Submarine groundwater discharge to Tampa Bay : nutrient fluxes and biogeochemistry of the coastal aquifer
Kroeger, Kevin D.
Swarzenski, Peter W.
Greenwood, Wm. Jason
MetadataShow full item record
KeywordSubmarine groundwater discharge; Watershed; Aquifer; Nitrogen; Phosphorus; Oxidation/reduction potential; Dissolved organic nitrogen
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.
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.
Suggested CitationMarine Chemistry 104 (2007): 85-97
Showing items related by title, author, creator and subject.
Russoniello, Christopher J.; Konikow, Leonard F.; Kroeger, Kevin D.; Fernandez, Cristina; Andres, A. Scott; Michael, Holly A. (2016-05-02)Submarine groundwater discharge (SGD) is a small portion of the global water budget, but a potentially large contributor to coastal nutrient budgets due to high concentrations relative to stream discharge. A numerical ...
The magnitude and origin of groundwater discharge to Eastern U.S. and Gulf of Mexico coastal waters Befus, Kevin Martin; Kroeger, Kevin D.; Smith, Christopher G.; Swarzenski, Peter W. (John Wiley & Sons, 2017-10-28)Fresh groundwater discharge to coastal environments contributes to the physical and chemical conditions of coastal waters, but the role of coastal groundwater at regional to continental scales remains poorly defined due ...
Geochemical and physical sources of radon variation in a subterranean estuary — implications for groundwater radon activities in submarine groundwater discharge studies Dulaiova, Henrieta; Gonneea, Meagan E.; Henderson, Paul B.; Charette, Matthew A. (2007-12-13)Submarine groundwater discharge (SGD), in form of springs and diffuse seepage, has long been recognized as a source of chemical constituents to the coastal ocean. Because groundwater is two to four orders of magnitude ...