Coral Calcification, Cells to Reefs

Allemand, Denis; Tambutté, Éric; Zoccola, Didier; Tambutté, Sylvie

doi:10.1007/978-94-007-0114-4_9

Cited by 309 publications

(271 citation statements)

References 246 publications

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“…3). Thus, although coral calcification is a biologically mediated process influenced by both external (e.g., light, temperature, food abundance) (35) and internal [e.g., production of organic matrices as templates (36) for skeletal formation] processes, our simple bioinorganic model nonetheless explains the first-order functional dependence of calcification rates on internal Ω cf (Fig. 4 A and B).…”

Section: Resultsmentioning

confidence: 90%

pH homeostasis during coral calcification in a free ocean CO ₂ enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

Georgiou

Falter

Trotter

et al. 2015

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

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Geochemical analyses (δ 11 B and Sr/Ca) are reported for the coral Porites cylindrica grown within a free ocean carbon enrichment (FOCE) experiment, conducted on the Heron Island reef flat (Great Barrier Reef) for a 6-mo period from June to early December 2010. The FOCE experiment was designed to simulate the effects of CO 2 -driven acidification predicted to occur by the end of this century (scenario RCP4.5) while simultaneously maintaining the exposure of corals to natural variations in their environment under in situ conditions. Analyses of skeletal growth (measured from extension rates and skeletal density) showed no systematic differences between low-pH FOCE treatments (ΔpH = ∼−0.05 to −0.25 units below ambient) and present day controls (ΔpH = 0) for calcification rates or the pH of the calcifying fluid (pH cf ); the latter was derived from boron isotopic compositions (δ 11 B) of the coral skeleton. Furthermore, individual nubbins exhibited near constant δ 11 B compositions along their primary apical growth axes (±0.02 pH cf units) regardless of the season or treatment. Thus, under the highly dynamic conditions of the Heron Island reef flat, P. cylindrica up-regulated the pH of its calcifying fluid (pH cf ∼8.4-8.6), with each nubbin having nearconstant pH cf values independent of the large natural seasonal fluctuations of the reef flat waters (pH ∼7.7 to ∼8.3) or the superimposed FOCE treatments. This newly discovered phenomenon of pH homeostasis during calcification indicates that coral living in highly dynamic environments exert strong physiological controls on the carbonate chemistry of their calcifying fluid, implying a high degree of resilience to ocean acidification within the investigated ranges.A tmospheric CO 2 has risen by more than 30% during the last century, causing a reduction in seawater pH of ∼0.1 units relative to preindustrial times, with a further reduction of 0.1-0.4 units predicted to occur by the end of this century (1). This process, commonly known as "ocean acidification," is expected to have severe impacts on calcifying marine organisms due to its effect on the thermodynamics of biomineralization (2). Our current understanding of the sensitivity of coral calcification to declining seawater pH has mainly been inferred from short-term laboratory-based studies that do not fully simulate real-world reef conditions, particularly the daily to seasonal variations in temperature, light, and pH (3-5). To address these shortcomings, we applied free ocean carbon enrichment (FOCE) technologies (6-9) to manipulate water chemistry in situ and thereby provide more realistic experimental conditions to investigate how future levels of acidification could affect marine organisms according to different representative concentration pathways (RCPs) (10). The FOCE system uses a flowthrough flume design that allows organisms to experience near natural conditions, in particular the daily and seasonal regimes of fluctuating temperature, light, and nutrients while maintaining offsets in flume water pH below ...

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Section: Resultsmentioning

confidence: 90%

pH homeostasis during coral calcification in a free ocean CO ₂ enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

Georgiou

Falter

Trotter

et al. 2015

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

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“…Some of the most striking examples of these effects are exhibited by scleractinian corals [7], yet despite the negative implications of these trends for coral reef ecosystems [8], progress has been slow in elucidating the mechanisms underlying the response of corals to high pCO 2 [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Effects of diurnally oscillatingpCO₂on the calcification and survival of coral recruits

et al. 2012

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Manipulative studies have demonstrated that ocean acidification (OA) is a threat to coral reefs, yet no experiments have employed diurnal variations in pCO 2 that are ecologically relevant to many shallow reefs. Two experiments were conducted to test the response of coral recruits (less than 6 days old) to diurnally oscillating pCO 2 ; one exposing recruits for 3 days to ambient (440 matm), high (663 matm) and diurnally oscillating pCO 2 on a natural phase (420 -596 matm), and another exposing recruits for 6 days to ambient (456 matm), high (837 matm) and diurnally oscillating pCO 2 on either a natural or a reverse phase (448 -845 matm). In experiment I, recruits exposed to natural-phased diurnally oscillating pCO 2 grew 6-19% larger than those in ambient or high pCO 2 . In experiment II, recruits in both high and natural-phased diurnally oscillating pCO 2 grew 16 per cent larger than those at ambient pCO 2 , and this was accompanied by 13 -18% higher survivorship; the stimulatory effect on growth of oscillatory pCO 2 was diminished by administering high pCO 2 during the day (i.e. reverse-phased). These results demonstrate that coral recruits can benefit from ecologically relevant fluctuations in pCO 2 and we hypothesize that the mechanism underlying this response is highly pCO 2 -mediated, night-time storage of dissolved inorganic carbon that fuels daytime calcification.

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“…the endpoint consequence of a stable and efficient functioning symbiosis. In this case, the zooxanthellae have been speculated to benefit host calcification via: (i) translocation of photosynthate to fuel active ion transport mechanisms and/or supply precursors required to synthesize the organic matrix that serves as the nucleating centre for CaCO 3 crystals; (ii) the uptake of animal metabolic waste products that may interfere with CaCO 3 precipitation, particularly phosphate that inhibit carbonate nucleation; and (iii) the increase in CaCO 3 saturation by CO 2 uptake and the maintenance of an oxygen environment (reviewed in Allemand et al, 2011). …”

Section: Introductionmentioning

confidence: 99%

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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Coral Calcification, Cells to Reefs

Cited by 309 publications

References 246 publications

pH homeostasis during coral calcification in a free ocean CO ₂ enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

pH homeostasis during coral calcification in a free ocean CO ₂ enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

Effects of diurnally oscillatingpCO₂on the calcification and survival of coral recruits

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

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Coral Calcification, Cells to Reefs

Cited by 309 publications

References 246 publications

pH homeostasis during coral calcification in a free ocean CO 2 enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

pH homeostasis during coral calcification in a free ocean CO 2 enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

Effects of diurnally oscillatingpCO2on the calcification and survival of coral recruits

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

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pH homeostasis during coral calcification in a free ocean CO ₂ enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

pH homeostasis during coral calcification in a free ocean CO ₂ enrichment (FOCE) experiment, Heron Island reef flat, Great Barrier Reef

Effects of diurnally oscillatingpCO₂on the calcification and survival of coral recruits