The source of Tyler Creek is in farmland in Rutland Township in Kane County. It flows east and south through new suburban developments and golf courses, an Elgin city park, a Kane County forest preserve, and the grounds of Judson College before joining the Fox River.
Aquatic biologists have developed a classification system for the macroinvertebrates of our streams and rivers. (“Macro” here means that the creatures can be seen with the naked eye.) The system divides the typical macroinvertebrate fauna into four broad categories based on pollution tolerance.
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Dragonfly naiads can tolerate moderate levels of pollution, but as predators–they feed on smaller insects and even on small fish–they are at the top of the food chain and can be harmed by metals and persistent organic chemicals that have entered the bodies of their prey. Crayfish, as scavengers, face similar problems. Some of our local streams have become attractive nuisances. Cleanup of conventional pollutants such as sewage has progressed to the point that dragonflies and crayfish can return, but now these creatures are helping metals and persistent organics enter the food chain.
Like earthworms, they feed by passing whatever they can swallow through their bodies, extracting any organic matter that happens to be present. A few years ago the bottom of Indiana Harbor was easily the most polluted place in the Great Lakes. It was loaded with sewage, heavy metals, and assorted toxic chemicals. Repeated sampling of the bottom mud showed that it was almost entirely without life. Only two living organisms were found, and they were both sludge worms.
The macroinvertebrate populations of streams and rivers are perfect examples of the effects pollution has on biodiversity. Thoroughly sample a stream; sample the headwaters where trees shade the water and keep the temperature low. Sample downstream where some of the water is open to the sun and temperatures fluctuate daily. Sample riffles and pools, slow water and fast, gravel bottoms and mud bottoms. Sample all this and you might find every insect, crustacean, mollusk, gastropod, and oligochaete mentioned in this article. Start adding fertilizer runoff, sewage and animal wastes, and industrial pollution, and you can see the diversity vanish. Reduce the stream to the level of the worst of our rivers and you may have nothing left but sludge worms. There may be millions of those, but where there was once an ecosystem, there is now only a single species. The ecological niches that used to be filled by stone flies and caddis flies and dragonfly naiads are empty. And the larger animals that once fed on these are gone too.
