Definitions for "Indicator species"
A species that by its presence indicates a particular set of environmental conditions (wet, dry, cold, warm, etc.).
An organism whose presence or absence suggests that certain environmental conditions prevail. It can be used to monitor how much of a factor is present, and how the environment is responding to stresses and changes.
A species that scientists used as a measure of the condition of a particular habitat, community or ecosystem.
Keywords:  bio, see
See bio-indicator.
An organism, who?s health or population numbers, are a gauge of pollution within an environment.
Keywords:  versus, polluted, clean, quality, help
Certain organisms, in part, that help determine water quality (clean versus polluted).