Chemistry Reference
In-Depth Information
validated the field calibration studies (e.g., Hester and Boyle 1982; Lea and Boyle 1989;
Boyle 1992; Boyle et al. 1995; Rosenthal et al. 1997). New and existing information was
provided by Spivack et al. (1993), Sanyal et al. (1995, 1996, 1997) on the paleo-pH of the
oceans based on stable boron isotopes
11
B). At this stage, however, this analysis
requires large sample size (milligram quantities). Hence presently it cannot be applied to
single species of benthic foraminifera. Spero et al. (1997) have shown that the CO
3
2−
ion
affects
(δ
18
O. The possible effects of physical parameters (i.e.,
temperature and pressure) on the distribution coefficient of some trace and minor
elements was shown by Rosenthal et al. (1997). Temperature effects on Mg distribution
coefficient in foraminifera have recently been shown (Nurnberg et al. 1996; Rosenthal et
al. 1997; Hastings et al. 1998; Rosenthal and Lohmann 2002). This has opened the
possibility of separating the ice volume effect from the temperature effect hidden in the
δ
13
C and possibly
δ
δ
18
O record (Elderfield and Ganssen 2000; Lear et al. 2000).
Despite the wide use of foraminifera in paleoceanographic reconstructions, it is well
recognized by all scientists involved in these studies that foraminifera are organisms that
precipitate their shells by a complex physiological process. This process is biologically
controlled (Lowenstam and Weiner 1989) and hence does not necessarily obey the
chemical thermodynamics associated with inorganic precipitation of CaCO
3
. These so-
called vital effects are observed both in stable isotopes and also in trace element
composition (e.g., Shackleton et al. 1973; Erez 1978; Erez and Honjo 1981; Boyle 1995;
Spero et al. 1997; Weiner and Dove 2003). In part the symbiotic algae that are found in
many species of planktonic and in shallow benthic foraminifera were often suggested as
the source of this variability (Erez 1978). However studies on deep benthic species and
other symbiont-barren species also demonstrate significant deviations from expected
isotopic and chemical equilibrium fractionations, and these must be connected to the
actual mechanism of shell formation (e.g., Erez 1993; Boyle 1995; Elderfield et al. 1996).
As a result of these deviations the paleoceanographic work is limited to only those
species that are close to equilibrium, or assumptions are made that the deviations are
constant with time (see below).
Subjects that will not be included
This review will not address the following subjects:
1.
Biomineralization in coccolithophores is of major importance for the pelagic
CaCO
3
production. Young and Henriksen (2003) discuss coccolithophorid
biomineralization in Chapter 7 of this volume.
2.
Biomineralization in hermatypic corals will not be included in the review,
although many inferences are made due to their importance in the global carbon
cycle and as paleoceanographic indicators. When similar phenomena are found
in corals and foraminifera, they will be discussed.
3.
Various aspects of mineralogy and crystallography in foraminifera and corals.
These subjects may be covered by other reviews in this volume and in the
classical topics of Lowenstam and Weiner (1989) and Simkiss and Wilbur
(1989).
4.
The structure, texture and skeletal architecture of foraminifera and the relations
between structure and function. These subjects have been discussed at length in
various papers and textbooks related mainly to their taxonomy (e.g., Loeblich
and Tappan 1964, 1986, 1987). Much is known about these subjects on various
levels from high resolution TEM and SEM and through light microscopy.
