How are an indicator species used to assess the pollution level in the environment?

Indicator species are organisms whose presence, absence, or abundance reflects the health of an ecosystem and can reveal the level of pollution in the environment. For example, certain aquatic species, like mayflies, are sensitive to water quality changes, and their decline can indicate increased pollution levels, such as low oxygen or toxic substances. By monitoring these species, scientists can assess the ecological impacts of pollutants and gauge the overall health of an ecosystem. Thus, indicator species serve as vital tools in environmental monitoring and assessment efforts.