Atmospheric deposition directly to coastal waters

Atmospheric N deposition can be an important source of N to coastal and open ocean ecosystems. The potential importance of N in atmospheric deposition has been recognized for over twenty years (e.g., CorreU and Ford, 1982 Duce, 1986 Paerl, 1985). Recognition of the importance of atmospheric deposition as a source of N to coastal waters increased rapidly following the analysis by Fisher and Oppenheimer (1991) for a number of coastal systems, including Chesapeake Bay. Atmospheric deposition to watersheds contributes to diffuse N loads in rivers as discussed previously in this chapter. In this section we are specifically referring to N deposited (wet and dry) direcdy to the surface of coastal and open ocean waters. 

In some estuaries and coastal embayments, atmospheric deposition direcdy to the water surface can account for a substantial fraction of N input (as much as 40% of the N inputs from river plus atmospheric inputs Table 9.6). Flowever, the relative importance of atmospheric deposition as an N source varies considerably among coastal systems and depends on a number of factors, including the nature of watershed N sources and the relative sizes of the contributing watershed and receiving estuary (Vahgura et ai, 2001). 

Receiving waters Percent DIRECT atmospheric N to water surface (%) Reference 

North Atlantic Shelf Western 45°-66°N 29-50 This chapter Nixon et al. (1996)  

Global Coastal and Open Ocean 15-42 This chapter 

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