Aquatic studies 101: DuPage ecologists raise mussels, a dragonfly that are basic to local waters

At an aquatic laboratory nestled in Warrenville’s Blackwell Forest Preserve, freshwater mussels grow in beakers, fish race up and down long holding tanks, and rare endangered dragonfly larva munch on aquatic pillbugs.

The Urban Stream Research Center, typically closed to the public, was established in 2012 as part of a Superfund project to restore portions of the West Branch DuPage River and Cress Creek. Today, the center manages lakes and fisheries in DuPage County, monitors its streams and rivers, and runs a robust species recovery program.

The program is built on the idea of “keeping common mussel species common.”

“The big question about freshwater mussels is, ‘why do we care about them?'” aquatic technician Everett Krause said during a tour of the center this week. “Well, freshwater mussels provide many ecosystem services. They are known as the livers of the rivers, or a biological water treatment plant. This is due to their filtering capabilities, where they’re able to filter in between six to 20 gallons of water per day per mussel.”

Mussels are vital to keeping freshwater streams and rivers healthy. As part of their cleaning duties, they filter out harmful algae, bacteria, heavy metals, silt and fine particulates.

Mussels lock pollutants in their tissue until they die, allowing the environment to “catch up” and naturally get rid of the materials at a slower rate than they occur, Krause said.

But mussels can do only so much. In the face of pollution, loss of habitat, invasive species and the negative effects of dams, freshwater mussels are “the most endangered group of organisms in the United States,” according to the Center for Biological Diversity.

Because of this decline, environmental groups have determined that propagation — breeding specimens by natural processes from the parent stock — is needed to help recover freshwater mussels.

Saving vital mussels

That’s where the DuPage County center comes in. District ecologists collect native mussels when they’re in their larval stage and raise them in highly specialized environments at the center.

When mussels are in their larval stage, they spend a few weeks attached to the gills of certain species of fish. So, ecologists at the center use an intricate plumbing system supplied with local creek water to rear mussels first with their host fish.

By hitching a ride, the tiny creatures are able to draw blood and safely grow out of the larval stage.

Once the mussels drop off — the fish are not harmed by this process — they’re raised in beakers, baskets and outdoor containers until they’re large enough to face nature on their own.

“In the wild, from the time of drop-off until the time of adulthood, which for the mussels realistically occurs right around a year or two old, about 0.00001% of the mussels that drop off will survive,” Krause said. “We can turn that around and get something more like 10% to 20%. It’s extremely more effective.”

From 2017 to 2022, the center released 28,417 mussels. In a thorough process that includes excavating release sites and counting mussels, ecologists have been able to determine a rough recovery rate of about 30%.

“With that 30% recovery, we know that our mussels are persisting out there,” Krause said. “We’re likely to get significantly more if we were able to excavate that whole stretch of river, but we’re not going to do that because when we excavate, that 20 square meters is getting completely torn up and any vegetation in that area is getting removed.”

The center rears a range of different species, such as the plain pocketbook, the giant floater and the wabash pigtoe. While some of the species have a life span of 10 years, others can live upward of 100 years.

The center also works with various conservation groups like the Forest Preserve District of Kane County and the McHenry County Conservation District to release native mussels in their waters as well.

Endangered dragonflies, too

While mussel propagation remains the flagship initiative of the center’s species recovery program, ecologists took on raising the federally endangered Hine’s emerald dragonfly in 2016 after being contacted by the U.S. Fish and Wildlife Service.

The species is the only federally endangered dragonfly species in the nation. Originally discovered in Ohio in the early 1900s, the green-eyed insect was thought extinct by the 1950s.

“No one observed them anymore. It was thought that the species had gone extinct, but in 1988, they were rediscovered right here in Illinois in the Des Plaines River Valley,” aquatic resources supervisor Andres Ortega said. “This is really, if you think about it, the heart of Hine’s emerald dragonfly country.”

The dragonfly is found in just four states: Illinois, Missouri, Wisconsin and Michigan. Due to the highly specific conditions that the Hine’s emerald needs to survive, the species is limited to small pockets of habitat within those states.

In Illinois, just 200 to 300 adult Hine’s emerald dragonflies are observed yearly. At such low numbers, especially for an insect, the Urban Stream Research Center decided to give them a helping hand.

Ecologists raise the dragonflies from eggs through their larval stage, releasing them when they emerge as adults. The larval stage of a Hine’s emerald is five years — an unusually long period.

Once an adult, the Hine’s emerald lives for three to six weeks. Currently, ecologists at the center don’t have a safe or effective way of tracking the insect after release.

“Unfortunately, right now, once release comes, it is kind of unknown how long they survive or if they reproduce,” Ortega said. “But that’s another thing we’re currently looking at is a way to potentially track them.”

In addition to tracking, Ortega said ecologists are focusing on raising the Great Plains Mudbug, a common species of crayfish that the Hine’s emerald relies on for habitat.

• Jenny Whidden, jwhidden@dailyherald.com, is a climate change and environment writer working with the Daily Herald through a partnership with Report For America supported by The Nature Conservancy. To help support her work with a tax-deductible donation, see dailyherald.com/rfa.