Coastal ocean atmospheric deposition

The major ions have two main escape routes from the ocean (1) incorporation into sediments or pore water and (2) ejection into the atmosphere as seasalt spray. This spray is caused by bursting bubbles that produce small particles, called aerosols, that range in diameter from 0.1 to 1000 pm. The annual production rate of seasalt aerosols is large, on the order of 5 x lO kg/y, but virtually all of it is quickly returned when the spray fells back onto the sea surfece. A small fraction (about 1%) is deposited on the coastal portions of land masses and carried back into the ocean by river runoff. As shown in Table 21.6, seasalts represent a significant fraction of dissolved solids in river runoff, especially for sodium and chloride. Due to the short timescale of this process, seasalt aerosol losses and inputs are considered by geochemists to be a short circuit in the crustal-ocean-atmosphere fectory. The solutes transported by this process are collectively referred to as the cyclic salts. ... 

Inputs of new N into coastal systems are more diverse than inputs to the open ocean and include compounds considered regenerated N sources in the open ocean. New N can be dehvered by rivers, runoff events, and atmospheric deposition and can include a whole spectrum of N compounds including NH4 , urea, and DON (e.g., Anderson et al., 2002 Glibert et al., 2001, 2005c MuIhoUand et al., 2007). Similarly NH4 derived from natural processes and anthropogenic activities can support new production in estuarine and coastal systems (see Chapter 9 by Seitzinger and Harrison and Chapter 11 by Paerl and Piehler, this volume). 

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. 

For open ocean regions atmospheric deposition is calculated as a percent of biological N2-fixation plus atmospheric deposition, assuming river N inputs are removed within coastal and shelf sediments. For continental shelves the range includes uncertainties in river N inputs for open ocean estimates, the range is that calculated with and without including DON in rainwater. See Fig. 6.6 for the contribution of atmospheric deposition in watersheds to river N export. 

Paerl, H. W., and Fogel, M. L. (1994). Isotopic characterization of atmospheric nitrogen inputs as sources of enhanced primary production in coastal Atlantic Ocean waters. Mar. Biol. 119, 635—645. Paerl, H. W., Dennis, R. L., and Whitah, D. R. (2002). Atmospheric deposition of nitrogen Implications for nutrient over-enrichment of coastal waters. Estuaries 25, 677—693. 

The other Nr sources to the ocean are riverine injection and atmospheric deposition. Over the last few decades, riverine inputs to the ocean have ranged from 13 TgN yr to 76 TgN yr with the more recent estimates 40-50 TgN yr (Table 4). These inputs to coastal regions have significantly altered the associated ecosystems (NRC, 2000 Rabalais, 2002). 

Iron may be supplied to the euphotic zone from advective and diffusive processes within the ocean as well as by atmospheric deposition of particulate matter to the ocean surface. In coastal areas the water composition can be affected by the contribution of rivers and in polar regions the glacier effect, in terms of ice melt and erosion during the ice flow, can be important. 

Inputs of nutrient N and P to the coastal zone which support new primary production are from the land by riverine and groundwater flows, from the open ocean by coastal upwelling and onwelling, and to a lesser extent by atmospheric deposition of nitrogen. New primary production depends on the... 

Chinese scholars have started research into the transportation of nutrients to the ocean via the atmosphere and its influence on the marine ecosystem in recent years. There were clear seasonal variations for most of the ions, and the concentrations of major ions from mban area rainwater were apparently higher than those in remote regions. By in situ incubation experiments in the coastal Yellow Sea, the atmospheric deposition with high nitrogen and low phosphorus in the Yellow Sea area was the major nutrient resource for ph3doplankton in the mixed layer during the water stratification period in summer. 

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