Some of the nitrogen polluting these waterways comes from crop fields and grazinglands. Both natural and agricultural ecosystems have a certain amount of nutrient loss. That's because rainfall dissolves and leaches nitrogen and other nutrients from soil into nearby streams and rivers that eventually feed coastal bodies of water. Nitrogen stimulates growth of aquatic flora and microbes, which often lower the amount of dissolved oxygen in the water. With little oxygen to sustain them, native fish and shellfish that are economically and environmentally important die or are displaced.
Wetlands are an excellent last line of defense for water quality.
He worked with agricultural engineer Frank J. Humenik at North Carolina State University in Raleigh, along with agricultural engineer Kenneth C. Stone, soil scientist Terry A. Matheny, and agricultural engineer Melvin H. Johnson at the ARS Coastal Plains Soil, Water, and Plant Research Center in Florence, South Carolina. It was part of a USDA Water Quality Demonstration Project in the Coastal Plain of North Carolina. Herrings Marsh Run provided us with good potential for establishing a wetland and cleaning up one of its streams. In this case, establishment was easy. The water depth at the lower end was about 6 feet, but much of the area was less than 2.