Ancient and Modern Geochemical Signatures in the 13,500-Year Sedimentary Record of Lake Cadagno

• DOI: 10.3389/feart.2021.754888
• Publication Date: 2022-01-31T05:46:19Z
• Authors: Jasmine S. Berg; Mathilde Lepine; Emile Laymand; Xingguo Han; Hendrik Vogel; Marina A. Morlock; Niroshan Gajendra; Adrian Gilli; Stefano M. Bernas...; Carsten J. Schubert; Guangyi Su; Mark A. Lever
• Keywords: Sedimentary organic matter; Biogeochemical Cycle

Although lake sediments are globally important organic carbon sinks and therefore habitats for deep microbial life, the lacustrine biosphere has thus far been little studied compared to its marine counterpart. To investigate impact of underexplored on sediment geochemical environment vice versa, we performed a comprehensive microbiological characterization sedimentary sequence from Lake Cadagno covering entire environmental history since formation following glacial retreat. We found that both gradients community shifts across ∼13.5 kyr subsurface record reflect redox changes in lake, going oxic anoxic sulfidic. Most activity occurs within top 20 cm sediment, where millimolar sulfate concentrations diffusing bottom water almost completely consumed. In deeper layers, remineralization is much slower but microorganisms nonetheless subsist fermentation, sulfur cycling, metal reduction, methanogenesis. The most surprising finding was presence deep, oxidizing groundwater source. This source generates an inverse gradient at could contribute matter sequestered energy-limited subsurface.