Calcium carbonate global

Fig. 1. Global distribution of seabed mineral deposits, where x represents chromite + barite titanium, zirconium, hafnium, and thorium tin I gold, platinum, and silver 3 sand and gravel shell, calcium carbonate gems marine polymetaUic sulfides phosphorites Cl cobalt cmsts S sulfur and B...

Langdon, C., Takahashi, T., Sweeney, C., Chipman, D., Goddard, J., Marubini, F., Aceves, H., Barnett, H., and Atkinson, M.J., Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef, Global Biogeochem. Cy., 14, 639-654,2000. 

Lerman, A. Mackenzie, F.T. 2005. 0O2 air-sea exchange due to calcium carbonate and organic matter storage, and its implications for the global carbon cycle. Aquatic Geochemistry, 11, 345-390. 

Milliman JD (1993) Production and accumulation of calcium carbonate in the ocean budget of a non-steady state. Global Geochem Cycles 7 927-957... 

In the preceding sections, we have discussed the marine processes that control calcium carbonate s formation, dissolution, and delivery to the seafloor. Their combined effects determine the geographic distribution of calcium carbonate in marine sediments seen in Figure 15.5. As noted earlier, the global distribution of calcareous sediments does not seem to follow that of plankton production. This points to the overriding importance of the processes that control the dissolution and sedimentation of calcium carbonate. 

Continental shelves and slopes comprise approximately 10 percent of the Earth s surface, and contain over half the sediments in the ocean (Heezen and Tharp, 1965 Gregor, 1985). Recent estimates of marine carbonate burial rates (e.g., Hay and Southam, 1977 Sundquist, 1985) indicate that between about 35 to 70 percent of Holocene carbonate deposition has taken place on continental shelves. In spite of their importance for carbonate accumulation and the global CO2 cycle, relatively few studies have been made on the chemical controls of calcium carbonate accumulation in these sediments, and most of these studies have been confined to near-shore environments. 

It is important to remember that this last calculation assumed that solid calcium carbonate was present in the system for example, the lake bed was limestone. It should be clear that the partial pressure of CO2 over a lake cannot usually exceed about 380 ppm, the global average atmospheric concentration, and thus, the calcium concentration cannot exceed a certain level if that partial pressure is to be maintained. In the above calculation, remember that the exponent —11.24 was based on a C02 partial pressure of 380 ppm. At this pressure and at a pH of 8.23 (which is what we just calculated), the calcium concentration is given by... 

Archer D. E. (1996a) An atlas of the distribution of calcium carbonate in sediments of the deep sea. Global Biogeochem. 

Berelson W. M., Hammond D. E., McManus J., and Kilgore T. E. (1994) Dissolution kinetics of calcium carbonate in equatorial Pacific sediments. Global Biogeochem. Cycles 8, 219-235. 

Catubig, N. R., Archer, D. E., Francois, R., deMenocal, P., Howard, W. Yu, E.-F. 1998. Global deep-sea burial rate of calcium carbonate during the last glacial maximum, Paleoceanogra-phy, 13, 298-310. 

Most of the concerns about global warming has been for land based plants. It can be seen from the proceeding paragraphs that the oceanic conversion of calcium carbonate by microorganisms and of carbon dioxide by plankton are perhaps more important in the regulation of our environment. Incidents such as an underwater volcanic explosion may affect this balance since they alter the temperature of water and the concentration of carbon dioxide in water and, consequently, its internal use and release to the atmosphere. 

In general, there is relatively little data available on the relative contributions made by different planktonic calcifying organisms (i.e. coccolithophores, foraminifera, pteropods) to the global production of calcium carbonate. Estimates of the coccoUth contribution to pelagic marine carbonate... 

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