Nutrients and Dissolved Organic Matter in the Altamaha River and Loading to the Coastal Zone

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Weston, Nathaniel B.
Hollibaugh, James
Sandow, Jack
Joye, S. B.
Hatcher, Kathryn J.
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Ammonium (NH₄+), nitrate+nitrite (NOx), dissolved inorganic phosphorus (DIP) and dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP) were measured in the Altamaha River and several tributaries during a two year period from September 2000 through September 2002. Temporal variations in concentration as well as nutrient and dissolved organic matter loading from the Altamaha to the coastal zone were determined. Loading rates were heavily dependent on river discharge, as was the form of nitrogen. All measured dissolved compounds in the Altamaha River were significantly correlated with river discharge (p<0.05) with the exception of NH₄. Concentrations of DOC, DON, DOP and DIP increased during periods of high flow, while levels of NOx dropped. This resulted in NOx dominating dissolved N loading during low river discharge, and DON increasing in importance during periods of high flow. Overall rates of C, N and P loading were much greater during high discharge times. Although loading rates of N were greater during high discharge, the shorter residence time in the coastal zone and the higher fraction of DON may alleviate some of the impacts of loading during high flow. Longer residence times and the availability of NOx for rapid uptake may contribute to coastal eutrophication during periods of low flow.
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