biotic indices Indicator species, when used as a guide to the level of a particular abiotic factor. For example, the presence of certain invertebrate groups in fresh water can be awarded a score that indicates the quality of the water. A scheme employing biotic indices has a scale ranging from 10 (clean water with diverse fauna) to 0 (grossly polluted water with no fauna or with only a few anaerobic organisms).

biotic indices Indicator species, when used as a guide to the level of a particular abiotic factor. For example, the presence of certain invertebrate groups in freshwater can be awarded a score that indicates the quality of the water.