Climate Change in the Chesapeake Bay Watershed: Effects on Riverine Discharge, Ecosystems, and Water Quality

Science Center Objects

The 64,000-square mile watershed that drains to the Chesapeake Bay is highly populated and has diverse land use, including forested, agricultural, and urbanized areas. Increased precipitation in the eastern United States over the last 100 years has affected stream flow and thus the loading of pollutants delivered to the bay. Such pollutants as suspended sediment and dissolved phosphorus and dissolved nitrogen enter the bay and cause environmental problems. These problems include rapid growth of algae because of the abundance of nutrients (nitrogen and phosphorus), causing huge areas of the bay to be covered in “algal blooms.” Once these algae die, they sink and decompose, using dissolved oxygen in the water to decompose. The use of dissolved oxygen for decomposition depletes the water of this essential gas, which is needed for other aquatic life. The result is “dead zones” in the bay, that is, areas of the water where there is no oxygen, technically termed anoxic. Suspended sediment delivered to the bay during high stream discharge events blocks sunlight to submerged aquatic vegetation (SAV), which need sunlight to grow.