Aspects of the Biogeochemistry of Magnesium 1. Calcareous Marine Organisms

Chave, Keith E.

doi:10.1086/626162

Cited by 597 publications

(412 citation statements)

References 6 publications

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“…Its incorporation into foraminiferal calcite is influenced by the temperature of the surrounding seawater during growth such that foraminiferal Mg/Ca ratios increase with increasing temperature. The temperature sensitivity of foraminiferal Mg/Ca ratios was first reported by Chave (1954) and Blackmon and Todd (1959) using X-ray diffraction. Later studies by Kilbourne and Sen Gupta (1973) using atomic absorption analysis and by Duckworth (1977) using electron microprobe analysis reinforced this finding.…”

Section: Introductionmentioning

confidence: 72%

Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures: a methodological overview and data compilation for the Last Glacial Maximum

Barker

Cacho

Benway

et al. 2005

Quaternary Science Reviews

236

163

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As part of the Multi-proxy Approach for the Reconstruction of the Glacial Ocean (MARGO) incentive, published and unpublished temperature reconstructions for the Last Glacial Maximum (LGM) based on planktonic foraminiferal Mg/Ca ratios have been synthesised and made available in an online database. Development and applications of Mg/Ca thermometry are described in order to illustrate the current state of the method. Various attempts to calibrate foraminiferal Mg/Ca ratios with temperature, including culture, trap and core-top approaches have given very consistent results although differences in methodological techniques can produce offsets between laboratories which need to be assessed and accounted for where possible. Dissolution of foraminiferal calcite at the sea-floor generally causes a lowering of Mg/Ca ratios. This effect requires further study in order to account and potentially correct for it if dissolution has occurred. Mg/Ca thermometry has advantages over other paleotemperature proxies including its use to investigate changes in the oxygen isotopic composition of seawater and the ability to reconstruct changes in the thermal structure of the water column by use of multiple species from different depth and or seasonal habitats. Presently available data are somewhat limited to low latitudes where they give fairly consistent values for the temperature difference between Late Holocene and the LGM (2-3.5 1C). Data from higher latitudes are more sparse, and suggest there may be complicating factors when comparing between multi-proxy reconstructions. r

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Section: Introductionmentioning

confidence: 72%

Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures: a methodological overview and data compilation for the Last Glacial Maximum

Barker

Cacho

Benway

et al. 2005

Quaternary Science Reviews

236

163

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“…In the case of the analyzed bryozoans, salinity is rather unimportant because our material came from a region where salinity showed little geographical variation (e.g., Karnovsky et al 2003;Walkusz et al 2009), while at the global scale of the crinoid data salinity is expected to vary more greatly. Following the study of Chave (1954), temperaturerelated variations in Mg content in skeletal carbonate have been documented in various groups, for example, molluscs (Taylor and Reid 1990) and bryozoans Taylor et al 2009). More recently, Findlay et al (2010b) showed a change in the Mg content of barnacle shells with latitude (and thus temperature), comparing temperate and Arctic representatives.…”

Section: Discussionmentioning

confidence: 99%

Patterns of magnesium content in Arctic bryozoan skeletons along a depth gradient

2012

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A growing body of evidence suggests that ocean acidification acting synergistically with ocean warming alters carbonate biomineralization in a variety of marine biota. Magnesium often substitutes for Ca in the calcite skeletons of marine invertebrates, increasing their solubility. The spatioenvironmental distribution of Mg in marine invertebrates has seldom been studied, despite its importance for assessing vulnerabilities to ocean acidification. Because pH decreases with water depth, it is predicted that levels of Mg in calcite skeletons should also decrease to counteract dissolution. Such a pattern has been suggested by evidence from echinoderms. Data on magnesium content and depth in Arctic bryozoans (52 species, 103 individuals, 150 samples) are here used to test this prediction, aided by comparison with six conceptual models explaining all possible scenarios. Analyses were based on a uniform dataset spanning more than 200 m of coastal water depth. No significant relationship was found between depth and Mg content; indeed, the highest Mg content among the analyzed taxa (8.7 % mol MgCO 3 ) was recorded from the deepest settings ([200 m). Our findings contrast with previously published results from echinoderms in which Mg was found to decrease with depth. The bryozoan results suggest that ocean acidification may have less impact on the studied bryozoans than is generally assumed. In the broad context, our study exemplifies quantitative testing of spatial patterns of skeletal geochemistry for predicting the biological effects of environmental change in the oceans.

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“…To do so, a proper understanding of past climate is required and reconstruction of past sea surface temperatures (SSTs) using geochemical proxies is an essential component of this. The most commonly used temperature proxies are the d 18 O and Mg/Ca ratios of planktonic foraminifera (Chave, 1954;Nurnberg et al, 1996) and the U K 0 37 index derived from the alkenones synthesised by haptophyte algae (Brassell et al, 1986). In contrast to the others, the U K 0 37 index is not directly influenced by seawater chemistry and is thus often considered as the most robust proxy for SST reconstruction (Herbert, 2003).…”

Section: Introductionmentioning

confidence: 99%

Application of the TEX86 temperature proxy to the southern North Sea

Herfort

Schouten

Boon

et al. 2006

Organic Geochemistry

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A novel temperature proxy, the tetraether index of lipids with 86 carbon atoms (TEX 86 ), was applied to the suspended particulate organic matter (POM) and sediment core tops from eight sites in the southern North Sea in different seasons. The TEX 86 -derived temperatures in many samples did not correlate with mean annual sea surface temperature (SST), but were shifted toward winter SST, apparently because Crenarchaeota are more abundant and metabolically active during periods of low primary production. This indicates that TEX 86 -derived SST estimates do not necessarily reflect annual mean SST and may provide essential information about seasonal SST palaeoreconstruction. High TEX 86 -derived SSTs were measured in the water of the river Rhine and in the sediment core tops and seawater from several stations in the southern North Sea. These sites were all characterised by important input of organic matter from soil and peat, as revealed by the relatively high values obtained with the new terrestrial proxy, the branched and isoprenoid tetraether (BIT) index. These data demonstrate that to reconstruct palaeotemperatures it is essential to estimate both TEX 86 and BIT indices to check that TEX 86 temperatures are not biased as a result of large terrestrial input. Important seasonal variations in TEX 86 -derived SST were also evident for the surface sediments of several stations characterised by extremely low sedimentation rates, indicating temporary settlement of laterally transported organic matter with a warmer temperature signal. This implies that sediment core top correlations between TEX 86 and mean annual SST should not be carried out in areas characterised by transient sediment deposition.

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Aspects of the Biogeochemistry of Magnesium 1. Calcareous Marine Organisms

Cited by 597 publications

References 6 publications

Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures: a methodological overview and data compilation for the Last Glacial Maximum

Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures: a methodological overview and data compilation for the Last Glacial Maximum

Patterns of magnesium content in Arctic bryozoan skeletons along a depth gradient

Application of the TEX86 temperature proxy to the southern North Sea

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