Entomology is the study of insects. Aquatic Entomology is the study of insects that live in the water during all or part of their lives. Many flying insects such as dragonflies, damselflies, caddisflies spend their larval youth in a stream, where they are the primary prey of fish. You can tell a lot about the quality of the water in a stream by the species living in it.
When trying to determine if a stream is clean or polluted, testing for chemicals or contaminants is very tricky and very expensive. For example, when polluted stormwater flows into a creek, it can kill many aquatic species as it moves downstream. A day or two after the storm, the creek water might run clean again but the impact of those long-gone pollutants is apparent in the loss of aquatic life.
To better measure the overall health of streams, Aquatic Entomologists have devised methods to sample the bottom-dwelling organisms called Benthic (bottom) Macro-Inverebrates or BMIs. These bioassessment methods measure the health of the aquatic community, which reflects the conditions in the stream over a much longer period of time than a single water sample can.
Aquatic Entomologists sample, count, and identify the BMIs in a stream. Most BMIs thrive in clean water; relatively few tolerate pollution or damage to the habitat. If the quality of the water and habitat is impaired, the species and number of BMIs will tell that story. In a way Aquatic Entomologists help “the bugs” explain what is happening in their environment, so we can improve water quality.