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.
摘要：
岩溶地区的生物碳泵（BCP）因其对全球碳汇缺失的重大贡献而受到多年的关注。BCP在喀斯特水生生态系统中产生的自生溶解有机物（Auto-DOM）的稳定性可能在碳汇缺失中起关键作用。然而,尚未彻底检查内陆水域中溶解有机物（DOM）的来源及其对浮游细菌的消耗。顽固的溶解有机质（RDOM）可能存在于喀斯特水生生态系统和海洋中。通过对沙湾喀斯特水碳循环试验场不同土地利用方式下的有色溶解有机质(CDOM)及CDOM与浮游细菌群落相互作用的研究,SW中国，我们发现C2作为浮游细菌矿化的Auto-DOM的荧光成分，可能具有RDOM的某些特征，是喀斯特水生生态系统中重要的DOM源。Auto-DOM的稳定比（Fmax（C2/（C1C2）））在冬季达到89.6±6.71％，在春季达到64.1±7.19％。此外，基于相关的网络分析确定浮游细菌群落受不同荧光类型的CDOM控制，其中C1（新的自动DOM），C3（常规异源DOM（Allo-DOM））和C4（由细菌矿化的Allo-DOM）与普遍存在的有机降解浮游细菌一起聚集在一个模块中；C2聚集在另一个紧密结合的模块中，提出了C2组分的特定微生物利用策略。此外,发现一些重要的浮游细菌和功能基因（包括化养异养生物和光合细菌）受到岩溶水生生态系统中高Ca2和溶解无机碳（DIC）浓度的影响。我们的研究表明，Auto-DOM可能是喀斯特生态系统中与Allo-DOM一样重要的碳汇，前者通常被忽略，因为它很容易和首先被浮游细菌矿化。
