You could be forgiven for thinking the parasitic, bloodsucking sea lamprey—armed with a mouth full of circular rows of sharp teeth—is some creation from a horror movie.
The parasitic fish are very real and have plagued the Great Lakes for a century with such voracity that, in decades past, they killed more fish than fisheries themselves harvested. Modern control methods using aquatic pesticides have blunted their impact, and now UW-Madison engineers are tracking those chemicals’ movement through short- and long-term impact on the environment.
“A lot of what people like me work on is chemicals that make their way into the water by accident,” says Christina Remucal, an associate professor of civil and environmental engineering at UW-Madison. “This is an instance where chemicals are added on purpose, so it’s an interesting angle to think about.”
Remucal’s group is focusing on 3-trifluoromethyl-4′-nitrophenol (TFM). TFM is commonly used and has been shown to be effective at killing lampreys while not being as toxic to other fish species. The group has researched lampricides for years. Remucal’s first PhD student, Megan McConville, studied sunlight’s role in breaking down the chemicals.
“What we found with lab and field studies was that they do photodegrade, but in most of the tributaries, the chemicals don’t see enough light that photodegradation has a major impact,” Remucal says.
They also found that TFM moves into the hyporheic zone—a layer of sediment at the bottom of rivers and streams where groundwater and surface water can mix. Remucal and McConville found that up to 30 percent of the lampricide reaches the hyporheic zone and then is slowly released back into the stream.
Now, Remucal and PhD student Bobbi Jo Helgemoe, in collaboration with Indiana University hydrologist Adam Ward, are working to understand what happens to these chemicals once they’re in the water.
The Great Lakes Fishery Commission, an organization created through a partnership between the United States and Canada, is funding the research.
The U.S. Fish and Wildlife Service releases lampricides into Great Lakes tributaries where the lampreys breed. This timing catches both adult lampreys and their young at a vulnerable time; lampricide treatments occur on a roughly four-year cycle.
“We know that when they treat the streams with the chemical, the same amount they put in does not come out at the other end right away,” Helgemoe says. “We know it’s going somewhere, so we’re hypothesizing that it is sticking to or breaking down in the sediment, or breaking down in the soil. It’s all about understanding where it ends up and being able to trace it better than we do now.”
Helgemoe has conducted lab experiments to study how TFM reacts with sediment in controlled environments. In summer 2020, she’ll go to Michigan’s Upper Peninsula to study real-world interactions when TFM is distributed in several rivers.
“We want to stay there for about two months after treatment to take as many samples as we can,” she says. “That way, we can get a long-term dataset to help us understand how long it’s staying there, how it’s interacting and what the levels are like. We’re also really hoping to be up there for a big storm event because we think that would have a big effect on movement.”
Sea lampreys, according to the Great Lakes Fishery Commission, were first spotted in Lake Ontario in 1835. Improvements to the Welland Canal in the late 19th and early 20th centuries allowed the parasites to bypass Niagara Falls—which had, until then, served as a barrier—and spread through the rest of the Great Lakes.
Lampreys spawn and spend their early lives in tributaries. Upon maturing, they migrate to lakes, where they attach to other fish to feast on their blood. A single lamprey can kill up to 45 pounds of fish in its lifespan, and one female lamprey can produce up to 100,000 eggs. Before effective control measures were implemented, sea lampreys in the Great Lakes killed more than 100 million pounds of fish per year, at tremendous cost to U.S. and Canadian commercial fishing across the region.
“They’ve had a really, really big impact on commercial fisheries in the Great Lakes,” Remucal says. “They’re a really problematic fish that’s been around for a long time.”
The project has implications beyond sea lamprey control efforts in the Great Lakes. Remucal, an expert on the fate of chemicals in water, says the research could have implications for better understanding how other chemicals—added intentionally or unintentionally—move through the environment after entering rivers.
“For example, wastewater has a lot of different pharmaceuticals and chemicals in it that are going to be discharged into a river at low concentrations, and a lot of people study that to see how they move around,” Remucal says. “This is a case where they’re adding a known concentration, and we know when and where they’re doing it. It’s basically adding a chemical tracer to the environment, and we can study it and how it moves around.”
Author: Alex Holloway