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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #121162
Title: SOURCES OF NUTRIENT POLLUTION TO COASTAL WATERS: IMPLICATIONS FOR ACHIEVING COASTAL WATER QUALITY GOALS

Author
item HOWARTH, ROBERT - MARINE BIOLOGICAL LAB.
item Sharpley, Andrew
item WALKER, DAN - MARINE POLICY CENTER

Submitted to: Estuaries
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2003
Publication Date: 1/20/2004
Citation: Howarth, R.W., Sharpley, A.N., Walker, D. 2004. Sources of nutrient pollution to coastal waters: implications for achieving coastal water quality goals. Estuaries. 25(4B):656-676.

Interpretive Summary: Nutrient pollution is currently the largest pollution problem in the coastal rivers and bays of the United States and is likely to increase globally as human use of inorganic fertilizers and fossil fuels - the two dominant sources of nutrients - continues to intensify, at least on a global basis. Much remains to be learned about the geographic extent and severity of eutrophication, the relative susceptibility of different coastal ecosystems, and the most effective nutrient control strategies. There is also a great need to better translate scientific knowledge into effective policy and management strategies, which requires an understanding of the complex oceanic, estuarine, and watershed processes that contribute to eutrophication. With this better understanding, more effective techniques can be developed for reducing and preventing nutrient pollution, eutrophication, and associated impacts.

Technical Abstract: Some 60% of coastal rivers and bays in the United States (U.S.) have been moderately to severely degraded by nutrient pollution. Both nitrogen (N) and phosphorus (P) contribute to the problem, although for most coastal systems, N additions cause more damage. Globally, human activity has increased the flux of N and P from land to the oceans by some 2- and 3- fold, respectively. For N, much of this increase has occurred over the past 40 years, with the increase varying from region to region. For example, human activity has increased the flux of N in the Mississippi River basin by some 4-fold, in the rivers of the northeastern U.S. by some 8-fold, and in the rivers draining to the North Sea by more than 10-fold. Sources of nutrients to the coast vary from site to site and from region to region. For some estuaries, sewage treatment plants are the largest single input. However, for most systems, non-point sources of nutrients are now of relatively greater importance, both because of improved point source treatment and control (particularly for P) and because of increases in the total magnitude of non-point sources (particularly for N) over the past 3 decades. In the U.S., N from animal wastes that leaks directly to surface waters or is volatilized to the atmosphere as ammonia may be the single largest source of N that moves from agricultural operations into coastal waters. In some regions, including the northeastern U.S., atmospheric deposition of oxidized N from fossil fuel combustion is the major flux from non-point sources. As the relative importance of these nutrient sources varies among regions and sites, so must appropriate and effective mitigation strategies. The regional nature and variability of nutrient sources require nutrient management efforts address large geographic areas.