Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean
Records of carbon dioxide concentrations (partial pressure expressed as pCO2) over Earth’s history provide trends that are critical to understand our changing world. To better constrain pCO2 estimations, here we test organic pCO2 proxies against the direct measurements of pCO2 recorded in ice cores....
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ftbryantuniv:oai:digitalcommons.bryant.edu:sci_jou-1065 2023-05-15T16:38:52+02:00 Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean Witkowski, Caitlyn R. van der Meer, Marcel T.J. Blais, Brian Sinninghe Damsté, Jaap S. Schouten, Stefan 2020-09-15T07:00:00Z application/pdf https://digitalcommons.bryant.edu/sci_jou/66 https://digitalcommons.bryant.edu/cgi/viewcontent.cgi?article=1065&context=sci_jou english eng Bryant Digital Repository https://digitalcommons.bryant.edu/sci_jou/66 https://digitalcommons.bryant.edu/cgi/viewcontent.cgi?article=1065&context=sci_jou Attribution 4.0 International (CC BY 4.0) CC-BY Science and Technology Faculty Journal Articles pCO2 Organic geochemical proxies Sapropels Phytol Alkenones Biochemistry Biophysics and Structural Biology Environmental Chemistry Oceanography and Atmospheric Sciences and Meteorology Other Environmental Sciences Physical Sciences and Mathematics text 2020 ftbryantuniv 2022-12-03T23:30:38Z Records of carbon dioxide concentrations (partial pressure expressed as pCO2) over Earth’s history provide trends that are critical to understand our changing world. To better constrain pCO2 estimations, here we test organic pCO2 proxies against the direct measurements of pCO2 recorded in ice cores. Based on the concept of stable carbon isotopic fractionation due to photosynthetic CO2 fixation (Ɛp), we use the stable carbon isotopic composition (δ13C) of the recently proposed biomarker phytol (from all photoautotrophs), as well as the conventionally used alkenone biomarkers (from specific species) for comparison, to reconstruct pCO2 over several Quaternary sapropel formation periods (S1, S3, S4, and S5) in the eastern Mediterranean Sea. The reconstructed pCO2 values are within error of the ice core values but consistently exceed the ice core values by ca. 100 µatm. This offset corresponds with atmospheric disequilibrium of present day CO2[aq] concentrations in the Mediterranean Sea from global pCO2, equivalent to ca. 100 µatm, although pCO2 estimates derived from individual horizons within each sapropel do not covary with the ice core values. This may possibly be due to greater variability in local CO2[aq] concentration changes in the Mediterranean, as compared with the global average pCO2, or possibly due to biases in the proxy, such as variable growth rate or carbon-concentrating mechanisms. Thus, the offset is likely a combination of physiological or environmental factors. Nevertheless, our results demonstrate that alkenone- and phytol-based pCO2 proxies yield statistically similar estimations (P-value = 0.02, Pearson’s r-value = 0.56), and yield reasonable absolute estimations although with relatively large uncertainties (± 100 µatm). Text ice core DigitalCommons@Bryant University |
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Open Polar |
collection |
DigitalCommons@Bryant University |
op_collection_id |
ftbryantuniv |
language |
English |
topic |
pCO2 Organic geochemical proxies Sapropels Phytol Alkenones Biochemistry Biophysics and Structural Biology Environmental Chemistry Oceanography and Atmospheric Sciences and Meteorology Other Environmental Sciences Physical Sciences and Mathematics |
spellingShingle |
pCO2 Organic geochemical proxies Sapropels Phytol Alkenones Biochemistry Biophysics and Structural Biology Environmental Chemistry Oceanography and Atmospheric Sciences and Meteorology Other Environmental Sciences Physical Sciences and Mathematics Witkowski, Caitlyn R. van der Meer, Marcel T.J. Blais, Brian Sinninghe Damsté, Jaap S. Schouten, Stefan Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean |
topic_facet |
pCO2 Organic geochemical proxies Sapropels Phytol Alkenones Biochemistry Biophysics and Structural Biology Environmental Chemistry Oceanography and Atmospheric Sciences and Meteorology Other Environmental Sciences Physical Sciences and Mathematics |
description |
Records of carbon dioxide concentrations (partial pressure expressed as pCO2) over Earth’s history provide trends that are critical to understand our changing world. To better constrain pCO2 estimations, here we test organic pCO2 proxies against the direct measurements of pCO2 recorded in ice cores. Based on the concept of stable carbon isotopic fractionation due to photosynthetic CO2 fixation (Ɛp), we use the stable carbon isotopic composition (δ13C) of the recently proposed biomarker phytol (from all photoautotrophs), as well as the conventionally used alkenone biomarkers (from specific species) for comparison, to reconstruct pCO2 over several Quaternary sapropel formation periods (S1, S3, S4, and S5) in the eastern Mediterranean Sea. The reconstructed pCO2 values are within error of the ice core values but consistently exceed the ice core values by ca. 100 µatm. This offset corresponds with atmospheric disequilibrium of present day CO2[aq] concentrations in the Mediterranean Sea from global pCO2, equivalent to ca. 100 µatm, although pCO2 estimates derived from individual horizons within each sapropel do not covary with the ice core values. This may possibly be due to greater variability in local CO2[aq] concentration changes in the Mediterranean, as compared with the global average pCO2, or possibly due to biases in the proxy, such as variable growth rate or carbon-concentrating mechanisms. Thus, the offset is likely a combination of physiological or environmental factors. Nevertheless, our results demonstrate that alkenone- and phytol-based pCO2 proxies yield statistically similar estimations (P-value = 0.02, Pearson’s r-value = 0.56), and yield reasonable absolute estimations although with relatively large uncertainties (± 100 µatm). |
format |
Text |
author |
Witkowski, Caitlyn R. van der Meer, Marcel T.J. Blais, Brian Sinninghe Damsté, Jaap S. Schouten, Stefan |
author_facet |
Witkowski, Caitlyn R. van der Meer, Marcel T.J. Blais, Brian Sinninghe Damsté, Jaap S. Schouten, Stefan |
author_sort |
Witkowski, Caitlyn R. |
title |
Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean |
title_short |
Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean |
title_full |
Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean |
title_fullStr |
Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean |
title_full_unstemmed |
Algal biomarkers as a proxy for pCO2: Constraints from late Quaternary sapropels in the eastern Mediterranean |
title_sort |
algal biomarkers as a proxy for pco2: constraints from late quaternary sapropels in the eastern mediterranean |
publisher |
Bryant Digital Repository |
publishDate |
2020 |
url |
https://digitalcommons.bryant.edu/sci_jou/66 https://digitalcommons.bryant.edu/cgi/viewcontent.cgi?article=1065&context=sci_jou |
genre |
ice core |
genre_facet |
ice core |
op_source |
Science and Technology Faculty Journal Articles |
op_relation |
https://digitalcommons.bryant.edu/sci_jou/66 https://digitalcommons.bryant.edu/cgi/viewcontent.cgi?article=1065&context=sci_jou |
op_rights |
Attribution 4.0 International (CC BY 4.0) |
op_rightsnorm |
CC-BY |
_version_ |
1766029212280422400 |