Interstitial geochemistry and hydrology of coral reef frameworks

4 Interstitial geochemistry and hydrology of coral reef frameworks 

Coral reef frameworks are partially lithified carbonate structures on which reef communities grow. Pore-waters of reef frameworks are mostly anaerobic and contain elevated levels of dissolved nutrients (Skyring Chambers, 1976 Buddemeier Oberdorfer, 1983 Corredor Capone, 1985 Sansone, 1985 Sansone etal., 1990). This is a common feature of many coral reefs (Sansone etal., 1990), and a direct result of oxidation of organic matter (Sansone etal., 1990 Tribble etal., 1990). The subsequent production of carbonic acid from the oxidation of organic matter lowers pore-water pH and reduces the activity of the carbonate ion, thus facilitating in situ dissolution of carbonate (primarily aragonite) (Sansone etal., 1990 Tribble etal., 1990). 

Reef pore-waters become anoxic at depths less than a meter into the framework, however, some reef pore-waters become anoxic within centimeters of the framework surface (Entsch etal., 1983 Haberstroh Sansone, 1999 Falter Sansone, 2000). Pore-water nutrient concentrations typically vary up to 3 pM DIP, 6pM N02 + N03 , 80 pM NH4+, 100 pM Si(OH)4 and 3.5 mM dissolved inorganic carbon (DIC) (Buddemeier Oberdorfer, 1983 Entsch etal., 1983 Corredor Capone, 1985 Sansone, 1985 Sansone etal., 1990 Tribble etal., 1990 Szmant Forrester, 1996 Haberstroh Sansone, 1999 Falter Sansone, 2000 Suzumura etal., 2002), although much higher concentrations can be found in more diagenetically altered pore-water (e.g. Florida Keys Szmant Forrester, 1996 Sansone etal., unpublished data). 

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