Authigenic CaCO3 precipitation contributes to the stabilization of algal-derived organic carbon in karst lake

Yingxun Du; Cheng Zhao; Xuexin Han; Shilin An; Zhendu Mao; Fan Xun; Ding He; Yongdong Zhang; Muhua Feng; Wenlei Luo; Qinglong L Wu; Peng Xing

doi:10.1016/j.watres.2025.123999

Authigenic CaCO₃ precipitation contributes to the stabilization of algal-derived organic carbon in karst lake

Water Res. 2025 Jun 10:285:123999. doi: 10.1016/j.watres.2025.123999. Online ahead of print.

Authors

Yingxun Du¹, Cheng Zhao¹, Xuexin Han¹, Shilin An¹, Zhendu Mao², Fan Xun¹, Ding He³, Yongdong Zhang⁴, Muhua Feng⁵, Wenlei Luo⁶, Qinglong L Wu⁷, Peng Xing⁸

Affiliations

¹ Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 211135, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² Center for Evolution and Conservation Biology, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
³ Department of Ocean Science and Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology, Clear Water Bay, New Territories, Hong Kong, 999077, China; State Key Laboratory of Marine Pollution, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, 999077, China.
⁴ School of Geography, South China Normal University, Guangzhou 510631, China.
⁵ Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 211135, China.
⁶ Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 211135, China; The Fuxianhu Station of Plateau Deep Lake Research, Chinese Academy of Sciences, Yuxi 653100, China; The Fuxianhu Station of Plateau Deep Lake Field Scientific Observation and Research, Yuxi 653100, China.
⁷ Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 211135, China; Center for Evolution and Conservation Biology, Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China; The Fuxianhu Station of Plateau Deep Lake Research, Chinese Academy of Sciences, Yuxi 653100, China; The Fuxianhu Station of Plateau Deep Lake Field Scientific Observation and Research, Yuxi 653100, China.
⁸ Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 211135, China. Electronic address: pxing@niglas.ac.cn.

PMID: 40561625
DOI: 10.1016/j.watres.2025.123999

Abstract

The carbonate weathering carbon sink constitutes a significant component of the global carbon budget. A growing body of research has identified the role of biological carbon pumps in the sequestration of inorganic carbon produced through carbonate weathering. Nevertheless, there has been considerable controversy surrounding whether carbon fixed by phytoplankton photosynthesis is stable over the long term. The present study speculated thatauthigenic calcium (Ca) precipitation induced by primary production facilitates the practical preservation of organic carbon (OC) in the karst lake sediment, which is important for the long-term stabilization of carbonate weathering carbon sinks. The primary sources of OC in surface and core sediments were analyzed in Lake Fuxian, a deep alpine lake in the karst region. Their molecular composition and potential interaction mechanism with Ca were investigated. The δ¹³C isotopic signature and OC:N molar ratio indicate that the sedimentary OC is predominantly derived from autochthonous photosynthesis. The significant positive correlation between the contents of Ca and total organic carbonsuggestes that Ca sedimentation is related to primary production. High-resolution mass spectrometry analyses reveal that molecules with abundant nitrogen atoms are bound to Ca-containing minerals in the sediment.The coprecipitation of amino acids during CaCO₃ formation in water facilitates the deposition and preservation of autochthonous OC in the sediment. Our finding demonstrated that the natural photosynthesis-induced calcium carbonate precipitation can substantially enhance the stability of carbonate weathering carbon sinks within karst regions, thus leading to a significant expansion in the existing understanding of carbon sink processes in these environments.

Keywords: Autochthonous organic carbon; Calcium; Coprecipitation; Karst lake; Sediment carbon sink.