Linking regional sources and pathways for submarine groundwater discharge at a reef by electrical resistivity tomography, ²²²Rn, and salinity measurements

Abstract

Submarine groundwater discharge (SGD) is an important component of the hydrologic cycle connecting terrestrial to marine environments. SGD in fringing reefs and its consequences on biogeochemistry and ecology remain mostly unexplored. The 222Rn activity and salinity of seawater indicate a substantial groundwater contribution throughout most of the 20 km2 studied tropical reef in Pangasinan, Philippines. Over 30 km of electrical resistivity profiles with a penetration depth of 12.5 m shows widespread zones within the reef that are much more resistive than porous reef rocks or sediment saturated with typical seawater. Some discrete resistive areas are located close to where seawater has 222Rn peaks and where geologic lineaments are likely located suggesting that these are preferential pathways for fresher groundwater discharging to the reef. SGD at the site could be a major ecological factor connecting the reef to the subsurface environment which in turn may lead to connections to land.

Chemical weathering fluxes from volcanic islands and the importance of groundwater: The Hawaiian example

“…Moore, 1996;Burnett et al, 2003;Moore et al, 2008) and islands (e.g. Cardenas et al, 2010;Huang et al, 2011). In particular, it has been demonstrated that SGD is a very important component of the hydrological balance of volcanic islands (e.g.…”

Groundwater‐derived dissolved inorganic and organic carbon exports from a mangrove tidal creek: The missing mangrove carbon sink?

“…Radon ( 222 Rn) is an excellent natural groundwater tracer because of its conservative nature and the high concentrations in groundwater relative to surface water. 222 Rn has been used successfully to trace groundwater inputs in lakes (Schmidt et al 2010), rivers (Cook et al 2006), estuaries (Charette and Buesseler 2004;Santos et al 2012a), coral reefs (Cardenas et al 2010), and the coastal ocean (Burnett et al 2006). The large range of systems where 222 Rn has been used to trace groundwater highlights the utility of this tracer.…”

Atoll Groundwater Movement and Its Response to Climatic and Sea-Level Fluctuations

“…SGD has been shown to play a major ecological factor connecting the reef to the subsurface environment, which, may in turn lead to connections to land e.g., [41,58,59]. The geochemical loading from SGD has been described as comparable to or exceeding those of surface runoff inputs, due to higher dissolved solids concentrations in groundwater and larger accumulative discharge zones [41,60].…”