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Title
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Temporal variation of groundwater nutrient flux dynamics into Santa Rosa Sound, North West Florida.
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Author
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Leach, Dana J.
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Abstract/Description
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Submarine groundwater discharge (SGD) is a pathway of nutrient loading into marine systems. SGD is described as the direct discharge of fresh or recirculated groundwater into the near-shore environment. This study aims to qualitatively identify nutrient transformation within the subterranean estuary (STE), which is a point of mixing between fresh groundwater and seawater where several chemical reactions occur. The biogeochemical conditions in porewater were identified using a push point...
Show moreSubmarine groundwater discharge (SGD) is a pathway of nutrient loading into marine systems. SGD is described as the direct discharge of fresh or recirculated groundwater into the near-shore environment. This study aims to qualitatively identify nutrient transformation within the subterranean estuary (STE), which is a point of mixing between fresh groundwater and seawater where several chemical reactions occur. The biogeochemical conditions in porewater were identified using a push point piezometer. A pieozomanometer survey was conducted to determine the nutrient flux into Santa Rosa Sound, Gulf Breeze, Florida. Nutrient concentration data were obtained by analyzing porewater samples from two sampling dates, June 16, 2019, and September 29, 2019. Upward velocity measurements were made on January 27, 2020. When comparing the two sampling dates, the subterranean estuary shifts from freshwater input into the system and salinity plots mimic the distribution of nitrogen within the STE. Phosphorus, pH, and oxidation-reduction potential (ORP) profiles were compared. In areas with low ORP and low pH, they indicate the possibility of iron oxidation and the possible presence of an "iron curtain". In this area, dissolved phosphorus is likely to precipitate from solution. Total dissolved inorganic nitrogen from porewater averaged 0.7 mmol d-1 per m shoreline. Upward velocity measurements showed that velocity increased with distance offshore, a trend that could be explained by a change of hydraulic conductivity and the patchiness of porewater substrate, where preferential flow through SGD favors sediments further offshore.
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Date Issued
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2020, 2020
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Identifier
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1202025463, WFE0000718
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Format
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Document (PDF)
