Most download

As a pivotal intertidal blue-carbon ecosystem, the seagrass-mangrove continuum is a focal point of contemporary blue-carbon research. In contrast to individual ecosystems, the continuum facilitates lateral carbon transport and redistribution between systems via tidal forcing—a process that profoundly influences regional and even global assessments of blue carbon budgets. However, the internal carbon cycling within the continuum and the multi-interface, multi-process coupling mechanisms of carbon sequestration remain a black box, representing one of the hot topics in blue carbon research. Here we systematically synthesize current understanding of carbon cycling in the seagrass-mangrove continuum, mapping key processes—from plant photosynthetic carbon sequestration, sediment carbon accumulation to aquatic carbon transformation, and gas exchange—within a novel, dual perspective of “vertical sequestration vs. lateral transport”. Special emphasis is placed on tide-driven lateral carbon fluxes (e.g., litter fall, DOC, POC, DIC), highlighting their central role in the continuum’s carbon dynamics. Given the complexity of intertidal habitats, future research on the coupled carbon cycling mechanisms within the seagrass-mangrove continuum remains a critical and underexplored field. In particular, key processes such as plant carbon fixation mechanisms, sediment carbon accumulation, and elemental exchange urgently require further investigation.

Deep-water sedimentary processes are key drivers that shape seafloor topography and actively participate in marine material cycles, thereby playing a crucial role in the formation of depositional systems and material cycling along continental margins and within deep-sea basins. The transport and transformation of carbon elements and carbon-containing substances are essential for sustaining organic life and maintaining climate stability. As an important end-member reservoir in this cycle, deep-sea sediments act as efficient sinks for atmospheric greenhouse gases, exerting significant regulatory effects on climate evolution over geological timescales. This study aims to elucidate the coupling mechanisms between distinctive deep-water sedimentary processes and organic carbon burial, providing a theoretical basis for establishing the “Shelf edge-slope-deep sea basin organic matter continuous transport system” and the “Deep-water organic carbon burial pyramid model”. By comprehensively analyzing representative deep-water organic carbon burial systems in global ocean basins, this research demonstrates that turbidity currents and bottom currents are the main dynamic mechanisms enabling the continuous transport of deep-water organic matter. The (micro)biological carbon pump, turbidity current carbon pump, bottom current carbon pump, and deep stratigraphic carbon pump together form the core framework for deep-water sedimentary carbon burial. Furthermore, the factors influencing deep-water organic carbon burial outcomes exhibit hierarchical characteristics. However, current research on deep-water organic carbon burial is still in its early stages, with limited case studies and mechanistic understanding, underscoring the urgent need to strengthen research on carbon burial processes in deep-water environments.

The sediment source-to-sink system serves as a critical link connecting active carbon pools (e.g., atmosphere, biosphere, hydrosphere) with the stable lithospheric carbon pool, playing a core buffering role in the global carbon cycle. As the core area of marine sedimentary carbon sinks, delta-shelf regions account for over 80% of the global marine sedimentary organic carbon flux while occupying less than 8% of the global ocean area. The processes and mechanisms of carbon burial in these regions are crucial for global carbon balance. This paper systematically reviews the source composition and sedimentary flux characteristics of terrestrial organic carbon in delta-shelf sedimentary systems, focuses on elaborating organic carbon source-to-sink tracing technologies, remineralization processes and their dominant mechanisms, analyzes the impacts of human activities on sedimentary carbon sinks, and discusses marine negative emission and carbon sequestration enhancement schemes based on sediment management. Studies show that the heterogeneity of terrestrial organic carbon, physicochemical conditions of the sedimentary environment, and human disturbance collectively regulate the migration, transformation, and burial efficiency of organic carbon. Currently, the potential of sedimentary carbon sinks has not been fully exploited; thus, it is urgent to promote the integration of sedimentary carbon sinks into the global climate governance system through methodological innovation, mechanism deepening, and technological development, so as to provide scientific support and feasible paths for achieving the temperature control goals of the Paris Agreement.

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.

To investigate how tidal dynamics influence the composition of dissolved metabolites in seawater, we collected seawater samples across a semidiurnal tidal cycle, spanning both the salinity and turbidity fronts of the Changjiang River Estuary in March 2023. Using high-resolution mass spectrometry-based untargeted metabolomics, a total of 1 379 metabolite molecules were annotated (annotation rate of 6.8%), covering 14 super classes. Among these, organoheterocyclic compounds, benzenoids, lipids and lipid-like molecules were dominant (accounting for 59.1%). The results indicated that the composition of metabolites was significantly influenced by tidal forces, with greater heterogeneity during ebb tide than flood tide, revealing a temporal asynchrony between tidal movement and metabolite compositional variation. Statistical analyses further demonstrated that metabolite compositions were significantly negatively correlated with salinity, and that non-conservative nutrients (nitrate, phosphate, and silicate) exerted strong influences on metabolite variations. These results suggested that terrestrial dissolved organic matter inputs were a primary driver, with their influence further modified by brackish water mixing. In addition, the correlation between turbidity and most metabolites was relatively week. However, substantial percentage changes in lipids and lipid-like substances were observed within the suspended sediment front, indicating that the transformation of dissolved organic matter driven by resuspension processes primarily occurs under strong hydrodynamic conditions. Analysis of differential metabolite during flood and ebb phases further showed that these substances were dominated by secondary metabolites, such as lipids and heterocyclic compounds. These substances might reflect regulation by microbial community interactions. Overall, this study highlights the short-term tidal influence on dissolved organic matter composition and provides new insights into how multi-scale physical processes regulate organic matter cycling in estuarine environments.

The vertical structure of phytoplankton is key to understand the biological carbon pump in the Southern Ocean-Indian sector. This study systematically analyzed the seasonal and interannual variability in the vertical distribution of chlorophyll a （Chl a） and phytoplankton carbon biomass （C_phyto） and their environmental drivers in this region， using satellite observations， BGC-Argo floats， and reanalysis data （2015-2018）， with a focus on the 2015/2016 El Niño event. Results showed that Chl a was mainly distributed in the upper 0-100 m， with a pronounced subsurface chlorophyll maximum layer （SCML） at 10-100 m. Seasonal variability was significant： during austral summer （Dec-Feb）， sufficient light （PAR>100 μmol·m^-2·s^-1） supported peak Chl a and C_phyto in the upper 0-100 m [ρ（Chl a）>0.75 mg·m^-3， C_phyto>20 mg·m^-3）. In austral winter （Jun-Aug）， reduced light availability and a deeper mixed layer collectively led to the dissipation of the SCML and the lowest annual values of Chl a and C_phyto [ρ（Chl a）<0.5 mg·m^-3， C_phyto<10 mg·m^-3]. The deepening of the mixed layer extended the vertical distribution of Chl a to approximately 200 m， whereas the vertical structure of C_phyto showed no corresponding significant change， leading to a pronounced decoupling between Chl a and C_phyto in the 0-200 m. During the 2015/2016 El Niño， enhanced Ekman pumping shoaled the thermocline， increasing nutrient supply to the euphotic zone and intensifying and prolonging the summer phytoplankton bloom [ρ（Chl a）>1 mg·m^-3， lasting about 7 months]. This study provides scientific support for accurately assessing the Southern Ocean’s carbon sink potential and predicting the impact of extreme climate events on the phytoplankton-driven carbon pump.

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.

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 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.

Coastal wetlands have a strong capacity for carbon capture and storage, playing a significant role in mitigating climate warming. Vegetation type is an important factor influencing the carbon storage. In this study, we measured the soil organic carbon (SOC), lignin, stable carbon isotope (δ¹³C), grain size, and iron content in the surface soil of three typical vegetation habitats (Phragmites australis, Phragmites australis-Tamarix chinensis, and Suaeda salsa) in the Yellow River Estuary wetland, and analyzed the content, source, and degradation characteristics of organic carbon. The results showed that the SOC content in the three vegetation habitats of the Yellow River estuary wetland ranged from 0.34% to 1.85%, with the highest in P. australis, which had an average value of 0.94%. The SOC content was jointly affected by vegetation type and clay content. The three-end-member Monte Carlo model calculation found that the soil organic carbon in the three vegetation habitats was mainly from terrestrial (47.7%±13.2%) and plant sources (36.3%±15.0%), with a relatively low marine source (16.0%±14.2%) (S. salsa>P. australis-T. chinensis>P. australis). The soil lignin in the three vegetation habitats all showed a mixture or single source of woody and herbaceous tissues, indicating that part of the soil organic carbon in the P. australis and S. salsa habitats originated from the upstream Loess Plateau. Iron oxides and water in the soil might reduce the degradation of lignin due to their protective effect on organic carbon and their inhibitory effect on aerobic respiration of microorganisms. This study showed that there were significant differences in the distribution, source, and degradation characteristics of soil organic carbon among different vegetation habitats.

The estuarine turbidity maximum (ETM) is a critical hub for the transport of particulate organic carbon (POC) from estuaries to ocean. To investigate the provenance and transport patterns of POC within the ETM, the Jiulong River ETM was selected as a research site. Hourly-resolved hydrological parameters, horizontally transported POC (collected via filtration), and vertically settling POC (collected using sediment traps) were systematically sampled. POC was analyzed for organic carbon isotopes, and the Monte Carlo end-member model was employed to analyze the relative contribution of different endmembers. Then the empirical orthogonal function (EOF) analysis was applied to examine and discuss the transport patterns and their driving mechanisms of POC within the ETM. The results revealed significant spatiotemporal variations in POC sources: surface POC was primarily of riverine sources (35.5%), while bottom POC was dominated by sedimentary sources (35.1%). Settling POC was also mainly derived from sedimentary sources, reaching up to 65% in high-flow flood tide periods. The bottom POC mass concentrations (0.8-8.4 mg·L^-1) showed a significant positive correlation with the magnitude of bottom tidal current velocity (absolute range: 0-0.5 m·s^-1). The peak settling flux of particles (227.1 mg·cm^-2·h^-1) occurred during low-flow periods (profile-averaged velocity <0.2 m·s^-1). Based on the results, it is find that tidal current velocity is a key factor regulating the sources and transport of POC within the Jiulong River Estuary’s ETM. It influences the horizontal transport, resuspension, and vertical mixing processes of POC through its magnitude, direction, and duration, thereby governing the provenance composition and mass concentration of POC. This control manifests specifically in three ways: a significant positive correlation exists between tidal current velocity and POC mass concentration, where high-velocity currents primarily drive the resuspension of sediments, making this process the main source of sedimentary POC; the alternating flow patterns of flood and ebb tides are the dominant control for the shifting predominance between river and marine POC; and velocity stratification (especially during the ebb tide stage) governs the vertical mixing intensity of POC from different sources. Moreover, from the perspective of how tidal current velocity regulates POC sources and transport processes within the ETM, this study summarizes the POC transport models for different tidal stages: During the flood tide, currents drive the input of marine POC. However, the high flow velocities cause significant sediment resuspension, resulting in the overall dominance of sedimentary POC. During the high slack tide, characterized by low flow velocities, particle settlement predominates, and sediment resuspension diminishes. This leads to a relative increase in the proportions of river or marine POC. Although the contribution of sedimentary POC decreases, it remains the dominant source overall. During the ebb tide, the outgoing currents facilitate the input of river POC. Meanwhile, the high flow velocities in the surface layer have a limited effect on adding sedimentary POC. The proportional distribution among the three POC sources is closely linked to the duration of the preceding high-velocity flood tide; generally, a longer duration leads to more pronounced dominance of sedimentary POC. During the low slack tide, which also features low flow velocities, settlement is again the primary process. The contributions of the three POC sources are generally comparable during this stage. These findings provide a valuable reference for a deeper understanding of the source-to-sink processes of POC within the ETM.

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.

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”.

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.

Black carbon (BC), a refractory organic carbon, is produced during the incomplete combustion of biomass and fossil fuels. Globally, an estimated 3%-10% of the annual BC production ultimately buried in marine sediments. As a critical component of the inert carbon pool, its spatiotemporal distribution and source-to-sink processes are essential for understanding global carbon cycling and climate evolution. Based on published BC data from nearly 1 000 marine sediment samples worldwide, this study reveals that BC contents vary widely, from 0.02 to 9.72 mg/g, with averaging 1.06 mg/g and accounting for an average of 15.1% of total sedimentary organic carbon. Spatial patterns are controlled by sediment grain size, organic carbon content, and depositional environments while temporal variations reflect the combined influence of climate change and human activities. Current knowledge of marine sedimentary BC sources predominantly assumes terrestrial dominance, with riverine transport, atmospheric deposition, and coastal erosion as primary input pathways. However, emerging evidence indicates that BC sinking fluxes in mid- to deep-ocean layers substantially exceed known terrestrial supply. This raises the possibility of potential unidentified sources. In addition, BC degradation and recycling processes within the marine systems remain poorly understood. Future research must prioritize source-to-sink dynamics in key areas (e.g., deep-sea environment) by integrating geochemical and organic molecular isotopic techniques to resolve BC cycling mechanisms and address current budget imbalances.

River deltas are critical global sinks for organic carbon (OC). To elucidate their evolutionary patterns under natural and anthropogenic influences, this study systematically reconstructs the OC burial history of the Changjiang Delta since the mid-to-late Holocene (8 ka BP), based on chronological, sedimentological, and organic geochemical data from 50 boreholes. The results revealed that the sediment accumulation rate was the core driver controlling the OC burial flux, with the two showing a strong positive correlation (r²=0.87). However, a significant decoupling existed between the OC burial flux and the total OC content, with the latter remaining stable within a low range of 0.41%-0.52% throughout the study period. This was primarily constrained by the dual effects of clastic dilution and particle size sorting. The provenance of OC showed a distinct phased evolution: from 8 to 2 ka BP, source variations were mainly driven by natural factors, with sea-level rise (8-5 ka BP) and the weakening of the East Asian Summer Monsoon (5-4 ka BP) successively leading to a decrease in the terrestrial OC fraction. Since 2 ka BP, human activities had become the dominant factor, profoundly reshaping the delta’s geochemical signals by altering sediment provenance zones within the catchment. This study unveils the complete process of the Changjiang Delta’s carbon sink function transitioning from a dynamic equilibrium under a natural background to being intensely disturbed in the Anthropocene, providing crucial scientific insights for understanding and predicting the vulnerability of deltaic carbon reservoirs in the context of global change.

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.

Under the dual pressures of global change and human activities, the impact of extreme storm events on estuarine sedimentary processes and carbon sink capacity has become increasingly prominent. However, traditional single-core methods face challenges in quantitatively characterizing the erosion-deposition processes and net carbon burial effects induced by storm events. In this study, we conducted repetitive coring at a fixed station near the Dayushan Island in the Hangzhou Bay, China in 2021 (before Typhoon Chanthu) and 2022. Through analysis of sedimentary structures, grain size and radionuclides, we identified an intense erosion-deposition event triggered by Typhoon Chanthu. Combined with elemental composition and organic geochemical indicators, we further quantitatively assessed its net impact on carbon burial. The results demonstrate that despite the efficient organic carbon preservation within the storm layer, the related intense erosion resulted in a net organic carbon deficit of 1 950±523 g·m^-2. This finding highlights a preservation bias of the storm layers in sedimentary records, leading to a systematic overestimation of the storm contribution to estuarine carbon burial in studies relying on single cores. The “repetitive coring-radionuclides tracing” methodology developed in this study provides a new paradigm for accurately assessing estuarine sedimentary processes and carbon cycling under non-steady-state conditions.

Seagrass meadows sediments are important marine carbon reservoirs, and accurately assessing their carbon stocks is fundamental to evaluate the carbon sink function of seagrass ecosystems. However, compared with organic carbon pools, the characteristics of inorganic carbon pools in the sediments of seagrass meadows remain poorly understood. This study focused on the tropical mixed seagrass meadows in Li’an Lagoon, Hainan. Through field sampling, we analyzed the inorganic carbon stock and its sources in sediments from areas dominated by Enhalus acoroides, Cymodocea rotundata, and Thalassia hemprichii, as well as from adjacent bare areas, thereby clarified the influence of seagrass growth on sedimentary carbon burial. The results show that inorganic carbon stocks in sediments in seagrass-covered areas are significantly higher than those in adjacent bare areas (59.84±24.55 Mg·ha^-1). Significant differences also exist among seagrass species: the inorganic carbon stocks in sediments associated with E. acoroides, C. rotundata, and T. hemprichii are 105.66±9.45 Mg·ha^-1, 96.09±31.36 Mg·ha^-1, and 75.05±8.17 Mg·ha^-1, respectively. Moreover, larger seagrass plants correspond to higher sediment inorganic carbon stocks. Carbonate stable-isotope analyses indicate that calcifying benthic organisms are the primary source of inorganic carbon in sediments within seagrass-covered areas, whereas sediments in adjacent bare areas mainly derive their inorganic carbon from calcifying epiphytic algae. Based on these findings, this study indicates that seagrass meadows enhance calcium carbonate production by increasing the abundance of calcifying benthic organisms, while their flow-attenuation and sediment-stabilization effects favor the burial of carbonate minerals. The combined effects of these processes result in a substantial increase in sedimentary inorganic carbon storage. Furthermore, we quantify the offsetting effect of CO₂ release associated with calcium carbonate formation on the organic carbon sink in seagrass meadows, providing a scientific basis for accurately evaluating the carbon-sink capacity of tropical mixed seagrass meadows.