Exploring the use of compound-specific carbon isotopes as a palaeoproductivity proxy off the coast of Adélie Land, East Antarctica

• Published in: Biogeosciences
• Main Authors: Ashley, Kate E., Crosta, Xavier, Etourneau, Johan, Campagne, Philippine, Gilchrist, Harry, Ibraheem, Uthmaan, Greene, Sarah E., Schmidt, Sabine, Eley, Yvette, Massé, Guillaume, Bendle, James
• Format: Other/Unknown Material
• Language: English
• Published: 2021
• Subjects: Antarctic; East Antarctica; The Antarctic; Antarc*; Antarctica; Sea ice
• Online Access: https://doi.org/10.5194/bg-18-5555-2021; https://bg.copernicus.org/articles/18/5555/2021/

The Antarctic coastal zone is an area of high primary productivity, particularly within coastal polynyas, where large phytoplankton blooms and drawdown of CO 2 occur. Reconstruction of historical primary productivity changes and the associated driving factors could provide baseline insights on the role of these areas as sinks for atmospheric CO 2 , especially in the context of projected changes in coastal Antarctic sea ice. Here we investigate the potential for using carbon isotopes ( δ 13 C) of fatty acids in marine sediments as a proxy for primary productivity. We use a highly resolved sediment core from off the coast of Adélie Land spanning the last ∼ 400 years and monitor changes in the concentrations and δ 13 C of fatty acids along with other proxy data from the same core. We discuss the different possible drivers of their variability and argue that C 24 fatty acid δ 13 C predominantly reflects phytoplankton productivity in open-water environments, while C 18 fatty acid δ 13 C reflects productivity in the marginal ice zone. These new proxies have implications for better understanding carbon cycle dynamics in the Antarctica coastal zone in future palaeoclimate studies.