Benthic foraminifera depth

Figure 10.20. Comparison of some trends through the Cenozoic. A. The 8180 content of benthic foraminifera (Savin et al., 1975 see also Prentice and Matthews, 1988). If the 5180 trend is primarily due to temperature, Cretaceous deep water temperatures were about 12°C warmer than today. B. Progressive change of the North Atlantic and Pacific carbonate compensation depth (CCD van Andel, 1975). C. The Sr/Ca ratio of planktonic foraminifera (Graham et al., 1982). D. Ridge volume (Pitman, 1978).

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). 

The5 0 in CaCOj tests of planktonic and benthic Foraminifera as a function of depth in a sediment core from the Equatorial Pacific, core V28-238. The scales are the same but offset by 5.3%o, the present-day planktonic-benthic difference. Modified from Shackleton and Opdyke(i973). 

The Cd/Ca quotient of benthic Foraminifera sampled from core tops (diamonds) and from the sediment depth of the last glacial maximum (circles) of eight cores from the North Atlantic at different vs ter depths. The difference in depth dependence illustrates the different profiles of dissolved cadmium in the North Atlantic at these times. Reproduced from Broecker (2002) as derived from the data in Boyle and Keigwin (1987). 

Nomaki et al. (2005a) reached a similar conclusion based on seafloor incubations at a bathyal site in Sagami Bay, Japan (1449 m water depth) using C-labeled algae (Dunaliella) deployed from a submersible. As on the Iberian margin, uptake of carbon by benthic foraminifera was rapid and substantially higher than for... 

Cornelius, N. Gooday, a. J. 2004. Live (stained) deep-sea benthic foraminifera in the western Weddell Sea trends in abundance, diversity and taxonomic composition in relation to water depth. Deep-Sea Research II, 51, 1571-1602. 

Deep-sea benthic foraminifera live on, and within, the sediment down to a depth of 10 cm below the seafloor (Corliss 1985 Gooday 1986 Mackensen Douglas 1989). After two decades of intensive research and collecting high-quality samples with the aid of multiple corers, there is no doubt that... 

In a study on the distribution in tests of live and dead benthic foraminifera in surface and subsurface sediments from 16 stations of intermediate water depths along the SW African continental... 

The difference between the O Neil et al. (1969) palaeotemperature equation and the Bemis et al. (1998) or Lynch-Stieglitz et al. (1999) palaeotemperature equations, and their respective calculations of isotopic equilibria for the infaunal and epifaunal species, could also be due to a carbonate ion effect within the sediment porewater profile. This appears plausible, because stable carbon isotopic compositions from benthic foraminifera show that infaunal taxa calcify in different porewater chemistry than epifaunal taxa (e.g. McCorkle et al. 1997). Since a 0.2 increase in pH (directly linked to the carbonate ion effect) results in a 8 0 depletion of c. 0.22%o (Zeebe 1999), the decrease in the pH of porewaters with sediment depth (e.g. Jahnke Jahnke 2004 Zhu et al. 2006) is likely to be reflected in the stable oxygen isotopic compositions of benthic for-aminiferal tests (Bemis et al. 1998), and one would expect the of infaunal taxa to be enriched... 

These platforms are the second important tropical to subtropical environment where high amounts of carbonate are produced and accumulated at water depths shallower than 50 m. The areal extension is about 0.8-10 km In contrast to reefs, on carbonate platforms production is mainly carried out by benthic red/green algae, mollusks and benthic foraminifera. Estimates of biotic and, to a much lesser extent, abiotic carbonate production on platforms range between 300-500 g CaCO m yr , which amounts to 4-10 mol yr on a global scale. Accumulation of platform carbonate is difficult to assess because a lot of it is dissolved or can be found as exported material in several 10 to 100 m... 

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