What’s Monitored

Ewww! Bug!!! - photo by Suzy Sanders


Learn more about the Biotic Index
Effects of organic pollution on macroinvertebrates

The pollution tolerances of the various macroinvertebrates included in the biotic index are based upon the macroinvertebrates' tolerance to dissolved oxygen concentrations in water.  Organisms are separated into four categories of pollution tolerance:  sensitive, semi-sensitive, semi-tolerant, and tolerant to pollution.  

It is expected that in a stream with good water quality, that macroinvertebrates that are both sensitive to and tolerant to pollution will be found.  No particular group or types of organisms will dominate the macroinvertebrate population of the stream.  With increased organic pollution (from nutrients found in fertilizers, sewage, and other sources) dissolved oxygen levels within the stream are expected to fluctuate more extremely and fewer pollution sensitive organisms will be found.  Macroinvertebrates that can tolerate lower oxygen levels will become more prevalent.  As organic pollution continues to increase, some pollution tolerant macroinvertebrates will become dominant and will be able to support large populations within the stream, while pollution sensitive or semi-sensitive organisms will be unable to survive.  

A shift in macroinvertebrates' food sources is expected with changes in amount of organic pollution in a stream.  In clean streams, food sources are usually from within the natural stream system, including leaf litter from trees in the riparian corridor of the stream.  In more organically-polluted streams, food might be supplied by other than natural sources, such as nutrients input as fertilizers through runoff or from faulty, un-maintained or satiated septic systems.  Increased nutrients will also stimulate plant and algal growth within a stream, offering yet another food source for macroinvertebrates in polluted streams.

Useful resources to learn more about aquatic macroinvertebrates:

There are a number of valuable resources to which you can refer to learn more about aquatic macroinvertebrates' life cycles, habits, and tolerances to pollution. This list of references below is by no means complete, but offers a glimpse of some books that are available to you to learn more about these organisms. Some of these books may be available for reference at your local Watershed Education Resource Center. Also see the useful links for monitoring page, for a listing of websites with information about macroinvertebrates.

The majority of these references were provided to the WAV program by Jeff Dimick, Laboratory Supervisor & Research Specialist in the Aquatic Entomology Laboratory at the University of Wisconsin-Stevens Point. Jeff provided short descriptions about many of the references to help you determine if the reference is what you're looking for:

Eddy, S. and A. C. Hodson. 1982. Taxonomic keys to the common animals of the north central states. Burgess Publishing Company, 7108 Ohms Lane, Minneapolis, MN 55435.
A good, easy to use key for higher level identifications.

Hilsenhoff, W.L. 1995. Aquatic insects of Wisconsin: keys to Wisconsin genera and notes on biology, distribution and species. Publication No. 3 of the Natural History Museums Council. University of Wisconsin - Madison.
A technical book. Using this publication requires a dissecting microscope and a thorough understanding of aquatic insect morphology.

Larken, L.L. Monitor’s Guide to Aquatic Macroinvertebrates. Isaak Walton League Save Our Streams Program.

McCafferty, W.P. 1983. Aquatic Entomology: The Fishermen’s and Ecologist’s Illustrated Guide to Insects and Their Relatives. Jones and Bartlett Publishers.
A technical book directed at the layman. Taxonomy is out-of-date, but the flow charts for classifying organisms are still some of the best available.

Merritt, R.W. and K.W. Cummins. 1996. An introduction to the aquatic insects of North America (Third Edition) Kendall/Hunt Publishing Company, Dubuque, IA.
The current "big gun" for generic level identification of aquatic insects in North America. A very technical book. Using this publication requires a dissecting microscope, sometimes a compound microscope, and a thorough understanding of aquatic insect morphology.

Robertson, D.M. Robertson, D.J. Graczyk, P. J. Garrison, L. Wang, G. LaLiberte, and R. Bannerman. Nutrient Concentrations and Their Relations to the Biotic Integrity of Wadeable Streams in Wisconsin. USGS Publication 1772.

Thorp & Covich. 1991. Ecology and Classification of North American Freshwater Invertebrates. Academic Press.

Voshell, J.R. 2002. A Guide to Common Freshwater Invertebrates of North America. McDonald & Woodward Pub Co., Blacksburg, VA.
A good references for discussion of differences between groups of organisms, but not actually a taxonomic key in the classic sense. A good book for "picture keying" organisms.

Biomonitoring References:

Chutter, F. M. 1972. An empirical biotic index of the quality of water in South African streams and rivers. Water Resources 6: 19 - 30.

Gottfried, J. and V. H. Resh. 1979. Developing modules for field exercises in aquatic entomology. In: Innovative teaching in aquatic entomology. Canadian Special Publications of Fisheries and Aquatic Sciences. Department of Fisheries and Oceans, Ottawa, Ontario.

Hilsenhoff, W. L. 1977. Use of arthropods to evaluate water quality of streams. Technical Bulletin Number 100, Department of Natural Resources, Box 7921, Madison, WI 53707.

Hilsenhoff, W. L. 1978, unpublished. Revisions of the biotic index.

Hilsenhoff, W. L. 1982. Using a biotic index to evaluate water quality in streams. Technical Bulletin Number 132, Department of Natural Resources, Madison, WI.

Hilsenhoff, W. L. 1987. An improved biotic index of organic stream pollution. The Great Lakes Entomologist Vol. 20, No. 1. 31 - 39.

Hilsenhoff, W. L. 1988. Rapid field assessment of organic pollution with a family-level biotic index. Journal of the North American Benthological Society 7(1): 65 - 68.

Hilsenhoff, W. L. 1998. A modification of the biotic index of organic stream pollution to remedy problems and permit its use throughout the year. The Great Lakes Entomologist Vol. 31, No. 1. 1 - 12.

Lenz, B. N. And M. A. Miller. 1996. Comparison of aquatic macroinvertebrate samples collected using different field methods. U. S. Department of the Interior, U. S. Geological Survey Fact Sheet FS-216-96.

Lillie, R. A. and R. A. Schlesser. 1994. Extracting additional information from biotic index samples. The Great Lakes Entomologist Vol. 27, No. 3. 129 - 136.

Lillie, R. A., S. W. Szczytko and M. A. Miller. 2003. Macroinvertebrate data interpretation guidance manual. Wisconsin Department of Natural Resources, Madison, WI.

Narf, R. P., E. L. Lange, R. C. Wildman and R. C. Lathrop. 1982. A statistical evaluation of the Hilsenhoff biotic index. Report to Wisconsin Department of Natural Resources, Bureau of Water Quality.


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