Evidence for carbon cycling in a large freshwater lake in the Balkans over the last 0.5 million years using the isotopic composition of bulk organic matter

Zanchetta, Giovanni; Baneschi, Ilaria; Francke, Alexander; Boschi, Chiara; Regattieri, Eleonora; Wagner, Bernd; Lacey, Jack H.; Leng, Melanie J.; Vogel, Hendrik; Sadori, Laura

Abstract

© 2018 Elsevier Ltd In the DEEP core from the Lake Ohrid ICDP drilling project, the carbon isotope composition of bulk organic matter (δ 13 C TOC ) over the last 516 ka shows a negative correlation with total organic carbon (TOC) and total inorganic carbon (TIC). This relationship is marked by periods of lower δ 13 C TOC values corresponding to higher TIC and TOC. Along with TOC/TN, the correlation between δ 13 C TOC and δ 13 C TIC suggests that most of the organic matter in the core is from aquatic primary production within the lake. The combination of TOC, TIC, and δ 13 C TOC is able to disentangle long-term glacial/interglacial cycles and, to a lesser extent, millennial scale climate variability. Over the longer term, δ 13 C TOC shows modest variability, indicating that the δ 13 C of the dissolved inorganic carbon (DIC) pool is stabilised by the supply of karst spring water characterised by δ 13 C DIC influenced by the bedrock δ 13 C value, and the long residence time of the lake water and well mixed upper water column promoting equilibration with atmospheric CO 2 . However, comparison between arboreal pollen (AP%), TIC and TOC data indicates that the δ 13 C TOC signal is modulated by the leaching of soil CO 2 through runoff and spring discharge, changes in primary productivity, and recycling of organic matter within the lake, all affecting δ 13 C DIC . Exceptionally low δ 13 C TOC during some interglacial periods (e.g. MIS7 and MIS9) possibly indicate rapid intensification of organic matter recycling and/or increasing stratification and enhanced methanogenesis, even if the latter process is not supported by the sedimentological data.

Citation

Zanchetta, G., Baneschi, I., Francke, A., Boschi, C., Regattieri, E., Wagner, B., Lacey, J. H., Leng, M. J., Vogel, H., & Sadori, L. (2018). Evidence for carbon cycling in a large freshwater lake in the Balkans over the last 0.5 million years using the isotopic composition of bulk organic matter. Quaternary Science Reviews, 202, 154-165. https://doi.org/10.1016/j.quascirev.2018.10.022

• Journal Article Type: Article
• Acceptance Date: Oct 14, 2018
• Online Publication Date: Oct 22, 2018
• Publication Date: Dec 15, 2018
• Deposit Date: Oct 25, 2018
• Publicly Available Date: Oct 23, 2019
• Journal: Quaternary Science Reviews
• Print ISSN: 0277-3791
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 202
• Pages: 154-165
• DOI: https://doi.org/10.1016/j.quascirev.2018.10.022
• Keywords: Pleistocene; Paleolimnology; Europe; Stable isotopes; Organic matter; Lake Ohrid
• Public URL: https://nottingham-repository.worktribe.com/output/1189668
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0277379118301665
• Contract Date: Oct 25, 2018