to ensure a free flowing outlet by trapping beavers and removing beaver dams. Irregular heavy rain events are more difficult to control. The 2012 flood virtually wiped out the harvest of that season on some lakes.

“It just seems like the last 10 years or so that I can really speak to, we’ve been getting these big June, July rain events, not this year, but, those definitely can have an impact,” Thompson said, “And when that occurs year after year, that really impacts the rice and creates conditions that are better for other plant species to move in.” 

The DNR isn’t the only organization keeping track of wild rice lakes. The 1854 Treaty Authority preserves and protects the rights of the Grand Portage and Bois Forte Bands of the Lake Superior Chippewa in the 1854 ceded territory.

Resource Management Division Director Darren Vogt said, “We since 1998 have been monitoring a group of about 10 lakes and rivers to track wild rice abundance over time, and wild rice naturally fluctuates, so we get some good years, bad years, but we’re starting to see over time kind of a long-term potentially slow decline of wild rice.”

Their research has pointed to the same challenges facing rice as the DNR. Higher frequency of heavy rain events, competing vegetation, and pests related to rising water temperatures.

“There’s a fungal disease that we’re seeing more on these hot, humid nights. We’re starting to see more fungal diseases in rice in northeastern Minnesota we didn’t see before,” Vogt said.

As is the case with the Sentinel Lakes Program, a long-term set of observations will be the best tool in identifying the cause of these variables that are leading to a decline in wild rice and ultimately mitigate them.

Vogt said, “Again, we’ve been monitoring the same proud of water since 1998 which is slowly turning into a longer data set, but other entities, too, are starting to monitor more wild rice lakes, so we’re trying to build this regional data base of wild rice information.”

The Fond du Lac Band of Lake Superior Chippewa has joined the multi-agency effort to restore the wild rice harvest in our region, even though the five harvestable lakes they care for have not reflected the same decline. Natural resource manager Thomas Howes says this is because of the level to which their lakes are maintained.

Howes said, "We've invested millions over the years monitoring water level, manipulating plant communities, doing receding when necessary, and so there's a lot of attention given to these, these are the garden for our people."

They have partnered with the DNR on maintaining Big Rice Lake.

"They said, 'hey, we need assistance,' and we were able to lend our expertise to them. And so, that's grown into a full-blown partnership now where we're two of the three airboats up there cutting vegetation to bring manoomin back," Howes said.

Howes says the Fond du Lac Band has a responsibility to join in the regional efforts.

"Ojibwe people, manoomin has always taken care of us for hundreds of years since we've been in this region. And so, as it struggles in places, it's our job to reciprocate and advocate for it or actually physically restore it in places," Howes said.

If a declining trend in wild rice harvest were to continue, it would have devastating cultural implications.

Howes said, "It's also central to everything that we do ceremonially from birth to death and everything in-between. It's absolutely critical. And so, the decline of it more broadly throughout the region is of course concerning."

Credits

Brandon Weathers

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