Dissolved Oxygen

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A good level of dissolved oxygen (DO) is essential for aquatic life. In fact, DO levels are generally used as a measurement of water quality and an indicator of a water body’s ability to sustain desired aquatic life. Dissolved oxygen is actually microscopic bubbles of free (not chemically combined) oxygen gas that are dissolved in water. In general, DO help to: sustain aquatic life, help prevent foul odors…..

How does DO get into the water?

There are a number of ways dissolved oxygen gets into water bodies. For example, oxygen concentrations are higher in the air (31%) in comparison to those in bodies of water (fraction of 1%). Where water and air meet, the huge concentration difference causes oxygen molecules from the air to dissolve in water. When wind stirs the water, or as waves creates more surface area, more diffusion occurs. Think of this like a cup of coffee that has sugar added to it. Without aid, the sugar will dissolve. However, if you stir the cup of coffee, the sugar will dissolve more rapidly.

What disrupts DO levels in water?

There are a number of things that impact the levels of dissolved oxygen in the water. Pollution and temperature are two major influencers of DO levels. Here is a breakdown on how each influences dissolved oxygen.

Pollution: Pollution contributes to oxygen demanding matter. This means that matter such as lawn clippings, soils from erosion and river/stream bank runoff, sewage, or even simply nutrients that stimulate the growth of organic matter, will require significant levels of oxygen in the decomposition process. This means that pollution causes a decrease in the average dissolved oxygen concentrations in water.

Temperature: Simply put, the warmer the water is, the more difficult it is for it to hold dissolved oxygen. There are a number of ways around this problem, one of which is shading. Shading the pond will naturally help keep the water temperatures cooler.

information courtesy of: www.waterontheweb.org