Use of Macroinvertebrates in Stream
What is stream biomonitoring?
Stream biomonitoring is the study of what
biological organisms are present in a stream. Based on what organisms are
present, you can get an idea of what the stream water quality is like.
What are macroinvertebrates?
Macroinvertebrates are organisms which are
large enough to be seen with the naked eye, yet are generally small. They
lack a backbone and inhabit all types of water habitats. Most aquatic
macroinvertebrates are insects, but others include worms, crayfish, snails, and
How do macroinvertebrates indicate stream quality?
1) They are affected by the conditions of the
stream, including pollution.
2) They are fairly sedentary, and therefore
cannot escape pollution events.
3) Specific species are more or less tolerant
of pollution. Presence or absence of certain species indicates good
or poor water quality.
4) They are fairly simple to sample and
What are the drawbacks to using macroinvertebrates to
indicate stream quality?
1) They do not respond to all types of
2) Their presence or absence may be due to
other factors than pollution (water current, substrate of stream, drought
3) Their abundance and distribution may vary
4) They may disperse into and out of areas
where they normally do or do not occur.
Do the benefits of using macroinvertebrates for monitoring
stream quality outweigh the drawbacks?
Yes. Keeping in mind the limitations
listed in the drawback section, a properly designed stream biomonitoring survey
will give you a very good idea of the water quality of a stream.
Are there different types of stream biomonitoring?
There are 2 major types. (1) Surveys
before and after a known pollution event. (2) Sampling at regular
intervals throughout a specific time period.
Are there different sampling designs?
There are many different sampling
designs, but they fall into 2 main categories:
(1) qualitative- a general assessment of organisms
(2) quantitative- an actual numerical count of different
organisms present in order that statistics can be used more accurately.
The Ackerly Creek Subwatershed biomonitoring was done at regular
intervals over two years, and was a quantitative study. Click on the Ackerly
Creek Subwatershed link to learn more about our particular study.