Summary #
Macroinvertebrates — insects, worms, crustaceans, and other small organisms that live on the stream bottom — are widely used as biological indicators of water quality. This page introduces the main groups of macroinvertebrates found in Pennsylvania streams and provides guidance on identification.
Macroinvertebrates are a valuable water quality indicator when evaluating aquatic environments. Biological communities reflect the overall ecological health and integrity of a stream, providing links to the type and amount of pollution impacting a specific aquatic ecosystem. Because macroinvertebrates have limited migration patterns, a sessile mode of life and are well suited for their site specific locations, they are excellent indicators of localized stream health. Assessing biological communities is often a practical, low cost way of evaluating non-point sources of pollution degrading aquatic habitats. When sampling for macroinvertebrates, look in riffle areas (shallow areas,
with an abundance of rocks and oxygenated water to support macroinvertebrate life) and limit your search to the spring and fall. Winter sampling is not representative of the macroinvertebrate communities due to their unavailability. Some macroinvertebrates are more sensitive than others to pollution. A stream that is being impaired by AMD may be indicated by the absence of generally pollution sensitive macros and the dominance of generally pollution tolerant groups.
The EPA’s “Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates, and Fish” is designed to provide basic aquatic life data for water quality management purposes such as problem screening, site ranking, and trend monitoring. This publication is critical resource to all organizations undertaking a stream assessment.
Sources/Links (as provided in the source text):
Related Pages #
- Developing a Monitoring Plan
- Water Quality — What biological monitoring tells us
- Collection Methods — How to collect biological samples
Source and Last Reviewed #
Source: AMR Clearinghouse (amrclearinghouse.org). Migrated to AML-Connect. Last Reviewed: 2026-03-13.
[Admin note: Some external links in this article may be outdated. Verify before relying on them. Flag dead links for removal or replacement.]
Tags: monitoring, sampling, education
