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Jason Hutchison and Scott Kreuzman
Ecology class, BIO 342, Biology Department, DePauw University
Fall semester 2005

Crayfish are a good indicator of water quality in streams.  Changes in pH and dissolved oxygen content are stressful to crayfish inhabiting freshwater ecosystems.  High levels of dissolved oxygen may be stressful to crayfish because of physiological effects or because higher oxygen levels allow invasion of aquatic plant species.  A lower pH (more acidic conditions) could stunt growth of crayfish, with lasting effects even after the pH returns to normal levels.  We investigated the effects of water quality on the size and abundance of crayfish in Big Walnut Creek in the DePauw Nature Park. 

We hypothesized that higher levels of human activity within a watershed would have a negative effect on water quality and that crayfish would be smaller and less abundant in areas with lower water quality. 

We measured stream temperatures and collected water samples to test for pH, dissolved oxygen content, phosphate levels, and nitrate levels. 

Results and Discussion
Our water samples were slightly more acidic, with lower dissolved oxygen content, slightly lower nitrates, and a trace of phosphates.  More water samples should be collected next time monitoring is conducted.  We found no crayfish in the stream, apparently because crayfish cannot be collected during winter months.