1. Biotic indices and Indicator species

2. Remember about canaries in coal mines? Indicator species – Use of a living organism that is sensitive to certain environmental conditions. Their presence or absence (or any change in their population numbers) will tell you something about the environment. They are used to detect environmental changes (like pollution)

3. Very sensitive organisms - must have high levels of Oxygen and very little organic matter in the water. The cleaner the water, the higher the number of sensitive organisms

4. Moderately sensitive organisms

5. Species tolerant to pollution - can live in water with low oxygen levels and high amounts of organic matter

6. Biotic indices Biotic indices are used to monitor environmental changes. Only organisms that are sensitive to specific environmental conditions are used in the biotic index. Example: Species are counted. The more sensitive organisms you have in the area, the higher the quality of water. Sampling can give an idea of the overall health of the river or stream.