News Releases - 2003

Rock River Algae Growth Generating "Release" Reports

Springfield, Ill. -- Weather and water conditions in northwestern Illinois have been just right to promote growth of a particular type of brown algae, and the resulting unattractive "foam" has caused numerous calls to the IEPA office in Rockford reporting what viewers perceive as a major industrial or agriculture waste release.

Charles Corley, Interim Regional Manager for Water Pollution Control in the Rockford field office, says the phenomenon occurs nearly every year in late summer and early fall, but some years the brown stuff is more noticeable and generates more public response.

"We certainly encourage people to notify us whenever they see what could be an environmental problem, like spills or releases of waste," Corley said, "but in this case investigation has shown the brown matter is a natural condition"

Primarily, the growth is the result of warm river temperatures and low water levels in areas where bottom conditions encourage turbulence. Diatoms, minute algae-sized organisms with unique uniform geometrical shapes, and other algae thrive there, and as they undergo a series of life cycles, the insect larvae and other macroinvertibrates generate bacterial enzymes that have a detergent effect as they break down their food sources.

Students looking for science projects, or anyone else motivated to closely inspect the material, will find it includes dead organisms, algae, diatoms and detritus --- matter sloughed off by the organisms as they live and die --- as well as some living macroinvertebrates.

Combining the right water temperature at the lower river levels, an uneven stream bottom that creates "riffles" or turbulence, and a bit of surface tension produces brown frothy mats.

Corley says the foam will become less noticeable and disappear as the weather cools in early fall, when rainfall normally also increases, raising water levels and reducing the turbulence. While unattractive, it's part of the normal life cycle of the river, he said.

Diatrom blooms are periodically reported in other parts of the state as well, when conditions are right elsewhere for their generation.