High stability of autochthonous dissolved organic matter in karst aquatic ecosystems: Evidence from fluorescence

Fan Xia; Zaihua Liu; Min Zhao; Qiang Li; Dong Li; Wenfang Cao; Cheng Zeng; Yundi Hu; Bo Chen; Qian Bao; Yi Zhang; Qiufang He; Chaowei Lai; Xuejun He; Zhen Ma; Yongqiang Han; Haibo He

doi:10.1016/j.watres.2022.118723

High stability of autochthonous dissolved organic matter in karst aquatic ecosystems: Evidence from fluorescence

Water Res. 2022 Jul 15:220:118723. doi: 10.1016/j.watres.2022.118723. Epub 2022 Jun 7.

Authors

Fan Xia¹, Zaihua Liu², Min Zhao³, Qiang Li⁴, Dong Li⁵, Wenfang Cao⁶, Cheng Zeng³, Yundi Hu³, Bo Chen⁷, Qian Bao⁸, Yi Zhang⁹, Qiufang He¹⁰, Chaowei Lai¹¹, Xuejun He¹, Zhen Ma⁶, Yongqiang Han¹, Haibo He⁶

Affiliations

¹ State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China; Puding Karst Ecosystem Research Station, CAS, Chinese Ecosystem Research Network, Puding 562100, China.
² State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China; Puding Karst Ecosystem Research Station, CAS, Chinese Ecosystem Research Network, Puding 562100, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China. Electronic address: liuzaihua@vip.gyig.ac.cn.
³ State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China; Puding Karst Ecosystem Research Station, CAS, Chinese Ecosystem Research Network, Puding 562100, China.
⁴ Key Laboratory of Karst Dynamics, Ministry of Nature Resources/Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China.
⁵ State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China.
⁶ State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China.
⁷ Guizhou University of Finance and Economics, Guiyang 550025, China.
⁸ State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China; Key Laboratory of Land Resources Evaluation and Monitoring in Southwest China of Ministry of Education, Sichuan Normal University, Chengdu 610066, China.
⁹ State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China; University of Chinese Academy of Sciences, Beijing 100049, China; Resources and Environmental Engineering, Guizhou Institute of Technology, Guiyang 550008, China.
¹⁰ Chongqing Key Laboratory of Karst Environment, School of Geographical Sciences, Southwest University, Chongqing 400700, China; Key Laboratory of Karst Dynamics, Ministry of Nature Resources/Guangxi, Institute of Karst Geology, Chinese Academy of Geological Sciences, Guilin 541004, China.
¹¹ State Key Laboratory of Environmental Geochemistry, CAS, Institute of Geochemistry, Guiyang 550081, China; School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China.

PMID: 35696806
DOI: 10.1016/j.watres.2022.118723

Abstract

Biological carbon pump (BCP) in karst areas has received intensive attention for years due to their significant contribution to the global missing carbon sink. The stability of autochthonous dissolved organic matter (Auto-DOM) produced by BCP in karst aquatic ecosystems may play a critical role in the missing carbon sink. However, the source of dissolved organic matter (DOM) in inland waters and its consumption by planktonic bacteria have not been thoroughly examined. Recalcitrant dissolved organic matter (RDOM) may exist in karst aquatic ecosystem as in the ocean. Through the study of the chromophoric dissolved organic matter (CDOM) and the interaction between CDOM and the planktonic bacterial community under different land uses at the Shawan Karst Water-carbon Cycle Test Site, SW China, we found that C2, as the fluorescence component of Auto-DOM mineralised by planktonic bacteria, may have some of the characteristics of RDOM and is an important DOM source in karst aquatic ecosystems. The stability ratio (Fmax_(C2/(C1+C2))) of Auto-DOM reached 89.6 ± 6.71% in winter and 64.1 ± 7.19% in spring. Moreover, correlation-based network analysis determined that the planktonic bacterial communities were controlled by different fluorescence types of CDOM, of which C1 (fresh Auto-DOM), C3 (conventional allochthonous DOM (Allo-DOM)) and C4 (the Allo-DOM mineralised by bacteria) were clustered in one module together with prevalent organic-degrading planktonic bacteria; C2 was clustered in another tightly combined module, suggesting specific microbial utilization strategies for the C2 component. In addition, some important planktonic bacterium and functional genes (including chemotrophic heterotrophs and photosynthetic bacteria) were found to be affected by high Ca²⁺ and dissolved inorganic carbon (DIC) concentrations in karst aquatic ecosystems. Our research showed that Auto-DOM may be as an important carbon sink as the Allo-DOM in karst ecosystems, the former generally being neglected based on a posit that it is easily and first mineralized by planktonic bacteria.

Keywords: Autochthonous dissolved organic matter; BCP; EEM-PARAFRAC; Karst aquatic ecosystem; Planktonic bacteria; Stability.

MeSH terms

Bacteria
Carbon
Dissolved Organic Matter*
Ecosystem*
Seasons
Spectrometry, Fluorescence

Substances

Dissolved Organic Matter
Carbon