For years, biologists have analyzed fish tissue to gauge the water quality in rivers. But in the Ohio River, researchers are now looking at bugs, too.

Ryan Argo and Jamie Wisenall are standing in the shallows of the Ohio River, just outside Owensboro. With long nets, they reach towards the river bottom, scooping up the sediment.

They wade back to the boat, and examine their haul…lots of larvae, and one identifiable leech.

Argo and Wisenall are biologists with the Ohio River Valley Water Sanitation Commission, or ORSANCO. For the past seven months, they’ve spent hours of their time on the river, looking for bugs.

ORSANCO is an interstate commission responsible for regulating pollution on the Ohio River. Its biologists are charged with collecting data about the health of the river. And this year, for the first time, they’ve developed an index that looks at macroinvertebrates—or bugs—to determine whether the river is healthy.

The index is a way to determine water quality by looking at the quantity and quality of bugs in the river. It involves complicated calculations, but the premise is simple. Biologist Rob Tewes says some bugs are harbingers of health.

“Those are your mayflies, stoneflies and caddisflies,” he said. “By and large those species of those genera are fairly intolerant. And when you have high numbers and high diversity of those three species, by and large it’s agreed upon by the scientific community that you have a pretty good environment there from a water quality standpoint to support those organisms.”

Indexes aren’t anything new. ORSANCO has been sampling fish tissue for years, and using indexes to analyze the data. But macroinvertebrate indexes have historically been used on smaller tributaries. The recently-developed method for the Ohio River is one of the first times a bug index has been used on a body of water this large and complex.

Ryan Argo developed the index. He says using both fish tissue and macroinvertebrate indexes will give regulators a more complete picture over how factors like pollution and invasive species affect the Ohio River as a whole.

“And that’s kind of why you have more than one index because you can kind of assume that if there’s something going wrong with the fish, there’s something that’s going wrong with what the fish are eating,” Argo said. “That’s why we wanted to have another indicator, to basically give our assessments more strength and more power.”

The Ohio River serves a lot of different functions: it’s a major transportation thoroughfare, and provides water for electricity to coal-fired power plants and hydroelectric dams. And, oh yeah, it’s the drinking water for more than 3 million people. Tewes says it’s that last fact that makes the biologist’s work so important.

“So there’s a lot of impacts happening here, so trying to figure out how the bugs relate to that and how to relate those back to ultimately, the river being a source of water for municipalities is kind of a big deal,” he said.

The biologists take 10 samples from the river sediment, then motor downriver a bit to where a flag sticks out of the bank. Argo wades over, and pulls on a rope lying on the river bottom. Slowly, a concrete block emerges, with columns of masonite rising out of it.

“It’s basically like a macroinvertebrate condo,” he says.

This “condo” is covered with mud from the river. When  Argo carefully rinses the mud off into a bucket, then runs it through a sieve, the residents of the “bug condo” appear. Those samples, along with the ones collected from the river bottom, go into jars and are preserved with alcohol. Later, they’ll go to a lab, where scientists will identify the species. All of this data plays a part in the macroinvertebrate index, and when several years worth are collected the biologists will have more information to use when determining water quality.

Erica Peterson reports on energy and the environment for WFPL. She is also Enterprise Editor.