珊瑚共生体碳代谢特征研究进展

珊瑚礁作为一种典型的海洋生态系统,具有巨大的固碳和储碳潜力。然而,目前对于珊瑚礁的净碳能力(碳释放与碳吸收)仍存在争议,主要归因于珊瑚共生体碳代谢的多样性和复杂性。珊瑚礁在生物钙化、呼吸过程中向大气释放二氧化碳(CO₂);但在生物合成和沉积过程中却可以将碳进行固定与埋藏;为此,珊瑚礁的碳源碳汇身份还有待明确。现有部分研究表明,共生体通过碳代谢可以促进珊瑚礁吸收大气中的CO₂。此外,珊瑚礁和海岸带蓝碳生态系统通常表现出很强的连通性,珊瑚共生体碳代谢能有效提高海岸带盐沼植被、海草床、海洋浮游植物等生物的碳汇功能。为了加深对珊瑚礁碳源-碳汇功能的理解,综述了珊瑚共生体的碳代谢特征,梳理了共生体中碳的关键生态过程(有机碳的迁移、无机碳的转化、两者的赋存状态),总结了细菌-虫黄藻-病毒在共生体碳代谢中的作用,评述了珊瑚礁碳源-碳汇特征及影响因子。旨在阐明珊瑚共生体碳代谢的关键过程,并基于此寻求有效的珊瑚礁碳增汇技术,形成以碳增量为主的珊瑚保护与修复技术,提升珊瑚礁在蓝碳生态系统中的贡献。

Characterization of carbon metabolism in coral symbiont

As a typical marine ecosystem, coral reefs possess huge carbon reserves and strong carbon sequestration potential. However, the net carbon capacity (carbon release and carbon uptake) of coral reefs remains controversial, mainly due to the diversity and complexity of carbon metabolism of the coral symbiont. Coral reefs release carbon dioxide into the atmosphere during biological calcification and respiration. They can also bury carbon during biosynthesis and deposition. Therefore, their identity as a net carbon source or sink remains unclear. The study of carbon metabolism in coral reef ecosystems is a frontier subject under the umbrella of carbon neutrality studies. Existing studies have demonstrated that symbionts could directly promote coral reef absorption of atmospheric CO₂ through carbon metabolism and exhibit ecosystem connectivity functions that improve the carbon sink functions of salt marsh vegetation, seagrass bed, and marine phytoplankton. To deepen our understanding of coral reef carbon source and sink functions, this paper reviews the carbon metabolism characteristics of coral symbionts, identifies key ecological processes involving carbon in symbionts (migration of organic carbon, transformation of inorganic carbon, and occurrence status), summarizes the roles of bacteria-zooxanthellae-viruses in symbiont carbon metabolism, and reviews factors the cause controlling coral reef carbon source and sink functions.In addition, this paper summarizes relevant information regarding bacterial community composition, functional differences, and metabolic pathways that can all affect coral carbon metabolism. Deep-sea cold-water corals use bacteria as a carbon source and viruses can change the metabolic rate and utilization efficiency of coral reef organic carbon flow by switching strategies. Photosynthesis and respiration of zooxanthellae affect coral carbon metabolism, and the influence of temperature and light on these two metabolic processes has been extensively studied. The purpose of the paper is to deepen our understanding of the carbon metabolism of coral symbionts, in addition to seeking an optimal carbon sinking technology based on coral reefs. It calls for further exploration of the assessment technology of coral reef carbon sink function and ways to increase the sink in future studies, so as to form the coral protection and restoration technology based on carbon increment, and enhance the contribution of coral reefs to the blue carbon ecosystem. This paper provides a helpful progressive summary covering carbon metabolism characteristics of coral symbionts, analysis of the source sink paradox, and finally coral reefs'' negative carbon emission potential, to further our understanding of the carbon source sink model of coral reef ecosystems, and to gather scientific evidence for its entry into the "blue carbon club".