The presence, condition, and numbers of the types of fish, insects, algae, plants and other aquatic life can provide accurate information about the health of a specific waterbody such as a river, stream, lake, wetland, estuary or coral reef.
For EPA's Report on the Environment, an indicator is a numeric value derived from actual measurements of apressure, state or ambient condition over a specified geographic domain, whose trends over time represent or draw attention to underlying trends in the condition of the environment. Key indicator criteria are:
- the indicator is useful
- the indicator is objective
- the indicator is transparent and reproducible
- the underlying data is characterized by sound collection methodologies, data management systems to protect its integrity, and quality assurance procedures
- data are available to describe changes or trends
- the data are comparable across time and space, and representative of the target population.
Therefore, biological indicators are defined here as a numerical value(s) derived from actual measurements, has known statistical properties, and conveys useful information for environmental decision making. It can be a measure, an index of measures, or a model that characterizes an ecosystem or one of its critical components.
The primary uses of an indicator are to characterize current status and to track or predict significant change. With a foundation of diagnostic research, an ecological indicator may also be used to identify major ecosystem stress.
Read more About Bioindicators.