Silica cycle marine

A box model fiar the marine silica cycle is presented in Figure 6.11 with respect to the processes that control DSi and BSi. An oceanic budget is provided in Table 16.3 in which site-specific contributions to oceanic outputs are given. This table illustrates that considerable uncertainty still exists in estimating the burial rate of BSi. Regardless, burial of BSi is responsible for most of the removal of the oceanic inputs of DSi, with the latter being predominantly delivered via river runoff. This demonstrates the importance of the biological silica pump in the crustal-ocean-atmosphere factory. 

Conversely, perturbations in the burial rate of BSi have the potential to alter the marine silica cycle. For example, changes in sea level affect the expanse of continental shelf Since BSi burial is more efficient in shelf sediments (because of better preservation), a topographic change that alters the spatial extent of this depositional environment has the potential to alter the size of the DSi reservoir. 

DeMaster, D.J. (2002) The accumulation and cycling of biogenic silica in the Southern Ocean revisiting the marine silica cycle. Deep-Sea Res. II, 49, 3155-3167. 

Two aspects of the cycling of silica in marine sediments make pore-water H4Si04 interesting and important. There is increasing evidence in support of the breakdown and... 

From the foregoing, it can be seen that the amount of silica annually fixed by marine organisms (ca. 25 Pg y ) is approximately balanced by the amount annually dissolved from their siliceous tests (ca. 24 Pgy" ). Moreover, these quantities exceed by more than an order of magnitude the yearly amounts of silica contributed to the world ocean from external sources (rivers, interstitial waters, etc.) or removed from it by burial in marine sediments (Heath, 1974 Wollast, 1974). Thus, it is apparent not only that the marine silica cycle is biologically controlled, but also that the biological subcycle of the marine silica cycle acts as a quasi-closed system. 

Fig. 7.3.2. Diagrammatic representation of major processes and silica reservoirs in the marine silica cycle.

Anthropogenic Trace Elements in the Ocean. Atmospheric Input of Pollutants. Carbon Cycle. Conservative Elements. Hydrothermal Vent Fluids, Chemistry of. Marine Silica Cycle. Metal Pollution. Nitrogen Cycle. Platinum Group Elements and their Isotopes in the Ocean. Refractory Metals. River Inputs. Transition Metals and Heavy Metal Speciation. 

Changes. Marine Silica Cycle. Ocean Carbon System, Modeling of. Radioactive Wastes. Stable Carbon Isotope Variations in the Ocean. Tritium-Helium Dating. 

Figure 3 STELLA model of the global marine silica cycle showing internal and external sources of silicate to the system, internal recycling, and burial of biogenic silica in the seabed. The various reservoirs are shown as rectangles, whereas the fluxes in and out of the reservoirs are shown as arrows with regulating valves (indicating relationships and functional equations). The flux values (indicated by numbers inside the boxes) have units of 10 mol y . ...

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