What is Dissolved Oxygen?
The amount of dissolved oxygen in the water is critical to the survival of Chesapeake Bay's aquatic life. Low dissolved oxygen is often the result of eutrophication, which occurs when there are too many nutrients (such as nitrogen and phosphorus) in the water which cause dense algal blooms to grow. When the algae die and decompose, the decomposition process uses up dissolved oxygen in the water, reducing the oxygen available for fish, blue crabs, and other organisms, which may become stressed or even die.
How is Dissolved Oxygen measured?
Dissolved oxygen was measured at approximately 159 stations, up to 7 times between June and September, using a water quality probe from the bottom to the surface of the water column at one meter intervals. The proportion of time that dissolved oxygen was below the threshold at each station was calculated and then spatially averaged into reporting regions.
Criteria Thresholds (mg L-1)‡
‡ U.S. Environmental Protection Agency (2003)