Dissolved Oxygen

Learn how much oxygen the Bay’s living creatures need to survive, and what happens when low-oxygen areas form.

Laura Fabian from the Maryland Department of Natural Resources (DNR) explains why oxygen is so important to underwater life and how it is used to measure water quality in the Chesapeake Bay. (Matt Rath/Chesapeake Bay Program)

Dissolved oxygen (DO) is the amount of oxygen that is present in the water. It is measured in milligrams per liter (mg/L), the number of milligrams of oxygen dissolved in a liter of water.

Infographic shows the minimum dissolved oxygen concentrations that animals at different depths of the Chesapeake Bay need to survive.
Each species in the Bay needs certain levels of dissolved oxygen to survive. There is typically less dissolved oxygen at the bottom of the Bay or a river, and more closer to the surface.
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The infographic divides the Chesapeake Bay's water column into six levels, based on depth. The infographic includes drawings of different animals at different depths, next to the minimum amount of oxygen those animals need to survive. On the Bay's bottom, where a bristle worm is shown, species need dissolved oxygen concentrations of at least 1mg/L. Above that, where a fish known as a spot is shown, species need dissolved oxygen concentrations of at least 2 mg/L. Above that, where a crab and bay anchovy are shown, species need dissolved oxygen concentrations of at least 3mg/L. Above that, where an alewife is shown, species need dissolved oxygen concentrations of at least 4mg/L. Above that, where a white perch, yellow perch, American shad, and hard clam are shown, species need dissolved oxygen concentrations of at least 5mg/L. And at the top of the Bay's water column, where a striped bass is shown, species need dissolved oxygen concentrations of at least 6mg/L.