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

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.

The post Treating lakes for Eurasian watermilfoil with herbicides can harm young fish first appeared on Wisconsin Sea Grant.

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Marie Zhuikov

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.

The post Sea Grant hires new emerging contaminants staff scientist first appeared on Wisconsin Sea Grant.

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Marie Zhuikov