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: K. E. Ashley, X. Crosta, J. Etourneau, P. Campagne, H. Gilchrist, U. Ibraheem, S. E. Greene, S. Schmidt, Y. Eley, G. Massé, J. Bendle
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2021
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Antarctic; East Antarctica; The Antarctic; Antarc*; Antarctica; Sea ice
• Online Access: https://doi.org/10.5194/bg-18-5555-2021; https://doaj.org/article/2a2ac4d27eca4e0eaa92ec913d5bc7a2

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.