Microbes play a key role in the loss of oxygen from surface waters. As the organic molecules are broken down by microbes, oxygen is removed from the system and must be replaced by exchange at the air-water interface. Each step above results in consumption of dissolved oxygen. If high levels of organic matter are present in a water, microbes may use all available oxygen. The introduction of excess organic matter may result in a depletion of oxygen from an aquatic system.
Anaerobic microbes obtain energy from oxygen bound to other molecules such as sulfate compounds.
Thus, anoxic conditions result in the mobilization of many otherwise insoluble compounds. Low dissolved oxygen levels may occur during warm, stagnant conditions that prevent mixing. In addition, high natural organic levels will often cause a depletion of dissolved oxygen. Requires the addition of divalent manganese solution, followed by a strong alkali, in a stoppered glass bottle. The dissolved oxygen oxidizes to manganous hydroxide precipitate.