Macroinvertebrate Community Index
Macroinvertebrate Community Index (MCI) is an index used in New Zealand to measure the water quality of fresh water streams. 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.
Source: Wikipedia — Macroinvertebrate Community Index (CC BY-SA 4.0)