
Blue-green algae colors the water and Derrick Mayoleth's kayak along the south shore of Devil's Lake on Nov. 28.
A blue-green algae bloom in Devil’s Lake persisted for more than a month this fall — an uncommon sight in recent years — but despite some anecdotal reports of skin irritation, a water sample showed toxin levels remained safe.
Known for its usually pristine waters, Devil’s Lake State Park draws more than 2 million visitors per year, many of whom swim, kayak and fish in the lake. Linda Higgins, Baraboo, said she noticed the algae in early December. It looked like “fluorescent green paint in the water,” gave the whole lake a green tint and smelled “really bad,” like sewage, she said.
A resident since 1985, Higgins said she’s never seen the lake like that. But Richard Lathrop, a retired lake scientist who has been monitoring the water for decades, said blue-green algae blooms happen occasionally at the park.
“We’ve seen these kinds of algae blooms in the past in the fall. It’s not that unusual,” Lathrop said, adding that this one got more attention and was seen by more people than usual because it persisted for so long.
Legacy phosphorus
Lathrop works part time with the Wisconsin Department of Natural Resources to regularly sample Devil’s Lake water and operate a pipe, installed in 2002, which acts as a siphon to remove phosphorus from the lake and keep it from flooding. The 374-acre body of water reaches depths of up to 47 feet, but it doesn’t have a natural outlet, so the higher levels of precipitation in recent decades caused it to frequently flood the north shore parking lot prior to the pipe’s installation, he said. Lathrop has modified the pipe a couple of times over the years to increase its flow rate and efficiency.

Blue-green algae can be seen in Devil's Lake on Nov. 28. The late fall bloom was unusual but Wisconsin Department of Natural Resources officials said it posed no serious health risks.
Blue-green algae, or — more accurately — cyanobacteria, feed off of nutrients like phosphorus, of which Devil’s Lake has “tremendous amounts,” left over from more than a century of pollution from resorts and cottages that used to surround the lake, Lathrop said. A broken sewer drain also leaked sewage into the lake for nearly a decade in the 1970s and contributed to many blooms at the time, he added.
Since running the pipe, the water quality has improved, but Lathrop said Devil’s Lake still has about three to four times as much phosphorus in its deep-water bottom sediments as Lake Mendota in Madison. He expects it will take “decades and decades” for the pipe to remove all of the legacy phosphorus.
Lathrop said he’s running the pipe more often now and at a higher flow rate to prevent flooding due to higher precipitation, one of the many effects of climate change. That means the pipe is siphoning more surface water, rather than deep water, which means it’s removing less phosphorus than before. However, he doesn’t think the change has been significant enough to contribute to this year’s bloom.
Testing for toxins
Lathrop said he could see algae forming throughout the water column — meaning from surface to bottom — when he sampled it Nov. 3. He could tell a bloom might be coming, but it wasn’t dense enough yet.
Something’s going on with the water quality at Devil’s Lake State Park. I’ve got some emails out there to see what I can find out.. I haven’t seen this kinda green in Devil’s Lake in.. well, since the pipe was put in… pic.twitter.com/qAkqiM2SDq
— Skillet Creek Media (@skilletcreek) November 30, 2020
He sampled it again on Dec. 1. Taken where algae had by then concentrated along the south shore, the sample was tested for four common toxins, three of which were not found. The fourth, microcystin, was detected at a “very low level,” known as the level of quantification, which is the lowest point it can be accurately measured in the lab, Lathrop said. He noted the level of toxin was more than 15 times lower than the Environmental Protection Agency’s health limit, meaning it would be considered safe for swimming, even for children.
“One would easily conclude that the water was not a health concern at the time of sampling for any people swimming, which they weren’t because the water was cold, or for any dogs that might come up and drink the water,” he said.
Gina LaLiberte, statewide algal blooms coordinator for the DNR, said for such a concentrated sample of blue-green algae, the very low toxin levels are “good news.” The tests found two species of cyanobacteria.
Causes
LaLiberte said she thinks the blooms were the result of natural processes from an unusually warm fall and the high level of nutrients in Devil’s Lake.
Like other deep lakes, it stratifies during the summer, meaning distinct layers of water sit at different temperatures and don’t mix throughout the water column. As it cools in the fall, that layering breaks down (known as “overturn”), helped along by wind that mixes the water column.
The stratified bottom layer can — and does, at Devil’s Lake — have a higher level of nutrients than the rest of the column. When they mix together, algae feeds off of it and grows, LaLiberte said. She noted that cyanobacteria are present in every water body in the state, at least in low levels.
According to state climatology records, the region has had temperatures 4-5 degrees Fahrenheit above normal over the last month, basically extending the growing period, she said. LaLiberte said warm weather during fall overturn helped the bloom form, and a persistent wind blew it around, causing it to accumulate in noticeable areas near the shore.
LaLiberte said the DNR is keeping an eye on the bloom’s conditions. It isn’t doing anything to treat it, she said, because that can be expensive and the chemical treatment can cause blue-green algae to release any present toxins to the water in “one big dose.” She expects this one to dissipate on its own as the water continues to cool, if it hasn’t already.
Bathroom issue
Derrick Mayoleth, who owns Skillet Creek Media and frequently blogs about the park, tweeted about the water quality issue Nov. 30 and wrote a blog post Dec. 1. Some people told him a swimmer reported skin irritation as early as August.
“I haven’t seen this kinda green in Devil’s Lake in.. well, since the pipe was put in…” Mayoleth wrote on Twitter.
Over the summer, Higgins swam in the lake daily until it got too cold in mid-September. She heard similar reports from other swimmers who kept going into October.
Mayoleth and Higgins speculated that the bloom may have been caused in part by people using the lake as a toilet while the bathrooms were closed over the summer due to COVID-19.
While LaLiberte said it’s never good to add nutrients to the lake by urinating in it (or defecating, which can introduce pathogens), she declined to speculate on how much it would take to cause a blue-green algae bloom.
Lathrop was more certain: “I can tell you there’s so much nutrients in the bottom of this lake that the peeing in the water would not constitute what caused this bloom,” he said.
Safety
Blue-green algae exposure can cause stomach cramps, diarrhea, vomiting, headache, fever, muscle weakness or difficulty breathing in humans, according to the DNR. Pets can show similar symptoms.
LaLiberte said exposure usually occurs from ingesting water while swimming, inhaling algae in water droplets when water skiing or tubing and having skin contact with algae. Anyone who experiences symptoms they suspect were caused by blue-green algae can report their illnesses to the Department of Health Services via an online form. She said she didn’t think there had been any reports this fall about Devil’s Lake.
Everyone should assess the water conditions before getting into any body of water, no matter where they are, LaLiberte said. If it has visible scum, noticeable discoloration or green particles, don’t swim there.
“It’s important for people to always check out water conditions before they’re going into water for swimming or other recreation,” she said. “And especially if you have small children or pets going into the water to swim, be really observant of the water and if you have any concerns about it, just stay out and keep kids and pets out as well.”
Scientists still don’t know all of the triggers that cause cyanobacteria to produce toxins, she said. Conditions can change rapidly, making it difficult to monitor water safety.
Blooms can be reported to DNRHABS@wisconsin.gov, including size, duration, water body name, town name, county name and photos.
Editor's note: This story has been updated to correct the definition of "level of quantification" and to clarify how phosphorus levels in Devil's Lake compare to Lake Mendota.
Fave 5: Reporter Susan Endres shares her top stories of 2020
We reporters at Capital Newspapers have been asked to share our five favorite, most memorable or otherwise noteworthy stories from 2020, a year I think many of us would prefer to forget. As tempting as it was to choose only stories from the before (COVID) times, I compiled a list spanning the year that ranges from education in Baraboo and Portage to the local impacts of the coronavirus pandemic. This year has been nothing if not historic.
And yes, of course I chose more than five. I wouldn't be Susan Endres if I was decisive.
We've seen dramatic changes to our daily lives, but through it all, we continue to report on the important happenings in our community and hold the powerful to account.
Here's hoping for a better 2021.
Sauk and Columbia County residents struggle to make ends meet as they face barriers with unemployment amid shutdown.
News of a Baraboo child’s suicide mobilized the community, not just in efforts to find her before her death was known, but also to address men…
History will surely remember the coronavirus pandemic, but almost two dozen residents in Portage and Baraboo want to ensure that its effect on…
Despite a still unsolved murder this fall at Devil’s Lake State Park, local law enforcement authorities say the park remains “very safe.”
More teachers are moving from district to district than in the past, according to several area teachers and administrators. Some are strugglin…
A one-day pop-up shop at Portage High School offered cookies, chocolates and candy in exchange for acts of kindness in February.
Sans the usual hugs and visible smiles, students and their families arrived at Gordon L. Willson Elementary School nervous and excited about s…

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

A Baraboo Fire & Rescue team member secures safety equipment on the edge of a cliff Monday during a training exercise at Devil's Lake State Park.

Visitors walk along South Lake Drive on Oct. 27 at Devil's Lake State Park. Service calls to Sauk County dispatch and DNR wardens about the park have skyrocketed in recent years, according to records released to the News Republic.

Capt. Jeremy Plautz, of the Wisconsin Department of Natural Resources, leads a press conference Wednesday afternoon at the Roznos Meadow trailhead at Devil's Lake State Park near Baraboo. He confirmed there was a death near the park's south shore, but didn't supply any other details on the incident or investigation.

Jamie Esser, Middleton, sets up a “tip-up” to suspend a live minnow as bait under the water Saturday morning at Devil’s Lake State Park near Baraboo. It was the Department of Natural Resources’ Free Fishing Weekend, meaning anyone could fish almost anywhere without a license or trout stamp. Esser said he comes to Devil’s Lake often to fish. “It’s beautiful,” he said. “Best park in the state.” Another free fishing weekend will be June 6-7.

Baraboo Fire & Rescue team member Dave Schrofer, second from left, leans back to descend the face of a cliff Monday as his fellow team members help lower him down. The Baraboo Fire Department worked alongside UW Med Flight physicians and Wisconsin Department of Natural Resources conservation wardens to conduct cliff rescue training at Devil's Lake State Park.

Emergency responders carry an injured climber to an ambulance at the East Bluff Trail entrance in Devil's Lake State Park in August 2019.

The sun descends on a quiet evening Nov. 17 at Devil's Lake State Park's south shore. Service calls to Sauk County dispatch and DNR wardens about the park have skyrocketed in recent years, according to records released to the News Republic.

A DNR warden truck sits at the entrance of the East Bluff Trail as visitors hike at Devil's Lake State Park in August 2019. Emergency responders were in the area to rescue an injured climber. During the summer, there are 10 wardens assigned to Sauk County state parks, including the warden supervisor.

Hikers walk the Grottos and CCC trails April 24, 2019, on the south side of Devil's Lake State Park near Baraboo.

Jeremy Plautz, captain for the south-central region of the Wisconsin Department of Natural Resources, gives a press conference Wednesday afternoon at the Roznos Meadow trailhead at Devil's Lake State Park near Baraboo. He confirmed there was a death near the park's south shore, but didn't supply any other details on the incident or investigation.

Detective George Bonham of the Baraboo Police Department directs traffic near Devil's Lake State Park following a homicide at the park Wednesday. The suspect was still at large.

A couple consult a map Oct. 8 at Devil's Lake State Park near Baraboo. The most popular state park drew visitors all year but was closed for a short time in spring due to the COVID-19 pandemic.

Two-year-old Trace Porter, Evansville, picks stones Thursday morning on the north shore at Devil's Lake State Park near Baraboo.

Two-year-old Trace Porter, Evansville, picks stones Thursday morning on the north shore at Devil's Lake State Park near Baraboo. His mother, Tanya Porter, said they come to the area once a year to see the changing leaves and go to Ski-Hi Fruit Farm. Baraboo isn't quite at peak fall color yet, according to the Wisconsin Fall Color Report, which predicts the peak will be in the third week of October, but Porter said the trees were plenty colorful. "It's beautiful," she said. "You couldn't pick a better day than this."

Sauk County Sheriff Chip Meister said visitors who were taking photos Wednesday at Devil's Lake State Park should call the Sauk County crime tip line in case they have pictures that could help an investigation into the homicide of a 24-year-old near the south shore, which initial reports indicate was a stabbing. The suspect is still at large.

A tree downed during the storm overnight Thursday blocks the road to Devil's Lake State Park's Nature Center on Friday morning near Baraboo.

A tree downed during the storm overnight Thursday blocks the road to Devil's Lake State Park's Nature Center on Friday morning near Baraboo.

A rock climber scales a wall near the CCC trail at Devil’s Lake State Park.

Visitors walk a dog May 2 along the south shore at Devil's Lake State Park near Baraboo. The park reopened May 1 with limited hours and capacity after being closed for most of April due to COVID-19 concerns and crowding. More than 2.6 million people have visited the park annually in recent years, according to the state Department of Natural Resources.

Visitors hike May 2 at Devil's Lake State Park near Baraboo. The park reopened May 1 with limited hours and capacity after being closed for most of April due to COVID-19 concerns and crowding. More than 2.6 million people have visited the park annually in recent years, according to the state Department of Natural Resources.

Visitors hike and fish May 2 at Devil's Lake State Park near Baraboo. The park reopened May 1 with limited hours and capacity after being closed for most of April due to COVID-19 concerns and crowding. More than 2.6 million people have visited the park annually in recent years, according to the state Department of Natural Resources.

An angler fishes May 2 at Devil's Lake State Park near Baraboo. The park reopened May 1 with limited hours and capacity after being closed for most of April due to COVID-19 concerns and crowding. More than 2.6 million people have visited the park annually in recent years, according to the state Department of Natural Resources.

Beachgoers sunbathe at the north shore of Devil's Lake on June 16. The Wisconsin Department of Natural Resources announced plans to open group campsites that allow up to 50 people starting Monday, including those at Devil's Lake and the nearby Mirror Lake State Park.

Devil's Lake open May 2

Devil's Lake open May 2

Devil's Lake open May 2

Devil's Lake open May 2

Visitors to Devil's Lake State Park in Baraboo, Wis. gather on the park's north beach Friday, May 1, 2020. Gov. Tony Evers on Tuesday directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. JOHN HART, STATE JOURNAL

Carrying "crash pads" on their backs, bouldering enthusiasts Evan Stoddard, Anna Boatman and Ian Cotter-Brown, all of Madison, Wis. walk toward rocks at Devil's Lake State Park in Baraboo, Wis. Friday, May 1, 2020. Gov. Tony Evers on Tuesday directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. JOHN HART, STATE JOURNAL

Rock Springs, Wis. siblings Lyla, Elijah and Marci Clingerman, ages 2, 9, and 5 respectively, enjoy a dip in the waters of Devil's Lake during a visit to State Park in Baraboo, Wis. Friday, May 1, 2020. Gov. Tony Evers on Tuesday directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. JOHN HART, STATE JOURNAL

Ann Rowley of Madison, Wis. shares a bench and a blanket with her grandchildren, Anczi Willams, 4 and her brother, Tomi, 7, also of Madison, during a visit to Devil's Lake State Park in Baraboo, Wis. Friday, May 1, 2020. Gov. Tony Evers on Tuesday directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. JOHN HART, STATE JOURNAL

A concessions and boat rental facility at Devil's Lake State Park in Baraboo, Wis. remains closed to the public Friday, May 1, 2020. Gov. Tony Evers on Tuesday directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. JOHN HART, STATE JOURNAL

Kayaks at Devil's Lake State Park are arranged on the park's north beach in Baraboo, Wis. Friday, May 1, 2020. Gov. Tony Evers on Tuesday directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. Boat rentals, concessions and rest room facilities are still not available to visitors, however. JOHN HART, STATE JOURNAL

Bouldering enthusiasts gather on rocks at Devil's Lake State Park in Baraboo, Wis. Friday, May 1, 2020 after Gov. Tony Evers directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. From left are Ian Cotter-Brown, Eric Cashman, Anna Boatman and Evan Stoddard. JOHN HART, STATE JOURNAL

Visitors to Devil's Lake State Park in Baraboo, Wis. walk along the shore of the park's north beach Friday, May 1, 2020. Gov. Tony Evers on Tuesday directed the Department of Natural Resources to reopen 34 state parks and forests that he had ordered closed earlier this month in response to the COVID-19 pandemic. JOHN HART, STATE JOURNAL

Wisconsin's lakes -- such as at the popular Devil's Lake State Park near Baraboo -- have always invited exploration, especially in summer.

The Kunneman family hike the East Bluff trail at Devil’s Lake State Park.

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Devil’s Lake State Park is one of the Wisconsin State Parks Governor Evers has closed, in an effort to slow the spread of the Novel Coronavirus on April 9, 2020. RUTHIE HAUGE

Dave and Nicolette Solomita of Madison have a family outing Monday with their children, from left, Melody, 7, A.J., almost 2, and Abby, 3, at Devil's Lake State Park near Baraboo. Nicolette Solomita said the family was “surviving” with schools closed due to the coronavirus pandemic.

A sign at Devil's Lake State Park near Baraboo notifies the public that the park remains open on Monday. As of Tuesday, all Wisconsin state parks and trails are open and fees have been waived for the duration of the public health emergency, but the Wisconsin Department of Natural Resources advises people to maintain social distancing and to not congregate in groups of 10 or more.

People walk in small groups Monday afternoon along a trail at Devil's Lake State Park near Baraboo. As of Tuesday, all Wisconsin state parks and trails remain open and fees have been waived for the duration of the public health emergency, but the Wisconsin Department of Natural Resources advises people to maintain social distancing and to not congregate in groups of 10 or more.

Mary and David Paulson, from DeForest, snowshoe Thursday morning on the Steinke Basin Trail at Devil's Lake State Park near Baraboo. They said they snowshoe often but have only traveled to Devil's Lake for it twice so far this winter due to the -- until recently -- lack of snow.

Jamie Esser, left, passes a trout to his son, Hunter Haavind, both of Middleton, while ice fishing Saturday morning at Devil’s Lake State Park near Baraboo. Though they said they have a license, it was the Department of Natural Resources’ Free Fishing Weekend, meaning anyone could fish almost anywhere without a license or trout stamp. Esser said he comes to Devil’s Lake often to fish. “It’s beautiful,” he said. “Best park in the state.” Another free fishing weekend will be offered June 6-7.

Hunter Haavind, Middleton, ice fishes Saturday morning at Devil’s Lake State Park near Baraboo. It was the Department of Natural Resources’ Free Fishing Weekend, meaning anyone could fish almost anywhere without a license or trout stamp. Another free fishing weekend will be June 6-7.

Jamie Esser, Middleton, prepares a line while ice fishing Saturday morning with his son and a friend at Devil’s Lake State Park near Baraboo. Though they have a license, it was the Department of Natural Resources’ Free Fishing Weekend, meaning anyone could fish almost anywhere without a license or trout stamp. Esser said he comes to Devil’s Lake often to fish. “It’s beautiful,” he said. “Best park in the state.” Another free fishing weekend will be June 6-7.

The Friends of Devil's Lake State Park are seeking a fundraising consultant to help with efforts to build a new interpretive center at the park.

An ice fisherman walks onto the lake Monday morning at Devil's Lake State Park near Baraboo.

The Friends of Devil's Lake State Park are seeking a fundraising consultant to help with efforts to build a new interpretive center at the park, which would take over the educational functions currently being served at the Nature Center, pictured Monday morning.

A sign marks the Grottos and CCC trails April 24, 2019, on the south side of Devil's Lake State Park near Baraboo.

Det. George Bonham of the Baraboo Police Department talks to a driver shortly after noon Wednesday on South Shore Road at Devil's Lake State Park. He said he wasn't letting any vehicles or people on foot through to the park's south shore because authorities are searching for a suspect on foot.

Baraboo Fire Chief Kevin Stieve coordinates mock rescue operations with members of the Civil Air Patrol and other local first responders Aug. 29 at Devil's Lake State Park.

Emergency responders put an injured climber into an ambulance Friday afternoon at the East Bluff Trail entrance in Devil's Lake State Park.

Baraboo Fire & Rescue basket tender Dave Schrofer ascends a cliff face Monday during rescue training at Devil's Lake State Park.

Baraboo Fire & Rescue team member Dave Schrofer, left, helps a fellow team member playing the role of an injured person May 13, 2019, during cliff rescue training at Devil's Lake State Park. Baraboo's rope team rescued a woman who fell about 50 feet off the east bluff Saturday at the park.

A Baraboo Fire & Rescue team member secures a safety harness on the edge of a cliff Monday during a training exercise at Devil's Lake State Park.
Follow Susan Endres on Twitter @EndresSusan or call her at 745-3506.