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Massage of the Clean Water Act of 1972 brought many improvements to surface waters by curbing much of the toxic and organic pollution going into waterways. But 42 years later, we have yet to make significant reductions in two major pollutants in our rivers, lakes, and coastal sounds-the nutrients nitrogen and phosphorus. Although nitrogen pollution overall has gone down in U.S. streams and rivers since 2004, it remains a serious problem in many waterways, and phosphorus pollution has gone up significantly.1 The problem is especially challenging in that the deleterious effects of nitrogen and phosphorus often occur hundreds or thousands of miles from where the nutrients originate.

Why have these two nutrients proven so tough to get under control? And are current regulatory and programmatic efforts enough to turn this situation around?

Too Much of a Good Thing

The basics of nutrient pollution are simple enough. Nitrogen and phosphorus occur naturally in soil and water and, with respect to nitrogen, in the air we breathe. They also are added to the environment by humans, principally as fertilizers. These fertilizers enhance the growth not just of crops on land but also of algae and aquatic plants in the waters where they end up.2

Above certain levels, nitrogen and phosphorus cause algae to grow faster than ecosystems can handle. When algae die, the decomposition process consumes oxygen. Nutrient pollution also affects submerged aquatic vegetation, but in a different way: The nutrient-enriched sediment that comes off fields and impervious surfaces decreases the light available for these plants, and the shading leads to their death. Then they, too, consume oxygen as they decompose.3

Large algal blooms can entirely eliminate the oxygen in a body of water, a condition known as hypoxia that kills virtually all aquatic organisms unable to escape these so-called dead zones. According to an ongoing anaylsis by the Virginia Institute of Marine Sciences, the area of oceanic dead zones increased by one-third between 1995 and 2007.4 The hypoxic zone that forms in the Gulf of Mexico each summer varies in size from year to year but averages approximately 5,500 square miles, or roughly the size of the state of Connecticut.5