Results of the 2011-2013 assessment period indicate that:
What is dissolved oxygen? 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.
Excess nutrients and sediment are among the leading causes of the Chesapeake Bay’s poor health. Both can impact the clarity of water and the amount of algae and oxygen it contains. This indicator measures the achievement of water quality standards in the Bay for the latter environmental factor, known as dissolved oxygen.
Like humans, all of the Bay’s living creatures need oxygen to survive. But the amount of oxygen an animal needs can vary depending on the animal’s size and habitat.
Water quality standards for the Bay were developed in 2003 by the U.S. Environmental Protection Agency (EPA). Within these standards, five aquatic habitats—also called “designated uses”—were identified, each with its own criteria for dissolved oxygen, water clarity/underwater grasses and chlorophyll a. If the Bay and its tidal tributaries are to function as a healthy ecosystem, all designated uses must meet all clean water criteria.
In 2014, the Chesapeake Bay Program adopted a goal to reduce pollution and achieve the water quality necessary to protect human health and support the region’s underwater resources.
The methodology used to calculate this indicator considers the achievement or non-achievement of water quality standards for dissolved oxygen in 193 tidal water segments containing four designated uses. Ninety-two segments contain the open-water habitat designated use, 18 contain the deep-water habitat designated use, 10 contain the deep-channel habitat designated use and 73 contain the migratory spawning and nursery habitat designated use.
This indicator uses a surface area-weighted approach, which takes the relative size of each segment into account and ensures we report the best available measure of water quality standards achievement in the Bay.
The Chesapeake Bay Program also tracks a dissolved oxygen indicator that measures volume (as opposed to surface area) in attainment of water quality standards for dissolved oxygen in the open-water, deep-water and deep-channel habitat designated uses.
Chesapeake Bay Program