Prokaryotes in the WAIS Divide ice core reflect source and transport changes between Last Glacial Maximum and the early Holocene

• Published in: Global change biology 2018-05, Vol.24 (5), p.2182-2197
• Main Authors: Santibáñez, Pamela A., Maselli, Olivia J., Greenwood, Mark C., Grieman, Mackenzie M., Saltzman, Eric S., McConnell, Joseph R., Priscu, John C.
• Format: Article
• Language: English
• Subjects: Airborne sensing; Antarctic ice core; Antarctic Regions; Archaea - classification; Bacteria - classification; Black carbon; Burning; Deglaciation; early Holocene; Environmental conditions; Glaciation; History, Ancient; Holocene; Ice; Ice Cover - microbiology; Last Deglaciation; Last Glacial Maximum; Mathematical models; Meltwater; Models, Theoretical; Periodic variations; Periodicity; Prokaryotes; Sodium; Statistical analysis; Statistical models; Temporal variations; Time Factors; Time series; Tracers; Transport; Visual observation; West Antarctic Ice Sheet Divide
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.14042

We present the first long‐term, highly resolved prokaryotic cell concentration record obtained from a polar ice core. This record, obtained from the West Antarctic Ice Sheet (WAIS) Divide (WD) ice core, spanned from the Last Glacial Maximum (LGM) to the early Holocene (EH) and showed distinct fluctuations in prokaryotic cell concentration coincident with major climatic states. The time series also revealed a ~1,500‐year periodicity with greater amplitude during the Last Deglaciation (LDG). Higher prokaryotic cell concentration and lower variability occurred during the LGM and EH than during the LDG. A sevenfold decrease in prokaryotic cell concentration coincided with the LGM/LDG transition and the global 19 ka meltwater pulse. Statistical models revealed significant relationships between the prokaryotic cell record and tracers of both marine (sea‐salt sodium [ssNa]) and burning emissions (black carbon [BC]). Collectively, these models, together with visual observations and methanosulfidic acid (MSA) measurements, indicated that the temporal variability in concentration of airborne prokaryotic cells reflected changes in marine/sea‐ice regional environments of the WAIS. Our data revealed that variations in source and transport were the most likely processes producing the significant temporal variations in WD prokaryotic cell concentrations. This record provided strong evidence that airborne prokaryotic cell deposition differed during the LGM, LDG, and EH, and that these changes in cell densities could be explained by different environmental conditions during each of these climatic periods. Our observations provide the first ice‐core time series evidence for a prokaryotic response to long‐term climatic and environmental processes. Prokaryotic microorganisms are crucial drivers of biogeochemical cycles on Earth. Despite this role, few long temporal records of microorganisms exist. Long‐term studies are necessary to understand the relationship between microorganisms and major climate transitions. We present the first long‐term (~17,400 year) record of prokaryotic cell concentration from a deep Antarctic ice core. This record reveals that airborne prokaryotes responded differently during climatic periods ranging from the Last Glacial Maximum to the early Holocene. Collectively these findings reveal that ice cores offer a unique medium to study the effects of climate on biological systems and global biogeochemical cycles.