This study investigated how two COVID-19 drugs, azithromycin (AZM) and hydroxychloroquine (HCQ), affect marine meiobenthic communities. We conducted 30-day microcosm experiments to assess the effects of these pharmaceuticals on coastal sediment communities. Treatments included controls, low and high doses of each drug (31.62 and 63.24 μg L−1), and combinations of both compounds.Both amphipods and copepods showed concentration-dependent changes in community structure. Amphipod abundance declined under pharmaceutical exposure, while the dominant control species, Paraniphargus valesi, was eliminated from HCQ2 and AZM1/HCQ2 and strongly reduced in most other treatments. Tolerant species such as Microdeutopus versiculatus increased under stress. Amphipod species richness declined in all treatments except AZM1, whereas Shannon-Wiener diversity (H′) decreased only in HCQ2, AZM1/HCQ1 and AZM2/HCQ2; both indices correlated negatively with HCQ but not with AZM concentration. ANOSIM and SIMPER confirmed community differences between treated and control groups, ranging from 19.8% to 54.7% (amphipods) and 32.3% to 45.1% (copepods), with R-statistics approaching 1. SIMPER identified the loss of P. valesi and Stenothoe monoculoides as major contributors to community restructuring.Copepod assemblages showed similar responses, including altered abundance patterns and reduced species richness. In copepods, cluster analysis and nMDS clearly separated pharmaceutical-treated samples from controls, whereas in amphipods only HCQ2 and the mixtures separated clearly.Overall, these findings demonstrate that COVID-19 pharmaceuticals can act as potent marine stressors at concentrations representing elevated-exposure scenarios for contaminated coastal waters, with combined exposures producing community-level effects that, in terms of dissimilarity, partly exceeded those of single-drug treatments.
Ocean alkalinity enhancement (OAE) is a marine carbon dioxide removal (mCDR) strategy that increases seawater alkalinity and promotes atmospheric CO2 uptake. However, the stability of stored carbon remains uncertain, particularly when carbonate saturation favors secondary calcium carbonate precipitation. In this study, we evaluate how regional seawater chemistry controls aragonite saturation state (ΩAr) under pH-equilibrated OAE conditions, in which seawater is enriched in dissolved inorganic carbon (DIC) while pH remains close to the natural seawater value. Near-surface seawater conditions were selected from ocean regions using GLODAPv2.2023 data, and ΩAr was calculated for baseline conditions and scenarios of +500, +1000, and +2000 μmol kg−1 added DIC. The data show that the carbonate chemistry is not uniform among regions. Thus, although the same DIC additions were adopted in all regions, the post-treatment ΩAr differed because of the non-uniform initial seawater chemistry. High temperature, high salinity, and high pH regions feature higher aragonite supersaturation and move toward the ΩAr = 7 threshold more easily, whereas colder or lower salinity regions remain far from this level. After a DIC addition of 1000 μmol kg−1, most regional median ΩAr values remain below ΩAr = 7. In contrast, after a DIC addition of 2000 μmol kg−1, several sites fall into dangerously higher supersaturation conditions. These findings indicate that carbonate supersaturation and secondary precipitation risk depend strongly on the receiving seawater chemistry. Therefore, OAE should not be evaluated using a universal alkalinity dosage. An assessment of the region-specific carbonate chemistry is necessary before selecting the treatments and deployment sites.
Global shipping underpins international trade and constitutes a major source of greenhouse gas (GHG) emissions. As route security risks, trade frictions, and supply chain restructuring intensify, geopolitical disruptions are reshaping shipping activity and its emissions patterns. Based on high-frequency global Automatic Identification System (AIS) data for 2024, this study constructs a GHG emission inventory for global merchant vessels, and analyzes its spatial distribution, vessel-type emission composition, operational modes, and geopolitical variations. The results show that global merchant ships emitted 937.910 million tonnes of CO2e in 2024, exhibiting pronounced spatial clustering, with the North Atlantic, Mediterranean-Suez, Malacca Strait-South China Sea, and Trans-Pacific corridors forming the principal emission corridors. Container ships, oil tankers, and bulk carriers together accounted for 72.73% of total emissions; at sea operations accounted for 75.3%, berthing-mode emissions for 19.0%, and main-engine emissions for 70.2%. Geopolitical disruptions were associated with substantial and persistent spatial redistribution of shipping emissions in 2024. Emissions along the Red Sea and Suez routes sharply declined from January to March, while emissions along the Cape of Good Hope route increased. This opposing spatial pattern is consistent with route redistribution during the Red Sea crisis. Changes in emissions along the China-U.S. and China-Vietnam routes coincided with the escalation of U.S.-China trade tensions and reflect changes in regional trade and transshipment patterns. These findings highlight how geopolitical conditions can affect shipping decarbonization pathways and underscore the need to incorporate geopolitical risk resilience into emission reduction policies for achieving the IMO net-zero target.
The planet is currently facing a triple crisis driven by climate change, biodiversity loss, and pollution. While the effects of environmental contaminants on reproduction, neurological function, and immune processes are well established in model species, far less is known about their impacts on marine sentinels such as cetaceans. Although contaminant burdens can be quantified, there is a lack of validated biomarkers that reliably capture molecular and cellular effects, limiting robust impact assessment and conservation strategies. Cetaceans exhibit unique physiological and metabolic adaptations, including specialised lipid dynamics and life-history traits, complicating direct extrapolation from model organisms. Here, we review current knowledge of biomarkers associated with three major contaminant classes: persistent organic pollutants (POPs), heavy metals, and microplastics. Candidate biomarkers such as cytochrome P4501A1, acetylcholinesterase, and metallothioneins are well characterised in experimental systems but show inconsistent responses in cetaceans, influenced by ecological, physiological, and methodological factors. Emerging evidence indicates that microplastics may drive gut inflammation, microbiome disruption, and systemic stress responses, although validated biomarkers remain scarce. Overall, we highlight the limitations of single-marker approaches and the need for integrative frameworks capturing complex, multi-stressor responses across biological scales. Future efforts should prioritise robust, early-warning biomarkers that account for species-specific physiology, trophic ecology, and cumulative exposure. Progress will require cross-disciplinary collaboration, integration of multi-omics tools, and improved standardisation of methods. Strengthening biomarker frameworks in cetaceans is essential for advancing marine conservation and understanding shared risks to ocean and human health.
This study investigates the distribution, fractionation, sources, and ecological risks of potentially toxic elements (PTEs) in coastal sediments from Yanbu, an industrial region along the Red Sea. Surface sediments from 10 sites were analyzed for Fe, Mn, Zn, Cu, Pb, Ni, Co, and Cd using sequential extraction, pollution indices, multivariate statistics, and positive matrix factorization (PMF). Mean total concentrations (mg/kg) followed the order Fe (5313.60) > Mn (268.60) > Zn (101.93) > Cu (31.87) > Ni (22.38) > Co (6.32) > Pb (5.36) > Cd (0.28), suggesting substantial lithogenic contributions. Although residual fractions exceeded 50% for all elements, Cd, Cu, Mn, and Zn exhibited appreciable labile fractions, indicating potential mobility and bioavailability. Mean risk assessment code (RAC) values indicated medium risk for Cu (24.24%), Mn (21.51%), Cd (20.86%), Zn (19.69%), Pb (18.09%), Co (17.31%), and Ni (16.70%), whereas Fe presented low risk (8.78%). The conventional ecological risk index (RI = 37.9) indicated low regional risk, contrasting with the speciation-based index (AIT = 0.57), which suggested elevated risk associated with metal bioavailability. Spatial assessment identified localized pollution hotspots at stations 5–6 (NPI > 7). PMF attributed 68% of the metal load to direct anthropogenic sources, increasing to 82% when mixed sources were included. These findings highlight the importance of integrating total concentrations, chemical fractionation, ecological indices, and source apportionment to distinguish regional contamination levels from localized bioavailability concerns. This study provides a baseline for environmental monitoring and sustainable management of industrially influenced coastal sediments along the Red Sea.
