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. (15th December 2018)

• Record Type: Journal Article
• Authors: Zanchetta, Giovanni; Baneschi, Ilaria; Francke, Alexander; Boschi, Chiara; Regattieri, Eleonora; Wagner, Bernd; Lacey, Jack H.; Leng, Melanie J.; Vogel, Hendrik; Sadori, Laura
• Is Part Of: Quaternary science reviews. Volume 202(2018)
• Page Start: 154
• Page End: 165
• Publication Date: 2018-12-15
• Subjects: Pleistocene -- Paleolimnology -- Europe -- Stable isotopes -- Organic matter -- Lake Ohrid; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quascirev.2018.10.022
• Languages: English
• ISSNs: 0277-3791

Abstract

Abstract: In the DEEP core from the Lake Ohrid ICDP drilling project, the carbon isotope composition of bulk organic matter (δ 13 CTOC ) 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 CTOC values corresponding to higher TIC and TOC. Along with TOC/TN, the correlation between δ 13 CTOC and δ 13 CTIC 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 CTOC is able to disentangle long-term glacial/interglacial cycles and, to a lesser extent, millennial scale climate variability. Over the longer term, δ 13 CTOC 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 CDIC 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 CO2 . However, comparison between arboreal pollen (AP%), TIC and TOC data indicates that the δ 13 CTOC 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 δ 13 CDIC . Exceptionally low δ 13 CTOC 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. Highlights: The organic matter δ 13 C in Lake Ohrid's DEEP core is most from primary productivity. DIC from the karst springs and atmospheric CO2 equilibration dominate Lake Ohrid. Soil CO2 drives of the organic matter δ 13 C over interglacial/glacial periods.