Removal of organic magnesium in coccolithophore calcite

Blanco‐Ameijeiras, Sonia; Lebrato, Mario; Stoll, Heather; Iglesias‐Rodríguez, M. Débora; Méndez-Vicente, Ana; Sett, Scarlett; Müller, Marius; Oschlies, Andreas; Schulz, Kai G.

doi:10.1016/j.gca.2012.04.043

Cited by 33 publications

(28 citation statements)

References 59 publications

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“…3), and typically <5 mmol mol À1 . There is, however, a more subtle discrepancy between measurements of extremely low placolith coccolith Mg/Ca, in the region of 0.1-0.3 mmol mol À1 (Stoll et al, 2001;Blanco-Ameijeiras et al, 2012) and values up to an order of magnitude higher ($0.5-3 mmol mol À1 ) (Stoll et al, 2007a,b,c;Mü ller et al, 2011). The ion probe data presented here for fossil placoliths across the E/OT and cultured C. braarudii are mostly within the higher, $0.5-3 mmol mol À1 range of Mg/Ca.…”

Section: Effects Of Variable Preservation On Coccolith Trace Metal Comentioning

confidence: 98%

Trace metal (Mg/Ca and Sr/Ca) analyses of single coccoliths by Secondary Ion Mass Spectrometry

Prentice¹,

Jones²,

Lees³

et al. 2014

Geochimica et Cosmochimica Acta

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Section: Effects Of Variable Preservation On Coccolith Trace Metal Comentioning

confidence: 98%

Trace metal (Mg/Ca and Sr/Ca) analyses of single coccoliths by Secondary Ion Mass Spectrometry

Prentice¹,

Jones²,

Lees³

et al. 2014

Geochimica et Cosmochimica Acta

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“…A5). Average Mg/Ca values for foraminiferal tests and nannofossils are determined based on foraminiferal Mg/Ca data from Site 1171 (Shevenell et al, 2004;Shevenell et al, 2008) and coccolith Mg/Ca data from culture experiments (Stoll et al, 2001;Ra et al, 2010a;Ra et al, 2010b;Müller et al, 2011;Blanco-Ameijeiras et al, 2012;Müller et al, 2014). The uncertainties for all assumed parameters are propagated through the mass balance calculation utilizing a Monte Carlo approach.…”

Section: Effect Of Abundance and Composition Of Fossil Components On mentioning

confidence: 99%

Quantifying the effect of diagenetic recrystallization on the Mg isotopic composition of marine carbonates

Chanda

Fantle

2017

Geochimica et Cosmochimica Acta

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The Mg and Sr isotopic compositions (δ 26 Mg and 87 Sr/ 86 Sr) of pore fluids and bulk carbonates from Ocean Drilling Project Site 1171 (South Tasman Rise; 2148.2 m water depth) are reported, in order to evaluate the potential of diagenesis to alter carbonate-based geochemical proxies in an open marine system. Given the trace amounts of Mg in marine carbonates relative to coexisting pore fluids, diagenesis can alter carbonate δ 26 Mg, a promising proxy for seawater δ 26 Mg that may help elucidate long-term changes in the global Mg cycle. Constraints on the effect of diagenetic recrystallization on carbonate δ 26 Mg are therefore critical for accurate proxy interpretations. This study provides context for assessing the fidelity of geochemical proxyreconstructions using the primary components (i.e., foraminiferal tests and nannofossils) of bulk carbonate sediments.We find that pore fluid δ 26 Mg values (on the DSM3 scale) at Site 1171 increase systematically with depth (from -0.72‰ to -0.39‰ in the upper ~260 m), while the δ 26 Mg of bulk carbonates decrease systematically with depth (from -2.23‰ to -5.00‰ in the upper ~260 m). This variability is ascribed primarily to carbonate recrystallization, with a small proportion of the variability due to down-hole changes in nannofossil and foraminiferal species composition. The inferred effect of diagenesis on bulk carbonate δ 26 Mg correlates with downcore changes in Mg/Ca, Sr/Ca, Na/Ca, and 87 Sr/ 86 Sr. A depositional reactive-transport model is employed to validate the hypothesis that calcite recrystallization in this system can generate sizeable shifts in carbonate δ 26 Mg. Model fits to the data suggest a fractionation factor and a partition coefficient that are consistent with previous work, assuming calcite recrystallization rates of ≤7%/Ma constrained by Sr geochemistry. In addition, either partial dissolution or a distinctly different previous diagenetic regime must be invoked in order to explain aspects of the elemental chemistry and 87 Sr/ 86 Sr of relatively deep sediments from Holes A and C. This study indicates that the dynamics of a given sedimentary system can significantly alter bulk carbonate geochemistry, and presents a framework for considering the potential impact of such alteration on picked archives such as foraminiferal tests and nannofossils. Ultimately, this study contributes to the development of δ 26 Mg as a proxy for seawater δ 26 Mg by quantifying the susceptibility of carbonate δ 26 Mg to diagenetic alteration, particularly in sediments in open marine systems. This study suggests that because of the sensitivity of carbonate δ 26 Mg to diagenetic recrystallization, it can, in certain systems, be used to quantify the impact of diagenesis on carbonate-based geochemical proxies.

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“…The transport of Mg in coccolithophores presumably differs from Sr and Ca and it is likely associated with specific ion transporters and channels (Mackinder et al, 2010;Holtz et al, 2013) as in bacteria and higher plants (Legong et al, 2001). A relation between the coccolithophore Mg / Ca ratio and temperature is still under discussion and complicated by the nontrivial removal of organically bound Mg (Blanco-Ameijeiras et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Here we present the partitioning coefficients for Sr and Mg and the related coccolith Sr / Ca and Mg / Ca ratios from laboratory culture experiments in which temperature and carbonate chemistry of the growth medium were tightly controlled and monitored. Calcite samples were cleaned with a newly developed organic matter removal procedure (Blanco-Ameijeiras et al, 2012). Our findings should be considered when assessing possible changes in the biogeochemical cycling of Ca, Sr and Mg due to ocean warming and acidification and, furthermore, when applying palaeoproxies based on Sr / Ca and Mg / Ca coccolith ratios.…”

Section: Introductionmentioning

confidence: 99%

Influence of temperature and CO<sub>2</sub> on the strontium and magnesium composition of coccolithophore calcite

et al. 2014

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Abstract. Marine calcareous sediments provide a fundamental basis for palaeoceanographic studies aiming to reconstruct past oceanic conditions and understand key biogeochemical element cycles. Calcifying unicellular phytoplankton (coccolithophores) are a major contributor to both carbon and calcium cycling by photosynthesis and the production of calcite (coccoliths) in the euphotic zone, and the subsequent long-term deposition and burial into marine sediments. Here we present data from controlled laboratory experiments on four coccolithophore species and elucidate the relation between the divalent cation (Sr, Mg and Ca) partitioning in coccoliths and cellular physiology (growth, calcification and photosynthesis). Coccolithophores were cultured under different seawater temperature and carbonate chemistry conditions. The partition coefficient of strontium (DSr) was positively correlated with both carbon dioxide (pCO2) and temperature but displayed no coherent relation to particulate organic and inorganic carbon production rates. Furthermore, DSr correlated positively with cellular growth rates when driven by temperature but no correlation was present when changes in growth rates were pCO2-induced. Our results demonstrate the complex interaction between environmental forcing and physiological control on the strontium partitioning in coccolithophore calcite and challenge interpretations of the coccolith Sr / Ca ratio from high-pCO2 environments (e.g. Palaeocene–Eocene thermal maximum). The partition coefficient of magnesium (DMg) displayed species-specific differences and elevated values under nutrient limitation. No conclusive correlation between coccolith DMg and temperature was observed but pCO2 induced a rising trend in coccolith DMg. Interestingly, the best correlation was found between coccolith DMg and chlorophyll a production, suggesting that chlorophyll a and calcite associated Mg originate from the same intracellular pool. These and previous findings indicate that Mg is transported into the cell and to the site of calcification via different pathways than Ca and Sr. Consequently, the coccolith Mg / Ca ratio should be decoupled from the seawater Mg / Ca ratio. This study gives an extended insight into the driving factors influencing the coccolith Mg / Ca ratio and should be considered for future palaeoproxy calibrations.

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Removal of organic magnesium in coccolithophore calcite

Cited by 33 publications

References 59 publications

Trace metal (Mg/Ca and Sr/Ca) analyses of single coccoliths by Secondary Ion Mass Spectrometry

Trace metal (Mg/Ca and Sr/Ca) analyses of single coccoliths by Secondary Ion Mass Spectrometry

Quantifying the effect of diagenetic recrystallization on the Mg isotopic composition of marine carbonates

Influence of temperature and CO<sub>2</sub> on the strontium and magnesium composition of coccolithophore calcite

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Removal of organic magnesium in coccolithophore calcite

Cited by 33 publications

References 59 publications

Trace metal (Mg/Ca and Sr/Ca) analyses of single coccoliths by Secondary Ion Mass Spectrometry

Trace metal (Mg/Ca and Sr/Ca) analyses of single coccoliths by Secondary Ion Mass Spectrometry

Quantifying the effect of diagenetic recrystallization on the Mg isotopic composition of marine carbonates

Influence of temperature and CO&lt;sub&gt;2&lt;/sub&gt; on the strontium and magnesium composition of coccolithophore calcite

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Influence of temperature and CO<sub>2</sub> on the strontium and magnesium composition of coccolithophore calcite