Abstract
The reconstruction of past climate variability using physical and geochemical parameters from lake sedimentary records is a well-established and widely used approach. These geological records are also known to contain large and active microbial communities, believed to be responsive to their surroundings at the time of deposition, and proceed to interact intimately with their physical and chemical environment for millennia after deposition. However, less is known about the potential legacy of past climate conditions on the contemporary microbial community structure. We analysed two Holocene-length (past 10 ka BP) sediment cores from the glacier-fed Ymer Lake, located in a highly climate-sensitive region on south-eastern Greenland. By combining physical proxies, solid as well as fluid geochemistry, and microbial population profiling in a comprehensive statistical framework, we show that the microbial community structure clusters according to established lithological units, and thus captures past environmental conditions and climatic transitions. Further, comparative analyses of the two sedimentary records indicates that the manifestation of regional climate depends on local settings such as water column depth, which ultimately constrains microbial variability in the deposited sediments. The strong coupling between physical and geochemical shifts in the lake and microbial variation highlights the potential of molecular microbiological data to strengthen and refine existing sedimentological classifications of past environmental conditions and transitions. Furthermore, this coupling implies that microbially controlled transformation and partitioning of geochemical species (e.g., manganese and sulphate) in Ymer lake today is still affected by climatic conditions that prevailed thousands of years back in time.
Highlights
Our ability to reconstruct past climate relies on the use of palaeoclimate proxies
Microbial cells that make up these communities are deposited on the sediment surface and buried over time (Starnawski et al, 2017), and the community composition is influenced by a number of environmental conditions that are controlled by the prevailing climate conditions at the time of deposition
By applying multivariate statistics on these parameters, we show that the microbial population structure captures and reflects previously inferred shifts in palaeoenvironmental conditions at Ymer Lake
Summary
Ymer Lake Microbiology and Palaeoclimate archives like marine and lacustrine sediment sequences (e.g., Mayewski et al, 2004; Wanner et al, 2008; Sundqvist et al, 2014; Davies et al, 2015; Domaizon et al, 2017). Alongside these conventional proxies, complex microbial communities are present in the sediments. Similar connections have been observed in sediments from lacustrine settings, highlighting the important roles of catchment hydrology, lake water geochemistry and depositional conditions in controlling microbial populations (Vuillemin et al, 2016, 2018)
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