Blue carbon cycling in mangrove ecosystems is proving to be more complex than previously thought. The objective of this study was the application of structural equation modelling (SEM) to capture such complex and varying data types and provide a holistic understanding of mangrove blue carbon cycling using data from the Indian Sundarban as a test case. We found that SEM was effective at integrating multiple data types and characterizing the processes and variables that regulate the nature and magnitude of CO fluxes within a mangrove ecosystem, including atmosphere-hydrosphere, atmosphere-pedosphere, and net ecosystem exchange. Overall, this study finds that atmospheric, water, and soil temperatures were the main and common drivers of CO effluxes towards the atmosphere from the entire ecosystem, waterbodies, and soils of mangrove ecosystems, respectively. We conclude that SEM is useful for combining data from different sources, gaining an overarching view of the complex biogeochemical cycling of the blue carbon ecosystems.

The high number of offshore platforms at the end of their productive phase offers the opportunity of their re-use and the development of effective management solutions, such as the possibility of utilizing them as ecological observatories for monitoring marine ecosystems and their biological resources. Here, through a multiparametric observatory deployed at an unproductive offshore platform, located in the Central Adriatic Sea (Mediterranean Sea), we collected data for 13 months on benthopelagic fish assemblage and habitat conditions. A total of 155.5 h of high-frequency (30 min) video-monitoring, recorded higher fish abundances during spring-summer periods during daytime, while fish diversity was highest in autumn. Some environmental variables contributed significantly to explain the overall community variance. Our results suggest that offshore platforms can be re-converted into ecological observatories, to collect relevant amounts of information that can be difficulty obtained with alternative approaches, contributing to our understanding of changes occurring in open water ecosystems.

With the development of the cruise industry, the associated pollution and social impact issues are becoming more severe. The objective of this study is, therefore, to identify the significant impact factors in the cruise development process and to analyze their effects on the natural environment, economy and society. To this end, the study first identified the dimensions and criteria through interviews with experts and a literature review, grouping the dimensions of impact cost into 'natural environment', 'economic' and 'social' using the best-worst method (BWM) resulting in four impact factors included under each dimension, totalling 12 criteria. Methodologically, these criteria were sorted by weight using BWM, resulting in the six most influential factors, which were, in order, 'wastewater, oil pollution and toxic substances', 'exhaust gas and noise', 'low consumption willingness and failure to meet expectations', 'causing urban congestion and traffic jams', 'changing the residents' original lifestyle' and 'vectors of infectious disease transmission'. Following this, the causal diagrams between the various criteria were drawn with the causal relationships between the factors analyzed using the decision-making trial and evaluation laboratory (DEMATEL) method. The results of the study showed that 'causing urban congestion and traffic jams' is the key core factor directly affecting the other five. These findings can assist the cruise industry and the local government in formulating effective preventive and improvement measures to minimise the negative environmental and social impacts of cruise development and to ensure the sustainable development of the industry. This study also has important implications for future management and policy formulation in the cruise industry.

Heavy metal pollution in aquatic ecosystems can lead to harmful accumulation in organisms like stingrays, posing potential health risks to humans. To assess this risk, 45 stingrays were sampled from Johor Waters (Pontian, Muar, and Batu Pahat) and analyzed for heavy metal content using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The average concentrations of Cu, Zn, As, Cd, Pb, and Hg in the fillets were 0.982±0.637, 31.3±5.93, 93.57±24.5, 0.039±0.047, 0.158±0.036, and 0.592±0.424 μg/g dw, respectively. Arsenic (As) was found at the highest concentration. The study indicates that fish size does not directly influence heavy metal accumulation and that metal levels vary by location. Calculated consumption limits for different metals are crucial for human safety. This data is valuable for evaluating contamination risks and guiding future research to protect marine ecosystems in Johor Waters.

Jellyfish blooms can significantly impact marine food webs, biochemical processes and human health, disrupting various economic sectors, including fisheries, aquaculture and tourism. Thus, understanding the regional drivers and patterns of jellyfish occurrence is key for developing effective management strategies. The Portuguese man o' war (Physalia physalis) is a hazardous, cosmopolitan siphonophore of particular concern, requiring a deeper ecological understanding to effectively guide mitigation efforts. Our study reveals that the occurrence of P. physalis in both the North Atlantic (Azores, Portugal) and the Southeast Pacific (Australian East Coast) is driven by region-specific wind patterns and increased primary productivity (>30 % model contribution), with warming conditions emerging as an additional occurrence driver on the Australian East Coast (∼20 % model contribution). These insights resulted from machine learning models (Boosted Regression Trees) trained with high-resolution environmental data against field data describing the temporal variability of P. physalis occurrence (North Atlantic: 2008-2021; Southeast Pacific: 2016-2020). The models achieved excellent predictive performance (AUC North Atlantic: 1.00; AUC Southeast Pacific: 0.92) and allowed hindcasting occurrences over 30 years, uncovering contrasting trends between the two regions, with decadal fluctuations in the Azores and a significant increase in occurrence over time on the Australian East Coast. Overall, we provide a better understanding of the drivers and patterns of P. physalis occurrence, which can support the development of coastal management strategies. Importantly, the anticipated changes in productivity and temperature conditions in both regions may result in increased blooms in the years to come, further exerting impacts on the ecosystems, human health, and the economy.

This study investigates sediment samples from the Indian Sundarbans' mangrove habitat, where most samples were alkaline and hypersaline, except for one acidic sample. Elemental analysis revealed poor sediment quality, with elevated Enrichment Factors (2.20-9.7), Geo-accumulation indices (-2.19-1.19), Contamination Factors (0.61-3.18), and Pollution Load Indices (1.04-1.32). Toxic metal ions, including Pb, Cu, Ni, Cd, Zn, and Cr, were identified as key contributors to compromised sediment quality. These metals inhibit crucial sediment enzymes, such as CMC-cellulase, β-glucosidase, aryl sulfatase, urease, and phosphatases, essential for nutrient cycling and organic matter decomposition. A negative correlation was found between heavy metals and biodiversity, as indicated by the Shannon index, and a similar trend was observed with fungal load. The study highlights the adverse effects of persistent trace metals on the fungal community, potentially disrupting the mangrove ecosystem and suggests using manglicolous fungi as biological indicators of environmental health.

This study extensively investigated the abundance of microplastics in Thiruvottiyur coastal area of Chennai, India, before and after Cyclone Michaung. The results demonstrated a significant correlation between microplastic distribution and aftermath rainfall. The concentration of microplastics in sediments increased from 150 ± 48 particles kg to 186 ± 21 particles kg after the cyclone. In seawater, the concentration rose from 1.28 particles L to 3.65 particles L, respectively. Heavy metals such as Al, Mg, Zn, Cr, Pb, Cu, Cd, Co, and As were detected on the surface of microplastics, demonstrating their vectorization potential for co-contaminants. After exposure, these microplastics induced oxidative stress in Artemia franciscana with increased superoxide dismutase (SOD), catalase, and reactive oxygen species (ROS). Fluctuations in weather conditions lead to heterogeneous changes in microplastic distribution, revealing the seasonal dynamics of microplastics. This study will provide background information to devise strategies for mitigating microplastic pollution in the marine environment.

Global warming poses a significant threat to coral reefs. It has been assumed that mesophotic coral ecosystems (MCEs, 30 to 150 m depths) may serve as refugia from ocean warming. This study examined the acclimation capacity and thermal tolerance of two shallow coral species, Porites cylindrica and Turbinaria reniformis, transplanted to mesophotic depths (40 m) for 12 months. Fragments from 5 and 40 m were exposed to control (28 °C), moderate (30 °C), and high (32 °C) temperatures over 14 days. MCE-acclimated fragments showed higher thermal thresholds and survival rates, delayed onset of bleaching, and less decline in photosynthesis efficiency (Fv/Fm) compared to shallow fragments. Both species maintained high thermal tolerance despite prolonged exposure to cooler temperatures of mesophotic depth. These findings suggest that low light intensity in MCEs can act as a modulator of bleaching, supporting the potential of these ecosystems as refugia for shallow corals in a rapidly changing world.

The Canadian Arctic is a large and diverse geographic area that encompasses a wide variety of environmental conditions and ecosystems. Over recent decades, marine transportation has increased across the Arctic and, as a result, so has the likelihood of an oil spill. The study of oil spills in the Arctic presents unique challenges compared to temperate marine environments, due to remoteness, cold temperatures and the presence of snow and ice throughout much of the year. This review summarizes and discusses the fate of oil in the Canadian Arctic. A brief introduction to the Canadian Arctic and sources of potential petroleum spills is provided, followed by discussions of the behaviour of oil in ice and freezing temperatures, oil-sediment interactions, and the weathering and natural remediation of oil under Arctic conditions. A summary of perspectives concludes the review, with emphasis on possible areas of future work to address research gaps.

The Baltic Sea highly susceptible to the proliferation of Phytoplankton blooms. Present work examines the long-term trend and spatio-temporal variability of satellite derived chlorophyll concentration (Chl a) in the Baltic Sea during the period 2004-2021. Furthermore, the influence of water quality and meteorological parameters on Baltic Sea primary productivity has been analyzed using robust Generalized Additive Models (GAM) and Granger Causality statistical test. Statistically significant increasing trend in chlorophyll a concentration is observed in the Baltic Sea at the 95 % confidence interval. GAM model reveals that the most significant controlling factor is sea surface temperature (p < 0.0001), followed by nitrate and phosphate. Both GAM and Granger Causality tests confirm that water quality parameters are the major drivers in limiting the growth of Phytoplankton blooms in the Baltic Sea. Summer bloom shows in-phase relationship with Sea surface temperature and out of phase relationship with the phosphate nutrient.

This study aimed to evaluate metals and polycyclic aromatic hydrocarbons (PAHs) adsorption on new plastic fishing nets in both laboratory and quasi-real scenario (nets submersed in marina seawater) experiments as well as in situ monitoring of these contaminants in water and sediments in lost fishing gears hotspots. The latter was inconclusive as environmental contaminants levels were very low. Laboratory experiments showed metals (copper and lead) and PAHs adsorption depended on the thickness and polymeric composition of the net, being lower in thinner nylon nets. Experiments in the marina, also showed significant contaminants adsorption, which increased over time, probably due to biofilm formation on net surface. This work showed the potential role of fishing gears as skins of pollutants, increasing organisms' exposition to contaminants present in the environment. So, initiatives to prevent the loss of fishing gear and to retrieve them are needed to reduce and/or eliminate their environmental impact.

This paper describes the microplastic problems on five sandy beaches along the Skikda coastline (southwestern Mediterranean, northeastern Algeria), defining their magnitudes, spatial-temporal distributions, shapes, polymer types, impacts, and potential sources. The data presented in this study were collected during two field surveys in May (spring) and September (autumn/fall) of 2019. Overall, the average abundance of microplastics across all beaches was 6174 items/m in spring and 6183 items/m in autumn, representing the highest level of MPs ever reported in Algeria. The most common microplastic types found were fragments, pellets, foams and fibers, accounting for >98 % of the microplastic shapes collected in this study. Our findings highlight the persistence of MPs on the studied beaches and that environmental factors such as currents, wind directions, beaching, sedimentation, dunes, and fragmentation all significantly impact the distribution and accumulation of plastic debris on beaches.

This study investigated the operational effectiveness and social acceptance of bioplastic gillnets made from a biobased polyester blend used to develop a monofilament 0.33 mm in diameter, with linear density of 108 tex, tenacity of 24.4 cN/tex and breaking force of 3.12 daN. The bioplastic gillnets were tested on 10 small-scale, in-shore vessels operating in the Mediterranean for 12 months. Findings demonstrate reduced effectiveness of the bioplastic nets compared to conventional nets, with reduced strength and increased stiffness influencing catch rates. Economic concerns and performance issues are critical factors affecting the acceptance of bioplastic nets by fishermen. The study highlights the need for continued research and development to improve the mechanical properties and performance of biobased fishing gear, and for the adoption of policy measures to incentivize the uptake and use of sustainable alternatives that can mitigate the impacts of lost or discarded fishing gear on marine ecosystems.

The drifting speed and trajectory of fish aggregation devices (FADs) influence tuna aggregation behavior. Based on expertise, fishermen modify FAD structures to slow down drifting speed, but few studies quantify material and structure effects on this speed. To address this, 14 different types of FAD models were tested under 5 different current velocities in a flume tank and compared drifting using pairwise Wilcoxon tests. Results indicate that 1) FAD models covered with netting exhibited higher drifting speeds than the others. 2) It is feasible that replacing the netting bundle with the cotton rope of the same diameter for constructing submerged structure effectively slows down the drifting speeds of FADs. 3) Additionally, FAD models with a floating structure aspect ratio close to 1 exhibited slower drifting speeds compared to other designs when the submerged structure is the same.

With global warming, extreme weather frequently occurs, yet the consequences remain unexplored. A total of 156 heat waves and their characteristics were detected on the basis of a temperature dataset from 1954 to 2022 in Jiaozhou Bay (JZB). The increment is 0.62 times decade for the number of heat waves, 6.65 days decade for the sum of participating heat wave days and 0.66 days for the duration of each heat wave. The intensity of heat waves showed regular fluctuations with progressively shorter periods. Based on the dataset of 12 stations in JZB from 2003 to 2022, the zooplankton abundance was significantly greater during heat waves, which was strongly attributed to the greater abundance of copepods and gelatinous zooplankton during heat waves. However, the responses of plankton to heat waves were seasonally heterogeneous. Our study provides new insight into and a scientific basis for understanding the effects of heat waves on offshore plankton ecosystems.

This research evaluated the emission characteristics of old ships during typical operations, under varying cruising speeds, and during lock transit, using a shaft power meter and PEMS. The research revealed that upstream and downstream low-load voyages accounted for 67.9 % and 65.4 % of the total voyage, respectively. The average emission factors of CO, NO and CO were highest under lock transit with 17.13±0.51 g/kWh, 16.2±0.62 g/kWh and 1075.37±5.72 g/kWh, respectively, while SO was highest under manoeuvring with 0.46 ± 0.001 g/kWh. Emissions are closely correlated with engine speed, with the largest emissions at cruising, and emissions at departure and docking significantly concentrated in the 10-15 % and 5-10 % loads. This research emphasizes the importance of considering low-load operating conditions in engine test cycles and provides data support for maritime decarbonization and emission reduction strategies. Future research should continue to explore the emission characteristics of old ships.

Microplastics are everywhere, including marine sediment. In this study, we evaluated the degradation of polyester, rayon, and cotton sewing threads over nine months when buried in marine sediment in Waitematā Harbour, Auckland, New Zealand. Polyester tensile strength was tested pre- and post-burial to track changes over time. Fourier-transform infrared spectroscopy (FTIR) analysis enabled the examination of the change to the chemical structural integrity of the polyester molecules over time. After one month, rayon and cotton degraded and were invisible to the eye, while visible signs of polyester degradation were apparent after 6 months of burial. This was confirmed by both tensile strength testing and FTIR chemical analysis. While microplastic pollution remains a serious problem, these findings show that at least one type of common plastic does degrade when buried in marine sediments. This likely has implications for seafloor ecosystem functionality and provides hope for plastic circular economy infrastructure.

The oil spill resulting from the grounding of the MV Wakashio on a reef off the coast of Mauritius in July 2020 was the world's first major spillage of Very Low Sulfur Fuel Oil (VLSFO) since the implementation of a Global Sulfur Cap from January 2020. In this study, we examine sediments collected in March 2023 from two Mauritius mangrove systems. Analyses by both gas chromatography-mass spectrometry and comprehensive two-dimensional gas chromatography confirmed, by comparison of molecular biomarkers, the presence of Wakashio VLSFO in one of the mangrove systems. The spilled oil had undergone extensive weathering resulting in substantial losses of toxic mono- and polycyclic aromatic compounds. Applying WebGNOME-ADIOS oil spill models to compare the fate of Wakashio VLSFO with traditional fuels suggests that more of the VLSFO would evaporate, naturally disperse, and undergo sedimentation compared to traditional fuels that were more likely to remain floating.

Sharks, are highly vulnerable to fishing pressures, a key factor in their global population decline. Chemical pollution, however, especially metal and metalloid contamination, poses significant additional risks. Of around 520 shark species, about 170 are threatened, including the Sphyrna genus (hammerheads). This review examines contamination in these sharks and its ecological and human health implications. A scientometric review indicates limited research, mainly on juveniles and only mercury contamination, with scarce data on other metals, life stages, and consumption thresholds. The findings also indicate a certain amount of Colonial Science concerning ecotoxicological Sphyrna spp. assessments. The expected link between ecotoxicological risks and Sphyrna spp. threat status remains inconclusive due to insufficient data. Notably, larger hammerhead species do not always exhibit higher contamination levels, suggesting that local environmental factors may influence contamination more than biological characteristics. More research is required to understand how environmental pressures impact shark vulnerability and inform conservation strategies.

The Philippines are projected to be a top contributor to oceanic plastic pollution by 2025, ranking first globally for riverine plastic emissions. However, comprehensive empirical data on litter leakage is lacking, impeding accurate estimates and mitigation efforts. We conducted the first thorough assessment of plastic within a 100 km radius of Davao City, Mindanao, Philippines using a stratified random sampling design. We detected 13,970 debris items across 309 transects from 33 coastal, 27 river, and 44 inland sites, and collected 1405 debris items from 27 sea surface trawls. Riverbanks showed the highest plastic pollution densities, averaging 3.6 items per m. Food wrappers and labels, both whole and fragmented, were the most abundant items across all site types, highlighting the Filipino "tingi" culture of buying and trading in small quantities. We recommend focusing on river hotspots and commonly reported items, particularly food packaging and sachets, to manage plastic pollution effectively.