Macroinvertebrates are an excellent indicator of freshwater stream health. The presence and absence of certain macroinvertebrates can tell us whether a body of water is heavily polluted or if it is in good health. In this field study, we will learn how to identify common macroinvertebrates found in freshwater streams. With this knowledge we will use sampling techniques to collect macroinvertebrates in a local stream and determine its health using a pollution tolerance index rating.