Macroinvertebrate Monitoring

Macroinvertebrates are organisms that are large (macro) enough to be seen with the naked eye and lack a backbone (invertebrate). They inhabit all types of running waters, from fast moving streams to slow moving muddy rivers. Examples of aquatic macroinvertebrates include insects in their larval or nymph form, crayfish, clams, snails, and worms. Aquatic macroinvertebrates are good indicators of stream quality because:

  • They are affected by the physical, chemical, and biological conditions of the stream.
  • They can't escape pollution and show the effects of short- and long term pollution events.
  • They may show the cumulative impacts of pollution.
  • They may show the impacts from habitat loss not detected by traditional water quality assessments.
  • They are a critical part of the stream's food web.
  • Some are very intolerant of pollution.
  • They are relatively easy to sample and identify.

The basic principle behind the study of macroinvertebrates is that some are more sensitive to pollution than others. Therefore, if a stream site is inhabited by organisms that can tolerate pollution and the more pollution sensitive organisms are missing a pollution problem is likely.

At each site, a total of five 60 second kick samples were taken in and around each transect and composited into one sample. Kick net samples were collected using a D-frame net with a 500 um mesh. Substrates, submerged vegetation, algal mats and/or other habitat elements were kicked, disturbed and collected. Large debris were examined, picked and removed from the D-net as each sample was transferred into a sieve bucket. The entire sample was transferred to a sample container with a final concentration of 70% ethanol, labeled and sealed. Samples were kept at ambient temperature for transporting and storage.

In the laboratory, samples were rinsed with deionized water and re-submerged in 90% ethanol until picking and identification. Picking samples consisted of examining all organic and inorganic material for macroinvertebrates, picking the organisms and discarding the debris. Dissecting microscopes and magnifying glasses were used to aid in the picking and identification of organisms. All organism, with the exception of Chironomids, were identified down to the genus/species level. Midges were identified at the family level. In the future,Chirononmids may be identified to the genus/species level. All samples were archive using 90% ethanol in tightly sealed containers.