UWM held its annual Undergraduate Research Symposium in April, showcasing the work of student researchers across many disciplines. Here, meet four students in the College of Letters & Science who presented their work focusing on water quality.
Hungry hemimysis eat plastics and algae
Hemimysis are tiny, invasive, aquatic creatures that have infiltrated the Great Lakes over the last decade, including Lake Michigan. Invasive species obviously pose a threat by disrupting ecosystems, but two biological sciences majors have identified two specific harms that these animals may bring to the local environment.
Xiayou Lowery and Kristin Huelsbeck presented their project, titled “Experimental Evidence That Invasive, Crustacean Zooplankton Hemimysis Feeds on Both Microalgae and Microplastic Particles,” at the UWM Undergraduate Research Symposium in April. Mentored by Professor John Berges, the pair’s experiment explored how hemimysis’ diets may impact the foodchain in Lake Michigan.
Biological sciences majors Xiayou Lowery and Kristin Huelsbeck studied the invasive species hemimysis and its diet. Photo by Sarah Vickery.
Biological sciences majors Xiayou Lowery and Kristin Huelsbeck studied the invasive species hemimysis and its diet. Photo by Sarah Vickery.
Specifically, hemimysis are voracious eaters who like to feast on both microplastics and microalgae.
Using a device built by one of Berges’ graduate students, Lowrey and Huelsbeck captured hemimysis from Lake Michigan. Lowery focused on microplastics; Huelsbeck on microalgae.
“I fed them different sizes of microplastics ranging from about 50 to 30 micrometers to see what they would and could ingest,” Lowrey explained. The creatures took readily to fluorescent plastic beads about 30 micrometers in diameter. Once they had ingested the microplastics, Lowrey could track their consumption by examining the animals under a microscope with a blue light to illuminate the fluorescence.
Microplastics are particles that have been broken down from larger pieces of plastic over time. They can be introduced into the environment through pollution, littering, the sewer system, and even through washing machine water – plastics in synthetic fabrics are also a source of microplastics.
“Those microplastics can make their way through the food web when smaller fish eat those hemimysis, and so on. Eventually, we eat those fish, and we could be ingesting microplastics,” Lowrey said.
There is some good news, however: “This species secretes often. Within three hours, they’ll clear their entire digestive tract,” Lowrey said. “Most of the time, when fish eat them, they might not even have microplastics in their system.”
Huelsbeck’s experiment has implications for the species that rely on microalgae in Lake Michigan.
“We knew that they ate zooplankton, but we didn’t know if they eat native species of algae,” Huelsbeck said. “I exposed them to low-tide concentrations of algae and let them feed, and we found that they were eating (the algae). The implication of that is this might affect other species that might rely on the algae, and how this could impact algae populations in the Lake.”
Huelsbeck measured the amount of algae in the water before and after she let the hemimysis eat using a flow cytometer. She found the creatures were avid munchers: They ate 1,000 cells per creature per hour.
Both students agree more research is needed. Huelsbeck would like to study the species that rely on hemimysis for food. Lowrey wants to know about the long-term effects of microplastics on the hemimysis, and if they will cause a decrease in the population – and a subsequent decrease in populations that depend on hemimysis as food.
A phosphate failure leads to new ideas
John Folena was looking for a way to remove phosphorus from wastewater and runoff. He didn’t find it – but he did accidentally find a way to filter out nitrates instead.
Folena, a geosciences major working under the mentorship of UWM postdoctoral researcher Martin Dangelmayr, presented his research at the UWM Undergraduate Research Symposium in April. Folena’s project, “Phosphate Sorption and Removal From Dairy Effluent Using Zeolites and Pumice,” was aimed at finding a way to filter a harmful chemical from the wastewater of Clockshadow Creamery, a Milwaukeebased cheesemaker.
Phosphates are known to cause adverse environmental impacts. While their presence in fertilizers can help plants grow, phosphates in wastewater can lead to harmful algal blooms in local waterways. The state of Wisconsin recently lowered the acceptable threshold of those chemicals allowable in wastewater, down to .05 milligrams per liter.
Unfortunately, phosophates are extremely difficult to remove.
Folena hoped to start with the “cheapest, fastest, easiest,” potential solution so that wastewater producers could use the research as a starting point. Zeolites – think aquarium gravel – and pumice – a ground-up volcanic rock – are easily available and inexpensive, so they were an ideal material to try as a filter.
He started by taking the wastewater and removing the solid matter with a vacuum pump (“There were a couple of inches of organic crud at the bottom,” Folena said). When he had plain wastewater left, he added it to test tubes with samples of zeolites and pumice, and even varied the levels of acidity of the water to see if that impacted the phosphate sorption.
What is sorption, exactly?
“Adsorbtion is like adhesion, where it’s only surface-level,” Folena explained. “The idea is that the phosphate would be attracted to the surface of the (material).”
After the samples had time to sit, Folena added a molybdenum compound to the water that turns blue in the presence of phosphates. The bluer the water, the higher the concentration of phosphates. Then, he used a spectrometer to measure the wavelengths of the blue light emitted and compared the samples to known values to measure how much phosphorus was left in the water.
It was a lot.
“We saw basically no reduction,” Folena said. “We found that the untreated (wastewater) contained about 6.5 milligrams of phosphate per liter, and in the treated wastewater, we had about 6 milligrams per liter.”
That’s a reduction of just .5 milligrams per liter. Given that the reduction was fairly consistent across the samples, Dangelmayr, Folena’s advisor, thinks that the phosphate that was removed was probably consumed by microbes in the wastewater, rather than filtered out by the zeolites or pumice.
But there was an unexpected finding. Dangelmayr and Folena asked a scientist in UWM’s School of Freshwater Sciences to test the water, just to collect additional data. His data showed something surprising.
“It wasn’t our goal, but it was still a good result. We got an almost 80% reduction in nitrates,” Folena said. “Nitrates and phosphates do very similar things in the environment. We failed what we were aiming for, but we saw massive reductions where we weren’t.
“As far as I’m concerned, we were always testing nitrate,” he joked.
Folena and his advisor still aren’t sure exactly why nitrate instead of phosphate was filtered out, but they would like to continue testing to find the reason. Even though their initial hypothesis was incorrect, the experiment shows what a challenge municipalities face as they try to remove harmful chemicals from their wastewater.
PFAS infiltrates Milwaukee waterways
Perfluoroalkyl and polyfluoroalkyl substances, or PFAS substances, are commonly known as “forever chemicals.” Composed of long chains of carbon atoms bonded with a fluorine atom, these compounds are infiltrating groundwater across the United States.
“The reason these are of interest is because the carbonfluorine bond is one of the strongest in chemistry, so it doesn’t degrade easily. The half-life is about 90 years,” said Abigail Werry. “Once these chemicals get into the environment, they stay there.”
Werry is a biological sciences major who is also pursuing a minor in chemistry and a certificate in forensic science. Her latest research, which she presented at the UWM Undergraduate Research Symposium in April, focused on “Examining Perfluorooctane Sulfonic Acid and Perfluorooctanoic Acid Levels in Drinking Water and Groundwater in the Milwaukee Area.”
Specifically, Werry wanted to know if and where PFAS chemicals have contaminated water in and around the Milwaukee metro area. It’s important to know because, while the long-term effects of PFAS exposure are unknown, some studies have suggested that these chemicals have adverse health impacts, including impacts on reproductive and immune health.
There are about 4,700 types of PFAS chemicals, and they primarily come from a type of foam that firefighters use to quell fires. It’s also found in the spray used to de-ice planes at airports. They can also leech into the groundwater from landfills.
With that in mind, Werry decided to test for the presence of PFAS chemicals in areas near airports and landfills, as well as areas away from those places, to compare the difference. She hiked into fields and woods to take samples of natural groundwater, and she also tested drinking water by asking residents in various locales for samples from their tap. She even tested public drinking fountains – “I actually went to a lot of Kwik Trips because they have bubblers,” Werry said.
With her samples gathered, Werry went back to the lab for testing. She used a process called reverse phase liquid chromatography and paired it with mass spectrometry.
It’s an involved process, but Werry had to run different experiments to find the most effective parameters for her testing machines to achieve the highest sensitivity in her water analysis. After she found the best optimization, she applied them to the analyzation process to find the concentration of PFAS chemicals in her ground and drinking water samples.
Her experiment focused on two chemicals: PFOA and PFOS. “We found that there were detectable samples of PFOA, but there are many PFOS contaminants. We found quantifiable amounts of it,” Werry noted.
About 46% of her drinking water samples showed amounts of PFOS contamination. In groundwater samples 5 miles or more away from airports and landfills, 43% showed PFOS contamination, whereas 80% of groundwater samples taken within a 5-mile radius of airports or landfills showed contamination.
“I was a little surprised at the difference in terms of the samples that were and weren’t near airports and landfills,” Werry said. “I don’t want to worry anyone who might live near these sites, but it is something to think about. What are the cities and counties doing about these contaminants? At the end of the day, they will keep bioaccumulating as people drink water.”
The EPA has proposed safe limits for several PFAS chemicals as 3 to 4 parts per trillion in drinking water. Some of Werry’s samples showed contamination ranging from .013-.018 parts per billion, which means that those water sources are contaminated well above the proposed limit. However, government agencies don’t think these levels will cause significant harm – Werry says no one needs to switch to bottled water just yet.
“But because we don’t have a way to get them out of the environment, we need to make sure we’re not constantly adding more,” she said.
All articles by Sarah Vickery, College of Letters & Science