Climate driven carbon and microbial signatures through the last ice age

Abstract

Ice cores preserve diverse materials as millennial-scale proxies for Earth's history. While major ions and elemental analyses are commonly investigated in palaeoclimate reconstructions, the integration of biological measurements is rapidly developing. Although the limited number of data herein impose constraints on broader generalisations, we show that microbial assemblages and organic matter (OM) composition from Byrd Station and West Antarctic Ice Sheet Divide ice cores may serve as palaeoecological markers from the Last Glacial Maximum (LGM; section ∼20.5 ka BP) and last deglaciation periods (LD; section ∼14.5 ka BP), reflecting environmental changes. Fluorescent analyses determined OM from both cores to have similar amino acid-like signatures; however, more comprehensive molecular characterisation showed only 12 % overlap in molecular formulae, with Byrd OM being more chemically labile. Microbial diversity in both cores was low, and together with predicted metabolic capabilities, differed significantly between communities. Variation in OM composition and microbial diversity reflects changes in environmental sources and deposition patterns onto the Antarctic Ice Sheet during distinct climate periods, with OM composition potentially shaping microbial communities post-deposition. Combining detailed microbial and OM composition analyses created a unique window into the past, providing a way to characterise carbon composition and potential metabolic processes as a function of environmental change.