Macroinvertebrate Community Index

[1] The presence or lack of macroinvertebrates such as insects, worms and snails in a river or stream can give a biological indicator on the health of that waterway.

[5] Any changes that may occur in macroinvertebrate communities that lead to a reduction in diversity increase the dominance of pollution-tolerant invertebrates, such as oligochaetes and chironomids.

[6] Thus, a lack of species diversity and low biotic index scores of inhabitant macroinvertebrates may be an indicator of poor water quality.

[7] The risk of water quality degradation is the greatest in low-elevation areas, where high intensity agriculture and urban development are the dominant land uses.

[8] Macroinvertebrate communities are the preferred indicators of aquatic ecosystem health because they are very easy to both collect and identify, and have short life spans, thus responding very quickly to changes in their environment.

The combination of widespread use and good performance of the MCI and the QMCI in detecting water quality in aquatic ecosystems has sparked interest in further refinement of the methods in New Zealand.

In a study conducted on 88 rivers, Scarsbrook et al. (2000) concluded MCI is more useful than the QMCI for recognizing changes in stream water quality over time.

[11] In August 2019, the Ministry for the Environment released a draft National Policy Statement for Freshwater Management, and a report from Scientific and Technical Advisory Group that recommended including three different measures, MCI, QMCI and Average Score Per Metric (ASPM).

[13] There have been several other factors such as water temperature, invertebrate life histories and dissolved oxygen levels that have all been explained as causes of seasonal variability.