Evaluations of carbon and dissolved material material transport by submarine groundwater discharge in coastal zone of East Asia

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Submarine groundwater discharge (SGD) is recognized as an important pathway from land to ocean, not only for water and dissolved material transports but also for ecosystem in the coastal zone. The seepage meters (for SGD flux), piezometers (for groundwater potential and dissolved material transports), optic fiber cable (for sea bottom temperature) and resistivity (fresh-salt water distribution) measurements had been made to evaluate the flux and quality of the SGD in several palaces in East Asia, including, Korea, Taipei, Bangkok, Manila, Osaka.A multidisciplinary approach was recently taken to assess the potential importance of groundwater seepage to nutrient inputs into Manila Bay, The Philippines. Three lines of seepage meters were installed in transects along the coast at Mariveles, Bataan Province during the period between 8-10 January 2005. The seepage rates along the northern most line showed the highest submarine groundwater discharge (SGD) at rates of 7.1-10.9 cm day^<-1>. The overall average seepage flux was 5.1±5.4 cm/day with a range of 0-26cm/day. Additional methodologies employed included automatic seepage meters, resistivity measurements, and use of natural radon as a groundwater tracer. Seepage meter and tracer results provided consistent results of estimates of SGD into Manila Bay. Both methods also showed that seepage fluxes are not steady-state but are modulated by the tides. Resistivity profiles show that the saline-freshwater interface moves on a tidal time scale. Our results show that dissolved inorganic nitrogen (DIN) fluxes via SGD are comparable in magnitude to DIN fluxes from each of the two major rivers that drain into Manila Bay