A visual estimate, which can indicate recent precipitation or runoff. Oxygen is necessary in the water for plant and animal survival. High oxygen levels support greater diversity in species and indicate better water quality. Faster moving water can increase levels of oxygen and indicate whether a water body is running or standing water. Invertebrates are often used as an indicator of water quality.
Some species live in limited conditions, such as at higher levels of oxygen saturation.
High percentages of Ephemeroptera and Trichoptera can indicate good water quality. Caution must be taken in these interpretations because habitats all over the world vary and there is great variability within invertebrate orders. Mollusca Bibliography Allen, T.F.H, Thomas W. Hoekstra. 1993. Toward a Definition of Sustainability . Implementing an Ecological Approach to Land Management.