Fatty acid carbon isotopes: a new indicator of marine Antarctic paleoproductivity?

• Main Authors: Ashley, Kate, Bendle, James, Crosta, Xavier, Etourneau, Johan, Campagne, Philippine, Gilchrist, Harry, Ibraheem, Uthmaan, Greene, Sarah, Schmidt, Sabine, Eley, Yvette, Massé, Guillaume
• Format: Text
• Language: English
• Published: 2020
• Subjects: Antarctic; The Antarctic; Antarc*; Antarctica; Sea ice
• Online Access: https://doi.org/10.5194/bg-2020-124; https://www.biogeosciences-discuss.net/bg-2020-124/

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 paleoclimate studies.