Image_6_Composition of planktonic foraminifera test-bound organic material and implications for carbon cycle reconstructions.jpeg

• Main Authors: Tommaso Paoloni, Babette Hoogakker, Alba Navarro Rodriguez, Ryan Pereira, Erin L. McClymont, Luigi Jovane, Clayton Magill
• Format: Still Image
• Language: unknown
• Published: 2023
• Subjects: Oceanography; Marine Biology; Marine Geoscience; Biological Oceanography; Chemical Oceanography; Physical Oceanography; Marine Engineering; organic matter; planktonic foraminfera; gas chromatography; liquid chromatography; lipids; particulate organic matter proxy; Planktonic foraminifera
• Online Access: https://doi.org/10.3389/fmars.2023.1237440.s007; https://figshare.com/articles/figure/Image_6_Composition_of_planktonic_foraminifera_test-bound_organic_material_and_implications_for_carbon_cycle_reconstructions_jpeg/24235561

Introduction Foraminiferal shells are extensively used to reconstruct the marine environment in the geological past. The foraminifera test-bound organic material (FBOM), sheltered by the test from potential diagenetic alteration and contamination, has great feasibility to improve our understanding of carbon and nitrogen cycling. The FBOM δ 13 C has been proposed as a proxy for reconstructing past environmental conditions. However, to fully exploit the proxy potential of FBOM, its molecular composition and the influence of the latter on the FBOM δ 13 C need to be assessed. Method Here we use a novel combination of gas chromatography-mass spectrometry, flame ionization detection (GC-MS/FID) and liquid chromatography organic carbon and nitrogen detection (LC-OCD/ OND) analyses to study the FBOM chemical composition. Results Our results indicate that polysaccharides and proteins dominate FBOM, as proposed by earlier studies, with no evidence of detectable lipids (alkyl lipids, trimethylsilyl ethers of fatty alcohols, trimethylsilyl esters of fatty acids and steranes derivatives were targeted). Discussion Previous studies suggested that FBOM δ 13 C may be used to reconstruct past atmospheric CO2 concentrations. However, our results indicate that the use of FBOM δ 13 C to reconstruct CO2 carries an approximate uncertainty of ±21 ppm for past atmospheric CO2 abundance. We suggest that FBOM δ 13 C can be used as a novel proxy to reconstruct particulate organic material (POM) δ 13 C. This is also supported by the recently confirmed minor fractionation between POM and FBOM δ 13 C.