Microbial Fe(III) reduction as a potential iron source from Holocene sediments beneath Larsen Ice Shelf

• Published in: Nature Communications
• Main Authors: Jung, Jaewoo, Yoo, Kyu-Cheul, Rosenheim, Brad E., Conway, Tim M., Lee, Jae Il, Yoon, Ho Il, Hwang, Chung Yeon, Yang, Kiho, Subt, Christina, Kim, Jinwook
• Format: Text
• Language: English
• Published: Nature Publishing Group UK 2019
• Subjects: Article; Antarctic; Larsen Ice Shelf; Southern Ocean; Antarc*; Ice Sheet; Ice Shelf; Ice Shelves
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6923428/; http://www.ncbi.nlm.nih.gov/pubmed/31857591; https://doi.org/10.1038/s41467-019-13741-x

Recent recession of the Larsen Ice Shelf C has revealed microbial alterations of illite in marine sediments, a process typically thought to occur during low-grade metamorphism. In situ breakdown of illite provides a previously-unobserved pathway for the release of dissolved Fe(2+) to porewaters, thus enhancing clay-rich Antarctic sub-ice shelf sediments as an important source of Fe to Fe-limited surface Southern Ocean waters during ice shelf retreat after the Last Glacial Maximum. When sediments are underneath the ice shelf, Fe(2+) from microbial reductive dissolution of illite/Fe-oxides may be exported to the water column. However, the initiation of an oxygenated, bioturbated sediment under receding ice shelves may oxidize Fe within surface porewaters, decreasing dissolved Fe(2+) export to the ocean. Thus, we identify another ice-sheet feedback intimately tied to iron biogeochemistry during climate transitions. Further constraints on the geographical extent of this process will impact our understanding of iron-carbon feedbacks during major deglaciations.