Dissolved oxygen
What is it? This is the amount of gaseous oxygen dissolved in the water. Oxygen gets into the water in various ways, including absorbing it from the atmosphere, by rapid movement of the water, or as a product of photosynthesis.
Why is it important? Oxygen is what gives the water life! Fish and plants alike depend on certain levels of oxygen to survive!
What does it mean? The concentration refers to the amount of oxygen (milligrams) dissolved in every litre of water. Dissolved Oxygen changes over the seasons. Both temperature and the depth of your sample may change the levels. For the best results, trends throughout the year should be compared to previous years.
Understanding basic levels
- 0-2 mg/L: not enough oxygen to support life
- 2-4 mg/L: only a few fish and aquatic insects can survive
- 4-7 mg/L: good for many aquatic animals, low for cold water fish
- 7-11 mg/L: very good for most stream fish