Chen, Xin and Jing, Jin and Nie, Yaguang and Zhang, Jifeng and Dong, Liang and Huang, Xianyu and Emslie, Steven D. and Liu, Xiaodong
(2023)
Carbon isotope ratios of n-alkanoic acids: new organic proxies for paleo-productivity in Antarctic ponds.
Advances in Polar Science, 34 (4).
pp. 304-317.
Abstract
Primary productivity in the Antarctic aquatic environment with simple ecosystems is sensitive to climate and environmental fluctuations. We investigated δ13C values for n-alkanoic acids derived from phototrophic organisms in a lacustrine sediment core (IIL3) to indicate primary productivity in ponds on Inexpressible Island in the western Ross Sea, Antarctica. Short-chain n-alkanoic acids (C14–C18) were abundant in the IIL3 sediment profile. The carbon isotope ratios of short-chain n-alkanoic acids in the sediment samples and floating microbial mats were similar, indicating that the short-chain n-alkanoic acids in the IIL3 sediment profile predominantly originated from phototrophic organisms. The δ13C values for the short-chain n-alkanoic acids varied widely through the sediment profile, and 13C-enrichment of n-alkanoic acids was most likely related to high productivity due to carbon-limited conditions caused by enhanced photosynthetic efficiency. The δ13C values for the n-alkanoic acids changed over the past 3200 years in similar ways to organic proxies for aquatic productivity (n-alkanoic acid and sterol sedimentary fluxes). C16 n-alkanoic acid was enriched in 13C in periods of high aquatic productivity ~750–1650 and 3000–3200 a BP but depleted in 13C in periods of relatively low productivity ~150–600 and 2500–3000 a BP. The results indicated that carbon isotope ratios of lipids from phototrophic organisms could be used as new proxies to reconstruct paleo-productivity in Antarctic lakes and ponds and therefore improve our understanding of past climate changes.
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