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What is a macroinvertebrate?
Macroinvertebrates are small organisms without a backbone. Some common macroinvertebrates found in wetlands are: dragonfly
nymph, worms, snails, beetles, leeches, mayflies, caddisflies, small crustaceans and other insects.
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| Dragonfly nymph |
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| Snail and clams |
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| Small crustacean |
Why sample macroinvertebrates?
Macroinvertebrates are useful indicators of the health or condition of wetlands and other water bodies. They
respond to many kinds of pollution, including chemical pollution and physical disturbance to the landscape around the site,
wetland structure, and hydrology. There are several advantages of using macroinvertebrates:
- Invertebrates are commonly and widely found in many types of wetlands.
- Invertebrates respond with a range of sensitivites to many kinds of pollution, for this reason
they are commonly used in toxicity testing to develop water quality standards.
- Many aquatic invertebrates complete their life cycles in wetlands, so they are exposed directly
to the physical, chemical and biological conditions within the wetland. Invertebrates with longer life cycles such as
dragonflies, may signal that conditions remained healthy for the duration of their development.
- Aquatic invertebrates are important in wetland food webs for wildlife.
(Taken from "A Citizen's Guide to Biological Assessment of Wetlands, the Macroinvertebrate Index
of Biological Integrity" Dr. Judy Helgen, MPCA 2002)
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| Volunteers collect a bottletrap sample. |
How do we sample?
Volunteers work as a team to
collect one complete dipnet sample and one complete bottletrap sample from each wetland site. The dipnet sample
is collected by sweeping a large net through the water in or near vegetation. This sampling technique provides
the widest number of species. A bottletrap sample is collected by submerging specially designed 2 liter bottles,
mounted on a dowel, about 6 inches below the surface of the water (see photo below). Bottletrapping allows us to catch
the actively swimming predators. For more specific sampling information please refer to:
Macroinvertebrate Sampling Protocols Macroinvertebrate Metrics
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Wetland Health Evaluation Program
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