Assessing scleractinian corals as recorders for paleo-pH: Empirical calibration and vital effects

Hönisch, Bärbel; Hemming, N. Gary; Grottoli, Andréa G.; Amat, Asmiaty; Hanson, Gilbert N.; Biȷma, Jelle

doi:10.1016/j.gca.2004.03.002

Cited by 184 publications

(136 citation statements)

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“…However, under the naturally and highly dynamic pH conditions within the Heron Island reef flat, corals seemingly exert a much stronger physiological control of pH cf , which overrides the seasonal ambient depression in seawater pH, as well as the superimposed FOCE induced decrease in seawater pH . Reinterpretation (11) of previous laboratory work using P. cylindrica colonies under depressed pCO 2 conditions (29) indicates that pH up-regulation was taking place at the site of calcification in this species; these previous experiments, however, kept CO 2 constant throughout the experiment and therefore did not capture the dynamic nature of many natural reef environments. We note that the finding from our study of strong pH homeostasis as exhibited along the major growth axis of the coral skeletons occurs despite the large range in δ 11 B for intercolonial (Fig.…”

Section: Resultsmentioning

confidence: 94%

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: 94%

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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“…Therefore, proxy records from the geologic record sensitive to oceanic carbon dynamics are highly desired to place modern pH trends into context (e.g., Hönisch et al, 2012.). Biogenic proxy archives calcifying within the surface waters of the global oceans have the unique potential to reveal spatial and temporal patterns and trends in pH using boron isotopes (e.g., Anagnostou et al, 2012;Shinjo et al, 2013).…”

Section: Y-w Liu Et Al: Environmental Controls On the Boron And Stmentioning

confidence: 99%

Environmental controls on the boron and strontium isotopic composition of aragonite shell material of cultured <i>Arctica islandica</i>

2015

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Abstract. Ocean acidification, the decrease in ocean pH associated with increasing atmospheric CO 2 , is likely to impact marine organisms, particularly those that produce carbonate skeletons or shells. Therefore, it is important to investigate how environmental factors (seawater pH, temperature and salinity) influence the chemical compositions in biogenic carbonates. In this study we report the first highresolution strontium ( 87 Sr / 86 Sr and δ 88 / 86 Sr) and boron (δ 11 B) isotopic values in the aragonite shell of cultured Arctica islandica (A. islandica). The 87 Sr / 86 Sr ratios from both tank water and shell samples show ratios nearly identical to the open ocean, which suggests that the shell material reflects ambient ocean chemistry without terrestrial influence. The 84 Sr-87 Sr double-spike-resolved shell δ 88 / 86 Sr and Sr concentration data show no resolvable change throughout the culture period and reflect no theoretical kinetic mass fractionation throughout the experiment despite a temperature change of more than 15 • C. The δ 11 B records from the experiment show at least a 5 ‰ increase through the 29-week culture season (January 2010-August 2010), with low values from the beginning to week 19 and higher values thereafter. The larger range in δ 11 B in this experiment compared to predictions based on other carbonate organisms (2-3 ‰) suggests that a species-specific fractionation factor may be required. A significant correlation between the pH (pH shell − pH sw ) and seawater pH (pH sw ) was observed (R 2 = 0.35), where the pH shell is the calcification pH of the shell calculated from boron isotopic composition. This negative correlation suggests that A. islandica partly regulates the pH of the extrapallial fluid. However, this proposed mechanism only explains approximately 35 % of the variance in the δ 11 B data. Instead, a rapid rise in δ 11 B of the shell material after week 19, during the summer, suggests that the boron uptake changes when a thermal threshold of > 13 • C is reached.

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“…The B content, typically measured as B/Ca, has been linked to the carbonate ion concentration in seawater [84], while the isotopic composition appears to be controlled by seawater pH [83]. From the isotopic perspective, the best calibrations exist for planktonic [85] and benthic [86] foraminifera and shallow-water corals [87]. There are difficulties with this approach, including the challenges in making accurate and precise analyses [88].…”

Section: (Iii) Carbon Cyclingmentioning

confidence: 99%

Palaeoceanography: motivations and challenges for the future

Robinson

Siddall

2012

Phil. Trans. R. Soc. A.

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The ocean interacts with the atmosphere, biosphere and cryosphere in a complex way, modulating climate through the storage and transport of heat, nutrients and carbon. As such, it is important that we understand the ways in which the ocean behaves and the factors that can lead to change. In order to gain this understanding, we need to look back into the past, on time scales from recent decadal-scale change, through the abrupt changes of the Pleistocene and back to times when the Earth's climate was significantly different than the Holocene. A key challenge facing the field of palaeoceanography is to combine data and modelling in a common framework. Coupling palaeo-data and models should improve our knowledge of how the Earth works, and perhaps of more direct societal relevance, might enable us to provide better predictive capabilities in climate modelling. In this discussion paper, we examine the motivations, past successes and challenges facing palaeoceanographic studies. We then suggest a number of areas and approaches that we believe will allow palaeoceanography to continue to provide new insights into processes that affect future climate change.

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Assessing scleractinian corals as recorders for paleo-pH: Empirical calibration and vital effects

Cited by 184 publications

References 50 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

Environmental controls on the boron and strontium isotopic composition of aragonite shell material of cultured <i>Arctica islandica</i>

Palaeoceanography: motivations and challenges for the future

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Assessing scleractinian corals as recorders for paleo-pH: Empirical calibration and vital effects

Cited by 184 publications

References 50 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

Environmental controls on the boron and strontium isotopic composition of aragonite shell material of cultured &lt;i&gt;Arctica islandica&lt;/i&gt;

Palaeoceanography: motivations and challenges for the future

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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

Environmental controls on the boron and strontium isotopic composition of aragonite shell material of cultured <i>Arctica islandica</i>