Macroinvertebrates are organisms lacking a backbone and that are visible to the naked eye. In freshwater streams, they include the insects, crustaceans (crayfish and others), mollusks (clams and mussels), gastropods (snails), oligochaetes (worms) and others.
In most streams and rivers, the larval insects dominate the macroinvertebrate community. These organisms provide an excellent tool for stream quality assessment work.
The macroinvertebrates, being rather restricted to their immediate habitat, cannot escape changes in water quality. If a mild-to-severe pollution problem impacts the creek, a considerable period of time may be required for the macroinvertebrates to fully recover former community structure. It becomes obvious, therefore, that these organisms can provide a relative view of the overall quality of a stream at any given moment.
Literally thousands of different species of macroinvertebrates have been found in Kentucky' s 89,000 miles of streams and rivers. Each taxonomic grouping has specific requirements that the stream must provide for its members to survive and flourish. By determining which species inhabit a stream, one can determine the quality of the water. In addition, the number of macroinvertebrates in a given portion of a favorable stream bottom can reveal possible adverse conditions as well as the relative abundance of species along with the percentage of the stream community they compose.
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