Copper (Cu) and zinc (Zn) are common trace metal contaminants in marine environments that, despite their importance for the health of marine organisms, can be toxic. Recently, the stable isotopes of these elements have emerged as powerful tracers for studying their cycles. Thus, this review aims to connect urban and marine interfaces under a “land-sea continuum” framework to understand the complex sources, pathways, and transformations of Cu and Zn in urbanized coastal environments, a perspective currently lacking in the literature. Here, we briefly establish the sampling and analytical aspects of isotope measurement of these elements in the natural matrices of marine realms, providing a recent compilation of reference materials for analytical control. The principles of isotope fractionation are introduced and contextualized within coastal ecosystems. We summarize the isotopic signatures of major anthropogenic sources—including road-deposited sediments, non-exhaust traffic-related emissions, industrial waste, and metallurgical byproducts—and highlight the challenges of distinguishing them when isotopic ranges overlap. In parallel, natural baselines such as ores, soils, suspended particulate matter (SPM), and riverine inputs are also reviewed to contextualize environmental variability. The review examines how source isotope signatures evolve with further isotope fractionation during estuarine transport and transfer processes in the water-sediment-biota interface. Finally, this review also identifies future research directions to trace the sources, pathways, and sinks of these contaminants along the land-sea continuum, as well as the legacy and ongoing impact of urban metal pollution at catchment-to-coastal scales.

Fishing gears are conventionally made from non-biodegradable materials including polyamide (PA). When lost in the ocean, these gears have long-lasting impacts, including marine littering, microplastics production, leaching of chemicals, and an extended period of ghost fishing due to its durability. The use of biodegradable co-polyester material such as polybutylene succinate co-adipate-co-terephthalate (PBSAT) and polybutylene succinate-co-butylene adipate (PBSA) as fishing gear materials have been considered as a potential solution to reduce the associated impact. Ocean is a complex environment in which multiple degradation paths can occur for plastic materials, and decoupling of factors could aid in understanding the impact of each potential factor. In this study, the focus is on the impact of pure water hydrolysis phenomena on biodegradable co-polyester PBSAT and PBSA in comparison to PA monofilaments through accelerated aging at 40 °C, 60 °C, 70 °C and 80 °C. As a single factor accelerated aging process, the prediction of loss of mechanical strength over time was possible at other temperatures namely 2 °C, 10 °C, 15 °C, 20 °C and 30 °C. Different end-of-life criteria were used. This study concluded that solely through pure hydrolysis, a drastic reduction of the time to reach end-of-life criteria was observed by using biodegradable monofilaments instead of PA, but still longer than the expected service time. For example, at 2 °C, it would take approximately 10 years, 20 years and 1000 years for PBSAT, PBSA and PA to have lost 50 % of their initial stress at break respectively.

From the scientific viewpoint, the deepest ocean includes the least known regions on Earth. Advanced technologies, complex logistics and very specific expertise, requiring adequate funding, are needed for in situ observation of the deep sea. In this paper we present the results of the inspection of the floor of the deepest site in the Mediterranean Sea, the 5122 m in depth Calypso Deep in the Ionian Sea, with the Human Occupied Vehicle (HOV) Limiting Factor by Caladan Oceanic in 2020. The dive videos show the floor of the Calypso Deep littered by anthropogenic debris, with litter concentrations among the highest ever recorded in a deep sea environment. The dominant litter category by material type is plastics, accounting for 88 % of the identified litter items. No interactions have been found between litter and the rare life forms identified so far in the deep Ionian Sea. This illustrates that the deep sea is often a final sink for pollution and as such deserves more attention on associated processes and impacts. Harmonized monitoring and assessment should include the deep sea areas in order to enable efficient mitigation. Our findings provide a strong argument in favour of the urgent implementation at global scale of policy actions to reduce ocean littering thus easing the conservation of unique marine habitats, including the deepest on Earth. Our results also appeal to the society at large in terms of consumption habits, waste reduction, care of the environment and the pressing need for action to protect our ocean.

Coastal ecosystems in Pacific Island Countries and Territories are vital to local livelihoods, yet increasingly face pressures from urbanization. In Fiji, the Greater Suva Urban Area, where one-third of the nation's population live, exemplifies these challenges. This study examines spatial and temporal water quality variations in the coastal zone, focusing on physicochemical, nutrients, and clarity parameters. Using a Seabird Scientific SBE19 CTD and Thermo Scientific Orion™ AQUAfast™ colorimeter, coupled with hierarchical clustering and principal component analysis, six water quality clusters were identified, influenced by oceanic processes, river inputs, and anthropogenic activities. Key findings highlight nutrient enrichment near urban centers particularly at the Kinoya Sewage Treatment Plant outfall, where ammonia exceeded 17.8 mg/L, and significant variation observed in nitrate (up to 0.24 ± 0.06 mg/L) and nitrite (up to 0.24 ± 0.06 mg/L) concentrations near river mouths. Seasonal runoff contributed to elevated turbidity (up to 3.5 NTU) and total suspended solids (up to 14.7 mg/L) levels during wet months. Salinity, and temperature exhibited strong spatial and seasonal variability, reflecting land-ocean interactions and restricted water exchange. These findings emphasize the need for targeted action to mitigate nutrient pollution, urban runoff, and wastewater impacts. This study provides a cost-effective monitoring framework for water quality management, offering insights for sustainable coastal resource management in Fiji and other Pacific regions amidst urbanization and climate change.

Driven by eutrophic conditions, AM (algal mat) proliferation is now ubiquitous in coastal areas generating significant ecological and economic impacts. The need to mitigate negative effects has prompted the exploration of removal methods, but neither the success nor the impacts on intertidal mudflats have been assessed. Limited success using a specially-adapted vessel, prompted a shift to manual removal by hand-rake at two UK (Portsmouth and Poole) and two French study sites (Brittany and Normandy). Significant reductions in AM biomass and percentage cover were only observed at one site (Portsmouth), in contrast to significant temporal effects throughout the 180 days at each site. Significant effects of removal on the benthos and birds were also limited to an increase in organic content at Brittany and a reduction in macrofaunal abundance at Poole but with all sites dominated by temporal effects. To assess if AM removal can be used to ameliorate excess nitrogen (N) we calculated the amount of N that could be removed from a site and its potential cost-effectiveness (price of N credit after subtraction of removal costs) within an NTS (Nutrient Trading Scheme). N export by AM removal is influenced by site and season, for example, 66 kg N ha−1 yr−1 (winter) to 95 kg N ha−1 yr−1 (summer) at Poole. N removal rates from some sites (Poole, all seasons; Brittany, autumn) are comparable to other Nature-Based Solutions (NBSs) such as clam aquaculture. However, a single annual AM harvest at these sites yields lower N removal rates compared to seaweed, mussel, and oyster aquaculture. Using a global mean N credit price, the removals at Poole and Portsmouth have medium/high cost-effectiveness across all seasons, potentially generating up to half a million pounds of N credits, which could be increased if post-harvesting value-chains were maximised e.g. biofuel production. Although, implementation at scale could rapidly reduce the many impacts of AMs and contribute to the blue-green bioeconomy revolution, to improve water quality, AM removal must be framed within a multifaceted management process. Previous article in issue

Rayon fibres are well-known materials that were primarily utilised as reinforcement in tyres. Today these materials are perceived as a promising substitute for synthetic fibres, exhibiting good mechanical characteristics and biodegradation in many environments. This paper investigates their potential use for marine structures. It first describes the tensile properties of the fibres and their derived yarns and ropes. These properties are then monitored during seawater ageing and the ultimate biodegradation is characterised by respirometry tests. Both material scales demonstrate rapid degradation rates under biotic conditions (90 % strength reduction after 2 weeks for yarns and 6 months for small ropes) and a relative stability in abiotic conditions. Additionally, the fibres show rapid bio-assimilation rates. The rope construction is demonstrated to have a significant impact on the degradation kinetics, suggesting possible strategies to enhance durability. The results indicate that these rayon fibre ropes may offer an attractive alternative to synthetic fibre ropes to reduce impact where there is a high risk of rope loss at sea.

Human sewage is the main source of contamination of environmental waters with human enteric viruses, that can contaminate food such as shellfish. Metagenomic represents a new way of analyzing viral diversity through an a priori massive parallel sequencing approach. However, the precise identification of enteric viruses in sewage or shellfish matrices, is still challenging due to the low viral load, large diversity of viral genera and the large amounts of matrix masking viral sequences. This work compared three commercial kits using capture-based enrichment during the library preparation, for the diversity of detected enteric viruses and for the identification of viral strains in sewage and shellfish samples, focusing on four families impacting human health. Triplicate libraries were prepared for each sample and each kit. All three kits allowed the characterization of a variety of viral genera. In sewage samples, a large number of long contigs was obtained allowing a precise identification of more than 35 strains. In shellfish samples, long contigs were rarer but allowed the identification of one human astrovirus and one norovirus strains. Of the tested kits, one displayed lower variation between replicates, allowed to sequence a higher diversity of viruses from the four families of interest and yielded a higher number of nearly-whole genomes.

International audience | Polycyclic aromatic hydrocarbon (PAH) contamination in industrial soils poses significant environmental challenges, necessitating cost-effective bioremediation approaches like tree-based phytoremediation. However, the defence mechanisms and adaptability of trees to PAH exposure remain poorly understood, while the identification of molecular markers could help in the detection of toxicity symptoms. This study explores the molecular response of Populus canadensis to a phenanthrene (PHE) contamination gradient (from 100 to 2000 mg kg−1) using RNA-seq analysis of roots and leaves after 4 weeks of exposure. Both differentially expressed genes (DEGs) and DRomics, a dose–response tool, identified transcriptomic changes, with about 50% of deregulated genes responding significantly at a benchmark dose (i.e. minimal dose that produces a significant effect) below 400 mg PHE kg−1. The highest number of DEGs was found both at a low concentration (200 and 700 mg kg−1) and at the highest concentrations (1500–2000 mg kg−1) for both roots and leaves. Ethylene signalling genes were activated via ABA-independent pathways at low concentrations and ABA-dependent pathways at high concentrations. Across the gradient, responses to oxidative stress were triggered, including reactive oxygen species scavenging and phenylpropanoid biosynthesis, specifically at 1500–2000 mg kg−1. Additionally, PHE disrupted pathways related to plant responses to biotic stress. These findings revealed unexpected dose-dependent transcriptomic shifts, demonstrating poplar’s adaptive defence mechanisms against PHE toxicity.

Increased pharmaceutical usage has led to their widespread presence in aquatic environments, resulting in concerns regarding their potential environmental impacts. Antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs) like citalopram, are frequently detected in European surface waters. Acute laboratory studies have demonstrated that citalopram can inhibit algal growth, immobilise Daphnia magna, and may result in foot detachment (i.e. the inability to adhere to a substrate) in snails. However, research on long-term citalopram exposure is scarce, and our understanding of its effects on aquatic community- and ecosystem-level is limited. Therefore, we investigated the impact of 13-week exposure to 0.01, 0.1, 1, 10 and 100 μg/L citalopram in outdoor freshwater mesocosms, focusing on water quality variables (i.e. pH, dissolved oxygen, electrical conductivity, temperature, algal chlorophyll-a, turbidity) and the structure of aquatic communities, with a special focus on mollusc foot detachment (Lymnaea stagnalis, Planorbis sp. and the total snail population). We found that environmentally relevant citalopram concentrations did not affect water quality variables, bacterial composition, zooplankton and macroinvertebrate communities. In contrast to expectations based on literature, snail foot detachment was not observed while the tested concentrations overlapped with the reported effect concentrations. This is in line with the absence of indirect adverse effects of foot detachment, such as population changes that could be the result of an increased vulnerability to predation or the inability to feed or reproduce. Reported sublethal effects in the literature, as found in laboratory studies, do not appear to lead to population- or community-level impacts in a semi-field experiment within the concentration range tested in this study. The experimental outcomes suggest that environmentally relevant concentrations of citalopram might not pose a threat to water quality variables, bacterial composition, zooplankton and macroinvertebrate communities, and snail foot detachment.

The co-occurrence of pesticides, pharmaceuticals, and MPs has resulted in combined toxicity and high risks to ecosystems and human health. However, understanding on the interactions among co-occurring pollutants in soils remains limited. This study focused on adsorption behaviour of a pesticide mixture (chlorpyrifos (CPF), pendimethalin (PDM) and pyraclostrobin (PCS)) in three soils (sandy soil (S1), loamy soil (S2), and silt soil (S3)) to examine the absorption behaviour of pesticides in the presence of the pharmaceutical compound albendazole (ALB) and starch-based microplastics (MPs). The results showed that ALB significantly decreased (p < 0.05) the adsorption of CPF, PDM, and PCS by 29 %–41 % in S1. The adsorption of CPF (+20 %) and PCS (+101 %) in S2 were significantly enhanced but PDM (−22 %) adsorption was inhibited by ALB. ALB also significantly (p < 0.05) promoted CPF and PCS adsorption in S3 by 39 % and 120 %, respectively, but did not change PDM adsorption. In soil-MP matrices, ALB significantly reduced the adsorption of CPF (−25 %), PDM (−26 %), and PCS (−21 %) in the S1-MP matrix, but no significant change in the S2 and S3-MP matrices was observed. Moreover, MPs significantly (p < 0.05) increased the adsorption of the pesticide mixture by 120–730 %, but reduced ALB adsorption by 11–24 % in soils. Further, regardless of ALB presence, correlation analysis suggested that Kd of pesticides showed positive correlations (p < 0.01) to soil organic matter, specific surface area, and clay content in soil matrices without MP-contamination, while no significant positive correlation between Kd of pesticides and soil properties was observed in soil-MPs matrices. This study indicates that co-occurring pollutants could alter the adsorption behaviour of pesticides in soil and thereby affect their bioavailability and mobility in the soil ecosystem. Further study is urgently needed to assess the ecotoxicity of co-occurring multi-contaminants, as well as their potential transport to other environmental compartments.