Gavin Dehnert

https://www.seagrant.wisc.edu/news/pfas-in-municipal-drinking-water-new-grant-designed-to-improve-risk-communication-in-wisconsin/

Summer scholars dip toes into water-related careers: Part two

On: August 21, 2023

In: Anne Moser, aquaculture, Climate change, Emma Hauser, Gavin Dehnert, green infrastructure, herbicides, Natalie Chin, PFAS, Sharon Moen, Summer scholars, Tim Campbell, Wisconsin Water Library

In this second part of a two-part series on Wisconsin Sea Grant’s Summer Outreach Opportunities Program Scholars, we introduce six more scholars working on five projects.

***

What did you do this summer?

A seagull enjoys summer at Bradford Beach in Milwaukee.
Photo credit: Wisconsin Sea Grant

It’s a question that, in the middle of August, might prompt panicked reexamination of how you spent the long, warm days of a fleeting season.

For Wisconsin Sea Grant’s Summer Outreach Opportunities Program scholars, the answers come easily.

This summer, 12 undergraduate students from across the country spent a jam-packed 10 weeks collaborating with outreach specialists on coastal and water resources projects across Wisconsin. Scholars conducted research, engaged kids and adults and shared the stories of Great Lakes science, all while working alongside mentors to explore careers and graduate education in the aquatic sciences.

Whether they wrangled fish in Green Bay or researched green infrastructure in Ashland, scholars have much to share about how they spent their summers. Here’s a snapshot of the final five projects in our series.

Project: Climate Change and Green Infrastructure

It’s summer in Ashland, Wisconsin, and summer scholar Alexander Wuethrich is already thinking about winter.

Summer scholar Alex Wuethrich. Photo credit: Alex Wuethrich

Wuethrich, a senior at Northland College majoring in climate science with a minor in physics, is working under the mentorship of Climate and Tourism Outreach Specialist Natalie Chin to research the ways the city of Ashland can use green infrastructure to absorb and slow the flow of stormwater into Lake Superior. He’s focusing on rainwater—but also snow.

Wuethrich explained that the city receives so much snow in winter that crews remove it from city streets and take it to a snow dump site. The current location makes it easy for polluted runoff to enter local waterways.

“Right now, [the site] is at the top of a ravine that leads into a river,” said Wuethrich. As the snow melts, water carries all the sediment, salt and pollutants picked up from city streets into the river, which leads to Lake Superior.

One option is constructing a wetland, which can slow down water and allow sediments to settle out. Wetland plants can also remove heavy metals. Said Wuethrich, “It’ll bring out a lot of those contaminants that we want to keep out of the water system.”

The city can also take measures to prevent pollutants from being on the street in the first place. Enter the street sweeper.

“Learning about how much of a difference [street sweeping] can make was a real eye-opener for me,” Wuethrich said. Working along sweeper routes for three days, he discovered they do more than just tidy up roads. “[Street sweepers] can also pick up heavy metals and other things from cars…like lead and copper that’ll naturally wear off.” Street sweepers also collect dust and sediment before rainwater washes them into the lake.

In addition to getting a crash course in public works, Wuethrich has been using GIS to map storm sewers and catchment basins in the city and developed educational materials on green infrastructure and how to maintain stormwater ponds in the city. He also created a list of trees that, if approved by the city council, would shape what trees can be planted along city streets. The list prioritizes salt- and drought-tolerant native species that could adapt to a warmer, climate-changed future.

The summer scholar experience has underlined that getting involved matters. Said Wuethrich, “It makes a big difference what your local administrators are doing.”

Project: Eat Wisconsin Fish

For Jojo Hunt and Crow Idnani, this was the summer of fish. Paired with Food-Fish Outreach Coordinator Sharon Moen and Aquaculture Outreach and Education Specialist Emma Hauser in Superior, Wisconsin, the scholars spent their summers immersed in the commercial fishing and aquaculture industries across the state: visiting producers, learning about the industry and sharing what they’ve learned. Both scholars completed projects that seek to educate and connect consumers with fish caught or farmed in Wisconsin.

Jojo Hunt gives the thumbs up next to a large tank of fish

Jojo Hunt at the UW-Stevens Point Northern Aquaculture Demonstration Facility. Photo credit: Jojo Hunt

Hunt, a junior at the University of Denver majoring in GIS with minors in computer science and math, is updating the fish finder map on the Eat Wisconsin Fish website, which helps consumers find local businesses that raise or sell Wisconsin fish.

“The main goal of the map is to bring more attention and awareness to where [the businesses] are and what they do and hopefully break some of those stereotypes,” she said, pointing to the misconception that farm-raised fish is unsustainable.

Hunt is also experimenting with different map-making tools to feature profiles of the producers alongside the data. “I thought it’d be kind of nice to see those right under the map to make the points have a story,” said Hunt.

Crow Idnani at the UW-Stevens Point Northern Aquaculture Demonstration Facility. Photo credit: Crow Idnani

Idnani is also working to dispel myths about aquaculture by suggesting updates to A Consumer’s Guide for Wisconsin Farm-Raised Fish, a publication of the UW–Stevens Point Northern Aquaculture Demonstration Facility (NADF) and the Wisconsin Department of Agriculture, Trade and Consumer Protection. The current guide provides an overview of the aquaculture industry in Wisconsin but can get overly technical. Idnani, a sophomore at Cornell University majoring in environmental science with an eye toward science communication, is reviewing the guide through a consumer lens so that it is more useful for the general public.

A creative piece is in the works, too. Idnani is also writing an article tracing the life of an Atlantic salmon at NADF, from when the fish hatches to when it is harvested. Idnani, Hauser and Moen plan to pitch the story to a regional publication to get it in front of audiences outside the aquaculture industry.

From measuring and sorting Atlantic salmon at the NADF facility to preparing shore lunches and teaching kids about aquaculture, the scholars have—unsurprisingly—learned a lot about all things fish.

Said Idnani, “I never grilled a fish until coming here; I never handled a live fish until coming here. It’s been a lot of firsts, but I’ve enjoyed it.”

Projects: PFAS Bioaccumulation in Plants and Animals Associated with Aquatic Ecosystems

Assessing Aquatic Plant Management Tools for Invasive, Native and Nontarget Organisms in Lake Ecosystems

Summer scholar Britta McKinnon. Photo credit: Britta McKinnon

Britta McKinnon and Heidi Wegehaupt spent their summers in lakes and labs working to paint a more complete picture of how contaminants enter and impact aquatic ecosystems. The scholars participated in two research projects: one focused on poly- and perfluoroalkyl substances (PFAS), and the other on herbicides.

McKinnon, a junior at UW–Milwaukee majoring in aquatic sciences, focused primarily on PFAS. Under the direction of Emerging Contaminants Scientist Gavin Dehnert, she identified potential sources of PFAS in northern Wisconsin. McKinnon paid special attention to airports, which use PFAS-containing foams to extinguish fires, as well as landfills and papermills. She noted lakes that may be affected by contaminated runoff.

PFAS can persist in water for a long time. Sometimes called “forever chemicals,” they do not break down easily and can get taken up by plants and animals—and eventually humans—in a process known as bioaccumulation. McKinnon developed a series of factsheets explaining what PFAS are, how they enter and move through the environment and the concerns they pose for human health.

In sharing information with others, she learned a lot about PFAS herself. For example: PFAS are not one substance but many. “I had no idea that there are thousands of different types,” said McKinnon.

Herbicides, not PFAS, were the subject of Heidi Wegehaupt’s research this summer. Working with Dehnert and aquatic invasive outreach specialist Tim Campbell, Wegehaupt collected water and fish samples across three lakes in northern Wisconsin to determine how the herbicide 2,4-Dicholrophenoxyacetic acid affects nonnative Eurasian watermilfoil, the intended target, and nontarget aquatic organisms.

Said Wegehaupt, “Each waterbody has a unique ecological composition, meaning they all react to herbicides differently.”

Knowing how the herbicide affects nontarget species like fish will help lake associations make informed decisions about how to manage invasive species on their lake.

In collecting samples from different lakes, Wegehaupt, a senior at UW–Madison majoring in conservation biology with a certificate in environmental studies, learned she loved fieldwork.

“My favorite part of this experience so far has been spending time at the lakes we’re sampling and just taking the time to enjoy being outside. Getting to know the lakes we work on and talking with locals has been enlightening to my experience as a whole,” said Wegehaupt.

McKinnon, on the other hand, was excited about the lab work. In addition to her PFAS research, McKinnon helped the research team test the impacts of herbicides on fish scale growth. It reminded her of her favorite class, chemistry. Said McKinnon, “I found that I’m in love with the laboratory aspects.”

Neither scholar had previous experience in environmental toxicology but both used the summer to explore which aspects of the research process resonated with them.

Said Wegehaupt, “I still have one year left at UW, so hopefully this opportunity helps me form a path for the future.”

Project: Expanding Voices Heard in the Wisconsin Water Library

India-Bleu Niehoff helps children with an activity at the library. Photo credit: Wisconsin Sea Grant

As a summer scholar with the Wisconsin Water Library at UW–Madison, India-Bleu Niehoff learned quickly that working at a small library means variety is routine.

“It’s a special academic library, which basically means you do everything,” said Niehoff.

There’s the minding of books, of course—over 35,000 about the Great Lakes and waters of Wisconsin—but then there’s the sharing of books through blog posts, book clubs and library programming across the state. Alongside Senior Special Librarian and Education Coordinator Anne Moser, Niehoff led lessons on shipwrecks and sturgeon and coached kids how to use remotely operated vehicles (ROVs) constructed from clothes hangers.

A rising graduate student in library and information studies, Niehoff was game for it all.

One of her projects was to help coordinate the fall edition of the Maadagindan! Start Reading! book club. A collaboration between Wisconsin Sea Grant, the Wisconsin Water Library and the Great Lakes Indian Fish and Wildlife Commission, Maadagindan! brings together parents and educators to discuss children’s books about Ojibwe culture and language. Meetings also feature an honored guest, usually the author, illustrator or a member of the Ojibwe community who speaks to the themes or importance of the book.

Niehoff researched and helped select the four books, all of which are written by Indigenous women authors. It was difficult to choose just four. As she learned, it’s easy to get lost down the dazzling rabbit hole of books.

“Once you start searching, you keep finding,” she said.

Niehoff also wrote blog posts for the Water Library’s Aqualog blog, the first of which centers on underrepresented groups in nature. The two-part post outlines resources about the history of racism in conservation as well as organizations working to make the outdoors accessible to everyone. The second post, currently under development, will feature resources about Indigenous women in STEM.

India-Bleu Niehoff leads an activity about Great Lakes shipwrecks

Niehoff leads an activity about Great Lakes shipwrecks. Photo credit: Wisconsin Sea Grant

Said Niehoff, “I’ve really enjoyed looking into stuff I’m passionate about and interested in and then accumulate it and make it something that’s available to other people.”

And let’s not forget about the shipwrecks and sturgeon. Niehoff and Moser travelled across the state, from Madison to Sheboygan to Eau Claire, delivering Great Lakes education programming for kids at local libraries. They read books, led kids in the Japanese art of gyotaku and printed fish on paper and played Great Lakes trivia. Watching Moser, Niehoff learned how to engage kids when reading aloud.

Everybody was learning something.

“Going to local communities and sharing this information [was] really enjoyable. Especially because it’s not just kids, it’s parents and whatever grown-up that’s with them,” said Niehoff.

The summer scholar experience allowed Niehoff to experience many different aspects of working at a library, from cataloguing books to leading kids in crafts. Struck by the breadth of the discipline, she’s got a lot to think about going into her first year of grad school.

Said Niehoff, “There are so many different directions you can go.”

The post Summer scholars dip toes into water-related careers: Part two first appeared on Wisconsin Sea Grant.

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Jenna Mertz

Using soft skills to communicate hard science

On: May 2, 2023

In: 2 4 D herbicide, Gavin Dehnert, how to create effective scientific posters, Midwest SETAC Meeting poster session 2023, Serena George

Serena George’s poster was runner-up for best poster for the Midwest SETAC Meeting poster session. She is working with Gavin Dehnert, Wisconsin Sea Grant’s emerging contaminants scientist. Image credit: Serena George, University of Wisconsin-Madison

By Serena George, University of Wisconsin-Madison

Research usually entails following strict protocols and replicating experiments. For the Midwest SETAC (Society of Environmental Toxicology and Chemistry) Meeting poster session, which was held in Milwaukee in mid-April, I thought I would take the opposite approach. I wanted to share the story behind my research and communicate science in a fun and accessible way – showing that research has an exciting plot of overcoming challenges, discovering new things and prompting more questions.

The meeting’s theme was “Applied Environmental Science in Addressing Emerging Contaminants.” My poster followed the story of one such contaminant, the herbicide 2,4-D (2,4-Dichlorophyenoxyacetic acid). Chemicals are often viewed as the “supervillains” in toxicology research, but I tried to frame my 2,4-D character in a different light as he struggled to come to terms with his power and worked diligently to ensure the safety of his fish friends. Emotion can often fuel a scientist’s passion for research, and I think characters can help portray this often-unspoken side of research in a unique way.

This comic-style poster has all the elements of a traditional poster, but I distilled the scientific details to only highlight the essential components (because I am standing at my poster during the session to fill in the details). I also incorporated tips from the #betterposter Generation 2 on YouTube (How to create a better research poster in less time). I used an attention-grabbing title with the main finding as the subheading. The key results and main figures are in the center, already translated for the reader into plain language.

I had so much fun designing this poster and seeing others engage with it. I think it was ultimately successful in attracting viewers and prompting in-depth conversations. Who knows, maybe one day there will be a sequel!

Serena George (left) and Gavin Dehnert with Serena’s poster at the Midwest SETAC Meeting. Submitted photo.

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Wisconsin Sea Grant

New project tests Ceded Territories for PFAS at request of tribes

On: April 3, 2023

In: Andre Bennett, Christine Custer, Emily Cornelius Ruhs, Eve Muslich, Gavin Dehnert, Great Lakes Indian Fish and Wildlife Commission, Jonathan Gilbert, Lac Courte Orielles Ojibwe University, lake water, maple sap, maple syrup, Ojibwe Ceded Territories, PFAS, quantifying PFAS, Robert Flynn, Sean Strom, tree swallows, University of Chicago, University of Wisconsin-Madison, USGS, Voigt Intertribal Task Force, walleye, wild rice, Wisconsin Department of Natural Resources, wolves and PFAS levels, Zhewaab Reggie Cadotte

Eve Muslich, University of Wisconsin-Madison, pours maple sap from a collecting bag into a bottle for testing for PFAS. Image credit: Bonnie Willison, Wisconsin Sea Grant

April 3, 2023
By Marie Zhuikov

When Jonathan Gilbert, director of biological services with the Great Lakes Indian Fish and Wildlife Commission, received a report about levels of PFAS (per- and poly-fluoroalkyl substances) in wolves taken during the 2021 hunting season in Wisconsin, he was flummoxed. The scientific report contained terms and measurements that he, even as a biologist, didn’t understand. Gilbert’s quest for answers led to a larger project that is testing maple syrup, walleyes and lake water for PFAS in areas of the Midwest where Ojibwe tribal members harvest food.

During the wolf season, hunters volunteered their wolf remains to GLIFWC for PFAS testing. Gilbert said about 40% of the wolves had detectable levels of these chemicals. He was given Gavin Dehnert’s name as someone who could help answer his questions about the PFAS report. Dehnert, an emerging contaminants scientist, specializes in PFAS. Dehnert works for Wisconsin Sea Grant, a sister agency to the University of Wisconsin Water Resources Institute (WRI).

Jonathan Gilbert, Great Lakes Indian Fish and Wildlife Commission. Image credit: Bonnie Willison, Wisconsin Sea Grant

“So, I called him up and we had a nice conversation and he answered all my questions and educated me quite a bit on this,” Gilbert said.

Gilbert needed to present the wolf data to the Voigt Intertribal Task Force – a group composed of 10 of the 11 Ojibwe tribes that harvest from Ceded Territories in parts of Minnesota, Wisconsin and Michigan. The task force ensures safe harvest limits and is advised by GLIFWC. Gilbert invited Dehnert to attend the meeting.

Dehnert said, “We spent probably two to three hours just listening to the questions they had, concerns they had – big questions they were really hoping to answer.” Those questions involved PFAS levels in fish, wild rice, and maple syrup and other things tribal members harvest on a regular basis.

“Gavin kept saying, ‘Well, we don’t know, we don’t know.’ But he took what he heard there, and he wrote up a grant proposal to test the waters in rice lakes and in walleye lakes, and to test the sap of maple trees. That’s exactly what the tribes were telling him they were really concerned about,” Gilbert said.

The three-year tribally driven project, “Quantifying PFAS bioaccumulation and health impacts on economically important plants and animals associated with aquatic ecosystems in Ceded Territories,” was recently funded by the U.S. Geological Survey’s Water Resources Research Act Program, the same program through which WRI is funded.

The project has three goals: 1) Assess aquatic environments for PFAS contamination in the Ceded Territories, 2) Determine the accumulation of PFAS in different plants and animals and 3) Understand the health impacts from PFAS exposure. In addition to Dehnert and Gilbert, the project involves Emily Cornelius Ruhs with the University of Chicago, Sean Strom with the Wisconsin Department of Natural Resources, and Christine Custer and Robert Flynn with USGS.

“Zhewaab” Reggie Cadotte, Native American Studies Faculty and Cultural Coordinator, Lac Courte Orielles Ojibwe University, and Gavin Dehnert, Wisconsin Sea Grant, inspect a maple tree for sap sampling on Lac Courte Orielles tribal land in northern Wisconsin. Image credit: Bonnie Willison, Wisconsin Sea Grant

Dehnert said that part one of the project will explore lakes where there’s high harvests of walleye and other fish species and wild rice in Ceded Territories. Researchers will look for the presence of PFAS and determine the levels.

Maple trees were tapped for maple sap collection on Lac Courte Orielles tribal lands to determine levels of PFAS. Image credit: Bonnie Willison, Wisconsin Sea Grant

Part two involves understanding the bioaccumulation of PFAS in harvestable goods. “If we know that it’s in the water source where these walleye or wild rice are living, we want to be able to have some sort of correlation between how much PFAS is in the lake water and then how much is then getting into the fish and wild rice,” Dehnert said. Gilbert stressed that they don’t know how much PFAS moves from the water into fish and plants. They will also test vats of maple sap harvested by tribal members.

Part three will look at impacts on organisms that live in the aquatic environments, focusing on tree swallows. This part, led by Ruhs, will explore how PFAS can impact the immune function of tree swallows in different life stages, from nestlings to adults. The swallows are considered an indicator species for contaminated water because they feed near their nesting area almost solely on aquatic insects. Researchers will take blood samples from the birds and look at white blood cell count and antibodies.

Part one will begin this spring with sampling of maple sap and lake water in 25 lakes.

Dehnert is looking forward to the project.

“It’s not focusing on just science for science. There’s a true actionable side to it. That was why we chose the plants and animals that were highly harvested by these tribes. If you’re finding high concentrations of PFAS in these types of harvestable goods, they are going to disproportionately impact the tribes because they are relying on them for their sustainability and food consumption. Sometimes in science people might look at different plants and animals that don’t really have a cultural tie. So that, to me, has always been why we got so excited about this project,” he said.

A research project team collects maple tree sap for PFAS sampling on Lac Courte Orielles tribal land in spring 2023. Pictured, left to right, are Eve Muslich, University of Wisconsin-Madison; Andre Bennett, Lac Courte Orielles Ojibwe University; Gavin Dehnert, Wisconsin Sea Grant; Jonathan Gilbert, Great Lakes Indian Fish and Wildlife Commission; and “Zhewaab” Reggie Cadotte, Lac Courte Orielles Ojibwe University. Image credit: Bonnie Willison, Wisconsin Sea Grant

The post New project tests Ceded Territories for PFAS at request of tribes first appeared on WRI.

News Release | WRI

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In: Angelo Cozzola, Aquatic Toxicology journal, effect of fluidone on fathead minnows, eurasian watermilfoil and hydrilla herbicides, Gavin Dehnert, William Karasov, Wisconsin Department of Natural Resources

Herbicide Study Finds Good News, Bad News for Use of Fluridone in Lakes

On: March 15, 2022

In a study recently published in the journal, “Aquatic Toxicology,” researchers found that while concentrations of the herbicide fluridone similar to those used when it’s applied to lakes to control Eurasian watermilfoil and hydrilla did not kill fathead minnows, it can impact fish health in more subtle ways.

Eurasian watermilfoil is an invasive water plant that grows so densely it can make boating, fishing and swimming unpleasant and difficult. Image credit: Gavin Dehnert, Wisconsin Sea Grant

“The good news for fluridone is that it didn’t really have any impacts on survivorship or even on fish growth, which was to be expected. But when we looked at some of the more sensitive endpoints, particularly prey capture and endocrine disruption, we see that at certain concentrations there seems to be an impact,” said Gavin Dehnert, research team member and Wisconsin Sea Grant’s emerging contaminants scientist.

Fluridone is one of the major active ingredients in commercial aquatic herbicides. It affects the entire plant by inhibiting its ability to photosynthesize, which eventually leads to death. The Wisconsin Department of Natural Resources (DNR) is interested in using herbicides containing fluridone as an alternative to those containing 2,4-D, which preliminary research has found can be toxic to fish.

Dehnert said that before commercial use, the Environmental Protection Agency (EPA) mandates testing of fluridone to ensure it does not impact fish survival and growth parameters such as length and weight. This testing is done with very high concentrations and recommendations are derived.

“The problem is, they (the EPA) rarely test the actual lower concentrations that they say are safe for the lake,” Dehnert said. “That’s usually a big question mark. It’s like, well, they just said it was safe, but is it actually?”

The research team, led by William Karasov with the Department of Forest and Wildlife Ecology at the University of Wisconsin-Madison, exposed fathead minnows (Pimephales promelas) to concentrations of fluridone that would be found in a lake during treatment. Unlike 2,4-D, which only needs to be applied once, fluridone herbicides could require several applications to a lake to be effective over a minimum of 45 days but usually 90 days. The minnows were exposed to the chemical in the lab for 35 days and then a subsequent generation of larval minnows from the original test group was exposed for 65 days.

Larval fathead minnows were tested for impacts from the aquatic herbicide fluridone. Image credit: Gavin Dehnert, Wisconsin Sea Grant.

After 30 days of fluridone exposure, the adult male fish showed an increased number of nuptial tubercules, which can indicate endocrine disruption. Dehnert explained that some herbicides, especially when they are used at low concentrations, can mimic fish hormones. The tubercules are found near the minnows’ noses and increase or decrease in number depending on how much androgen and estrogen a fish produces. “That’s really important because it could have major impacts on reproduction,” Dehnert said.

The researchers also found that the fishes’ livers were enlarged and that their ability to catch prey decreased significantly when exposed to fluridone, which could be because it impairs their ability to move. Previous studies suggest fluridone can act as a neurotoxin.

The DNR funded the study because, as Dehnert said, “In the state of Wisconsin, everybody likes to fish. So, we’re trying to make sure we protect them as much as possible.”

Other members of the team included Angelo Cozzola and Amber White, all with UW-Madison.

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Sea Grant project faves, Gavin Dehnert

On: January 12, 2022

In: 2 4 D and fish, Gavin Dehnert, herbicides, Kerry Kaufman, Klint Hischke, Menominee Tribal School

The calendar has flipped to 2022. Our staff members are ready to tackle new projects in the coming 12 months, which also happens to mark Sea Grant’s 50th anniversary. Before they move more deeply into the new year, however, some staff members took a moment to retain the glow of their favorite 2021 project. Gavin Dehnert shared his thoughts. He’s our emerging contaminants scientist.

My favorite project of 2021 is one that looked at the impacts of aquatic herbicides, such as 2,4-D, on nontarget organisms. In particular, we wanted to learn more about the interplay of 2,4-D and early life stages of freshwater fish—while bridging the gaps between laboratory and field work. We have a video and a story about the project.

The best part about this research is that its main goal is to help management agencies like the Wisconsin Department of Natural Resources make scientifically informed risk assessment decisions for aquatic invasive species that can protect nontarget organisms.

On top of the actionable science, this project allowed me to communicate with a variety of stakeholders, while meeting some wonderful people. I was able to team with Kerry Kaufman, who works at the Menominee Tribal School in Neopit, and Klint Hischke, a science teacher there who also instructs the students on aquaponics. We collaborated on aquatic science lessons and activities.

Students and instructors from the Menominee Tribal School in Neopit, Wisconsin. Image credit: Gavin Dehnert

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Wisconsin Sea Grant

Treating lakes for Eurasian watermilfoil with herbicides can harm young fish

On: October 14, 2021

In: 2 4 D, Eurasian watermilfoil, Gavin Dehnert, herbicides, toxicity to fish

Wisconsin Sea Grant’s emerging contaminants scientist, Gavin Dehnert, earned his Ph.D. by studying the effects of commercial 2,4-D herbicide exposure on the development and behavior of freshwater fish at different life stages. Now, he’s taking his research out of the lab and into the natural environment, where 2,4-D herbicides are used to treat lakes for the invasive plant, Eurasian watermilfoil.

During his doctoral studies, Dehnert found that exposure to concentrations of 2,4-D similar to those allowed during application to lakes significantly decreased survival in fathead minnow larvae and also other young fish species such as walleye, yellow perch, largemouth bass, northern pike, white crappies and white suckers.

“We saw an increase in about 20 to 35% mortality of the young fish when exposed to 2,4-D,” Dehnert said. “But we kept getting this big question: We know what happens in the laboratory, but what happens in the real world?”

With funding from the Wisconsin Department of Natural Resources, Dehnert designed two sets of experiments this summer in lakes that were undergoing 2,4-D treatments. For the first,

One of two lakewater systems Dehnert uses. In this one, water is taken directly from a lake that had 2,4-D applied, then distributed to tanks where the fish are held. Image credit: Gavin Dehnert, Wisconsin Sea Grant

The second employed an in-lake exposure system. Young fish were put in the lake in two-liter buckets with holes in them covered in mesh, which allowed water and food to pass through, but not the fish.

Dehnert explained, “This allowed us to see what goes on during an actual herbicide treatment. It’s applied to the entire lake and we look at what goes on with the fish.”

He anticipates a possible higher mortality in the lake setting because there are more variables at play. “I would expect more like a 35 to 45% decrease in survivorship because there are more stressors on the fish – temperature changes, storms, nutrient runoff, etcetera. That’s why it’s important to do this experiment in a natural lake setting, so we can get those real-world scenarios,” Dehnert said.

Dehnert is just beginning to process the data from his lake experiments and expects to finish up next year (2022).

Wisconsin lake associations are interested in Dehnert’s work because they want to eradicate Eurasian watermilfoil. Besides the use of an herbicide, the invasive plant can be controlled by manually removing the plants or by introducing beetles that eat it.

“All of these lake associations want to make sure they’re causing the least amount of impact to the other organisms in the lake,” Dehnert said. “So, it’s really exciting to work with them to determine the risks of the different control methods. How do we get rid of this invasive species but keep intact what we already have in the lake?

“Let’s understand what could happen, so we can make an educated decision on whether the benefits outweigh the cons,” he said.

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Sea Grant hires new emerging contaminants staff scientist

On: May 5, 2021

In: emerging contaminants scientist postion, Gavin Dehnert, PFAS

To address contaminants of emerging concern that pose threats to Great Lakes ecosystems and public health in Wisconsin, Sea Grant created an emerging contaminants scientist position. After a nationwide search, Gavin Dehnert was hired, and he begins work on May 3.

Emerging contaminants include pharmaceuticals, personal care products, perfluoroalkyl and polyfluoroalkyl substances (PFAS) and pesticides. Although many of these compounds are detected at low levels in surface waters, they may have adverse impacts on aquatic ecosystems.

“Wisconsin Sea Grant has long funded researchers who strive to increase knowledge about contaminants affecting Great Lakes ecosystems,” said David Hart, Wisconsin Sea Grant assistant director for extension. “The National Sea Grant Office has identified contaminants of emerging concern in aquatic environments as needing increased investment. Gavin brings a wealth of experience that will help us build research partnerships addressing emerging contaminants and bridge research with outreach and education efforts.”

Gavin Dehnert. Submitted photo

If Dehnert’s name sounds familiar, it’s because he has a history with Wisconsin Sea Grant. Dehnert recently completed a Wisconsin Water Resources Science-Policy Postdoctoral Fellowship, where he worked with the Wisconsin Department of Health Services (DHS) to develop groundwater standards for 22 drinking water contaminants, including 16 forms of PFAS. He also helped create a hazard index risk assessment, which offers guidance when mixtures of PFAS are found in water.

Additionally, Dehnert gained outreach experience through his fellowship. The PFAS drinking water standards were released through the governor’s office last year. “That was an experience like none other,” Dehnert said. “Giving a press conference – I felt like a TV star. I would definitely not have done something like that if I hadn’t been in the fellowship.”

His emerging contaminants position will put all these skills to use through the lens of actionable science – sound science guided by strong relationships with stakeholders, coupled with effective outreach and communication. Dehnert met many of those stakeholders during his fellowship.

“That network is one of the best things the fellowship gave me,” he said. “I’m also excited to continue both research and outreach. There’s no point in doing the research if you’re not able to share it or help move forward with actionable science. I’m excited to learn more about the different emerging contaminants that are coming to light and use science to further inform how we make decisions.”

Dehnert has undergraduate degrees in marine science and biology from the University of Miami, and a Ph.D. in integrative biology with a focus on toxicology from the University of Wisconsin-Madison where he studied the effects of herbicide 2,4-D exposure on the development and behavior of fish at different life stages.

Connect with Dehnert via email at dehnert2@aqua.wisc.edu or (608) 263-5348.

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