Submarine Groundwater Discharge in the Sarasota Bay System: Its Assessment and Implications for the Nearshore Coastal Environment

Authors

B. M. Mwashote, Florida State University
M. Murray, Florida State University
W. C. Burnett, Florida State University
J. Chanton, Florida State University
Sarah Kruse, University of South FloridaFollow
A. Forde, University of South Florida

Document Type

Article

Publication Date

2-2013

Keywords

groundwater discharge, seepage meters, 222Rn and CH4 geochemical tracers, subseafloor resistivity, nutrient flux, Sarasota Bay Florida

Digital Object Identifier (DOI)

https://doi.org/10.1016/j.csr.2012.12.002

Abstract

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, ²²²Rn and methane, CH₄), 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 (NO₂+NO₃), 0.1–9.1 μM (NH₄) and 0.2–1.4 μM (PO₄). 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 ²²²Rn model (p=0.67; α=0.05; n=18). CH₄ was found to be useful for qualitative SGD assessments. CH₄ and ²²²Rn were correlated (r₂=0.31; α=0.05; n=54). Large scale resistivity surveys showed spatial variability that correlates more clearly with lithology than with SGD patterns.

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Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Continental Shelf Research, v. 53, p. 63-76

Scholar Commons Citation

Mwashote, B. M.; Murray, M.; Burnett, W. C.; Chanton, J.; Kruse, Sarah; and Forde, A., "Submarine Groundwater Discharge in the Sarasota Bay System: Its Assessment and Implications for the Nearshore Coastal Environment" (2013). School of Geosciences Faculty and Staff Publications. 912.
https://digitalcommons.usf.edu/geo_facpub/912