Marine plastic debris (MPDs) provide artificial substrates for microalgal attachment, but how water-column phytoplankton and plastic-associated periphyton respond to environmental conditions associated with freshwater-seawater mixing remains poorly understood. We conducted a 30-day mesocosm experiment by mixing freshwater (salinity 0) and seawater (salinity 35) to establish three treatments: estuarine salinity (ES; ∼15), brackish coastal salinity (BCS; ∼30), and coastal salinity (CS; ∼35). Polypropylene attachment plates were used to examine periphyton development. In the water column, ES showed a late Chl. a maximum on day 20, BCS peaked earlier on day 10, and CS maintained low biomass with relatively stable Fv/Fm until day 20. The ES bloom did not persist despite high nitrate+nitrite concentrations, indicating possible constraints from low phosphate availability, nutrient imbalance, and low-salinity stress. On the plastic plates, Chl. a accumulated most rapidly in CS, with significantly different accumulation rates among treatments (ANOVA, F = 403.06, p < 0.001); CS showed a much higher rate (6.16 ± 0.02 μg cm-2 day-1) than ES (1.42 ± 0.23 μg cm-2 day-1) and BCS (1.24 ± 0.25 μg cm-2 day-1). Periphyton communities were dominated by diatoms, especially Navicula sp., which accounted for more than 94% of the CS periphyton community during the late phase. These results indicate that water-column phytoplankton and plastic-associated periphyton responded differently to salinity-associated environmental conditions. Overall, our findings highlight the capacity of MPDs to support distinct microalgal communities under contrasting estuarine-coastal conditions.
Seasonal oxygen depletion in stratified coastal bays drives shifts in dissolved organic matter (DOM) composition and microbial community structure, yet how DOM composition and microbial assemblages co-reorganize during the subsequent recovery phase remains poorly understood. We examined bottom-water DOM and prokaryotic assemblages across four cruises (August-October 2019) in a seasonally low-oxygen bay of the North Yellow Sea, where stratification breakdown generated a pronounced dissolved oxygen (DO) recovery gradient (2.5-7.2 mg L-1). Integrating bulk and fluorescent DOM characterization, FT-ICR MS molecular profiling, and 16S rRNA sequencing of free-living (FL) and particle-attached (PA) fractions, we show that DOM reorganization along this gradient was selective rather than uniform. DOC concentrations and a blue-shifted marine humic-like component increased with rising DO, while SUVA254 and red-shifted humic-like components declined. FT-ICR MS identified 1919 redox-sensitive formulae (RSFs) partitioned into DO-negative (sulfur-enriched) and DO-positive (CHON-enriched) pools, indicating systematic molecular-level compositional shifts during reoxygenation. Prokaryotic community composition co-varied significantly with DO independently of temperature and differed markedly between FL and PA lifestyles, although the magnitude of compositional turnover along the gradient was comparable in the two fractions (DO × lifestyle interaction, p = 0.575). Bipartite co-occurrence networks nevertheless revealed that FL communities maintained significantly denser associations with RSFs than PA communities. Together, these findings indicate that the seasonal oxygen-recovery transition acts as a selective geochemical filter, restructuring both DOM molecular composition and DOM-microbe associations in a lifestyle-dependent manner in organically enriched coastal systems.
Pharmaceuticals and personal care products (PPCPs) have emerged as contaminants of increasing environmental concern due to their continuous release, widespread occurrence, and persistence in aquatic ecosystems. Although numerous studies have investigated their occurrence, transformation, and removal, a comprehensive synthesis linking their environmental fate, associated risks, and remediation strategies remains limited. This review addresses this knowledge gap by integrating current understanding of PPCP sources, transport pathways, transformation processes, ecological and human health impacts, and emerging treatment technologies. PPCPs enter surface water, groundwater, and drinking water primarily through domestic, hospital, and industrial effluents, while the limited removal efficiency of conventional wastewater treatment plants facilitates their environmental persistence. Following their release, PPCPs undergo sorption, photodegradation, and microbial transformation, producing metabolites that may exhibit equal or greater toxicity than their parent compounds. Their occurrence has been associated with endocrine disruption, antimicrobial resistance, and chronic toxicity in aquatic organisms, highlighting the need for effective mitigation strategies. Current remediation approaches, including advanced oxidation processes, membrane filtration, adsorption, and biological treatments, offer significant potential but remain constrained by cost, scalability, and operational limitations. Overall, this review concludes that sustainable management of PPCPs requires an integrated framework combining advanced treatment technologies, comprehensive environmental monitoring, standardized risk assessment, and strengthened regulatory policies to minimize their long-term impacts on aquatic ecosystems and human health.
Plastic pollution has become a significant concern for marine environments with adverse effects on critical ecosystems such as coral reefs. Marine plastic litter items transform into new variants after prolonged exposure to the environment and interactions with organic and inorganic materials. While earlier documented variants such as plastiglomerates and plasticrusts are chiefly formed between plastic and abiogenic substrates, this study introduces plasticorals, a new form of plastic litter variant formed from plastic materials thermally adhered to or agglutinated to coral rubble. Plasticorals were incidentally observed on three beaches in Okinawa Island, Japan, during routine marine litter surveys. The plastic components of these plastic-coral agglutinate samples, examined with Raman spectroscopy showed spectral consistencies with polyethylene and polypropylene. The infiltration of skeletal pores and plastic coral interface were visualized using micro-CT scanning and microscopy. This new plastic variant provides fresh perspectives on the persistence of plastic litter in coral reef environments and highlights the potential for plasticorals to serve as future stratigraphic markers within the contemporary sedimentary record of tropical reef systems. We recommend further studies to better understand formation processes, distribution, and potential ecotoxicological impacts of plasticorals on coral reef environments.
Shipping noise is a pervasive form of underwater noise pollution, yet its effects on benthic invertebrates remain poorly integrated into spatial risk assessments. The Atlantic sea scallop (Placopecten magellanicus), a benthic bivalve supporting the world's largest wild pectinid fishery, detects low-frequency sound (100-500 Hz), overlapping the dominant range of shipping noise. Previous experiments documented life-stage-dependent valve-closure responses, with juveniles showing higher response probabilities than young adults, particularly at 100-150 Hz. We combined commercially exploited scallop-bed distributions, life-cycle information, experimentally derived acoustic dose-response relationships, and probabilistic shipping-noise models to assess the probability that shipping noise may elicit valve closure across scallop habitats in the Gulf of St. Lawrence. Particle-acceleration dose-response relationships were converted into pressure-level response functions compatible with the modeled mean-square sound pressure spectral density level, Lp,f. Their integration generated seasonal response-probability maps at 125 Hz, the modeled frequency located between the experimental frequencies of strongest response. Response probability showed strong spatial and seasonal variability. The highest probabilities occurred near major shipping routes during winter and early spring. Juveniles showed higher response probabilities and broader affected areas than young adults, reaching >30% in some beds during winter months. Several peripheral beds displayed consistently low response probabilities and may function as acoustic refuges. Because these peaks coincide with periods of elevated energetic demand, shipping noise warrants consideration in cumulative-stressor assessments and marine spatial planning. To our knowledge, this is the first spatial mapping of shipping-noise-induced behavioral-response probability for a marine invertebrate. Maps are available through the Ocean Soundscape Atlas.
Phytoplankton play central roles in marine food webs and carbon cycling, yet their responses to recurrent low-level inputs of refined oils remain poorly understood. We used a 16-day mesocosm experiment to assess the response of a natural cold-temperate/subarctic phytoplankton assemblage from the Lower St. Lawrence Estuary to repeated maritime diesel exposure. Triplicate control mesocosms were compared with triplicate diesel-amended mesocosms receiving two additions during the pre-bloom and bloom phases, equivalent to a nominal final concentration of 5.6 mg L-1 and a simulated slick thickness of approximately 13 μm. Phytoplankton biomass, cell density, size structure, taxonomic composition, and pigments were monitored using flow cytometry, image analysis, microscopy, and HPLC. Diesel exposure did not inhibit initial exponential growth but was associated with a delayed post-bloom decline in phytoplankton biomass and cell density after Day 11, strongest in the microeukaryotic fraction and bloom-forming diatoms. Grazing dilution experiments and nutrient-amended assays indicated that biomass loss was unlikely to be primarily driven by microzooplankton grazing or nutrient limitation, while viral particle density patterns showed no clear treatment-related response. Instead, the decline was consistent with diesel-associated inhibition of phytoplankton growth and biomass accumulation, potentially amplified under late-successional conditions. Although the transition toward smaller phytoplankton groups was consistent with natural post-bloom succession, it was more pronounced under diesel exposure and accompanied by stronger losses of diatom-associated biomass and pigments. These findings suggest that recurrent low-level diesel inputs can alter phytoplankton succession, reduce diatom-associated carbon biomass, and potentially modify carbon-transfer pathways in cold coastal ecosystems.
Coastal plastic pollution is routinely quantified using abundance- and mass-based metrics. These metrics are effective for trend detection, regulatory reporting and international comparison, but by design they describe the magnitude of contamination rather than its internal organisation, its commercial attribution, or the functional behaviour of the items involved. Here we operationalise and internally validate the Taxonomy-Inspired Plastic Litter Indices (TIPLI), a modular set of diagnostic metrics intended to complement conventional monitoring. Twenty-seven indices spanning structural diversity, corporate attribution, functional traits, geo-environmental dynamics, hazard weighting and network organisation were computed for harmonised, item-level coastal litter datasets from six sites in Colombia, Morocco, Brazil, Italy, Panama and Spain (Canary Islands). Richness-based indices were strongly effort-dependent (Spearman rho with sample size 0.89-0.94) and estimated sample coverage was low at product level (0.005-0.698), so raw richness contrasts are not directly comparable among sites. The first ordination axis derived from the full index set was itself correlated with assemblage size (rho = -0.94, p = 0.005). After rarefaction to common effort, product richness converged to 19.2-22.0 products per 22 items, whereas abundance-weighted diversity retained a two-group separation. In contrast, corporate concentration, functional-trait, hazard and geo-environmental indices were insensitive to effort and were estimated without bias by non-parametric bootstrapping (coefficients of variation 1.1-32.4%). The descriptive configurations reported here are therefore presented as exploratory hypotheses rather than validated classes.
Nano‑copper oxide (CuO NPs), as a highly promising antibacterial agent in aquaculture, has demonstrated excellent performance against pathogens affecting cultured organisms. However, its application is accompanied by potential toxicity risks to both the cultured organisms and the entire aquatic ecosystem. In this study, CuO NPs was synthesised using a sodium hypophosphite liquid-phase reduction method, and then a toxicity experiment was conducted using 50 μg/L CuO NPs in M. galloprovincialis. Multiple endpoints at Cu distribution, enzyme activity, lipid peroxidation degree, immune-related gene expression, tissue pathology, and metabolic response were assessed in response to CuO NPs exposure. The multi-biomarker approach revealed that CuO NPs toxicity in M. galloprovincialis operated through a coordinated network of effects: tissue-specific Cu accumulation drives histopathological damage, oxidative stress, immune disruption and ultimately systemic metabolic reprogramming. At the metabolomic level, CuO NPs exposure induced a two-system metabolic shift in M. galloprovincialis, featuring lipid upregulation and amino acid downregulation, and six metabolites (three oxylipins up, three amino acids down) that highlighted their potential as sensitive biomarkers for nanomaterial contamination. These molecular-level alterations eventually led to pathological changes in the hepatopancreas and gills. The study could provide a theoretical basis for the toxicity assessment of nanomaterials in bivalves and offer effective support for environmental risk assessments.
Halophila beccarii is one of the 10 seagrass species at risk of extinction worldwide and is listed as Vulnerable (VU) by the IUCN. To expand the baseline data on H. beccarii seagrass beds and identify the primary factors influencing their spatial distribution, this study investigated the growth and environmental characteristics of H. beccarii seagrass beds in Huachang Bay in 2025. Factor analysis and Spearman correlation analysis were adopted to explore the relationships between seagrass traits and environmental variables. The results showed that the coverage, density and biomass of H. beccarii all exhibited a declining trend. Spatially, seagrass beds near the lagoon inlet and mid-lagoon zones maintained relatively stable ecological status, whereas inner lagoon habitats suffered obvious degradation driven by intensive mariculture. Data analysis revealed that the coverage, density and biomass of H. beccarii were significantly negatively correlated with salinity, indicating that salinity acts as the primary driving factor for the degradation of H. beccarii in this region. Additionally, eutrophication and heavy metal pollution resulting from the discharge of aquaculture wastewater from shrimp ponds around Huachang Bay may also have potential negative impacts on H. beccarii. Given that the H. beccarii seagrass beds in this area have undergone a certain degree of degradation, it is recommended that Huachang Bay Nature Reserve treat seagrasses as equally key protected targets in future management and strengthen relevant conservation and management measures.
This study presents a national-scale spatiotemporal assessment of documented oil spill events in Brazilian coastal waters and the Exclusive Economic Zone between 1980 and 2022, based on the OILSPILL-BR database, a standardized online platform developed to improve public access to historical oil spill records in Brazil. A total of 234 events greater than approximately 1 t were compiled, harmonized, classified, and analyzed according to spatial distribution, temporal evolution, spill size, source, cause, oil type, and affected ecosystem. The documented incidents, corresponding to approximately 28,080 t of oil released. The Southeast region, particularly São Paulo, concentrated most records and released volume, reflecting the overlap between offshore production, port infrastructure, petroleum logistics, maritime transport, and institutional monitoring. Hotspot analysis identified recurrent spill areas associated with major oil-handling and port zones, especially São Sebastião and Santos. Temporal results showed a decline in medium and large spills, consistent with regulatory, operational, and international pollution-prevention advances, while small spills increased after the 2000s, likely reflecting offshore expansion and improved reporting. Ships were the main source of incidents and released volume, pipelines were associated with high-volume events, and offshore platforms with recurrent small spills. The study highlights the need for unified, continuously updated national databases and demonstrates how OILSPILL-BR can support environmental management, emergency planning, risk assessment and broader decision support.
Phycotoxins produced by harmful microalgae pose increasing threats to coastal ecosystems, yet their occurrence patterns and environmental drivers remain poorly understood in semi-enclosed bays. In this study, a year-round survey was conducted in Qinzhou Bay, South China Sea from November 2021 to November 2022 to investigate the prevalence, phytoplankton sources, and environmental drivers of phycotoxins. Multiple toxin groups, including paralytic shellfish toxins (PSTs), lipophilic marine algal toxins (LMATs), and amnesic shellfish toxins (ASTs), were detected throughout the investigation, with gonyautoxins (GTX) analogues, pectenotoxin-2 (PTX2), homo-yessotoxin (hYTX), and domoic acid (DA) as dominant components. Toxin occurrence exhibited pronounced seasonality, with elevated diversity and concentrations in early summer (May-June), while offshore waters represented a relative accumulation region of phycotoxins. Integrated morphological and molecular analyses identified Alexandrium spp. as key PST producers, Pseudo-nitzschia spp. as dominant DA producers, while Dinophysis and Protoceratium reticulatum, Gonyaulax spinifera, and Lingulodinium polyedra were identified as potential sources of LMATs. Environmental analyses revealed contrasting ecological controls among toxin groups: PSTs and LMATs were strongly associated with warm, saline summer conditions and dinoflagellate proliferation, whereas DA displayed distinct environmental relationships linked to diatom dynamics. It's suggested that seasonal phytoplankton succession and environmental variability jointly regulate phycotoxin occurrence. These findings reveal clear seasonal windows and accumulation regions of phycotoxins in Qinzhou Bay. The results provide a scientific basis for harmful algal blooms monitoring, early-warning systems, and risk management in aquaculture-dominated coastal ecosystems of the Beibu Gulf.
Dredging activities can alter seabed morphology and benthic communities, with long-lasting ecological consequences. This study investigates the long-term morphosedimentary and biological evolution of the CNEXO dredging pit, located in the eastern Bay of Seine (English Channel, France), more than four decades after extraction ceased. A multidisciplinary approach combining bathymetric data (1981, 2002, 2025), sediment analyses and benthic community surveys (1995, 2010, 2025) was applied to evaluate physical infilling processes and ecological recovery. Bathymetric data indicates that the pit remains partially infilled in 2025, despite substantial sediment accumulation since 1981, particularly between 2002 and 2025. Pit sediments remain heterogeneous, comprising sand, mud, and gravel derived from slope erosion and post-extraction deposition. This heterogeneity, coupled with bathymetric gradients, exerts a strong structuring effect on benthic assemblages, with redundancy analysis (RDA) showing that sediment composition and depth explain approximately 32% of community variability. Biotic indices (taxonomic richness, abundance, Shannon diversity and Pielou's evenness) revealed higher diversity and abundance within the pit than at peripheral stations. Non-metric multidimensional scaling (nMDS) highlights clear spatial and temporal gradients, reflecting a gradual convergence of pit and peripheral communities over time, consistent with the ongoing siltation of the eastern Bay of Seine. Overall, the CNEXO pit remains morphologically and ecologically distinct from surrounding habitats, a pattern supported by the Ecological Quality Status indices (MUMARINEX, GPBI, M-AMBI, and EQA), underscoring the long-term legacy of intensive, fixed-point dredging. These findings reinforce ICES recommendations advocating extensive or semi-extensive extraction practices to facilitate faster physical and biological recovery of impacted marine ecosystems.
By combining satellite technology with ecological risk analysis, this study establishes a scalable global framework for tracking the environmental effects of chronic oil slicks. We used Sentinel-1 SAR from SkyTruth's Cerulean platform to detect surface slicks potentially attributable to over 24,000 fixed oil infrastructure and 326 FxO operating locations. We validated >2000 detections through expert review. This approach generates a replicable global database of offshore oil pollution sources, exemplifying a systematic method for identifying chronic polluters.We ranked offshore oil sources globally and within European and Mediterranean EEZs based on the percentage of satellite captures that contain attributed oil slicks. We overlaid validated slick locations with marine ecoregions, protected areas, and species occurrence data from the Map of Life. For nine identified chronically polluted regions—five global and four European/Mediterranean—we extracted species assemblages across concentric 50 km buffers. Chronic oil slicking correlated with consistent differences in assemblage composition and threatened species indicators. Species richness remains relatively stable across distance classes, but species composition shifts significantly. In European/Mediterranean waters, slick proximity explained >40% of the variation in community structure, surpassing the influence of fishing intensity or coastal proximity. Globally, polygons closer to chronic slick sites contain higher threatened-species representation in the Map of Life species lists. Beta diversity partitioning suggested that turnover dominated compositional differences among slick-proximate versus farther polygons, which supports compositional differences not explained by richness alone. These results pinpoint pollution hotspots with elevated ecological vulnerability, offering a pathway to align environmental monitoring with spatial conservation priorities.
This study investigated changes in nutrient sources and microbial community composition across a typhoon-associated runoff period in Lake Sihwa, an anthropogenically influenced artificial coastal lake. Stable isotope analyses (δ13CPOC, δ15NPN, δ15NNO₃, and δ18ONO₃) and water-column environmental DNA (eDNA) metabarcoding were combined to characterize nutrient sources and compare ecological conditions between the pre- and post-typhoon surveys. Before the typhoon-associated rainfall period, nitrate inputs were primarily associated with urban runoff, whereas particulate organic matter (POM) reflected a substantial autochthonous plankton contribution. In the post-typhoon survey, nitrate-source contributions were dominated by industrial (39 ± 23%) and wetland (39 ± 6%) catchments. POM isotopic signatures (δ13CPOC, -22.6 ± 3.3 ‰; δ15NPN, 8.0 ± 1.9 ‰) indicated an increased influence of marine-plankton-like organic matter in the lake. eDNA metabarcoding revealed a pronounced taxonomic reorganization, with community composition shifting from heterotrophic groups (e.g., Cercozoa and Bacteroidota) toward phototrophic and nutrient-responsive taxa (e.g., Ciliophora and Proteobacteria), while several nitrogen-cycle-associated groups within Actinobacteriota, Nitrospirota, Verrucomicrobiota, and Proteobacteria showed lower relative representation. The spatial correspondence between these community shifts and land-use, salinity, and nutrient gradients suggests that runoff-related nutrient redistribution and freshwater-seawater mixing were important factors associated with the observed ecological changes. These findings demonstrate the value of integrating stable isotope tracing and eDNA metabarcoding as complementary approaches for evaluating nutrient-source redistribution and ecological reorganization across episodic storm-associated runoff periods in artificial coastal ecosystems.
Bisphenol A (BPA) is a widely distributed endocrine-disrupting chemical in aquatic environments, yet its long-term toxicological effects in marine fish remain insufficiently understood. In the present study, marine medaka (Oryzias melastigma) were chronically exposed to BPA from the embryonic stage to sexual maturity for 140 days, and multiple endpoints were integrated to evaluate developmental performance, adult behavior and growth, histopathological alterations, oxidative stress responses, gene-expression responses, and intestinal microbiota changes. The measured BPA concentrations were 40.4 and 161.9 μg/L. Chronic BPA exposure significantly reduced embryonic heart rate and hatching success at 161.9 μg/L. In adults, BPA exposure was associated with altered spontaneous locomotor activity, and body mass was significantly increased in males at the high concentration. Histopathological analyses revealed hepatocellular vacuolization and lipid accumulation, ovarian follicular atresia, testicular structural disorganization, and intestinal villus damage. In addition, BPA exposure weakened antioxidant defense capacity in a tissue- and sex-dependent manner, as reflected by significant reductions in selected SOD and GSH-Px endpoints. Gene expression analyses further showed treatment-associated changes in genes related to neural regulation, the hypothalamic-pituitary-gonadal (HPG) axis, hepatic estrogen responsiveness, and intestinal immune and oxidative stress regulation. Moreover, chronic BPA exposure altered intestinal microbial community structure, with females showing more pronounced dysbiosis than males. Overall, these findings characterize the chronic multi-organ hazards of BPA in marine medaka under elevated contamination scenarios.
Microplastics (MPs) have become ubiquitous contaminants in marine ecosystems; however, their interactions with tropical macroalgae remain insufficiently understood. In this study, the abundance, size distribution, and polymer composition of MPs in seawater and on the surface of the cultivated macroalga Betaphycus gelatinus and wild Sargassum polycystum were investigated in Qizi Bay, Hainan, China. The mean MP abundance in seawater was 3.5 ± 0.69 items·L-1, with fibers being the dominant morphology and polyethylene (PE), polyamide (PA), and polypropylene (PP) identified as the major polymer types. Both macroalgal species exhibited relative MP enrichment potential, with Rm/Rs values of 184 and 244 for B. gelatinus and S. polycystum, respectively, indicating their capacity to retain MPs compared with surrounding seawater. Decontamination experiments further showed that combined dehydration-washing treatment significantly improved the removal of surface-associated MPs, achieving a maximum desorption efficiency of 92.21%. Orthogonal analysis indicated that washing time exhibited the strongest main effect among the tested parameters, with optimal desorption achieved under 8 h washing time, 40 mL washing volume, and 50 rpm shaking speed. Overall, cultivated B. gelatinus functions as a biological retention surface for MPs and provides opportunities for reducing the MP burden associated with harvested seaweed biomass through optimized processing strategies.
Microplastic exposure in fish has been increasingly assessed at the transcriptional level, yet findings remain dispersed across species, polymers, exposure routes, and tissues, limiting the identification of robust and transferable biomarkers. This scoping review examines which tissue-specific and cross-tissue transcriptional responses recur across available evidence and how they may support multi-gene biomarker development. Relevant experimental fish studies were identified through a structured PubMed search combining microplastic-, fish-, and transcription-related terms, followed by backward reference screening and forward citation chasing. Published studies reporting gene expression and transcriptomic outcomes in microplastic-exposed fish were synthesized with emphasis on tissues that both interface directly with the environment and show particle retention, including gills, gastrointestinal tract, skin, epidermal mucus, and related barrier compartments. The reviewed evidence indicates recurring transcriptional changes in epithelial integrity and junctional architecture, innate and adaptive immune signaling, redox balance and xenobiotic metabolism, ion transport and osmoregulatory control, and endocrine and metabolic regulation. However, the direction and magnitude of these responses vary with particle size, polymer chemistry, morphology, additives, co-contaminants, dose metrics, exposure route, and duration. Because single-gene readouts frequently overlap with responses to diverse stressors, tissue-aware, network-derived multi-gene signatures are proposed as a more specific approach to exposure diagnosis. Their feasibility is supported by the growing availability of RNA-seq datasets and established toxicogenomic workflows for module detection and classifier development. Opportunities for nonlethal biomonitoring include transcriptional signals from epidermal mucus and, prospectively, environmental RNA in surrounding water, although field application will require validation of RNA stability, shedding variability, and sampling procedures.
Nitrous oxide (N₂O) is a potent and ozone-depleting greenhouse gas, for which the contribution of marine macroalgae to coastal N₂O dynamics remains poorly understood. Here, we investigated N₂O emissions from incubations with the bloom-forming green macroalga Ulva lactuca under simulated warming and eutrophication scenarios. Specimens were exposed to three temperatures (24, 27, and 30 °C) and three nutrient conditions representing no nutrient enrichment, natural eutrophication, and anthropogenic eutrophication (0, 10, and 50% von Stosch's Enrichment Solution [VSES], respectively) in a fully crossed laboratory experiment. Gas samples were collected over 2-h static incubations and analyzed by gas chromatography to determine biomass-normalized N₂O fluxes. N₂O emissions were significantly affected by temperature, nutrient levels, and their interaction. The highest flux was recorded at 30 °C under 10% VSES, reaching 673.41 ± 46.07 ng N₂O-N g-1 h-1. N₂O concentrations (ppb) were positively and significantly correlated with macroalgal nitrate uptake rates. Although N₂O emissions increased under some enriched conditions, greater nutrient availability did not consistently result in higher emissions. These findings provide experimental evidence that U. lactuca may contribute to coastal N₂O dynamics under environmental conditions relevant to Ulva blooms. However, the magnitude of this contribution under natural bloom conditions remains to be quantified. The contribution of surface-associated microorganisms to the measured N₂O fluxes was not independently quantified. Given the increasing frequency of coastal macroalgal blooms worldwide, these findings highlight the potential relevance of Ulva-associated N₂O emissions to coastal nitrogen cycling and greenhouse gas dynamics.
The distribution of anthropogenic microparticles (AMPs) in reef sediments across different depths and along gradients of estuarine and urban influence remains poorly documented. This study provides baseline information on AMPs in sediments from intertidal (0-2 m), shallow (17-19 m), and mesophotic (30 m) reefs in the Southwestern Atlantic. Concentrations ranged from 73.27 to 1246.45 particles kg-1 dry weight, with the highest values recorded in intertidal reefs located closest to estuarine inputs. A total of 384 particles were recorded, predominantly fibers, while transparent and blue particles were the most common colors. Raman spectroscopy was used to identify particles, including plastic polymers such as polypropylene and polyethylene terephthalate (PET), as well as non-plastic particles composed of microcrystalline cellulose. Color composition differed among reef sites, with similar patterns observed in intertidal reefs adjacent to urbanized estuaries and in offshore shallow and mesophotic reefs. These findings provide baseline information on the occurrence, characteristics, and spatial distribution of anthropogenic microparticles in reef sediments across a tropical shelf gradient, contributing to a better understanding of microplastic and textile-derived contamination in understudied reef environments.
Environmental monitoring plans (EMPs) are essential for assessing and limiting the impacts of marine cage aquaculture. In the Mediterranean, EMPs are legally mandatory in many countries. However, inconsistencies in variable selection, analytical methods, and experimental designs limit regional comparability and hinder environmental assessments. This study evaluated EMPs from five finfish cage farms in southeastern Spain (2017-2022). We qualitatively compared sampling methodologies, measured variables, and experimental designs across physicochemical and biological components, and quantitatively assessed, using meta-analysis (logarithmic response ratios, random-effects models), which variables are most sensitive for detecting aquaculture-driven changes. Significant methodological inconsistencies were identified among consulting firms, particularly in variable measurement and analytical protocols. The meta-analysis identified suspended solids, chlorophyll-a, nitrate, ammonium, sediment organic matter, sediment redox potential, and dissolved oxygen as the most informative physicochemical indicators. Among biological variables, macrobenthic abundance showed the largest effect (substantially higher in impact areas), followed by faecal coliforms. Shannon-Wiener diversity and species richness were recorded across all farms but showed negligible effects, likely reflecting methodological inconsistencies rather than true ecological insensitivity. These results demonstrate the environmental effects of fish farming on surrounding ecosystems and highlight an urgent need for standardised EMP frameworks at the regional scale. Such frameworks must integrate both physicochemical and biological indicators with appropriate experimental design to enable reliable long-term assessment of marine aquaculture impacts.
