Importance of humic substances for carbon and nitrogen transport into southeastern United States estuaries

For the time period 1974-1993, fluxes were estimated of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) brought to the salt marshes of Georgia and South Carolina by eight rivers, which drain approximately 75% of the upland watersheds of these estuaries. During this period, concentrations of DOC and DON averaged 5-28 mg C l(-1) and 0.35-0.75 mg N l(-1), respectively. The DON represented 40-90% of the total dissolved nitrogen (TDN) in the rivers during that period. River inputs to the marsh estuaries averaged 32.4 +/- 8.8 thousand tonne yr(-1) for DOC and 27.8 +/- 10.0 hundred tonne yr(-1) for DON. These inputs represent approximately 0.6 and 0.15%, respectively, of the DOC and DON estimated to be produced in situ in the salt marshes. (C) 1999 Elsevier Science Ltd. All rights reserved.