During recent decades, the amount of nitrogen flowing into surface waters and estuaries in the northeastern USA has increased 10-fold or more. In estuaries such as the Chesapeake Bay, such large increases in nitrogen are severely damaging populations of aquatic plants and animals, and also increasing harmful and toxic algal blooms. Most of the coastal waters of the USA are seriously degraded. At the global and national scale, agriculture is the major source of nitrogen pollution. However, atmospheric deposition is also a major source in many regions, and it contributes 25 percent to 50 percent of the nitrogen inputs to Chesapeake Bay.

The Susquehanna River is the largest river east of the Mississippi in the USA, the largest tributary of Chesapeake Bay, and the single largest source of nutrients to the main stem of the Bay. Therefore, better understanding of the sources and sinks of nutrients and sediment in the Susquehanna River watershed will support better management of nutrients and water quality in the Chesapeake Bay. Research is needed urgently to identify the most important targets for nutrient reductions and the most cost-effective solutions.