The continental shelf regime under the United Nations Convention on the Law of the Sea (UNCLOS) marked the first time that the scope of coastal states’ sovereignty rights was extended to the deep-sea areas beyond 200 nautical miles. This provision not only endows coastal states with legal standing for the exploitation of deep-sea resources, but also fosters an institutional linkage between geoscience and international law. To date, a total of 109 submissions have been formally lodged with the Commission on the Limits of the Continental Shelf (CLCS), signifying that global continental shelf delineation has entered a new phase characterized by the high integration of scientific practice and legal procedures. Nevertheless, driven by the rapid advancement of science and technology and the sensitive impacts of geopolitics, continental shelf delineation is confronted with unprecedented challenges, which will exert a major influence on global ocean governance. Based on the 109 submissions received and 44 recommendations issued by the CLCS, this paper systematically sorts out the major progress and challenges in the delineation of continental shelves beyond 200 nautical miles from three dimensions: legal regimes, geoscientific theories, and practices. It aims to reveal how continental shelf delineation has evolved into a crucial driving force reshaping the global marine spatial order within the international deep-sea governance system where scientific evidence and legal institutions intersect, and further looks ahead to the development direction of continental shelf delineation in the context of scientific and technological progress, international cooperation, and global ocean governance.

Deep-sea mining, pivotal for humanity’s future development, is a current global hotspot attracting widespread international attention. This article synthesizes publicly available information from recent years to comprehensively analyze the status and challenges in the development of deep-sea mining regulations, the diverse stances and strategic interactions among key stakeholders, China’s position and actions in international seabed governance, and the critical challenges and potential pathways for the future of deep-sea mining. Particular focus is placed on analyzing the implications of the new Secretary-General of the International Seabed Authority (ISA) assuming office, and the profound impact this will have on both the formulation of regulations and the future trajectory of deep-sea mining.

Research on biogeochemistry in the Southern Ocean aims to uncover the unique structure of Antarctic marine ecosystems, elemental cycling processes, and their responses to global change. Such research holds significant scientific value and practical importance for understanding the mechanisms of the global climate system and supports the formulation of international Antarctic governance policies. Since the first Chinese National Antarctic Research Expedition (CHINARE) in 1984, the research team from the Second Institute of Oceanography (SIO), Ministry of Natural Resources, has pioneered China’s study of biogeochemistry in the Southern Ocean. Over the past four decades, through continuous participation in CHINARE missions, the team has systematically revealed the structure and function of Antarctic marine ecosystems and their coupling mechanisms with physical and chemical processes. This work has provided a solid scientific foundation for understanding the response of polar oceans to global change. This article systematically summarizes the team’s landmark achievements across different historical stages, reviews the development of China’s biogeochemistry in the Southern Ocean research from its inception to gradual strengthening, and looks ahead to the challenges and future directions in addressing climate change and supporting the building of a “Maritime Power”.

The United Nations Decade of Ocean Science for Sustainable Development (2021-2030) (hereinafter referred to as the “UN Ocean Decade”) is a global scientific initiative aimed at transforming and advancing the global ocean governance system through enhanced marine scientific research and innovation. By establishing a collaborative framework that spans disciplines, regions, and institutions, the initiative seeks to improve ocean observation capabilities, promote data and knowledge sharing, and strengthen the translation of scientific findings into policy and practice. As one of the participating countries in this initiative, China has systematically advanced related actions through the establishment of a national committee, the leadership of major scientific programs and construct Decade Collaborative Center. In this process, scientific research institutions have played a critical role in the implementation of scientific programs, technological innovation, and international cooperation. For instance, the Second Institute of Oceanography, Ministry of Natural Resources has led or deeply involved in several endorsed UN Ocean Decade actions that have established internationally recognized research and collaboration systems in areas such as conducting cutting-edge science and technology, and promoting capacity-building. Although significant progress has been made in the implementation of the UN Ocean Decade, global ocean governance still faces numerous challenges. These include disparities in technological capabilities and resource investments among countries, inadequacies in data-sharing mechanisms, and inefficiencies in translating scientific outcomes into policy. Additionally, geopolitical factors may also impact international cooperation. To achieve the goals set for 2030, further efforts are needed to deepen scientific innovation, improve open-sharing mechanisms, and strengthen inclusive collaboration, thereby promoting the establishment of a more equitable and effective global ocean governance system. In this process, research institutions worldwide can contribute to the realization of the UN Ocean Decade vision by continuing to participate in global observation networks, advancing digital and intelligent technologies, and supporting regional cooperation and capacity-building.

Terrestrial and marine ecosystems are the two core ecosystems of the earth’s surface, jointly sustaining global biodiversity and providing critical services such as material foundation, climate regulation, and civilization support for all life including humans. This article analyzes the essential differences between terrestrial and marine systems in spatial and ecological attributes, and explores the specific application of the “integrated land-sea coordination” concept in the construction and management of protected areas. The research concludes that: 1) Overemphasis on unified management tends to neglect regional particularities, leading to ineffective ecological protection and triggering socio-economic conflicts. 2) Mechanistically applying terrestrial ecological and geographical concepts to marine protected areas management may not only hinder the achievement of harmonious human-sea development goals, but also cause management closure, obstructing the sustainable use of marine resources. Based on this, this paper proposes differentiated management recommendations: Under the principle of “integrated land-sea coordination,” scientifically recognize and respect both the unity and differences of terrestrial and marine protected areas; strive to fill the marine observation data gap to support precise decision-making; establish phenological or seasonal dynamic management mechanisms based on marine species migration routes to implement more flexible conservation strategies.

Submarine cable and pipeline hold multifaceted strategic significance for national security, socio-economic development, and marine ecological environmental protection. This paper systematically reviews the evolution of China’s management policies for submarine cable and pipeline, traces the development trajectory of both the international legal framework and the domestic policy system. It analyzes the main existing issues such as administrative approval, protection management, spatial regulation, and national security. The study argues that with increasingly frequent marine development activities, lagging management mechanisms, and a complex and volatile international geopolitical landscape, submarine cable and pipeline face challenges including intensified competition for spatial resources and heightened security risks. The article proposes optimizing management policies across four dimensions: institutional restructuring, systematic protection, spatial governance, and security safeguarding. This approach aims to promote the construction of a forward-looking, efficient, and resilient governance system for submarine cable and pipeline. Such a system is essential to safeguard the implementation of China’s maritime strategy and ensure sustainable development.

The study of ocean bottom pressure (OBP) is great significance for understanding the mechanisms of sea level budget changes and deep ocean circulation. Based on 23 years of OBP data observed by the Gravity Recovery and Climate Experiment (GRACE) satellites, this study systematically reveals the spatiotemporal characteristics and mechanism of OBP variations in the Arabian Sea. There is a strong OBP oscillation center in the central area of the Arabian Sea. The OBP changes throughout the region are unified in space and time. It has significant seasonal variation features, showing a double-peak structure of negative anomalies in winter (January to March) and positive anomalies in summer (July to September). Combining the reanalysis data of ERA5, it is found that there is a dynamic divergence mechanism of OBP oscillation between the northern and southern areas of the Arabian Sea. The southern area is dominated by wind stress curl, with a negative correlation response leading OBP by 30° (about 1 month). The northern area is regulated by the wind-driven Ekman process, with Ekman pumping/suction leading by 1 month to trigger a positive correlation. This divergence mechanism is attributed to the boundary constraint effect of the meridional mean atmospheric pressure standard deviation. The impact of the Indian Ocean Dipole (IOD) on OBP shows seasonal asymmetry: in summer, OBP is significantly correlated with the dipole mode index (DMI) leading by 6 months, while in winter, the correlation between the mean OBP and the DMI in each mounth is not significance.

The ocean is a multi-sphere coupled system spanning the atmosphere, water column, sediments and biosphere, acts as the “blue engine” that regulates climate and global geochemical cycles. Only by sensing and quantifying marine environmental changes in a long-term, real-time, high-resolution and accurate manner, it can provide viable scientific support for the blue economy and global environmental governance. Benefiting from their miniaturization, rapid response, low power consumption and tolerance to extreme conditions, electrochemical sensors have become the key technique for in-situ observation of marine chemical parameters. This paper systematically introduces the working principles and performance of electrochemical sensors. Targeting the application scenario of collaborative multi-parameter monitoring along the full water-column profile from coastal waters to the deep sea, we review the latest technical progress of electrochemical sensors in monitoring key components such as pH, nutrients, dissolved oxygen, metal ions, electric fields, and deep-sea methane and hydrogen sulfide under extreme high-pressure and low-temperature conditions. The innovations range from traditional electrodes to nano-functional materials, solid-state ion-selective electrodes and semiconductor gas-sensitive devices. We focus on the challenges posed by deep-sea high pressure, high salinity, low temperature and low oxygen on sensor stability, selectivity and sensitivity, together with corresponding solutions. Finally, we outline future development trends toward intelligent, low-power, self-calibrating sensors capable of long-term deep-sea deployment.

Spaceborne synthetic aperture radar (SAR), with its all-weather and day-and-night imaging capability, has demonstrated tremendous value in ocean monitoring. This paper provides a systematic review of the current research status of spaceborne SAR technology in the field of marine monitoring, from the perspectives of ocean dynamic environmental parameters and maritime targets. For the former, we summarize mainstream SAR-based techniques and algorithms for monitoring ocean environmental parameters such as waves, internal waves, eddies, winds, currents, and seafloor topography, and further discuss the roles of multi-frequency, multi-polarization, and multi-mode SAR data in improving inversion accuracy. For the latter, we review SAR-based methods for the detection of maritime targets including sea ice, oil spills, vessels, and offshore infrastructures, highlight the importance of multi-polarization information in characterizing target scattering properties. In addition, this paper reviews and evaluates recent advances in applying artificial intelligence to SAR-based ocean monitoring and discusses future development directions for SAR ocean remote sensing technologies.

Seafloor massive sulfide (SMS) deposits represent critical strategic mineral resources, and the precise detection of their ore body structures is of great significance for deep-sea mineral exploration and evaluation. Near-seafloor transient electromagnetic detection and seafloor drilling are commonly employed techniques for probing ore body structures, yet they face challenges such as limited penetration depth and resolution, as well as low core recovery rates. Consequently, there is a pressing need for novel technological approaches to finely characterize the internal structures of ore bodies. Borehole-controlled source electromagnetic (BCSEM) method is an effective tool for terrestrial mineral exploration; however, its application and parameter selection in subsea environments remain in exploratory stages. This study employs forward numerical modeling of BCSEM for SMS detection to quantitatively analyze the characteristics of induced magnetic field responses under varying detection frequencies and borehole positional parameters. It evaluates the optimal detection frequency and examines the capability of multi-component cooperative observations to identify anomalies associated with sulfide ore bodies. The findings provide theoretical support for the optimized design of subsea BCSEM detection apparatus.

Small tropical lagoons are highly susceptible to eutrophication due to restricted hydrodynamic exchange and intensive land-based inputs. However, translating theoretical “environmental capacity” into actionable, spatially explicit control schemes remains a critical challenge. Taking the Xiaohai Lagoon in Hainan as a case study, this research establishes an integrated assessment framework coupling a two-dimensional hydrodynamic-water-quality model with grid-scale capacity accounting and multi-scenario load regulation. By integrating multi-source data, we quantitatively characterized the spatial heterogeneity of COD, DIN, and DIP and their remaining capacities. The results indicate: (1) Water quality exhibits a significant “inlet surplus-inner basin deficit” dual gradient. Under Class Ⅲ water quality targets, DIN is at critical saturation, while DIP acts as an “absolute rigid constraint” with zero remaining capacity; under Class II water quality targets, widespread nitrogen and phosphorus overload leads to capacity exhaustion. (2) Scenario simulations reveal that while hydrodynamic optimization engineering can release physical capacity, it has a “ceiling effect,” and the benefits are easily “offset” by incremental loads from socio-economic growth. (3) Only under a “deep source reduction” scenario coordinating the watershed and lagoon can the system breach physical thresholds, achieving Class II compliance in approximately 87% of the water area. The proposed “Accounting-Zoning-Reduction” framework facilitates a paradigm shift from gross total load control to precision governance characterized by “source reduction, spatial matching, and process optimization”, offering a transferable technical pathway for similar semi-enclosed coastal waters.