A simple biomineralization model to explain Li, Mg, and Sr incorporation into aragonitic foraminifera and corals
Introduction
Dissolved Li, Mg, Sr, and Ca all behave nearly conservatively in seawater, meaning that their ratios are approximately constant throughout the oceans. The oceanic residence times of these four elements are relatively long, on the order of 1 to 10 Ma, so that oceanic metal/Ca ratios are also relatively constant through time during the late Quaternary. Hence any changes in the metal/Ca of biogenic CaCO3 may potentially be attributed to variations in the environmental parameter(s) that affect metal partitioning into the mineral, such as temperature. Mg/Ca has been widely applied as a paleotemperature proxy in calcitic foraminifera (Nürnberg, 1995), while Sr/Ca has been similarly used in aragonitic corals (Beck et al., 1992). In both cases ancillary environmental parameters such as carbonate saturation state, and/or physiological parameters such as growth rate, often appear to overprint the temperature signal. For the elemental ratios that are not widely used as paleotemperature proxies, such as Sr/Ca in foraminifera and Mg/Ca in corals, such ancillary effects can obscure any temperature dependence. Improved characterization of the various influences on metal partitioning is therefore a crucial goal of paleoceanographic proxy development, with an eye toward greater understanding of the biomineralization process.
Following the pioneering work of Delaney et al. (1985), Li/Ca has received renewed attention in both foraminifera and corals, but has not yet seen widespread application as a paleoceanographic proxy. Several studies have demonstrated a negative correlation between biogenic Li/Ca and temperature, but significant ancillary influences such as calcification rate have also been suggested (e.g. Hall and Chan, 2004, Hathorne et al., 2013; Marriott et al., 2004a, Marriott et al., 2004b). Benthic foraminiferal Li/Ca from a holothermal depth transect was found to be positively correlated with seawater saturation state with respect to calcite (Lear and Rosenthal, 2006), leading to the suggestion that Mg/Ca and Li/Ca can be used in linear combination to solve for both paleotemperature and saturation state (Lear et al., 2010). Bryan and Marchitto (2008) showed that Mg/Li in several taxa of benthic foraminifera is better correlated to temperature than either Mg/Ca or Li/Ca alone, especially for the aragonitic Hoeglundina elegans ( for Mg/Ca, 0.90 for Mg/Li). They proposed that both Mg/Ca and Li/Ca reflect, in part, modification of the internal calcification pool, and that the ratio Mg/Li effectively corrects for physiological and/or saturation state influences, thereby isolating the temperature effect. A similar improvement using Mg/Li (or Li/Mg) has since been demonstrated in a diverse range of aragonitic corals, including deep sea taxa (Case et al., 2010, Montagna et al., 2014, Raddatz et al., 2013).
Here we further explore the relationship between Li/Ca and Mg/Ca in biogenic aragonites, and use it to construct a simple model of biomineralization. We then discuss the implications of that model for the coral Sr/Ca paleotemperature proxy.
Section snippets
Materials and methods
We present 11 new metal/Ca measurements in H. elegans from nine Holocene core tops (Table 1). Each sample contained ∼5–10 individuals >250 μm, which were crushed and reductively and oxidatively cleaned following the methods of Boyle and Rosenthal (1996). Samples were analyzed for a suite of trace and minor elemental ratios by high-resolution sector field ICP-MS, as described by Marchitto (2006). Long-term 1σ precision is 0.9% for Li/Ca, 0.5% for Mg/Ca, and 0.6% for Sr/Ca. Concentrations of
Li/Ca, Mg/Ca, and Li/Mg versus temperature
With the addition of new measurements from the deep sea, the weak negative correlation between Li/Ca and temperature reported for H. elegans (Bryan and Marchitto, 2008, Hall and Chan, 2004) becomes even weaker (, Fig. 1a). Aragonitic coral Li/Ca exhibits a considerably stronger negative correlation to temperature ( across multiple taxa, Fig. 1a), as has been noted previously (Case et al., 2010, Montagna et al., 2014). For Mg/Ca in H. elegans the correlation to temperature
Conclusions
We present a simple conceptual model that explains the remarkably similar behavior of Li/Mg between the aragonitic foraminifer H. elegans and various aragonitic coral taxa. We suggest that Li/Mg reflects the ratio between the abiotic partition coefficients and because neither Ca2+ pumping nor Rayleigh fractionation significantly alters the Li/Mg ratio of the calcifying fluid. This model is consistent with coral Sr/Ca if the Ca2+ pump barely discriminates against Sr2+. In contrast
Acknowledgments
We are grateful to Matthias López Correa and Andres Rüggeberg for providing access to the cold-water coral samples listed in Table S2, as well as to Riccardo Rodolfo-Metalpa for the Cladocora caespitosa samples. We thank Derek Weller for laboratory assistance. Ed Hathorne and an anonymous reviewer provided comments that improved this paper. This work was supported in part by US NSF grants OCE-0425522 and OCE-0648215 to Marchitto. McCulloch is supported by an ARC Laureate Fellowship (LF120100049
References (72)
- et al.
Stable isotopes in deep-sea corals and a new mechanism for “vital effects”
Geochim. Cosmochim. Acta
(2003) - et al.
Trace element proxies for surface ocean conditions: a synthesis of culture calibrations with planktic foraminifera
Geochim. Cosmochim. Acta
(2016) - et al.
, Sr, Mg and B in a modern Porites coral: the relationship between calcification site pH and skeletal chemistry
Geochim. Cosmochim. Acta
(2010) - et al.
Controls on Sr/Ca and Mg/Ca in scleractinian corals: the effects of Ca-ATPase and transcellular Ca channels on skeletal chemistry
Geochim. Cosmochim. Acta
(2011) - et al.
Stoichiometries of calcium and strontium transport coupled to ATP and acetyl phosphate hydrolysis by skeletal sarcoplasmic reticulum
Biochim. Biophys. Acta, Biomembr.
(1990) The role of magnesium in the crystal growth of calcite and aragonite from sea water
Geochim. Cosmochim. Acta
(1975)- et al.
Calcium isotope fractionation in modern scleractinian corals
Geochim. Cosmochim. Acta
(2006) - et al.
Skeletal growth dynamics linked to trace-element composition in the scleractinian coral Pocillopora damicornis
Geochim. Cosmochim. Acta
(2012) - et al.
Environmental and biological controls on Mg and Li in deep-sea scleractinian corals
Earth Planet. Sci. Lett.
(2010) Sea surface temperature and salinity reconstruction from coral geochemical tracers
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2006)
Li, Sr, Mg, and Na in foraminiferal calcite shells from laboratory culture, sediment traps, and sediment cores
Geochim. Cosmochim. Acta
Glacial deep ocean sequestration of CO2 driven by the eastern equatorial Pacific biologic pump
Earth Planet. Sci. Lett.
A biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate
Earth Planet. Sci. Lett.
The impact of crystal growth rate on element ratios in aragonite: an experimental approach to understanding vital effects
Geochim. Cosmochim. Acta
Experimental determination of growth rate effect on U6+ and Mg2+ partitioning between aragonite and fluid at elevated U6+ concentration
Geochim. Cosmochim. Acta
Element partitioning during precipitation of aragonite from seawater: a framework for understanding paleoproxies
Geochim. Cosmochim. Acta
Rayleigh-based, multi-element coral thermometry: a biomineralization approach to developing climate proxies
Geochim. Cosmochim. Acta
Sr/Ca and Mg/Ca vital effects correlated with skeletal architecture in a scleractinian deep-sea coral and the role of Rayleigh fractionation
Earth Planet. Sci. Lett.
Seawater transport during coral biomineralization
Earth Planet. Sci. Lett.
Calcium isotope fractionation in calcite and aragonite
Geochim. Cosmochim. Acta
Mg/Ca, Sr/Ca and Ca isotope ratios in benthonic foraminifers related to test structure, mineralogy and environmental controls
Geochim. Cosmochim. Acta
Li/Ca in multiple species of benthic and planktonic foraminifera: thermocline, latitudinal, and glacial-interglacial variation
Geochim. Cosmochim. Acta
Compositional and morphological features of aragonite precipitated experimentally from seawater and biogenically by corals
Geochim. Cosmochim. Acta
The co-precipitation of cations with CaCO3—IV. The co-precipitation of Sr2+ with aragonite between 16° and 96 °C
Geochim. Cosmochim. Acta
Effect of mineralogy, salinity, and temperature on Li/Ca and Li isotope composition of calcium carbonate
Chem. Geol.
Temperature dependence of delta Li-7, delta Ca-44 and Li/Ca during growth of calcium carbonate
Earth Planet. Sci. Lett.
An assessment of the Sr/Ca ratio in shallow water hermatypic corals as a proxy for sea surface temperature
Geochim. Cosmochim. Acta
13C and 18O isotopic disequilibrium in biological carbonates: II. In vitro simulation of kinetic isotope effects
Geochim. Cosmochim. Acta
Li/Mg systematics in scleractinian corals: calibration of the thermometer
Geochim. Cosmochim. Acta
The non-tropical coral Cladocora caespitosa as the new climate archive for the Mediterranean: high-resolution (∼weekly) trace element systematics
Quat. Sci. Rev.
Stable Sr-isotope, Sr/Ca, Mg/Ca, Li/Ca and Mg/Li ratios in the scleractinian cold-water coral Lophelia pertusa
Chem. Geol.
Light and temperature effects on Sr/Ca and Mg/Ca ratios in the scleractinian coral Acropora sp
Geochim. Cosmochim. Acta
Possible controls on Li, Na, and Mg incorporation into aragonite coral skeletons
Chem. Geol.
Deep-sea coral geochemistry: implication for the vital effect
Chem. Geol.
A numerical model of trace-element coprecipitation in a physicochemical calcification system: application to coral biomineralization and trace-element ‘vital effects’
Geochim. Cosmochim. Acta
A conceptual model for near-surface kinetic controls on the trace-element and stable isotope composition of abiogenic calcite crystals
Geochim. Cosmochim. Acta
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2023, Geochimica et Cosmochimica ActaCitation Excerpt :To further evaluate the growth rate effects in cation incorporation, it is instructive to compare the deep-sea coral data to inorganic experiments as well as other marine calcifying organisms, especially those that make aragonite. Recently it was discovered that the aragonitic benthic foraminifera Hoeglundina elegans shares the same Li/Mg–temperature relation with different coral species (Marchitto et al., 2018; Stewart et al., 2020). However, the Li/Ca, Mg/Ca and Sr/Ca ratios of H.elegans are lower than those of corals and closer to those of other calcitic foraminifera (Rosenthal et al., 2006; Bryan and Marchitto, 2008; Marchitto et al., 2018).