TY - JOUR
T1 - Submarine Groundwater Discharge in the Sarasota Bay System: Its Assessment and Implications for the Nearshore Coastal Environment
AU - Mwashote, B. M.
AU - Murray, M.
AU - Burnett, W. C.
AU - Chanton, J.
AU - Kruse, Sarah
AU - Forde, A.
PY - 2013/2/1
Y1 - 2013/2/1
N2 - A study was conducted from July 2002 through June 2006 in order to assess the significance of submarine groundwater discharge (SGD) to Sarasota Bay (SB), Florida. The assessment approaches used in this study included manual seepage meters, geochemical tracers (radon, 222 Rn and methane, CH 4 ), and subseafloor resistivity measurements. The estimated SGD advection rates in the SB system were found to range from 0.7 to 24.0 cm/day, except for some isolated hot spot occurrences where higher rates were observed. In general, SGD estimates were relatively higher (5.9–24.0 cm/day) in the middle and south regions of the bay compared to the north region (0.7–5.9 cm/day). Average dissolved inorganic nutrient concentrations within the SB water column ranged: 0.1–11 μM (NO 2 +NO 3 ), 0.1–9.1 μM (NH 4 ) and 0.2–1.4 μM (PO 4 ). The average N/P ratio was higher in the north compared to the middle and south regions of the bay. On average, we conservatively estimate that about 27% of the total N in the SB system was derived via SGD. The prevalence of shallow embayed areas in the SB system and the presence of numerous septic tanks in the surrounding settlements enhanced the potential effects of nutrient rich seepages. Statistical comparison of the quantitative approaches revealed a good agreement between SGD estimates from manual seepage meters and those derived from the 222 Rn model ( p =0.67; α =0.05; n =18). CH 4 was found to be useful for qualitative SGD assessments. CH 4 and 222 Rn were correlated ( r 2 =0.31; α =0.05; n =54). Large scale resistivity surveys showed spatial variability that correlates more clearly with lithology than with SGD patterns.
AB - A study was conducted from July 2002 through June 2006 in order to assess the significance of submarine groundwater discharge (SGD) to Sarasota Bay (SB), Florida. The assessment approaches used in this study included manual seepage meters, geochemical tracers (radon, 222 Rn and methane, CH 4 ), and subseafloor resistivity measurements. The estimated SGD advection rates in the SB system were found to range from 0.7 to 24.0 cm/day, except for some isolated hot spot occurrences where higher rates were observed. In general, SGD estimates were relatively higher (5.9–24.0 cm/day) in the middle and south regions of the bay compared to the north region (0.7–5.9 cm/day). Average dissolved inorganic nutrient concentrations within the SB water column ranged: 0.1–11 μM (NO 2 +NO 3 ), 0.1–9.1 μM (NH 4 ) and 0.2–1.4 μM (PO 4 ). The average N/P ratio was higher in the north compared to the middle and south regions of the bay. On average, we conservatively estimate that about 27% of the total N in the SB system was derived via SGD. The prevalence of shallow embayed areas in the SB system and the presence of numerous septic tanks in the surrounding settlements enhanced the potential effects of nutrient rich seepages. Statistical comparison of the quantitative approaches revealed a good agreement between SGD estimates from manual seepage meters and those derived from the 222 Rn model ( p =0.67; α =0.05; n =18). CH 4 was found to be useful for qualitative SGD assessments. CH 4 and 222 Rn were correlated ( r 2 =0.31; α =0.05; n =54). Large scale resistivity surveys showed spatial variability that correlates more clearly with lithology than with SGD patterns.
KW - groundwater discharge
KW - seepage meters
KW - 222Rn and CH4 geochemical tracers
KW - subseafloor resistivity
KW - nutrient flux
KW - Sarasota Bay Florida
UR - https://digitalcommons.usf.edu/geo_facpub/912
UR - https://doi.org/10.1016/j.csr.2012.12.002
U2 - 10.1016/j.csr.2012.12.002
DO - 10.1016/j.csr.2012.12.002
M3 - Article
VL - 53
JO - Continental Shelf Research
JF - Continental Shelf Research
ER -