Correlation of boron isotopic composition with ultrastructure in the deep‐sea coral <i>Lophelia pertusa</i>: Implications for biomineralization and paleo‐pH

Blamart, Dominique; Rollion‐Bard, Claire; Meibom, Anders; Cuif, Jean‐Pierre; Juillet-Leclerc, A.; Dauphin, Yannicke

doi:10.1029/2007gc001686

Cited by 97 publications

(120 citation statements)

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“…(2011)confirm previous studies (Allison et al, 2010;Blamart et al, 2007;Rollion-Bard et al, 2003) which made the assumption that the isotopic composition of boron in carbonate allows to calculate the pH of the calcifying solution(pH solution ) which is regulated by corals themselves during their calcification. In this assumption, a α value of 1.027 is used instead of 1.020 to determine pH solution .…”

Section: Impact On δ 11 B B/ca and Reconstructed Phsupporting

confidence: 77%

“…skeleton has been used with success to reconstruct paleo-pH of surface seawater and ocean acidification related to the inception and development of the industrial era (e.g., Douville et al, 2010;Liu et al, 2009;Shinjo et al, 2013a;Wei et al, 2009;Wu et al, 2013). Even if boron isotopes in corals are now considered to be directly the reflect of pH of the calcification fluid (Allison et al, 2010;Blamart et al, 2007;Rollion-Bard et al, 2003;Venn et al, 2011), Trotter et al(2011) highlighted that pH of the calcification in scleractinian corals depends on pH of seawater. In addition, experimental cultures of tropical corals such as genus Porites or Acropora at various seawater pH revealed empirical pH-δ 11 B calibration curves (Hönisch et al, 2004;Reynaud et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Lazareth

Soares-Pereira

Douville

et al. 2016

Geochimica et Cosmochimica Acta

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Geochemical proxies measured in the carbonate skeleton of tropical coral Porites sp. have commonly been used to reconstruct sea surface temperature (SST) and more recently seawater pH. Nevertheless, both reconstructed SST and pH depend on the preservation state of the skeleton, here made of aragonite; i.e., diagenetic processes and its related effects should be limited. In this study, we report on the impact of the presence of intra-skeletal calcite on the skeleton geochemistry of a live-collected Porites sp..The Porites skeleton preservation state was analyzed using X-ray diffraction and scanning electron microscopy. Sr/Ca, Mg/Ca, U/Ca, Ba/Ca, Li/Mg, and B/Ca ratios were measured at a monthly and yearly resolution using solution ICP-MS and multi-collector ICP-MS. Theδ 11 B signatures and the calcite percentages were acquired at a yearly timescale. The coral colony presents two parts, one with less than 3% calcite (referred to as "no-calcite" skeleton), the other one, corresponding to the skeleton formed during the last 4 yrs. of growth,with calcite percentages varying from 13 to 32% (referred to as "with calcite" skeleton). This intra-skeletal calcite replaces partly or completely numerouscenter of calcification (COCs). All geochemical tracers investigated are significantlyimpacted by the presence of calcite. Thereconstructed SSTdecreasesby about0.1°C per calcite-percent as inferred fromthe Sr/Ca ratio. Such impact reaches up to 0.26°C per calcite-percent for temperature deduced from the Li/Mg ratio. So, less than 5% of such intra-skeletal calcite does not prevent SST reconstructions using Sr/Ca ratio, but the percentage and type of calcite have to be determined before fine SST interpretation. Seawater pH reconstruction inferredfrom boron isotopes drop by about -0.011 pH-unit per calcitepercent. Such sensitivity to calcite presence is particularly dramatic for fine paleo-pH reconstructions. Here we suggest that after being brought to shallow waters following a cyclone, the studied coral was seasonally subjected to rainfall-related water freshening that could have mimicked a vadose environment like can be encountered on raised fossil coral reefs. Nevertheless, the process of calcite precipitation remains to be determined.

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Section: Impact On δ 11 B B/ca and Reconstructed Phsupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Lazareth

Soares-Pereira

Douville

et al. 2016

Geochimica et Cosmochimica Acta

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“…circadian) that are known to exist in cnidarians (see e.g., Vize, 2009). Thus, the microstructure banding that exists within the aragonite fibres of deep-sea (non-zooxanthellae) corals (see e.g., Blamart et al, 2007) are entirely consistent with the expectations of the proposed model.…”

Section: A New Conceptual Model Of Coral Biomineralisationsupporting

confidence: 75%

A new conceptual model of coral biomineralisation: hypoxia as the physiological driver of skeletal extension

Wooldridge

2013

Biogeosciences

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That corals skeletons are built of aragonite crystals with taxonomy-linked ultrastructure has been well understood since the 19th century. Yet, the way by which corals control this crystallization process remains an unsolved question. Here, I outline a new conceptual model of coral biomineralisation that endeavours to relate known skeletal features with homeostatic functions beyond traditional growth (structural) determinants. In particular, I propose that the dominant physiological driver of skeletal extension is night-time hypoxia, which is exacerbated by the respiratory oxygen demands of the coral's algal symbionts (= zooxanthellae). The model thus provides a new narrative to explain the high growth rate of symbiotic corals, by equating skeletal deposition with the "work-rate" of the coral host needed to maintain a stable and beneficial symbiosis. In this way, coral skeletons are interpreted as a continuous (long-run) recording unit of the stability and functioning of the coral–algae endosymbiosis. After providing supportive evidence for the model across multiple scales of observation, I use coral core data from the Great Barrier Reef (Australia) to highlight the disturbed nature of the symbiosis in recent decades, but suggest that its onset is consistent with a trajectory that has been followed since at least the start of the 1900s. In concluding, I outline how the proposed capacity of cnidarians (which includes modern reef corals) to overcome the metabolic limitation of hypoxia via skeletogenesis also provides a new hypothesis to explain the sudden appearance in the fossil record of calcified skeletons at the Precambrian–Cambrian transition – and the ensuing rapid appearance of most major animal phyla

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“…Elevating the pH at the site of calcification has been suggested for foraminifera (25) and in other organisms inferred from boron isotopic measurements [i.e., in corals (27)], but not directly measured in other unicellular calcifyers. The effect of pH elevation on calcite precipitation is two-fold.…”

Section: Discussionmentioning

confidence: 99%

Foraminifera promote calcification by elevating their intracellular pH

Nooijer

Toyofuku²,

Kitazato³

2009

Proc. Natl. Acad. Sci. U.S.A.

310

262

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Surface seawaters are supersaturated with respect to calcite, but high concentrations of magnesium prevent spontaneous nucleation and growth of crystals. Foraminifera are the most widespread group of calcifying organisms and generally produce calcite with a low Mg content, indicating that they actively remove Mg 2؉ from vacuolized seawater before calcite precipitation. However, one order of foraminifera has evolved a calcification pathway, by which it produces calcite with a very high Mg content, suggesting that these species do not alter the Mg/Ca ratio of vacuolized seawater considerably. The cellular mechanism that makes it possible to precipitate calcite at high Mg concentrations, however, has remained unknown. Here we demonstrate that they are able to elevate the pH at the site of calcification by at least one unit above seawater pH and, thereby, overcome precipitation-inhibition at ambient Mg concentrations. A similar result was obtained for species that precipitate calcite with a low Mg concentration, suggesting that elevating the pH at the site of calcification is a widespread strategy among foraminifera to promote calcite precipitation. Since the common ancestor of these two groups dates back to the Cambrian, our results would imply that this physiological mechanism has evolved over half a billion years ago. Since foraminifera rely on elevating the intracellular pH for their calcification, our results show that ongoing ocean acidification can result in a decrease of calcite production by these abundant calcifyers.benthic foraminifera ͉ foraminiferal evolution ͉ ocean acidification A large variety of organisms that form skeletons of calciumcarbonate have evolved over the last half billion years. Some groups precipitate predominantly aragonite, such as scleractinian corals (1) and calcareous chlorophytes (2), others mostly calcite, such as foraminifera (3), coccolithophores (4), and corraline Rhodophytes (2), and some a chimera of the two (5,6). The geological prevalence of the different groups is thought to be caused by successions in sea water chemistry: periods with relatively high Ca 2ϩ concentrations and low Mg 2ϩ concentrations (i.e., with low Mg/Ca ratios) have favored organisms precipitating calcite, while periods with relatively high Mg/Ca ratios (e.g., during the Neogene) have favored those forming aragonite (7-9). For foraminifera, the relation between ocean chemistry and their evolution is less clear (10) and possibly obscured by the existence of different calcification strategies in this group.Calcifying foraminifera are commonly divided into two groups according to their test (i.e., shell) structure: miliolid and hyaline. Miliolids precipitate calcite in the form of needles with a length of 2-3 m within cytoplasmic vesicles (11, 12) (see: 13 for the only known exception in this taxon). Before chamber formation, these needles accumulate in the cell and form a new chamber after simultaneous transport outside the test and assembly within an organic matrix (14). The needles forming the outer lay...

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Correlation of boron isotopic composition with ultrastructure in the deep‐sea coral Lophelia pertusa: Implications for biomineralization and paleo‐pH

Cited by 97 publications

References 49 publications

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

Intra-skeletal calcite in a live-collected Porites sp.: Impact on environmental proxies and potential formation process

A new conceptual model of coral biomineralisation: hypoxia as the physiological driver of skeletal extension

Foraminifera promote calcification by elevating their intracellular pH

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