Submarine Groundwater Discharge
Funding: ARC Discovery, Herman Slade Foundation, New Zealand Academy of Sciences
Investigators: Isaac Santos, Bradley Eyre
Background/ Summary
For decades, oceanographers have assumed that rivers, atmospheric deposition, and underwater volcanoes are the three major sources of elements to the oceans. In the last decade or so, however, submarine groundwater discharge (SGD) has emerged as a fourth major source of nutrients and trace metals to coastal environments. SGD can also be a source of anthropogenic contaminants to estuaries and drive coastal eutrophication and harmful algal blooms. We are currently using cutting edge tracer techniques to quantify SGD and to determine its biogeochemical significance along the Australian East coast and overseas. Radon and radium isotopes are excellent SGD tracers as they are highly enriched in groundwaters relative to surface waters and they are conservative in seawater. Our central hypothesis is that SGD can account for large imbalances in current regional and global carbon and nitrogen budgets.
Projects
Are groundwater inputs driving de-oxygenation, acidification and eutrophication in NSW estuaries? We are using a portable, continuous radon monitoring technology to determine whether SGD controls the water quality of the Richmond River estuary. Preliminary results indicate that acidic waters are entering the estuary via groundwater pathways.
Unraveling the Pathways of Nitrogen Cycling in Permeable Sandy Sediments in Tropical Coastal Systems. This project is addressing whether high coral reef productivity can be linked to seawater recirculation in coral cay islands. We suspect seawater recirculation in coastal aquifers (or saline SGD) efficiently recycles organic matter and releases nutrients to coral reefs.
Unravelling submarine groundwater discharge in New Zealand estuaries. This project is testing whether eutrophication in Tauranga Harbor (New Zealand) is driven by groundwater inputs or upwelling of deep ocean waters. We are using radon as a groundwater tracer. This project is cooperation with Dr. Karin Bryan (University of Waikato at Hamilton).
Relevant Publications
de Weys, J., Santos, I. R. and Eyre, B. D. Linking groundwater discharge to severe estuarine acidification during a flood in a modified wetland. Environmental Science and Technology 45, 3310-3316. JIF = 4.363. (ERA Rank *A).
Santos, I. R. and Eyre, B. D. 2011. Radon tracing of groundwater discharge into an Australian estuary surrounded by coastal acid sulphate soils. Journal of Hydrology (accepted November 2010)
Santos, I. R., Tait, D., Erler, D. and Eyre, B. D. The breathing of a coal cay: tracing tidally-driven seawater recirculation in permeable coral reef sediments. Journal of Geophysical Research - Oceans (accepted August 2010).
Santos, I.R., Peterson, R.N.; Eyre, B.D.; Burnett, W.C. 2010. Significant lateral inputs of fresh groundwater into a stratified tropical estuary: Evidence from radon and radium isotopes. Marine Chemistry, 121: 37-48
Burnett, W.C.; Santos, I.R.; Hicks, R.W. 2010. Use of automated radon measurements for rapid assessment of groundwater flow into Florida streams. Journal of Hydrology, 380: 298-304.
Peterson, R.N.; Santos, I.R.; Burnett, W.C. 2010. Evaluating groundwater discharge to tidal rivers based on a time series Rn-222 Approach. Estuarine Coastal and Shelf Science. 86:165-178.
Schmidt, A.; Gibson, J.J.; Santos, I.R.; Schubert, M.; Tattrie, K. 2010. The contribution of groundwater discharge to the overall water budget of two typical Boreal lakes in Alberta/Canada estimated from a radon mass balance. Hydrology and Earth System Sciences, 14: 79-89
Mwashote, B.M.; Burnett, W.C.; Chanton, J.; Santos, I.R.; Dimova, N.; Swarzenski, P.2010. Calibration and use of continuous heat-type automated seepage meters forsubmarine groundwater discharge (SGD) measurements. Estuarine Coastal and ShelfScience, 87(1):1-10
Santos, I.R.; Burnett, W.C.; Dittmar, T.; Suryaputra, I.; Chanton, J. 2009. Tidal pumping drives nutrient and dissolved organic matter dynamics in a Gulf of Mexico subterranean estuary. Geochimica et Cosmochimica Acta, 73: 1325-1339.
Li, X.; Hu, B.X.; Burnett, W.C.; Santos, I.R.; Chanton, J.P. 2009. Submarine ground water discharge driven by tidal pumping in a heterogeneous Aquifer. Ground Water, 47(4): 558-568.
Santos, I.R.; Burnett, W.C.; Chanton, J.; Dimova, N.; Peterson, R.N. 2009. Land or ocean? Assessing the driving forces of submarine groundwater discharge at a coastal site in the Gulf of Mexico. Journal of Geophysical Research, 114, C04012.
Peterson, R.; Burnett, W.C.; Dimova, N.; Santos, I.R. 2009. A comparison of measurement methods for radium-226 on manganese fiber. Limnology and Oceanography: Methods, 7: 196-205.
Santos, I.R.; Burnett, W.C.; Chanton, J.; Dimova, N.; Mwashote, B; Peterson, R.N. 2009. Extended time series measurements of submarine groundwater discharge tracers (222Rn and CH4) at a coastal site in Florida. Marine Chemistry 113, 137-147.
Updated: 03 May 2011