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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

Authors

Giovanni Zanchetta

Ilaria Baneschi

Alexander Francke

Chiara Boschi

Eleonora Regattieri

Bernd Wagner

Jack H. Lacey

Hendrik Vogel

Laura Sadori



Abstract

In the DEEP core from the Lake Ohrid ICDP drilling project, the carbon isotope composition of bulk organic matter (δ13CTOC) 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 δ13CTOC values corresponding to higher TIC and TOC. Along with TOC/TN, the correlation between δ13CTOC and δ13CTIC suggests that most of the organic matter in the core is from aquatic primary production within the lake. The combination of TOC, TIC, and δ13CTOC is able to disentangle long-term glacial/interglacial cycles and, to a lesser extent, millennial scale climate variability. Over the longer term, δ13CTOC shows modest variability, indicating that the δ13C of the dissolved inorganic carbon (DIC) pool is stabilised by the supply of karst spring water characterised by δ13CDIC influenced by the bedrock δ13C value, and the long residence time of the lake water and well mixed upper water column promoting equilibration with atmospheric CO2. However, comparison between arboreal pollen (AP%), TIC and TOC data indicates that the δ13CTOC signal is modulated by the leaching of soil CO2 through runoff and spring discharge, changes in primary productivity, and recycling of organic matter within the lake, all affecting δ13CDIC. Exceptionally low δ13CTOC 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.

Journal Article Type Article
Publication Date 2018-10
Journal Quaternary Science Reviews
Print ISSN 0277-3791
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 202
Pages 154-165
APA6 Citation Zanchetta, G., Baneschi, I., Francke, A., Boschi, C., Regattieri, E., Wagner, B., …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. doi:10.1016/j.quascirev.2018.10.022
DOI https://doi.org/10.1016/j.quascirev.2018.10.022
Keywords Pleistocene; Paleolimnology; Europe; Stable isotopes; Organic matter; Lake Ohrid
Publisher URL https://www.sciencedirect.com/science/article/pii/S0277379118301665

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