Dissolved oxygen concentration is an important indicator of habitat quality and ecosystem condition. It represents the balance between photosynthesis and respiration by all the living organisms in the Bay. The plot to the right displays two examples of vertical dissolved oxygen profiles collected using the CTD oxygen electrode.

Plot Description:
1. This profile was measured near the Bay Bridge on March 26, 1996. This example shows that the oxygen content of Bay water is not always uniform from surface to bottom. The surface waters had oxygen concentrations of about 9 milligrams per liter, while bottom waters had oxygen concentrations less than 6 milligrams per liter. These kinds of vertical variations often occur as a result of salinity stratification which slows the rate of vertical mixing of the water.

2. This profile was measured near the San Mateo Bridge on March 26, 1996. This example shows the typical condition of nearly-uniform oxygen concentrations from surface to bottom. Oxygen is added to the surface layers by atmospheric exchange and photosynthesis. Oxygen is mixed to the bottom waters by tidal and wind-driven stirring; this mixing is rapid in the absence of salinity stratification.