International Journal of Marine Science, 2025, Vol.15, No.6, 313-319 http://www.aquapublisher.com/index.php/ijms 131 Feature Review Open Access Roles of Marine Microorganisms in the Carbon, Nitrogen, and Sulfur Cycles Bing Wang, Qikun Huang Tropical Microbial Resources Research Center, Cuixi Academy of Biotechnology, Zhuji, 311800, Zhejiang, China Corresponding author: qikun.huang@cuixi.org International Journal of Marine Science, 2025, Vol.15, No.6 doi: 10.5376/ijms.2025.15.0029 Received: 12 Oct., 2025 Accepted: 27 Nov., 2025 Published: 17 Dec., 2025 Copyright © 2025 Wang and Huang, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Wang B., and Huang Q.K., 2025, Roles of Marine microorganisms in the carbon, nitrogen, and sulfur cycles, International Journal of Marine Science, 15(6): 313319 (doi: 10.5376/ijms.2025.15.0029) Abstract Marine microorganisms play a core role in the global biogeochemical cycle, especially in the cycles of the three key elements of carbon (C), nitrogen (N), and sulfur (S), which are of great significance for maintaining the functions of Marine ecosystems and regulating the global climate. This study systematically reviews the diversity, ecological distribution and metabolic mechanisms of Marine microbial communities involved in the C-N-S cycle. Through empirical cases in the anoxic zone of the Black Sea, the thermocline of the Pacific Ocean and polar sea areas, it demonstrates the regulatory role of microbial communities in specific Marine regions on regional element cycles. Meanwhile, this study also explored the application prospects of emerging approaches such as metagenomics, stable isotope probe technology, and synthetic biology in the functional research of Marine microorganisms. This study aims to provide a microbiological perspective for a deeper understanding of the Marine element cycle and offer theoretical support for Marine carbon sink management and climate regulation policies. Keywords Marine microorganisms; Carbon cycle; Nitrogen cycle; Sulfur cycle; Biogeochemical processes 1 Introduction The ocean, this blue area that covers most of the Earth's surface, is not merely a landscape. The cycles of key elements such as carbon, nitrogen and sulfur often take place here. They are related to the operation mode of the entire ecosystem and also influence the direction of the climate. Although these cycles are driven by the joint efforts of physical, chemical and biological processes, they are not clearly distinct but interrelated. Processes like carbon sequestration and nutrient regeneration, in the final analysis, are also closely related to the release and transformation of greenhouse gases (Dong et al., 2024). As for who is behind the scenes working on the transformation of these elements? It's not really large organisms, but rather those Marine microorganisms that we usually can't see - bacteria, archaea, phytoplankton, all of which are the main force. Whether it is photosynthesis, nitrogen fixation, nitrification, denitrification, or even sulfate reduction, all these processes cannot do without their intervention. In the past, people might have focused on some "mainstream paths", but now more and more research is beginning to pay attention to those small prokaryotes and facultites that were not well studied in the past. They perform well in some obscure but important cyclic links and are widely distributed, almost covering all kinds of Marine environments (Pajares and Ramos, 2019). But then again, this system is actually not that stable. Once the activity of microorganisms is affected, the entire cycle may go hayline. The factors influencing them are not simple at all - ocean warming, acidification, and hypoxia. These environmental changes may disrupt the rhythm of the microbial community, thereby affecting the transformation efficiency and circulation path of the entire system (Hutchins and Capone, 2022). This study aims to comprehensively analyze the current understanding of the role of Marine microorganisms in the carbon, nitrogen and sulfur cycles, with a focus on elaborating their functional diversity, ecological significance and response to global change. This study will review the mechanisms by which microorganisms mediate key transformation processes in the cycles of various elements, explore the progress made in identifying novel microbial groups and metabolic pathways in recent years, point out knowledge gaps and future research directions, especially in the context of human influence and climate change. By integrating the achievements of molecular, ecological and
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