Long-term monitoring led by researchers from Eastern Illinois University (EIU) has revealed that the type of turbulence in a stream is a driver of ecosystem rehabilitation success.

Anabela Maia and then-master’s student Carl Favata a few years ago joined a project started by fellow EIU researcher Robert Colombo to investigate changes in Kickapoo Creek. A section of the central Illinois stream had been restored in 2010 by the Illinois Department of Natural Resources and U.S. Geological Survey with support from private land owners.

Scouring keys and riffles were added to mimic the natural flow pattern that had been lost over decades of bank erosion and sedimentation.

“That changed the turbulence regime— less still water and more turbulence,” said Maia. “More turbulence of any kind is good because you get more oxygen, more mixing—it’s positive.

“But not all turbulence is equal.”

With the funding they received from the Illinois Water Resources Center to support the final two years of the study, Maia and Favata examined the effects of turbulence on longear sunfish—a common stream species that plays an important role in the health of Kickapoo Creek—and discovered their response varies by the direction of movement.

“You can think of a fan as provoking stream-wide turbulence,” explained Maia. “But if you have boulders, you’re getting horizontal turbulence. And if you have a flap going up and down under- water, you have vertical turbulence.”

When they exposed longear sunfish to a range of conditions in the lab, the researchers saw a surge in oxygen consumption linked to horizontal turbulence—similar to what happens to people running into a headwind.

The physiological impact wasn’t significant enough to suppress the longear population in Kickapoo Creek. In fact, their overall numbers went up in the years following the rehabilitation. But the new turbulence regime did alter their behavior as the fish searched for areas with calmer water and deeper pools.

The finding highlights the importance of designing instream rehabilitation to include the preferred regimes of sensitive species.

“The presence of species that are less tolerant is what’s going to be a good measure of restoration success and a sustainable habitat,” added Maia.

Yet, perhaps the most important outcome of the study, Maia emphasized, is that it demonstrates the importance of monitoring restored sites long term.

“The effects of restoration might not be visible right away. The habitat, most significantly the fish, recovered four years after restoration. It might be at least five years before we can actually say strongly that trends are the result of restoration.”

Go with the flow: Restoring streams with an eye toward turbulence