Highly branched isoprenoids as proxies for variable sea ice conditions in the Southern Ocean

• Published in: Antarctic Science
• Main Authors: Massé, Guillaume, Belt, Simon T., Crosta, Xavier, Schmidt, Sabine, Snape, Ian, Thomas, David N., Rowland, Steven J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2011
• Subjects: Antarctic; Arctic; East Antarctica; Southern Ocean; Antarc*; Antarctic Science; Antarctica; Phytoplankton; Sea ice
• Online Access: http://dx.doi.org/10.1017/s0954102011000381; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0954102011000381

Abstract Concentrations of a highly branched isoprenoid (HBI) diene determined in over 200 sediment samples from the Arctic co-vary with those of an HBI monoene (IP 25 ) shown previously to be a sedimentary sea ice proxy for the Arctic. The same diene, but not monoene IP 25 , occurred in nine sea ice samples collected from various locations around Antarctica. The diene has been reported previously in Antarctic sea ice diatoms and the 13 C isotopic compositions of the diene determined in two Antarctic sea ice samples were also consistent with an origin from sea ice diatoms (δ 13 C -5.7 to -8.5‰). In contrast, HBIs found in two Antarctic phytoplankton samples did not include the diene but comprised a number of tri- to pentaenes. In sediment samples collected near Adélie Land, East Antarctica, both the diene and the tri- to pentaenes often co-occurred. 13 C isotopic compositions of the tri- to pentaenes in three sediment samples ranged from -35 to -42‰ whereas that of the diene in a sediment sample was -18‰. We propose the presence of this isotopically 13 C enriched HBI diene in Antarctic sediments to be a useful proxy indicator for contributions of organic matter derived from sea ice diatoms. A ratio of the concentrations of diene/trienes might reflect the relative contributions of sea ice to phytoplanktonic inputs of organic matter to Antarctic sediments.