Aquatic macro-invertebrates are organisms that live underwater in streams and rivers, lack a backbone, and can be seen by the naked eye. Macroinvertebrates an an important link in the food web between the produces, such as leaves and algae, and higher consumers such as fish.​

The importance of macro-invertebrates is that they are bio-indicators, or organisms that inform us about the health of an ecosystem. Macroinvertebrates are sensitive to chemical, physical, and biological environmental stressors, which means that some of them are intolerant to pollution (require good water quality to survive) and some are tolerant to pollution (only thrive in poor water quality). In general, macro-invertebrates such as dragonflies and damselflies are indicators of good water quality, whereas snails, leeches, and worms are signs of poor water quality. Additionally, macroinvertebrates such as mayflies, water striders, water beetles and bugs, and scuds are moderately- sensitive to pollution, meaning that they live in water with fair quality. ​The reason to monitor macro-invertebrates is because chemical tests can only tell you so much, but the diversity and population of these organisms can reflect the quality of the water and how it's changing.

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