Date of Award

Fall 2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Ocean Science and Engineering

Committee Chair

Alan M. Shiller

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Troy Pierce

Committee Member 3

Natasha T. Dimova

Committee Member 4

Christopher T. Hayes

Committee Member 4 School

Ocean Science and Engineering

Committee Member 5

Davin J. Wallace

Committee Member 5 School

Ocean Science and Engineering

Committee Member 6

Stephan D. Howden

Committee Member 6 School

Ocean Science and Engineering

Abstract

Submarine groundwater discharge (SGD) is the advective flow of both fresh terrestrial groundwater and recirculating seawater through aquifer sediments, which is released into the coastal ocean. In this dissertation, I evaluated the impact of SGD on the distributions and input of trace metals and nutrients. In the Tuckean Swamp, an estuary in Australia dominated by coastal acid sulfate soils, I determined the impact of groundwater on Ba and U during the flood season, when the local aquifer is flushed out after a rapid increase in water table elevation. For Ba and U, groundwater contributed up to 18 and 66 % to the total surface water flux out of the Tuckean Swamp, respectively. This can have implications for the use of these elements as proxies of river influences, upwelling, and sea surface temperature on a regional scale. In the Mississippi Sound, an estuary in the northern Gulf of Mexico, the main sources of nutrients and trace metals to the estuary are thought to be from inputs of local rivers, and the occasional input of the Mississippi River from the opening of the Bonnet Carré Spillway. Using radium and radon, I evaluated the magnitude and distribution of SGD in the Mississippi Sound. I found that submarine groundwater discharge can dominate nutrient fluxes when the river discharge is low, suggesting that during the drier months of the year, SGD was main source of dissolved nutrients to the Sound. This has implications for biological parameters, as the dissolved materials from SGD are often reducing with a high oxygen demand (i.e., ammonium and methane), and the groundwater in itself is often lacking oxygen. This has potential to cause bottom up hypoxia along the coastline and in the western Sound, where the majority of the SGD is infiltrating into the Sound. Trace element inputs to the Mississippi Sound were dominated by river inputs and were affected by the opening of the Bonnet Carré Spillway. This work explores the importance of SGD versus river and surface runoff, and how all of these parameters combined can affect the water quality of coastal systems.

ORCID ID

0000-0003-0592-1952

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