The plants and animals in and around a waterway are excellent indicators of its health. The more diverse the populations, the better the waterway. If only a few species are present, the stream is most likely unhealthy.
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 macroinvertibrate 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.
Some organisms are very sensitive to pollution and will only inhabit clean, unpolluted water. Large numbers of these sensitive organisms indicate that the waterway is in good health. Other groups of organism are somewhat tolerant of pollution to very tolerant. As numbers of the pollution tolerant organisms increase and sensitive populations decrease, the health of the stream becomes is more precarious. Healthy streams have a diverse mixture of all groups, pollution sensitive and tolerant.
Pollution sensitive indexes have been developed for many organisms found in and around the waterways: insects, fish, algae, mussels, and bacteria. These indexes allow you to determine the health of the stream by surveying the population of organisms and calculating a Pollution Tolerance Index.
Common Biological Tests
Biological testing can involve any organism that is a part of the waterway, including bird and mammal interaction. The two most common biological testing methods, however, are the biotic index and fish shocking.
The biotic index uses a pollution sensitive index to determine the health of a waterway from the macro invertebrate population. Macro invertebrates are the insects, molluscs, and worms living in the streams and rivers. They are large enough to be seen with the naked eye. Macro invertebrates may also be referred to as benthic, or bottom dwelling, organisms.
Fish shocking is another method of
biological assessment. This method allows you to gain a fairly
accurate representation of the fish population size and diversity. A
similar pollution sensitive index to that of insects can be used on fish.