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Sponge Found in Chicago River

To Chris Parson, finding a freshwater sponge in the Chicago River was a classic case of a person being in the right place at the right time. On January 25, 2005, while preparing to work at Horner Park in Chicago with a sixth grade class from Waters School, Parson — then recently retired from his job at Friends of the Chicago River — found the first known sample of a freshwater sponge within the bounds of that river.

“Before I met the kids, I went to the east side of the river and collected some macroinvertebrates to show the kids when they got to the site,” Parson said. “I flipped over a piece of concrete rubble and saw what looked like a freshwater sponge. I had seen something similar on the Middle Fork in Lake Forest in 1997.

“I think that it’s serendipitous that I found them,” Parson said, “because I know what they look like. The Metropolitan Water Reclamation District of Greater Chicago does testing all the time, but they use a little scoop, and they scoop stuff out of the bottom. But sponges don’t generally live on the bottom, so they would have missed them.”

Parson then contacted Shedd Aquarium biologist Roger Klocek, who linked Parson with a reference book. Working with Barry Rogers, science chair at Northside College Prep High School, and one of his students, Leo Basset, Parson tentatively identified the sponge as Spongilla aspinosa. During that time, Klocek processed the sample that Parson had provided him, all but confirming the identity of the sponge, about which little is presently known.

“If the species is correct, we don’t know that much about its habitat requirements,” Parson said. “I’m waiting for an absolute diagnosis, or ID, from a couple of scientists in Europe on the species.”

Parson will continue to search farther north in the Chicago River for additional samples of the sponge, and for other species as well, while he attempts to learn more about Spongilla aspinosa’s tolerance for pollution, its habitat requirements, and the level of dissolved oxygen that it needs to survive.

— Kevin Murphy