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Submarine groundwater discharge to Tampa Bay : nutrient fluxes and biogeochemistry of the coastal aquifer

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dc.contributor.author Kroeger, Kevin D.
dc.contributor.author Swarzenski, Peter W.
dc.contributor.author Greenwood, Wm. Jason
dc.contributor.author Reich, Christopher
dc.date.accessioned 2007-05-01T20:20:51Z
dc.date.available 2007-05-01T20:20:51Z
dc.date.issued 2007-01-10
dc.identifier.citation Marine Chemistry 104 (2007): 85-97 en
dc.identifier.uri http://hdl.handle.net/1912/1598
dc.description This paper is not subject to U.S. copyright. The definitive version was published in Marine Chemistry 104 (2007): 85-97, doi:10.1016/j.marchem.2006.10.012. en
dc.description.abstract To separately quantify the roles of fresh and saline submarine groundwater discharge (SGD), relative to that of rivers, in transporting nutrients to Tampa Bay, Florida, we used three approaches (Darcy's Law calculations, a watershed water budget, and a 222Rn mass-balance) to estimate rate of SGD from the Pinellas peninsula. Groundwater samples were collected in 69 locations in the coastal aquifer to examine biogeochemical conditions, nutrient concentrations and stoichiometry, and salinity structure. Salinity structure was also examined using stationary electrical resistivity measurements. The coastal aquifer along the Pinellas peninsula was chemically reducing in all locations sampled, and that condition influences nitrogen (N) form and mobility of N and PO43−. Concentrations of NH4+, PO43− and ratio of dissolved inorganic N (DIN) to PO43− were all related to measured oxidation/reduction potential (pε) of the groundwater. Ratio of DIN: PO43− was below Redfield ratio in both fresh and saline groundwater. Nitrogen occurred almost exclusively in reduced forms, NH4+ and dissolved organic nitrogen (DON), suggesting that anthropogenic N is exported from the watershed in those forms. In comparison to other SGD studies, rate of PO43− flux in the seepage zone (μM m− 2 d− 1) in Tampa Bay was higher than previous estimates, likely due to 1) high watershed population density, 2) chemically reducing conditions, and 3) high ion concentrations in fresh groundwater. Estimates of freshwater groundwater flux indicate that the ratio of groundwater discharge to stream flow is not, vert, similar 20 to 50%, and that the magnitudes of both the total dissolved nitrogen and PO43− loads due to fresh SGD are not, vert, similar 40 to 100% of loads carried by streams. Estimates of SGD based on radon inventories in near-shore waters were 2 to 5 times greater than the estimates of freshwater groundwater discharge, suggesting that brackish and saline SGD is also an important process in Tampa Bay and results in flux of regenerated N and P from sediment to surface water. en
dc.description.sponsorship This work was supported by a USGS Mendenhall Postdoctoral Fellowship to K.D.K. and by the USGS Coastal and Marine Geology Program's (CMGP) Tampa Bay Project. en
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher Elsevier B.V. en
dc.relation.uri http://dx.doi.org/10.1016/j.marchem.2006.10.012
dc.subject Submarine groundwater discharge en
dc.subject Watershed en
dc.subject Aquifer en
dc.subject Nitrogen en
dc.subject Phosphorus en
dc.subject Oxidation/reduction potential en
dc.subject Dissolved organic nitrogen en
dc.title Submarine groundwater discharge to Tampa Bay : nutrient fluxes and biogeochemistry of the coastal aquifer en
dc.type Article en
dc.identifier.doi 10.1016/j.marchem.2006.10.012


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