Why is dissolved oxygen so important?
An adequate amount of dissolved oxygen in water is essential for the good health of all aquatic life. Oxygen enters water by direct absorption from the atmosphere or by plant photosynthesis. The oxygen is used by plants and animals for respiration and by aerobic (aerobic simply means “in the presence of oxygen”) bacteria which consume oxygen during the process of decomposition. Among other factors,the amount of oxygen water can hold is dependent on temperature. The basic rule of thumb is colder water has the ability to hold higher amounts of dissolved oxygen than warmer water. During the summer months, warmer air temperatures and seasonal low flows raise the water temperature of lakes, streams, and rivers. As water temperature rises, the amount of oxygen the water can hold decreases. The presence of organic materials compounds this problem. Organic materials may be naturally occurring, such as leaves and branches, or they may originate from pollution such as stormwater runoff or poorly
