Seasonal Changes in Submarine Groundwater Discharge and Associated Nutrient Transport into a Tideless Semi-enclosed Embayment (Obama Bay, Japan)
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We carried out a seasonal study of fresh submarine groundwater discharge (SGD) and associated nutrient fluxes in a semi-enclosed bay along a tideless coastal zone using a 222Rn and salinity mass balance model for a whole bay scale. The resulting SGD rates showed large intra-annual variability from 0.05 × 106 to 0.77 × 106 m3 day−1, which were controlled by seasonal changes in the interaction of multiple driving forces, including water table height and seawater level. The highest SGD rate in early spring was induced by heavy snow and low sea level, whereas the seasonal increase in sea level gradually suppressed fresh SGD rates. In summer, an elevated water table may induce higher SGD rates (approximately 0.4 × 106 m3 day−1) regardless of high sea levels. The highest SGD fraction in total terrestrial freshwater fluxes also occurred in summer (>40 %), due to the decreasing rate of surface river discharge. The seasonally averaged SGD rate was 0.36 × 106 m3 day−1. This value was similar to the annual groundwater recharge rate (0.33 × 106 m3 day−1) estimated by the water balance method in the basin. Nutrient fluxes from SGD were approximately 42, 65, and 33 % of all terrestrial fluxes of dissolved inorganic nitrogen, phosphorous, and silicate, respectively. The average fraction of SGD in the water fluxes including terrestrial and oceanic water was low (0.3 %), but that of nutrient fluxes increased to 20–38 %. Higher nutrient concentrations in groundwater compensated for the lower volumetric flux of groundwater. Because primary production was mostly restricted by phosphorous throughout the year, phosphorous-enriched nutrient transport via SGD would play an important role in biological production.
KeywordsSubmarine groundwater discharge Radon Nutrients Semi-enclosed embayment
We thank the captain and crew of the R/V Aoba of Obama Fisheries High School for their help with the observations. We are grateful to two anonymous reviewers for their helpful comments and suggestions. This work was financially supported by JSPS KAKENHI Grant Number 24658175 and was performed under the support of the Research Project “Human-Environmental Security in Asia-Pacific Ring of Fire: Water-Energy-Food Nexus (R-08-Init)” at the Research Institute for Humanity and Nature (RHIN).
- Burnett, W.C., P.K. Aggarwal, A. Aureli, H. Bokuniewicz, J.E. Cable, M.A. Charette, E. Kontar, S. Krupa, K.M. Kulkarni, A. Loveless, W.S. Moore, J.A. Oberdorfer, J. Oliveira, N. Ozyurt, P. Povinec, A.M.G. Privitera, R. Rajar, R.T. Ramessur, J. Scholten, T. Stieglitz, M. Taniguchi, and J.V. Turner. 2006. Quantifying submarine groundwater discharge in the coastal zone via multiple methods. Science of the Total Environment 367: 498–543.CrossRefGoogle Scholar
- Burnett, W.C., I.R. Santos, Y. Weinstein, P.W. Swarzenski, and B. Herut. 2007. Remaining uncertainties in the use of Rn-222 as a quantitative tracer of submarine groundwater discharge. In A new focus on groundwater-seawater interactions, ed. W. Sanford, C. Langevin, M. Polemio, and P. Province, 109–118. Perugia: IAHS Publ., 312.Google Scholar
- Del Amo, Y., O. Le Pape, P. Tréguer, B. Quéguiner, A. Ménesguen, and A. Aminot. 1997. Impacts of high-nitrate freshwater inputs on macrotidal ecosystems. I. Seasonal evolution of nutrient limitation for the diatom-dominated phytoplankton of the Bay of Brest (France). Marine Ecology Progress Series 161: 213–224.CrossRefGoogle Scholar
- Grossland, C. J., H. H. Kremer, H. J. Lindeboom, J. I. M. Grossland and M. D. A. Le Tissier. 2005. Coastal fluxes in the anthropocence. The IGBP Series, Springer. 231 pp.Google Scholar
- Kayane, I. 1980. Hydrology. Natural Geography Lecture Series 3: 98–102. Daimeidou Publishing Co. Japan (in Japanese).Google Scholar
- Kim, G., and D.-W. Hwang. 2002. Tidal pumping of groundwater into the coatal ocean revealed from submarine 222Rn and CH4 monitoring. Geophysical Research Letters 29. doi: 10.1029/2002GL015093.
- Kim, G., K.-K. Lee, K.-P. Park, D.-W. Hwang, and H.-S. Yang. 2003. Large submarine groundwater discharge (SGD) from a volcanic island. Geophysical Research Letters 30. doi: 10.1029/2003GL018378.
- Macintyre, S., R. Wannikhof, and J.P. Chanton. 1995. Trace gas exchange across the air-sea interface in freshwater and coastal marine environments. In: Biogenic trace gases: measuring emissions from soil and water, eds. Matson, P.A., Harris, R.C, 52–97. Blackwell Science Ltd.Google Scholar
- Matsui, A. 2011. Seasonal change in spring discharge of Unjou water and Tsushima’s famous water, Obama City, Fukui Prefecture, Japan. Ecology and Civil Engineering 13: 165–169 (in Japanese with English abstract).Google Scholar
- Michael, H.A., J.S. Lubetsky, and C.F. Harvey. 2003. Characterizing submarine groundwater discharge: a seepage meter study in Waquoit Bay, Massachusetts. Geophysical Research Letters 30. doi: 10.1029/2002GL016000.
- Nishida, H. 1980. Improved tidal charts for the western part of the North Pacific Ocean. Report of Hydrographic Researches 15: 55–70.Google Scholar
- Obama City Office. 2014. Investigation interim report for groundwater resources in Obama Plain. http://www1.city.obama.fukui.jp/category/page.asp?Page=2592. Accessed 1 Jul 2014.
- Redfield, A.C., B.H. Ketchum, and F.A. Richard. 1963. Chapter 2, the influence of organisms on the composition on sea-water. In The sea, vol. 2, ed. M.N. Hill, 26–77. New York: Wiley Interscience.Google Scholar
- Robinson, M., D. Gallagher, and W. Reay. 1998. Field observations of tidal and seasonal variations in ground water discharge to tidal estuarine surface water. Groundwater Monitoring & Remediation 18: 89–92.Google Scholar
- Sasajima, S., and K. Sakamoto. 1962. Subsurface geology and groundwater of Obama Plain, Fukui Pref., central Japan. Part 2: groundwater of Obama Plain. Memoirs of the Faculty of Liberal Arts, University of Fukui. Ser. II, Natural Science. (in Japanese with English abstract).Google Scholar
- Sato, T., R. Sugimoto, and O. Tominaga. 2013. Source of sedimentary organic matter in Obama Bay estimated from stable isotope and C/N ratios. Bulletin of the Japanese Society of Fisheries Oceanography 77: 1–9 (in Japanese with English abstract).Google Scholar
- Strickland, J.D.H., and T.R. Parsons. 1972. A practical handbook of seawater analysis. Second edition, Bulletin 167. Ottawa: Fisheries Research Board of Canada.Google Scholar
- Taniguchi, M. 2002. Tidal effects on submarine groundwater discharge into the ocean. Geophysical Research Letters 29. doi: 10.1029/2002GL014987.
- Taniguchi, M., T. Ishitobi, J. Chen, S. Onodera, K. Miyaoka, W.C. Burnett, R. Peterson, G. Liu, and Y. Fukushima. 2008b. Submarine groundwater discharge from the Yellow River Delta to the Bohai Sea, China. Journal of Geophysical Research 113. doi: 10.1029/2007JC004498.
- Turner, S.M., G. Malin, P.D. Nightingale, and P.S. Liss. 1996. Seasonal variation of dimethyl sulphide in the North Sea and an assessment of fluxes to the atmosphere. Marine Chemistry 54: 552–556.Google Scholar
- Valiela, I., K. Foreman, M. LaMontagne, D. Hersh, J. Costa, P. Peckol, B. DeMeo-Andreson, C. D’Avanzo, M. Babione, C. Sham, J. Brawley, and K. Lajtha. 1992. Couplings of watersheds and coastal waters: sources and consequences of nutrient enrichment in Waquiot Bay, Massachusetts. Estuaries 15: 443–457.CrossRefGoogle Scholar