Macroinvertebrates

Aquatic macroinvertebrates are small animals that live for all, or part, of their lives in water. There are many different types of macroinvertebrates such as dragonfly larvae, mosquito larvae, water fleas, beetles and snails. Some of these are sensitive to pollution whereas others can live in very polluted waters. Because of this variability in sensitivity to pollution, macroinvertebrates make good biological indicators. By sampling macroinvertebrate communities and looking at both the types and numbers of animals present we can get an idea as to how healthy a waterway is.

Sampling water quality on its own to assess river and estuary health gives us a good idea as to what contaminants are present in the waterway at the time of sampling. What it does not tell us is whether these contaminants are having an impact on the environment and, if so, to what extent. Examining the macroinvertebrate communities can give us a much better understanding of the overall impacts that any contaminants present are having on the environment.

A healthy waterway will have a large number of different types of macroinvertebrates present with no one type dominating the system. A polluted waterway will have only a few different types of macroinvertebrates present, often in large numbers and generally include things like aquatic worms, water fleas and non-biting midge larvae.

Assessing macroinvertebrates can be done in a number of different ways such as using the AUSRIVAS (AUStralian RIVer Assessment Scheme) models, using pollution grading systems such as SIGNAL (Stream Invertebrate Grade Number Average Level) and looking at community structure and complexity. They are also used in ecotoxicological studies.

Macroinvertebrates are one of the components of the environment being assessed as part of the South West Index of River Condition.

Related publications:

AUSRIVAS manual (van Looij 2009)
The Framework for the Assessment of River and Wetland Health (FARWH) for flowing rivers of south-west Western Australia: project summary and results (Water Science Technical Series report no. 39.
The Framework for the Assessment of River and Wetland Health (FARWH) for flowing rivers of south-west Western Australia: method development (Water Science Technical Series report no. 40)