Atmospheric Deposition and Nitrogen Pollution in Coastal Marine Ecosystems

Abstract

Since the first appreciation of the widespread occurrence of acid rain in North America (Likens and Bormann 1974), most public attention has focused on the acid component rather than effects from the associated elements in atmospheric deposition. The emphasis has been on freshwater ecosystems and forests in sensitive regions with relatively low buffering capacity. Effects of acid deposition on coastal marine ecosystems have usually not been considered, which makes sense in the context of acidity. Marine ecosystems are very well buffered, since they contain large amounts of dissolved carbonate and bicarbonate, and consequently are quite insensitive to acid inputs. Similarly, marine waters contain huge quantities of sulfate (∼ 28 mM) and thus are not sensitive at all to inputs of sulfate associated with acid deposition. On the other hand, nitrogen (N) pollution can cause severe degradation in coastal marine ecosystems, and the role of atmospheric deposition as a contributor of nitrogen to coastal waters has received increasing scrutiny over the past 15 years since Fisher and Oppenheimer (1991) noted that the nitrate anion associated with nitric acid in acid rain may be a major source of nitrogen to Chesapeake Bay.