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.
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.
Water Res. 2022 Jul 15;220:118723. doi: 10.1016/j.watres.2022.118723. Epub 2022 Jun 7.
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) 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 Ca 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.
由于岩溶地区的生物碳泵（BCP）对全球碳汇缺失的显著贡献，多年来一直受到广泛关注。岩溶水生生态系统中 BCP 产生的原地溶解有机物质（Auto-DOM）的稳定性可能在碳汇缺失中发挥关键作用。然而，内陆水中溶解有机物质（DOM）的来源及其被浮游细菌的消耗尚未得到彻底研究。与海洋一样，在岩溶水生生态系统中可能存在难降解溶解有机物质（RDOM）。通过在中国西南勺窝岩溶水碳循环试验场研究不同土地利用下的色溶有机物质（CDOM）和 CDOM 与浮游细菌群落的相互作用，我们发现 C2 作为被浮游细菌矿化的 Auto-DOM 的荧光组分，可能具有 RDOM 的一些特征，是岩溶水生生态系统中重要的 DOM 来源。冬季 Auto-DOM 的稳定性比（Fmax）达到 89.6±6.71%，春季达到 64.1±7.19%。此外，基于相关性的网络分析确定，浮游细菌群落受不同荧光类型 CDOM 的控制，其中 C1（新鲜 Auto-DOM）、C3（常规异源 DOM（Allo-DOM））和 C4（被细菌矿化的 Allo-DOM）与普遍存在的有机降解浮游细菌一起聚类在一个模块中；C2 聚类在另一个紧密结合的模块中，这表明 C2 组分具有特定的微生物利用策略。此外，还发现一些重要的浮游细菌和功能基因（包括化能异养菌和光合细菌）受到岩溶水生生态系统中高钙和溶解无机碳（DIC）浓度的影响。我们的研究表明，Auto-DOM 可能像岩溶生态系统中的 Allo-DOM 一样是一个重要的碳汇，而前者通常由于易被浮游细菌首先矿化而被忽视。
