Benthic foraminifera microhabitat

McCorkle D. C., Keigwin L. D., Corliss B. H., and Emerson S. R. (1990) The influence of microhabitats on the carbon isotopic composition of deep-sea benthic foraminifera. Paleoceanography 5, 161-185. 

Tachikawa K. and Elderfield H. (2002) Microhabitat effects on Cd/Ca and S C of benthic foraminifera. Earth Planet. Sci. Lett. 202,... 

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... 

Corliss, B. H. 1985. Microhabitats of benthic foraminifera within deep-sea sediments. Nature, 314, 435-438. 

Fontanier, C., Mackensen, A., Jorissen, F. j., Anschutz, P., Licari, L. Griveaud, C. 2006. Stable oxygen and carbon isotopes of live benthic foraminifera from the Bay of Biscay microhabitat... 

JORISSEN, F. J. 1999. Benthic foraminiferal microhabitats below the sediment-water interface. In SEN Gupta, B. K. (ed.) Modem Foraminifera. Kluwer Academic Publishers, Dordrecht, Boston, Eondon, 161-179. 

Linke, P. Lutze, G. F. 1993. Microhabitat preferences of benthic foraminifera - a static concept or a dynamic adaptation to optimize food acquisition Marine Micropaleontology, 20, 215-134. 

Chandler, G. T., Williams, D. F., Spero, H. 1. XiAODONG, G. 1996. Sediment microhabitat effects on carbon stable isotopic signatures of microcosm-cultured benthic foraminifera. limnology and Oceanography, 41, 680—688. 

The incorporation of oxygen isotopes into biogenic carbonate is complex and as Wefer et al. (1999) point out, the 8 0 value of a carbonate is a function of temperature, ice volume, selective growth in space and time, vital effects and post-depositional dissolution. The carbonate chemistry and pH of a benthic foraminifera s microenvironment or microhabitat also plays an important role in test isotopic composition (e.g. Spero et al. 1997 Bemis et al. 1998 Bijma et al. 1999 Wolf-Gladrow et al. 1999), with a 0.2 increase in pH resulting in a 8 0 shift of approximately — 0.22%o (Zeehe 1999). 

In summary, the cultured B. aculeata A8 C and A8 0 values are consistent with no microhabitat 8 C effect in culture, and a carbonate ion effect on shell isotopic composition. If the carbonate ion effect is similar to the planktic foraminifera effect (Spero et al. 1997), the most consistent results for both isotopes would be obtained using an equilibrium oxygen isotopic fractionation intermediate between the predictions of McCorkle et al. (1997) and Shackleton (1974). The isotopic offsets of the field specimens are consistent with a pore water 8 C influence on shell 8 C and no carbonate ion effect, and an equilibrium oxygen isotopic composition no higher than the McCorkle et al. (1997) prediction consideration of likely trends in pore water carbonate chemistry suggests an even lower equilibrium oxygen isotopic composition, similar to the prediction of Bemis et al. (1998). Thus these culture and fleld data, considered in the context of the carbonate chemistry of the culture and fleld systems, do not yield a consistent estimate of the equilibrium fractionation factor for 8 0 in benthic foraminiferal calcite. Further culture experiments, including carbonate chemistry manipulations, may help resolve this discrepancy. 

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