Calcifiers planktonic

These shallow-water deposits were the sole source of biogenic carbonate until the evolution and proliferation of planktonic calcifiers, namely the coccolithophorids and the foraminiferans, around 250mybp. This enabled a shift in the site of sedimentary carbonate acciunulation from the shallow waters to the deep sea. At present, about half of the sedimentary carbonates are being buried on the shelves and the other half in the deep sea and slopes. 

Prior to the advent of the coccolithophorids and planktonic foraminferans, 200 to 250 miUion years ago, all biogenic calcite precipitation must have been restricted to the shallow waters of the neritic zone. Thus, the evolution of the pelagic calcifiers ushered... 

If all of this carbon had remained in the atmosphere, it would have increased the size of this reservoir by about 40%. Fortunately (imless you take the perspective of the planktonic calcifiers), a large measure of this carbon dissolved into the ocean, so that the atmospheric reservoir increased by only 28%. 

The delivery of PIC and POC to the sediments depends on biological production in the surface waters. The input of terrestrial carbon is relatively minor. The relative proportions of PIC and POC generated in the surfece waters reflect the species composition of the plankton, i.e., calcifiers versus noncalcifiers. The success of detrital PIC and POC in surviving the trip to the seafloor is also dependent on the species composition of the plankton. As discussed in Chapter 23.5.4, the presence of biogenic hard parts confers protection on POC, inhibiting its remineralization. 

At this point, the vertical density structure for the past ocean can be reconstructed using benthic foraminifera only where the seafloor intersects the upper water column (ocean margins, islands, shallow seamounts). Although planktonic foraminifera calcify at various depth within the upper water column, we have no way to quantitatively reconstruct the depth at which they calcified. However, deep dwelling planktonic foraminifera can be used to reconstruct the spatial pattern of upper ocean flows (Matsumoto and Lynch-Stieglitz, 2003). 

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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