Connecting atmospheric nitrogen deposition to coastal eutrophication.


Paerl HW. Connecting atmospheric nitrogen deposition to coastal eutrophication. Environmental Science & Technology 2002;36(15):323A-326A.


[Excerpt]. Nitrogen (N) is the nutrient recognized as the “currency” of estuarine and coastal plant production and water quality status. Although N inputs are essential for maintaining the fertility of N-sensitive waters, excessive loading has created “too much of a good thing”. It can lead to habitat degradation, algal blooms, toxicity, hypoxia, anoxia, fish kills, and ultimately loss of biodiversity—all classic signs of eutrophication and the accompanying water quality and habitat degradation (1–3). Urban, agricultural, and industrial expansion into coastal zones has been accompanied by a precipitous rise in N loading, which is most readily observed as N-enriched surface and subsurface discharge. When considering all of the anthropogenic N inputs to coastal waters, atmospheric deposition has previously been a neglected source. However, this perception is changing. Recent watershed- and regional-scale studies point to atmospheric deposition of nitrogen (AD-N) as a highly significant and growing source of externally supplied, or “new”, N entering the coastal zone (4). During the past century, AD-N, much of which originates from combustion and agricultural emissions, has increased 10-fold and now accounts for more than 40% of new N-loading to coastal ecosystems (4). AD-N is both a local and a regional issue, because N emission sources may reside either within or far outside specific watersheds (5).