Earth and Environmental Sciences

Maritime governance is a systematic process by which humans address the complex issues in the ocean through rule-making, interest coordination, and technology application, aiming to achieve ecological protection, resource utilization, and balance of rights and interests. It requires adhering to the objective laws of the ecosystem while also taking into account the actual demands of countries at different development stages, ultimately achieving harmonious coexistence between humans and the ocean. Multilateral actors at the global level formulate policies, coordinate forces, set norms, and carry out actions to address common maritime security threats and challenges, and the actors, concepts, practices, and actions in this process collectively constitute the entire process of global maritime security governance. With the rapid development and widespread application of digital intelligence technologies, “Digital Twin Ocean” have gradually become prominent. Deep-sea development and governance, as well as the maintenance of biodiversity, have all become important topics in global maritime security governance. The evolution mechanism and logical framework of global maritime security governance are also gradually becoming clear. Based on a comprehensive thinking of history and reality, global maritime security governance has distinct characteristics of its era, multiple subjects, interconnected fields, and practical concepts. In the “Anthropocene,” under the coupled influence of new trends in multiple fields such as politics, economy, culture, technology, and ecology, global maritime security governance has developed in a more intelligent, systematic, and complex manner. This study concludes that the evolution mechanism and current situation of global maritime security governance provide a historical opportunity for all countries to re-examine the marine reality in the Anthropocene era to focus on the tasks and requirements in the governance process and strive to achieve truly global, diversified, balanced, and sustainable global maritime security governance.

Background The increasing prevalence of antimicrobial resistance (AMR), alongside the growing incidence of cancer, diabetes and adverse effects associated with antibiotics, chemotherapy and synthetic drugs, encourages researchers to find out natural products as a potential solution. In this context, a systematic approach was applied to extract ulvan from the edible green algae Ulva lactuca , known for its rich biochemical composition and to determine its multifunctional biomedicinal properties. Methods In this study, sulphated polysaccharide ulvan was extracted from U. lactuca through hot water extraction and the purified ulvan was characterized by various spectral analysis. Biomedical properties of the ulvan were determined through in vitro assays approaches. The biocompatibility of the ulvan was assessed by Artemia cytotoxicity and anticancer activity against human skin cancer (A431) cells. Results The organoleptic characteristics of ulvan revealed that it is odourless, whitish in colour, polar, powdery, and possesses gelling ability. Biochemical analysis indicated that ulvan exhibited high thermal stability under conditions ranging from 103.6 to 600 °C, with a near-neutral pH of 6.7–7.4, and contained substantial amounts of carbohydrates, alongside sulfate groups, uronic acids, and proteins. Spectroscopic analysis revealed the structural makeup and functional groups of the ulvan. The extracted ulvan exhibited promising free-radical scavenging activity (DPPH, FRAP, HPO, and TAA). Antimicrobial studies revealed that ulvan inhibited both bacterial and Candida strains, with MICs in the range of 50 to 90 µg/mL. It had also exhibited notable antibiofilm activity, as evidenced by inhibition of exopolysaccharide production, increased protein leakage, and ROS production in the tested pathogens, along with microscopic visualization confirming eradication of microbial adherence on glass surface. In vitro antidiabetic activity of ulvan showed promising α-amylase inhibitory activity, with an IC 50 of 78.43 µg/mL. The safety assessment of ulvan revealed minimal toxicity to Artemia salina nauplii (LC 50 : 147.8 µg/mL). The cytotoxicity of ulvan on A431 cells recorded an IC 50 value of 82.44 µg/mL. Conclusion Overall, this study elucidated the structural and biomedicinal attributes of ulvan, notably revealing its pronounced antibiofilm activity and selective cytotoxic effects against human skin cancer (A431) cells remains comparatively underexplored. Hence, this study substantiates its potential as a promising multifunctional therapeutic applications.

Previous studies have described the general spreading patterns of the Pechora plume in the southeastern Barents Sea, but its synoptic variability during the ice-free season remains largely unknown. In this study, we analyze Pechora plume dynamics on synoptic time scales during the ice-free season from 2015 to 2024 using satellite-derived sea surface salinity, sea surface temperature, and in situ observations. We reveal that the maximal plume area, reaching up to 55,000 km 2 , is not confined to the spring freshet period and may occur throughout the entire ice-free season under favorable wind forcing conditions. Wind primarily controls plume spreading through Ekman transport, while the timing and magnitude of peak river discharge determine freshwater volume and stratification. A time lag between the peak river discharge and freshwater inflow from Pechora Bay, i.e., the estuary of the Pechora River, to the open sea modifies the plume response to external forcing. Also, based on satellite data and in situ measurements, we reveal and describe two spreading patterns of the Pechora plume that received limited attention before. First, we identify large-scale northwestward advection of the outer part of the Pechora plume and its subsequent separation from the main part of the plume. The separated part of the plume (hereafter referred to as low-salinity lens) could drift more than 300 km towards Novaya Zemlya under northeasterly wind forcing. Second, we identify more than 30 wind-driven inflow events of the Pechora plume through the Kara Strait into the Kara Sea, which intensify inter-basin freshwater exchange between the Barents and Kara seas. These results significantly expand the current understanding on the Pechora plume dynamics and variability. It provides new insights for assessment the influence of the Pechora plume on the hydrological structure of the entire southeastern part of the Barents Sea.

Introduction Against the backdrop of the strong interdependence between global energy markets and maritime transport systems, fluctuations in crude oil prices may influence tanker port operations through adjustments in trade organization and transportation decisions. Methods Using a panel dataset covering 20 countries over the period 2018–2023, this study employs a two-way fixed effects model to identify the impact of oil price shocks on tanker port performance and further conducts robustness checks using a double machine learning approach. Results The results reveal pronounced loading–discharging asymmetries in the transmission of oil price shocks within the port operation chain. The effects are concentrated on the loading side: increases in oil prices significantly raise the median time vessels spend in port, the average gross tonnage of arriving tankers, and the average deadweight tonnage per vessel. In contrast, these three indicators are not statistically significant on the discharging side. Discussion From the perspective of port operations, this study provides additional empirical evidence on the transmission effects of oil price shocks. The findings not only offer Guida volatility but companies and port authorities in assessing operational pressure, optimizing resource allocation, and enhancing system resilience under oil price volatility, but also highlight the importance of incorporating energy market shocks into port operation monitoring and risk governance frameworks.

The European Union’s (EU) fishing fleet has struggled with overcapacity, which has led to overexploitation of fish stocks. Since the 2013 Common Fishery Policy (CFP) last reform, efforts to promote sustainable fisheries have resulted in healthier fish stocks and a reduction in fleet size. While EU fleets now comply with capacity limits, challenges remain, threatening sustainability and the fishing sector’s viability. Despite improvements since the reform, economic disparities and imbalances in fish resources persist. By collating expert knowledge and data analyses, this study examines if facing future challenges, such as energy transition and attracting young fishers, may require extra capacity to accommodate more efficient or alternative engines for greener fuels, and improve working conditions, in the context where country-specific capacity ceilings limiting the fishing capacity are not reached. However, current policies may limit short-term profitability of the current active fleet. At the same time, the EU fleet policy should ensure that fleet renewal, modernization, and profitability improvements, which may require additional capacity or not, alongside improved efficiency over time, do not result in an improved ability to catch fish that would exacerbate fleet imbalances, create overcapacity, or put more pressure on exploited stocks. Our findings indicate that the current EU fleet imbalance will likely worsen whenever capacity is reused, or extra capacity is granted without controlling for the ability to catch fish, and without monitoring for the right metrics beside fleet or vessels kW and GT. It appears optimistic to assume that reactivating unused fishing capacity or granting extra fishing capacity will not be used to catch even more fish. The findings aim to inform recommendations for improvement and to find applicable solutions within the EU framework, while addressing ongoing challenges in EU fisheries without compromising the fleet’s capacity to catch fish in ways that do not contribute to overcapacity and imbalance. It appears advisable that fishing capacity would best be managed at the fleet level, not reduced per individual vessel, to ensure balance with fisheries opportunities, support the energy transition, and safeguard socioeconomic resilience under the CFP.

Marine genetics play an essential role in biodiversity studies, ecosystem monitoring, and biotechnology, yet little is known about how marine genetic sequences are translated into commercial applications. Although international frameworks such as the BBNJ Agreement and the Convention on Biological Diversity address access and benefit sharing, effective implementation requires empirical insight into how marine genes are used. Here we analyze the Marine Bioprospecting Patent Database, a global catalog of marine-derived genes appearing in patents, by combining structural topic modeling and large language model-assisted classification of 1,676 patent texts to map technological themes and actor contributions across healthcare, agriculture, industrial, and foundational biotechnology. Private-sector filings prioritize industrial and agricultural applications, whereas research institutes and governmental actors disproportionately contribute foundational, cross-cutting tools that enable downstream innovation. A curated subset of 221 patent claims mentioning marine enzymes illustrates applications ranging from bioenergy and green chemistry feedstocks to diagnostics and therapeutics. While many inventions align with sustainability objectives, others deliver incremental gains or support applications with ambiguous, if not adverse, environmental implications. Targeted policy, funding, and stewardship are needed to maximize net sustainability benefits and ensure equitable benefit-sharing under international frameworks.

The Maldives is widely recognised as a hotspot for shark and batoid diversity in the Indian Ocean, yet regional multispecies patterns of elasmobranch occurrence remain poorly characterised. This study analyses a seven-year (2017-2024) opportunistic dive-log dataset comprising 12,732 SCUBA surveys and 142,994 observation records of sharks and batoids collected across 94 dive sites in Lhaviyani Atoll, central Maldives. In total, 28 species (14 sharks and 14 batoids) were recorded, including 23 species listed as threatened on the IUCN Red List (4 Critically Endangered, 12 Endangered, 7 Vulnerable). Elasmobranch relative abundance (sightings per hour of dive effort) and diversity peaked during the late southwest monsoon (August–September) and declined during the transitional period into the northeast monsoon (December–March), following the reversal of regional circulation and productivity fronts. Community composition shifted after 2021 towards greater diversity and evenness, while overall relative abundance declined. Effort-standardised relative abundance was modelled as a function of environmental and geomorphic variables using generalised additive models (GAMs). Results revealed that elasmobranch relative abundance was primarily driven by sea surface temperature, salinity, and surface current velocity (zonal and meridional components), with geomorphic complexity enhancing occurrence along reef slopes and sheltered slope habitats. For sharks, dissolved oxygen and chlorophyll a were also significant, whereas batoids’ relative abundance was influenced mainly by temperature, oxygen, and current velocity. Spatial kernel-density maps identified four persistent northern-rim elasmobranch activity hotspots, with sharks concentrated along exposed and semi-sheltered slopes and channels, and batoids distributed more broadly within lagoonal habitats. By characterising these spatial and environmental patterns, this study strengthens the scientific basis for targeted conservation and management at a time when national and international management frameworks for sharks and batoids are rapidly evolving.

Plastic pellets represent a significant threat to marine environments: beyond being pollutants themselves, they can act as vectors for other contaminants by absorbing organic pollutants and metals. In this study, synchrotron-based micro-X-ray fluorescence (micro-XRF) mapping was applied to spatially resolve heavy and trace metal distributions in environmental polyethylene pellets collected along the Tyrrhenian coast. By analyzing pellets exhibiting different degrees of yellowing and biofouling, the study explores the relationship between environmental exposure parameters and metal accumulation. The results distinguish surface-associated metals related to adsorption and biofouling from metals penetrating the polymer interior, particularly in aged pellets. This spatially resolved approach provides new insight into metal accumulation mechanisms and the associated environmental impact and potential risk to human health linked to plastic pellets.

The abundance of microplastics in estuarine waters can vary significantly throughout tidal cycles. However, the hydrodynamic mechanisms controlling the transport of these particles remain poorly integrated across available studies. Reported responses often differ according to tidal phases, tidal amplitude, estuarine hydrodynamics, and methodological approaches, limiting comparisons among studies and broader conceptual understanding. This review critically analyzes current evidence on the influence of tidal dynamics on the abundance and morphological characteristics of microplastics in estuarine waters, with emphasis on the hydrodynamic processes regulating the transport, retention, and redistribution throughout daily and lunar tidal cycles. The analysis reveals that microplastic responses to tidal forcing are highly variable and strongly influenced by tidal asymmetry and estuarine hydrodynamic conditions, including river discharge, current velocity, tidal pumping, mixing intensity, residence time, and estuarine front dynamics. Generally, ebb-dominated regimes favor microplastic export to the ocean due to the dominant role of river discharge, while flood-dominated regimes promote greater retention and recirculation associated with resuspension induced by tidal currents and landward transport. Spring tides intensify microplastic transport and resuspension due to increased hydrodynamic energy, while neap tides favor particle deposition. Tidal dynamics exert less influence on microplastic characteristics, although buoyancy particles may be transported more efficiently landward during flood tides. To synthesize current knowledge, we propose a conceptual framework integrating the main hydrodynamic controls and transport regimes governing microplastic dynamics in estuarine waters. We also propose an actionable framework with recommendations for sampling design in tidal estuaries to improve methodological standardization and comparability among studies.

As urban areas expand, the sustainable management of municipal water becomes a critical challenge, especially in arid and semi-arid regions facing severe water scarcity. Accurate assessment of urban plant water requirements (PWR) is essential for developing sustainable landscape architecture and resilient green infrastructure. In this study, a new quantitative equation (PWRq) was developed as a regional proof of concept to adjust reference evapotranspiration estimates for hyper-arid conditions. A Tree Morphology Coefficient (Ktm) is introduced to combine canopy features (form, height) and leaf traits (size, density) with an updated drought-resistance coefficient (Kdr). Field measurements of 277 mature trees, representing 27 native and introduced species in Riyadh and Jeddah, Saudi Arabia, were analyzed. The framework explicitly includes an empirical multiplier to account for extreme urban heat island (UHI) effects and aerodynamic canopy scaling. Instead of direct empirical validation, the PWRq model was benchmarked against established reference indices: Water Use Classification of Landscape Species (WUCOLS) and Simplified Landscape Irrigation Demand Estimation (SLIDE), showing strong alignment with established categorical indices and structural traits. The results confirm that the morphology-based method effectively makes previously subjective classifications objective. Notably, the quantitative assessment found that the dominant introduced species require about 3.5 times more water than native species. As a proof of concept, future research should empirically validate these findings against direct physical measurements, such as sap flow sensors or lysimeters. The proposed framework presents a practical, objective decision-support tool for municipal policymakers and landscape architects to optimize species selection, implement nature-based solutions (NBS), and achieve long-term sustainability in urban greening.

Post-disaster reconstruction programmes create an irreversible window for embedding or foreclosing residential energy efficiency at scale. This study examines the structural determinants of per capita residential electricity consumption (K_MES) across all 81 provinces of Türkiye over 2013–2022 using a balanced province-year panel. We develop two complementary panel models, both estimated by two-way fixed effects (province + year) with cluster-robust standard errors, and supported by GLS-AR(1) and random-effects GLS robustness checks. Note that K_MES measures the electricity component of residential energy use only; we, therefore, also estimate the building-stock model with a constructed total-energy dependent variable that combines residential electricity (H_MES) and natural-gas consumption (X_DG) in kWh-equivalent units. Model 1 isolates the macroeconomic transmission channel through which exchange-rate volatility shapes residential electricity demand. Because the USD/TRY rate has no cross-sectional variation, its identifying power in two-way fixed effects comes from its interaction with province-level natural-gas-heating exposure (sh_gas × EV_DA). The interaction is robustly negative across all full-sample specifications (β ≈ −0.022, p < 0.01), indicating that provinces with greater gas-heating penetration are buffered against currency-depreciation pass-through into electricity demand. Provincial GDP carries the dominant direct macro coefficient (β ≈ 0.27–0.29, p < 0.01), establishing income elasticity rather than the exchange rate as the headline aggregate driver. Model 2 decomposes the building stock by structural system, filler material, heating system, and heating fuel. The dominant predictors are the share of electric heating (β ≈ 1.16–1.27, p < 0.01) and the share of AC-only heating (β ≈ −1.0 to −1.13, p < 0.05), with a total-energy specification reaching R2 = 0.92. In the comparative subsample of the eleven Kahramanmaraş-affected provinces, masonry construction emerges as the dominant pre-disaster predictor of per capita electricity consumption (β = 14.04, p < 0.05), revealing structurally distinct stock characteristics that pre-date the February 2023 earthquake. Two re-framings are required. First, since the panel covers 2013–2022, the disaster-province estimates capture pre-disaster structural heterogeneity rather than post-disaster market rupture. Second, the macroeconomic mechanism that prior work attributed to the exchange-rate level is more accurately understood as a fuel-mix-mediated exposure channel. The combined evidence implies that mandatory building-code enforcement and natural-gas grid extension are complementary policy levers in the 488,000-unit Turkish Housing Development Administration reconstruction programme: gas grid expansion reduces the macroeconomic vulnerability of residential energy demand, while masonry-replacement construction standards address the largest pre-disaster structural determinant of energy intensity in the affected region.

Evapotranspiration (ET) is a fundamental process within the water cycle and the agricultural water balance, optimizing resource allocation, maintaining soil health, and enhancing ecosystem resilience to climate change. Because ET represents a primary consumptive use of irrigation on agricultural lands, enhancing water-use efficiency and sustainable water management requires accurate estimation of evapotranspiration to support long-term sustainability and productivity. This study offers an effective means to visualize spatial and temporal patterns of reference evapotranspiration (ETo) across various vegetation management practices. This study examined the impacts of agroforestry buffers (ABs), grass buffers (GBs), biofuel crops in an agroforestry watershed (BCa), and biofuel crops in a grass buffer watershed (BCg) on ETo, compared to a corn (Zea mays L.)–soybean (Glycine max L.) rotation (RC) for claypan soil in Northern Missouri, USA. The experimental watersheds were located at the Greenley Memorial Research Center, Missouri, USA. Campbell Scientific sensors and Photosynthetically Active Radiation (PAR) smart sensors were installed to measure net radiation, anemometers, humidity, and air temperature. All instruments were mounted on masts at a height of 2 m above ground level in crop, tree, grass, and biofuel areas. Measured meteorological data were recorded hourly from April to October during 2017 and 2018. Daily ETo predictions were calculated using the Penman–Monteith model. These ETo predictions were displayed across the landscape using Python-based GIS for selected dates (each Saturday) for the watersheds. The methodology was implemented using the software programs of Python 2.7.10 and ArcGIS 10.3.1. The results indicated that ETo increased by 11%, 17%, 18%, and 25% in 2017, and by 7%, 9%, 14%, and 20% in 2018 for AB, BCa, BCg, and GB, respectively, compared to RC management. This process may improve soil water recharge in perennial management systems. Accurate estimation of ET in agricultural regions is critical for understanding water balance, hydrological and ecosystem processes, and climate variability. Given that agriculture constitutes the majority of global water consumption, precise ET estimation is particularly significant for sustainable water management, especially in regions experiencing water scarcity. These outcomes may support effective planning and management of agricultural water resources by enabling optimized irrigation and agricultural production.

Ensuring food security is a top priority for China, and non-grain production (NGP) of cropland can substantially reduce food production. As the core grain production base in Shaanxi Province and even Northwest China, the Guanzhong region’s evolution of NGP is very important. Based on the single-phase remote sensing data and the time-series curve, this study identifies explicit non-grain production (E-NGP) and implicit non-grain production (I-NGP) of cropland in the Guanzhong region from 2001 to 2020. Spatial analysis and gradient analysis are applied to characterize the spatiotemporal dynamics, differences in reversibility, grain loss, and driving factors of E-NGP and I-NGP. The results show that the area of cropland used for NGP in the Guanzhong region has gradually increased over the past two decades. In 2020, the area of E-NGP reached 4212.06 km2, while that of I-NGP accounted for 8300.16 km2. The total cumulative loss attributed to NGP in 2020 reached 11.58 million tons, and the grain loss caused by I-NGP was approximately twice that of E-NGP. Moreover, cropland used for I-NGP exhibits greater instability and reversibility, making it more susceptible to human intervention than that under E-NGP. The cropland used for E-NGP is mainly distributed around urban areas, where it is often converted into construction land. The cropland used for I-NGP gradually expands from north to south, with areas south of the Weihe River increasingly converted into economic fruit forests. E-NGP is driven by both terrain and socioeconomic factors, while I-NGP shows a stronger natural geographical dependence. This study defines the scale boundaries and driving factors of NGP in the Guanzhong region, reveals its substantial threat to grain production capacity, and provides theoretical support for regional policy implementation and the formulation of refined cropland protection policies in the Guanzhong region.

Against the backdrop of the global green development concept, scientifically assessing the level of urban green transformation (UGT) in China and revealing its spatiotemporal evolution are critical for promoting high-quality development in the country. We constructed an evaluation index system based on four dimensions: economic, social, resource, and environmental transformation. Using the entropy method, we determined the scores for a comprehensive green transformation development index for 285 prefecture-level-and-above cities in China from 2000 to 2023. We further employed kernel density estimation, standard deviation ellipses, the Dagum Gini coefficient, and convergence models to systematically examine the dynamic evolution, regional disparities, and convergence characteristics pertaining to UGT. The key findings are as follows: (1) There is a steady upward trend in the overall level of UGT in China, with intra-regional differences gradually converging. However, a “better–getting-better” differentiation pattern exists, while there is no observable multi-peak polarization. (2) Based on the UGT level, cities in China can be classified into four types: leading areas, potential areas, catching-up areas, and lagging areas. Spatially, a gradient pattern consisting of “high in coastal areas and low in inland areas” was identified. The overall centroid of green transformation has shifted southward, with a northeast–southwest distribution direction. The spatial agglomeration pattern exhibits a transition from dispersion to concentration. (3) There is a decreasing trend in overall disparity among the eight major economic regions, with inter-regional disparity being the primary source, while intra-regional disparity in coastal areas has increased. (4) Regarding convergence characteristics, σ-convergence can be observed in all economic regions except the Eastern Coastal, Southern Coastal, and Middle Yangtze River economic regions. Both absolute β-convergence and conditional β-convergence were found for China overall and its eight comprehensive economic regions, with the highest convergence speed in the Northeast region and the lowest in the Middle Yangtze River region. Furthermore, spatial absolute β-convergence and conditional β-convergence are also present, indicating strong spatial dependence among cities. This study provides empirical evidence and policy references for promoting UGT and optimizing regional development layouts in China.

Calcium carbide slag is a highly alkaline solid waste generated during acetylene production, but its long-term accumulation causes land occupation and persistent environmental risks such as soil alkalinization and water pollution. To support circular economy and carbon emission reduction goals, in this study, we develop an integrated physical decontamination–mineralization process combining calcination, magnetic separation, sedimentation, and CO2 mineralization. After calcination, magnetic separation, and 8 h of gravity sedimentation, the removal efficiency of Si reaches about 67% (residual Si content reduces to 0.43%), while those of Fe and Al are 75.4% and 74.2%, respectively. The purified calcium-rich slurry is then used for CO2 mineralization. Under a solid-to-liquid ratio of 10% and a CO2 flow rate of 0.4 L/min, CO2 is fixed as carbonate solids, yielding calcite-type CaCO3 with 97.88% ± 0.35% purity. This process is centered on physical separation and uses no acids, alkalis, or ammonium salts, avoiding secondary pollution while achieving waste valorization and permanent CO2 sequestration. In this study, we provide a scalable, low-impact pathway for alkaline solid waste valorization and carbon emission reduction, contributing to sustainable consumption and production (SDG 12) and climate action (SDG 13).