岩溶碳汇是实现碳中和的重要手段,其稳定性是亟待解决的关键科学问题。地球上每年约45%的光合作用发生在水环境中,而岩溶区沉水植物如何影响岩溶碳汇稳定性仍不明确。以3条岩溶区河流中的沉水植物为研究对象,利用样方法、pH-drift技术和元素化学计量学,从定性和定量角度开展了沉水植物对岩溶碳汇稳定性的影响研究。结果表明:ZDR中沉水植物有8种,CTR中沉水植物有5种,HXR中沉水植物有7种,Shannon-Wiener多样性指数和Simpson优势度指数的趋势均为ZDR>HXR>CTR。在3条河流中沉水植物的优势种为苦草、海菜花、竹叶眼子菜和黑藻,且均具有利用$\mathrm{HCO}_{3}^{-}$的能力。ZDR、HXR和CTR中沉水植物的年固碳量分别为8.56×10³、4.83×10³ 和3.88×10³ g·m^-2·a^-1,平均值为5.76×10³ g·m^-2·a^-1,分别是草地的37.65倍和人工林的40.56倍。3条河流中沉水植物多样性越高,其固碳量也越高。总的来说,在岩溶水生态系统中沉水植物发挥着碳泵的作用,进而提高了岩溶碳汇的稳定性。

Karst carbon sinks are an important means of achieving carbon neutrality, and their stability is a key scientific issue that needs to be addressed. Approximately 45% of annual photosynthesis on Earth occurs in aquatic environments, yet how submerged plants in karst areas affect the stability of karst carbon sinks remains unknown. This study focused on submerged plants in three karst rivers. We employed quadrat sampling, pH-drift technology, and elemental stoichiometry to qualitatively and quantitatively examine the effects of submerged plants on the stability of karst carbon sinks. Our results showed that there were 8, 5, and 7 species of submerged plants in the ZDR, CTR, and HXR, respectively. The Shannon-Wiener diversity index and Simpson dominance index ranked as ZDR>HXR>CTR. In the three karst rivers, Vallisneria natans, Ottelia acuminata, Potamogeton wrightii, and Hydrilla verticillata were the dominant species, all of which had the ability to utilize $\mathrm{HCO}_{3}^{-}$. The annual carbon sequestration rates of submerged plants in the ZDR, HXR, and CTR were 8.56×10³ g·m^-2·a^-1, 4.83×10³ g·m^-2·a^-1, and 3.88×10³ g·m^-2·a^-1, respectively, with an average of 5.76×10³ g·m^-2·a^-1, which are 37.65 and 40.56 times higher than those of grasslands and man-made forests, respectively. The higher the diversity of submerged plants in rivers, the higher the carbon sequestration. Overall, submerged plants play a crucial carbon pump role in karst aquatic ecosystems, thereby enhancing the stability of karst carbon sink.