Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone Paleobarometer
Abstract The carbon isotope fractionation in algal organic matter (εp), including the long‐chain alkenones produced by the coccolithophorid family Noelaerhabdaceae, is used to reconstruct past atmospheric CO2 levels. The conventional proxy linearly relates εp to changes in cellular carbon demand rel...
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| Format: | Article |
| Language: | English |
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Wiley
2021-07-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2021GC009657 |
| _version_ | 1797637927385169920 |
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| author | Samuel R. Phelps Gwenn M. M. Hennon Sonya T. Dyhrman María D. Hernández Limón Olivia M. Williamson Pratigya J. Polissar |
| author_facet | Samuel R. Phelps Gwenn M. M. Hennon Sonya T. Dyhrman María D. Hernández Limón Olivia M. Williamson Pratigya J. Polissar |
| author_sort | Samuel R. Phelps |
| collection | DOAJ |
| description | Abstract The carbon isotope fractionation in algal organic matter (εp), including the long‐chain alkenones produced by the coccolithophorid family Noelaerhabdaceae, is used to reconstruct past atmospheric CO2 levels. The conventional proxy linearly relates εp to changes in cellular carbon demand relative to diffusive CO2 supply, with larger εp values occurring at lower carbon demand relative to supply (i.e., abundant CO2). However, the response of Gephyrocapsa oceanica, one of the dominant alkenone producers of the last few million years, has not been studied closely. Here, we subject G. oceanica to various CO2 levels by increasing pCO2 in the culture headspace, as opposed to increasing dissolved inorganic carbon (DIC) and alkalinity concentrations at constant pH. We note no substantial change in physiology, but observe an increase in εp as carbon demand relative to supply decreases, consistent with DIC manipulations. We compile existing Noelaerhabdaceae εp data and show that the diffusive model poorly describes the data. A meta‐analysis of individual treatments (unique combinations of lab, strain, and light conditions) shows that the slope of the εp response depends on the light conditions and range of carbon demand relative to CO2 supply in the treatment, which is incompatible with the diffusive model. We model εp as a multilinear function of key physiological and environmental variables and find that both photoperiod duration and light intensity are critical parameters, in addition to CO2 and cell size. While alkenone carbon isotope ratios indeed record CO2 information, irradiance and other factors are also necessary to properly describe alkenone εp. |
| first_indexed | 2024-03-11T12:55:17Z |
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| id | doaj.art-24e33e79e32c42a791b5789080a13885 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:55:17Z |
| publishDate | 2021-07-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-24e33e79e32c42a791b5789080a138852023-11-03T17:01:09ZengWileyGeochemistry, Geophysics, Geosystems1525-20272021-07-01227n/an/a10.1029/2021GC009657Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone PaleobarometerSamuel R. Phelps0Gwenn M. M. Hennon1Sonya T. Dyhrman2María D. Hernández Limón3Olivia M. Williamson4Pratigya J. Polissar5Department of Earth and Environmental Sciences Columbia University New York NY USADivision of Biology and Paleo‐Environment Lamont‐Doherty Earth Observatory of Columbia University Palisades NY USADepartment of Earth and Environmental Sciences Columbia University New York NY USADepartment of Earth and Environmental Sciences Columbia University New York NY USADivision of Biology and Paleo‐Environment Lamont‐Doherty Earth Observatory of Columbia University Palisades NY USADivision of Biology and Paleo‐Environment Lamont‐Doherty Earth Observatory of Columbia University Palisades NY USAAbstract The carbon isotope fractionation in algal organic matter (εp), including the long‐chain alkenones produced by the coccolithophorid family Noelaerhabdaceae, is used to reconstruct past atmospheric CO2 levels. The conventional proxy linearly relates εp to changes in cellular carbon demand relative to diffusive CO2 supply, with larger εp values occurring at lower carbon demand relative to supply (i.e., abundant CO2). However, the response of Gephyrocapsa oceanica, one of the dominant alkenone producers of the last few million years, has not been studied closely. Here, we subject G. oceanica to various CO2 levels by increasing pCO2 in the culture headspace, as opposed to increasing dissolved inorganic carbon (DIC) and alkalinity concentrations at constant pH. We note no substantial change in physiology, but observe an increase in εp as carbon demand relative to supply decreases, consistent with DIC manipulations. We compile existing Noelaerhabdaceae εp data and show that the diffusive model poorly describes the data. A meta‐analysis of individual treatments (unique combinations of lab, strain, and light conditions) shows that the slope of the εp response depends on the light conditions and range of carbon demand relative to CO2 supply in the treatment, which is incompatible with the diffusive model. We model εp as a multilinear function of key physiological and environmental variables and find that both photoperiod duration and light intensity are critical parameters, in addition to CO2 and cell size. While alkenone carbon isotope ratios indeed record CO2 information, irradiance and other factors are also necessary to properly describe alkenone εp.https://doi.org/10.1029/2021GC009657alkenonecarbon isotopepaleobarometrycoccolithophorecarbon dioxideirradiance |
| spellingShingle | Samuel R. Phelps Gwenn M. M. Hennon Sonya T. Dyhrman María D. Hernández Limón Olivia M. Williamson Pratigya J. Polissar Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone Paleobarometer Geochemistry, Geophysics, Geosystems alkenone carbon isotope paleobarometry coccolithophore carbon dioxide irradiance |
| title | Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone Paleobarometer |
| title_full | Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone Paleobarometer |
| title_fullStr | Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone Paleobarometer |
| title_full_unstemmed | Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone Paleobarometer |
| title_short | Carbon Isotope Fractionation in Noelaerhabdaceae Algae in Culture and a Critical Evaluation of the Alkenone Paleobarometer |
| title_sort | carbon isotope fractionation in noelaerhabdaceae algae in culture and a critical evaluation of the alkenone paleobarometer |
| topic | alkenone carbon isotope paleobarometry coccolithophore carbon dioxide irradiance |
| url | https://doi.org/10.1029/2021GC009657 |
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