Biological Response to Stress:

Organisms are subjected to a number and variety of stressors in the environment, therefore multiple measures of health are needed to help identify and separate anthropogenic-induced effects of stress from those effects caused by natural stressors.

Multiple measures of health include responses that represent different levels of biological organization, response time to stressors, and sensitivity and specificity to stressors.

Environmental stressors can have direct (through metabolic pathways) and indirect (through food and habitat availability) effects on organisms.

Bioindicators that can be measured to characterize the physiological condition of organisms in each stress zone (see above figure). Indicators in zone 1 are more sensitive to environmental stressors, while those indicators in zone 3 are less sensitive, but have higher ecological relevance.

The physiological condition of organisms can be characterized by three major stress zone based on the level of disability caused by environmental stressors.

If properly calibrated to higher level responses, the lower-level responses can be effectively used in environmental management and in the ecological risk assessment process.

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