Benthic macroinvertebrates are a community of organisms that live in the substrate (or benthos) found at the bottom of creeks, streams, rivers, lakes and wetlands. This interesting group of animals are generally large enough to see with the naked eye (macro), spend at least some portion of their life in an aquatic environment, and are all without backbones (invertebrate).
Typical benthic invertebrates are animals such as snails, crayfish, clams, leeches, worms and the larval stages of insects like dragonflies, mayflies, stoneflies and beetles that spend some or all of their lives in water. What makes these animals so interesting is that the health of a watercourse can be determined from the number and types of organisms found in the benthic samples!