微型生物在岩溶碳循环中的作用研究回顾与展望

全球气候变化问题使岩溶系统碳循环的研究倍受关注，有关微型生物及其碳酸酐酶在岩溶系统碳循环中的作用的认识也在不断深入。文章回顾了微型生物及其碳酸酐酶在碳酸盐岩风化以及碳酸盐岩沉积过程中的作用过程及作用机制，指出未来的研究需结合不同岩溶生态环境，量化微型生物及其碳酸酐酶对岩溶生态系统碳增汇的影响，为深入研究微型生物及其碳酸酐酶对岩溶碳汇的贡献、增加岩溶生态系统碳汇的能力、助力实现碳中和提供参考。 

Review and prospect of research on the role of micro-organisms in karst carbon cycle

The issue of global climate change has drawn much attention to the research on the carbon cycle of karst systems. Carbonate rock is the largest known carbon pool on the earth. It is easy to make CO₂ in the atmosphere sink continuously through karstification, and enter into the pedosphere and hydrosphere in the form of inorganic carbon, and actively participate in the global carbon cycle through a series of dynamic processes such as migration and transformation, resulting in carbon sink effect. On the other hand, under the catalysis and regulation of organisms during the geological history, the deposition of carbonate rocks can also absorb atmospheric CO₂ and produce a huge sink effect. Therefore, strengthening the study of weathering and depositional processes of carbonate rocks will help to study the karst carbon cycle and increase the karst carbon sink.Various microscopic organisms are distributed on the surface of carbonate rocks, and they have strong adaptability, which can affect the weathering and deposition processes of carbonate rocks through their own metabolism and the interactive network within the community. Carbonic Anhydrase (CA) is a zinc containing metalloenzyme, and it can efficiently catalyze the hydration of CO₂ (CO₂+H₂O?HCO₃?+H?). CA and CA producing microorganisms are widely distributed in the soil and water in the karst area, and CA has good relative stability in the karst environment. CA and CA producing microorganisms can significantly promote the dissolution of carbonate rocks, and can also significantly promote the deposition of carbonate rocks under certain conditions. At present, more and more researchers begin to pay attention to how to use CA or CA producing micro-organisms to increase the carbon storage in the karst area, so as to increase the karst carbon sink.At present, some studies have proved that bacteria, fungi, actinomycetes and microalgae isolated from karst areas can participate in the process of karst carbon cycle. A large number of studies have found that micro-organisms such as bacillus, phosphorus dissolving bacteria, microalgae and their CA can promote the weathering of carbonate rocks. At the same time, atmospheric CO₂ as a carbon source can be used by aquatic photosynthetic organisms, resulting in the migration and transformation process of "inorganic carbon → organic carbon → inert organic carbon", and finally forming a long-term stable carbon sink. Based on the results of the field in-situ soil column experiment and the indoor soil column simulation experiment, we estimated the annual increase in soil carbon storage caused by soil micro-organisms and their CA in the karst area of southwest China. The results showed that it was equivalent to the carbon emissions of China's thermal power plants in 2015 (the data came from the China Statistical Yearbook). It was considered that the soil micro-organisms and their CA in the karst area had the potential of carbon sequestration that could not be ignored. Micro-organisms promote the weathering of carbonate rocks mainly through mechanical and physical action, chemical degradation and enzymatic action such as production and secretion of CA. On the other hand, some micro-organisms such as cyanobacteria, bacillus, microalgae and their CA can also use atmospheric CO₂ and Ca2+ in the environment to induce calcium carbonate deposition, thereby realizing the capture of atmospheric CO₂. Micro-organisms promote the deposition of carbonate rocks mainly by capturing and adhering, performing metabolic activities to change environmental conditions, and producing biological enzymes such as secretions and CA. In addition, the weathering and deposition of carbonate rocks promoted by micro-organisms is a complex process involving multiple factors, which is related to the types of micro-organisms and the substances they secrete (enzymes, peptides, proteins, etc.), environmental conditions (pH, temperature, ion concentration, etc.), and various mechanisms can also interact. Researchers need to integrate various factors to reveal the mechanisms of micro-organisms promoting the weathering and deposition of carbonate rocks.At present, studies on the effects of micro-organisms and their CA on weathering and deposition carbon sinks of carbonate rocks are mainly based on laboratory simulation experiments, and mainly focused on the promotion of micro-organisms and their CA on weathering or deposition of carbonate rocks to increase karst carbon sinks. Therefore, this paper reviews the research results on the role and mechanisms of micro-organisms and their CA in weathering and deposition of carbonate rocks, and points out that in the future, it is necessary to quantitatively study the impact of micro-organisms and their CA on enhancement of carbon sinks in karst ecosystems in combination with different karst ecological environments. This review provides a reference for in-depth study of the contribution of micro-organisms and their CA to karst carbon sinks, and to increase the carbon sink capacity of karst ecosystems to help achieve carbon neutrality.