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NITROGEN CONCENTRATIONS IN LOADING SOURCES FOR THREE COASTAL LAGOONS FROM ATMOSPHERIC AND WATERSHED SOURCES, ADJACENT COASTAL MARSHES, TIDAL EXCHANGES
Citation:
LEHRTER, J. C., J. CEBRIAN, J. STUTES, A. HUNTER, A. CORCORAN, AND A. DUNSMUIR. NITROGEN CONCENTRATIONS IN LOADING SOURCES FOR THREE COASTAL LAGOONS FROM ATMOSPHERIC AND WATERSHED SOURCES, ADJACENT COASTAL MARSHES, TIDAL EXCHANGES. Presented at GERS Meeting, Pensacola Beach, FL, March 30 - April 02, 2005.
Description:
Abstract and Oral Presentation Gulf Estuarine Research Society.
Standing stocks and inputs of total dissolved nitrogen (TDN) to three coastal lagoons, hereafter referred to as Kee's Bayou, Gongora, and State Park, with varying adjacent land-use, geomorphology, and water residence time were quantified over an annual cycle. Inputs were from the atmosphere, watershed (surface runoff and groundwater), point sources, fringing marsh and tidal exchange. TDN water-column concentration was highest at Gongora and it did not differ significantly between the other two lagoons. There was tremendous variation across the three lagoons in TDN inputs as wet atmospheric deposition, with the input into Kee's Bayou being 200% and 50% larger than into State Park and Gongora. Watershed inputs were negligible owing to the lack of channeled flow into the lagoons and flat topography of surrounding land. Point-source inputs were only significant in Gongora through a culvert that ran from an adjacent golf course. Although marsh porewater and surface water TDN concentrations did not vary across lagoons, Gongora featured higher loading rates from the surrounding marsh due to a larger marsh area. Concentration measurements for incoming and outgoing tides showed that State Park generally exported TDN, whereas Kee's Bayou and Gongora imported TDN. It appears that the area of adjacent marsh, net tidal exchange, and the inputs from the adjacent golf course account for the higher TDN water column concentration in Gongora. State Park appears to maintain low TDN concentrations through relatively small loads and tidal mixing. Potential mechanisms for the low concentration at Kee's Bayou, despite considerable inputs, are discussed.