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Dataset S1 - Noelaerhabdaceae organic carbon isotope culture data compilation

Citation

Phelps, Samuel et al. (2021), Dataset S1 - Noelaerhabdaceae organic carbon isotope culture data compilation, Dryad, Dataset, https://doi.org/10.5061/dryad.bcc2fqzc7

Abstract

The carbon isotope fractionation in algal organic matter (Ep), including the long-chain alkenones produced by the coccolithophorid family Noelaerhabdaceae, is used to reconstruct past atmospheric CO2 levels. The conventional proxy linearly relates Ep to changes in cellular carbon demand relative to diffusive CO2 supply, with larger Ep 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 Ep as carbon demand relative to supply decreases, consistent with DIC manipulations. We compile existing Noelaerhabdaceae Ep 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 Ep 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 Ep 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 Ep.

Methods

G. oceanica RCC1303 was cultivated in triplicate batch culture at five different pCO2 levels. CO2 modification was achieved by continuously aerating the headspace of the culture flask. Alkenones were extracted using accelerated solvent extraction and carbon isotope ratios were measured by GC-IRMS. CO2 concentrations were calculated from measurements of pH, total alkalinity, temperature, and salinity. Cell sizes were measured by flow cytometry. Existing data were compiled from the literature. Cell sizes and carbon content were standardized to the middle of the photoperiod, where applicable.

 

Usage Notes

Missing values are noted with “NaN.” Data sources are listed in the references and explanatory columns (e.g. “Source of cell radius data”). Information in columns titled “Note on XYZ” (e.g. “Note on d13C_POC uncertainty”) reflect the source of information in the original publication.

Funding

National Science Foundation, Award: DGE16-44869

National Science Foundation, Award: OCE1314336

Center for Climate and Life at Columbia University

Lamont Climate Center

G. Unger Vetlesen Foundation

WSL Pure in partnership with Columbia University's Center for Climate and Life

Paul M. Angell Family Foundation

Earth Institute, Columbia University

Columbia University Bridge to PhD Program

Center for Climate and Life at Columbia University

Lamont Climate Center

Columbia University Bridge to PhD Program