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Dissolved Oxygen |
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Dissolved Oxygen (DO) is found in microscopic
bubbles of oxygen that are mixed in the water and occur between water molecules.
Stream systems both produce and consume oxygen. Oxygen enters the water by
absorption directly from the atmosphere or by aquatic plant and algae
photosynthesis. Oxygen is consumed in the water by respiration of aquatic
animals, decomposition of organic matter, and various chemical reactions. Levels
of dissolved oxygen are closely related to water temperature; the colder the
water, the more oxygen can be dissolved in the water. Therefore, DO
concentrations at one location are usually higher in the winter than in the
summer. Dissolved oxygen levels are
also affected by flow rate, the type and number of aquatic organisms, the number
of dissolved and suspended solids, and the amount of nutrients present in the
water. DO is one of the most important indicators of
a water body's ability to support aquatic life. It is essential for the basic metabolic processes of animals and plants
inhabiting our rivers and streams. Fish
"breathe" by absorbing dissolved oxygen through their gills. When oxygen levels fall too low, fish and many other marine organisms are
stressed and cannot survive. The
Alaska Department of Environmental Conservation standard for dissolved oxygen is
7 mg/l in waters used by anadromous fish. We measure dissolved oxygen using a Winkler
titration. The result is expressed
as a concentration, in mg/l, of water.
(Source: http://bcn.boulder.co.us/basin/data/BACT/info/index.html, http://www.epa.gov/owow/monitoring/volunteer/stream/)
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