Calcifiers benthic

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). 

The Mg/Ca and of benthic foraminifers are both influenced by the temperature of calcification. This link is the reason that a discussion of Mg/Ca is included in this review. As outlined above, the oxygen isotope composition of biogenic calcite is a function of the temperature and the oxygen isotope composition of the water in which the organism calcified. For benthic foraminiferal records it is widely assumed that mainly the ice volume changes drive the temporal variations in the of... 

This effect usually refers to low values of benthic foraminifera calcifying within the sediment porewater (McCorkle et al. 1997), or other specific microhabitats, for instance within a phytodetrital layer directly on the sediment surface (Mackensen et al. 1993). Generally, S C values of preferentially epifaunal foraminiferal species are affected by values of the bottom water... 

Benthic foraminifera regularly calcify close to equilibrium with the oxygen isotopic composition of seawater, thus stable oxygen isotopic composition of foraminifera (8 Oforam) typically reflect the 8 0 of the seawater in which they calcified and the water temperature during calcification. The stable oxygen isotopic composition of seawater... 

Before isotopic compositions from fossil benthic foraminiferal specimens are used in palaeoenviron-mental reconstructions, it is important to determine whether the shell chemistry of live individuals (i.e. those stained with rose Bengal Bernhard 2000) of a particular species reflect the conditions of the surrounding seawater, i.e. does the foraminifera calcify in isotopic equilibrium with the surrounding environment ... 

Discrepancies between the observed B WTs recorded during the collection of the mostly live benthic foraminiferal specimens and predicted BWTs (calculated using equations 6 and 7) point to the possibility that a seasonal isotope effect influences the S Oforam values of benthic foraminifera in Loch Sunart (Fig. 7). In particular, the similarity of the predicted BWT for samples collected in April to the observed BWT of samples collected in June/July suggests that live tests collected in the cool BWTs of April actually calcified during the warmer BWTs of the previous summer (Fig. 7). For example, the measured 8 Oforam of C. lobatulus collected from a BWT of 7.88 °C in April, 2001, 3delds a predicted BWT of 13.45 °C and is similar to the... 

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... 

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