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  • 1
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    Seawater temperature and buffering capacity modulate coral calcifying pH (2019)
    Nature Research
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Guo, W. Seawater temperature and buffering capacity modulate coral calcifying pH. Scientific Reports, 9(1), (2019):1189, doi:10.1038/s41598-018-36817-y.
    Description: Scleractinian corals promote the precipitation of their carbonate skeleton by elevating the pH and dissolved inorganic carbon (DIC) concentration of their calcifying fluid above that of seawater. The fact corals actively regulate their calcifying fluid chemistry implies the potential for acclimation to ocean acidification. However, the extent to which corals can adjust their regulation mechanism in the face of decreasing ocean pH has not been rigorously tested. Here I present a numerical model simulating pH and DIC up-regulation by corals, and use it to determine the relative importance of physiological regulation versus seawater conditions in controlling coral calcifying fluid chemistry. I show that external seawater temperature and buffering capacity exert the first-order control on the extent of pH elevation in the calcifying fluid and explain most of the observed inter- and intra-species variability. Conversely, physiological regulation, represented by the interplay between enzymatic proton pumping, carbon influx and the exchange of calcifying fluid with external seawater, contributes to some variability but remain relatively constant as seawater conditions change. The model quantitatively reproduces variations of calcifying fluid pH in natural Porites colonies, and predicts an average 0.16 unit decrease in Porites calcifying fluid pH, i.e., ~43% increase in H+ concentration, by the end of this century as a combined result of projected ocean warming and acidification, highlighting the susceptibility of coral calcification to future changes in ocean conditions. In addition, my findings support the development of coral-based seawater pH proxies, but suggest the influences of physicochemical and biological factors other than seawater pH must be considered.
    Description: This work was supported by the U.S. National Science Foundation Award ANT-1246387 and by the Woods Hole Oceanographic Institution through the Ocean Life Institute, Investment in Science Fund and an Early Career Award.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    A warm and poorly ventilated deep Arctic Mediterranean during the last glacial period (2015)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of American Association for the Advancement of Science for personal use, not for redistribution. The definitive version was published in Science 349 (2015): 706-710, doi:10.1126/science.aaa9554.
    Description: Changes in the formation of dense water in the Arctic Ocean and Nordic Seas (the ‘Arctic Mediterranean’, AM) likely contributed to the altered climate of the last glacial period. We examine past changes in AM circulation by reconstructing 14C ventilation ages of the deep Nordic Seas over the last 30,000 years. Our results show that the deep glacial AM was extremely poorly ventilated (ventilation ages of up to 10,000 years). Subsequent episodic overflow of aged water into the mid-depth North Atlantic occurred during deglaciation. Proxy data also suggest the deep glacial AM was ~2-3°C warmer than modern; deglacial mixing of the deep AM with the upper ocean thus potentially contributed to melting sea-ice and icebergs, as well as proximal terminal ice-sheet margins.
    Description: Funding was provided by a WHOI OCCI scholarship and OCCI grant 27071264 (DJRT); WHOI OCCI and NSF grants OIA-1124880 and OCE-1357121 (GG); the WHOI J. Lamar Worzel Assistant Scientist Fund, the Penzance Endowed Fund in Support of Assistant Scientists and NSF ANT-1246387 (WG); EU FP7 Marie Curie grant No. 298513 (MZ), grant DP140101393 (JY); and NERC grant NE/J008133/1 (SB).
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 3
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    Clumped isotope composition of cold-water corals : a role for vital effects? (2016)
    Elsevier
    Details
    Publication Date: 2016-09-23
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 179 (2016): 123-141, doi:10.1016/j.gca.2016.01.023.
    Description: The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes ‘clumping’ into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope ‘vital effects’ are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with CO2 hydration/hydroxylation reactions in the corals’ calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy.
    Description: This work was supported by a British National Environment Research Council studentship to P. Spooner (NE/K500823/1), National Science Foundation Grant NSF-ANT-1246387 and The Penzance Endowed Fund in Support of Assistant Scientists (WHOI) to W. Guo, and by funds from the European Research Council, the Leverhulme Trust and a Marie Curie Reintegration grant.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
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    Dual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures (2020)
    Nature Research
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Bajnai, D., Guo, W., Spötl, C., Coplen, T. B., Methner, K., Löffler, N., Krsnik, E., Gischler, E., Hansen, M., Henkel, D., Price, G. D., Raddatz, J., Scholz, D., & Fiebig, J. Dual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures. Nature Communications, 11(1), (2020): 4005, doi:10.1038/s41467-020-17501-0.
    Description: Surface temperature is a fundamental parameter of Earth’s climate. Its evolution through time is commonly reconstructed using the oxygen isotope and the clumped isotope compositions of carbonate archives. However, reaction kinetics involved in the precipitation of carbonates can introduce inaccuracies in the derived temperatures. Here, we show that dual clumped isotope analyses, i.e., simultaneous ∆47 and ∆48 measurements on the single carbonate phase, can identify the origin and quantify the extent of these kinetic biases. Our results verify theoretical predictions and evidence that the isotopic disequilibrium commonly observed in speleothems and scleractinian coral skeletons is inherited from the dissolved inorganic carbon pool of their parent solutions. Further, we show that dual clumped isotope thermometry can achieve reliable palaeotemperature reconstructions, devoid of kinetic bias. Analysis of a belemnite rostrum implies that it precipitated near isotopic equilibrium and confirms the warmer-than-present temperatures during the Early Cretaceous at southern high latitudes.
    Description: This work became possible through DFG grant “INST 161/871-1” and the Investment in Science Fund at Woods Hole Oceanographic Institution. The authors would like to thank Sven Hofmann and Manuel Schumann for their assistance in the joint Goethe University – Senckenberg BiK-F Stable Isotope Facility at the Institute of Geosciences, Goethe University Frankfurt. K.M. acknowledges funding through “DFG ME 4955/1-1”, E.K. through “DFG MU 2845/6-1”, D.S. through “DFG SCHO 1274/8-1” and “DFG SCHO 1274/11-1”, and M.H. through “DFG HA 8694/1-1”. C.S. acknowledges funding from the University of Innsbruck. A review of the manuscript by David Evans on behalf of the USGS is acknowledged.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
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    Theoretical estimates of equilibrium sulfur isotope effects in aqueous sulfur systems : highlighting the role of isomers in the sulfite and sulfoxylate systems (2017)
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 195 (2016): 171-200, doi:10.1016/j.gca.2016.09.021.
    Description: We present theoretical calculations for all three isotope ratios of sulfur (33S/32S, 34S/32S, 36S/32S) at the B3LYP/6-31+G(d,p) level of theory for aqueous sulfur compounds modeled in 30–40H2O clusters spanning the range of sulfur oxidation state (Sn, n = −2 to +6) for estimating equilibrium fractionation factors in aqueous systems. Computed 34β values based on major isotope (34S/32S) reduced partition function ratios (RPFRs) scale to a first order with sulfur oxidation state and coordination, where 34β generally increase with higher oxidation state and increasing coordination of the sulfur atom. Exponents defining mass dependent relationships based on β values (x/34κ = ln(xβ)/ln(34β), x = 33 or 36) conform to tight ranges over a wide range of temperature for all aqueous compounds (33/34κ ≈ 0.5148–0.5159, 36/34κ ≈ 1.89–1.90 from T ⩾ 0 °C). The exponents converge near a singular value for all compounds at the high temperature limit (33/34κT→∞ = 0.51587 ± 0.00003 and 36/34κT→∞ = 1.8905 ± 0.0002; 1 s.d. of all computed compounds), and typically follow trends based on oxidation state and coordination similar to those seen in 34β values at lower temperatures. Theoretical equilibrium fractionation factors computed from these β-values are compared to experimental constraints for HSO3−T(aq)/SO2(g, aq), SO2(aq)/SO2(g), H2S(aq)/H2S(g), H2S(aq)/HS−(aq), SO42−(aq)/H2ST(aq), S2O32−(aq) (intramolecular), and S2O32−(aq)/H2ST(aq), and generally agree within a reasonable estimation of uncertainties. We make predictions of fractionation factors where other constraints are unavailable. Isotope partitioning of the isomers of protonated compounds in the sulfite and sulfoxylate systems depend strongly on whether protons are bound to either sulfur or oxygen atoms. The magnitude of the HSO3−T/SO32− major isotope (34S/32S) fractionation factor is predicted to increase with temperature from 0 to 70 °C due to the combined effects of the large magnitude (HS)O3−/SO32− fractionation factor (1000ln34α(HS)bisulfite-sulfite = 19.9‰, 25 °C) relative to the (HO)SO2−/SO32− fractionation factor (1000ln34α(HO)bisulfite–sulfite = −2.2‰, 25 °C), and the increased stability of the (HS)O3− isomer with increasing temperature. We argue that isomerization phenomenon should be considered in models of the sulfur cycle, including models that describe the overall sulfur isotope fractionations associated with microbial metabolism (e.g., microbial sulfate reduction).
    Description: This work was supported by a NASA Earth and Space Sciences Fellowship (NESSF) granted to D.L. Eldridge (NNX12AL77H), NSF grant 1361945: Sulfur isotope studies of sulfide oxidation (J. Farquhar), and the Investment in Science Fund at WHOI (W. Guo).
    Description: 2018-09-26
    Keywords: Sulfur isotopes ; Sulfite ; Bisulfite ; Sulfoxylate ; Isotope effects ; Mass dependent ; Theoretical calculations
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 6
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    Ocean acidification has impacted coral growth on the great barrier reef (2020)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 47(19), (2020): e2019GL086761, doi:10.1029/2019GL086761.
    Description: Ocean acidification (OA) reduces the concentration of seawater carbonate ions that stony corals need to produce their calcium carbonate skeletons and is considered a significant threat to the functional integrity of coral reef ecosystems. However, detection and attribution of OA impact on corals in nature are confounded by concurrent environmental changes, including ocean warming. Here we use a numerical model to isolate the effects of OA and temperature and show that OA alone has caused 13 ± 3% decline in the skeletal density of massive Porites corals on the Great Barrier Reef since 1950. This OA‐induced thinning of coral skeletons, also evident in Porites from the South China Sea but not in the central Pacific, reflects enhanced acidification of reef water relative to the surrounding open ocean. Our finding reinforces concerns that even corals that might survive multiple heatwaves are structurally weakened and increasingly vulnerable to the compounding effects of climate change.
    Description: This work was supported in part by the U.S. National Science Foundation (OCE‐1737311), the Robertson Foundation, the Tiffany & Co. Foundation, the Atlantic Donor Advised Fund, the Investment in Science Fund and The Andrew W. Mellon Foundation Endowed Fund for Innovative Research at the Woods Hole Oceanographic Institution. The data generated in this study are included in the Supporting Information (Data Sets S1–S3) and are also being archived at NOAA National Centers for Environmental Information (NCEI)‐Paleoclimatology Data repository.
    Description: 2021-02-27
    Keywords: Ocean Acidification ; Coral Growth ; Indo‐Pacific Reefs ; Skeletal Density ; Climate Impact ; Great Barrier Reef
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    Clumped isotope composition of cold-water corals : a role for vital effects? (2016)
    Elsevier
    Details
    Publication Date: 2022-05-26
    Description: © The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 179 (2016): 123-141, doi:10.1016/j.gca.2016.01.023.
    Description: The carbonate clumped isotope thermometer is a promising tool for determining past ocean temperatures. It is based on the temperature dependence of rare isotopes ‘clumping’ into the same carbonate ion group in the carbonate mineral lattice. The extent of this clumping effect is independent of the isotope composition of the water from which carbonate precipitates, providing unique advantages over many other paleotemperature proxies. Existing calibrations of this thermometer in cold-water and warm-water corals suggest clumped isotope ‘vital effects’ are negligible in cold-water corals but may be significant in warm-water corals. Here, we test the calibration of the carbonate clumped isotope thermometer in cold-water corals with a recently collected and well characterised sample set spanning a range of coral genera (Balanophyllia, Caryophyllia, Dasmosmilia, Desmophyllum, Enallopsammia and Javania). The clumped isotope compositions (Δ47) of these corals exhibit systematic dependences on their growth temperatures, confirming the basis of the carbonate clumped isotope thermometer. However, some cold-water coral genera show Δ47 values that are higher than the expected equilibrium values by up to 0.05‰ (equivalent to underestimating temperature by ∼9 °C) similar to previous findings for some warm-water corals. This finding suggests that the vital effects affecting corals Δ47 are common to both warm- and cold-water corals. By comparison with models of the coral calcification process we suggest that the clumped isotope offsets in these genera are related to the kinetic isotope effects associated with CO2 hydration/hydroxylation reactions in the corals’ calcifying fluid. Our findings complicate the use of the carbonate clumped isotope thermometer in corals, but suggest that species- or genus-specific calibrations could be useful for the future application of this paleotemperature proxy.
    Description: This work was supported by a British National Environment Research Council studentship to P. Spooner (NE/K500823/1), National Science Foundation Grant NSF-ANT-1246387 and The Penzance Endowed Fund in Support of Assistant Scientists (WHOI) to W. Guo, and by funds from the European Research Council, the Leverhulme Trust and a Marie Curie Reintegration grant.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
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    Ocean acidification affects coral growth by reducing skeletal density (2018)
    National Academy of Sciences
    In:  PNAS Proceedings of the National Academy of Sciences of the United States of America, 115 (8). pp. 1754-1759.
    Details
    Publication Date: 2021-02-08
    Description: Ocean acidification (OA) is considered an important threat to coral reef ecosystems, because it reduces the availability of carbonate ions that reef-building corals need to produce their skeletons. However, while theory predicts that coral calcification rates decline as carbonate ion concentrations decrease, this prediction is not consistently borne out in laboratory manipulation experiments or in studies of corals inhabiting naturally low-pH reefs today. The skeletal growth of corals consists of two distinct processes: extension (upward growth) and densification (lateral thickening). Here, we show that skeletal density is directly sensitive to changes in seawater carbonate ion concentration and thus, to OA, whereas extension is not. We present a numerical model of Porites skeletal growth that links skeletal density with the external seawater environment via its influence on the chemistry of coral calcifying fluid. We validate the model using existing coral skeletal datasets from six Porites species collected across five reef sites and use this framework to project the impact of 21st century OA on Porites skeletal density across the global tropics. Our model predicts that OA alone will drive up to 20.3 ± 5.4% decline in the skeletal density of reef-building Porites corals.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1073/pnas.1712806115
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Dual clumped isotope thermometry resolves kinetic biases in carbonate formation temperatures (2020)
    Nature Research
    Details
    Publication Date: 2024-03-21
    Description: Surface temperature is a fundamental parameter of Earth’s climate. Its evolution through time is commonly reconstructed using the oxygen isotope and the clumped isotope compositions of carbonate archives. However, reaction kinetics involved in the precipitation of carbonates can introduce inaccuracies in the derived temperatures. Here, we show that dual clumped isotope analyses, i.e., simultaneous ∆47 and ∆48 measurements on the single carbonate phase, can identify the origin and quantify the extent of these kinetic biases. Our results verify theoretical predictions and evidence that the isotopic disequilibrium commonly observed in speleothems and scleractinian coral skeletons is inherited from the dissolved inorganic carbon pool of their parent solutions. Further, we show that dual clumped isotope thermometry can achieve reliable palaeotemperature reconstructions, devoid of kinetic bias. Analysis of a belemnite rostrum implies that it precipitated near isotopic equilibrium and confirms the warmer-than-present temperatures during the Early Cretaceous at southern high latitudes.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    Format: other
    Format: other
    Format: other
    Format: other
    Format: other
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Stable Isotope Cosmochemistry and the Evolution of Planetary Systems (2011)
    Mineralogical Society of America
    Details
    Publication Date: 2011-02-01
    Description: Stable isotopes record the evolution of planetary systems, beginning with stars coalescing from molecular clouds, followed by the nucleosynthesis of elements in stars, and proceeding to the accretion and differentiation of planets. Current stable isotope measurements range in scale from isotopic mapping of the Milky Way Galaxy with spectrographs on telescopes to the analysis of stardust with ion probes.
    Print ISSN: 1811-5209
    Electronic ISSN: 1811-5217
    Topics: Geosciences
    Published by Mineralogical Society of America
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