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The research, focusing on the analysis of nine trace elements, namely As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn, completely analyzed their quantities in both water and sediment inside the Rabnabad Channel. Samples were collected during the post-monsoon and analyzed by ICP-OES following acid digestion. The mean concentrations of elements in water and sediments are as follows: Fe > Mn > Pb > Cu > Ni > Zn > Cr > As>Cd, and Zn > Fe > Pb > Mn > As>Cu > Cr > Ni > Cd. To understand the state of ecological and human health risk, several indices were incorporated. Health risk assessment revealed that children posed higher risk than adults. PERI, TRI, and I geo indices for water sediment indicate a significant ecological risk. Moreover, Mn and Pb exhibit elevated HPI values and contribute substantially to contamination factors. Correlation and PCA implicate both anthropogenic and geogenic sources, such as agricultural practices, coal-based power plants, and the Payra seaport, in the elevated concentrations of Cd, Cr, Mn, and Fe in both water and sediment samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Honda Bay is considered as one of the mercury hotspots in the world due to its proximity to the abandoned Palawan Quicksilver Mine. In this study, a detailed sediment sampling conducted in between 2021 and 2022 where a total of 166 sediment samples were collected along the coast and analyzed for total mercury (THg) concentration. The study assessed mercury toxicity using the geoaccumulation index and compared Hg levels to sediment quality guidelines. The findings revealed a wide range of THg concentrations, from 0.0040 to 11.4702 mg/kg, with hotspots identified at the Honda Bay wharf and Tagburos River mouth. Mercury spreads to a large coastal area brought by tidal currents and the wave energy actions. The geoaccumulation index indicated moderate to strong Hg contamination in the vicinity of the hotspots and around 24.7-36.1 % of samples exceeded the sediment quality guidelines suggesting adverse biological effects in aquatic biota will frequently occur., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jessie O. Samaniego reports financial support was provided by Republic of the Philippines Department of Science and Technology. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Phosphorus (P) is an essential biogenic element in ecosystems; but excessive or insufficient P in coastal waters caused by human activities has led to serious ecological issues. However, the understanding of the dynamic processes of different P forms in high turbidity estuaries/bays, as well as their impact on eutrophication and coastal algal blooms, is still relatively limited. To address this issue, we analyzed P dynamics and their impact on eutrophication in Hangzhou Bay (HZB), which is typical of eutrophic and turbid bay worldwide. The concentration of particulate P (PTP) was 3-5 times higher than that of dissolved inorganic phosphorus (DIP). Seasonal sediment resuspension led to the accumulation of suspended particulate matter (SPM) and PTP with regional variation, both maintaining DIP concentrations above 1 μmol/L within the bay. Furthermore, 3000 tons of bioavailable P were retained in the fine-grained SPM, with the potential for outward transport, fueling subsequent harmful algal blooms. A comparative analysis of global coastal waters highlighted that different turbidity levels significantly affect P cycling. Therefore, understanding the relationship between SPM and P in highly turbid waters is crucial for effective management of eutrophication., Competing Interests: Declaration of competing interest All authors declare no conflict of interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Microplastic (MP) pollution has been widely reported across water matrices including in estuaries, which are important for the understanding of oceanic MPs. Estuaries can greatly alter the fate, transport, size distribution, and abundance of plastic pollution. The aim of this study was to quantify and characterize MP pollution in the Delaware Bay estuary USA, including the size distribution. Samples (N = 31) were collected from the mouth of the Delaware River to the coastal ocean including multiple frontal zones across two sampling campaigns (2019 and 2022). MP were extracted from the collected particles using wet peroxide oxidation and density separation with saturated sodium chloride. Particles collected on 500 μm mesh sieves were analyzed via Fourier transform infrared (FTIR) spectroscopy. Across all samples, 324 of the 1015 particles analyzed were MP, and 11 macroplastics were observed. MP concentrations ranged from below detection to 4.12 MP/m 3 (mean 0.34 ± 0.80 MP/m 3 ). No significant differences were observed between sampling sites; nonetheless, the two highest MP concentrations were observed when sampling along frontal zones with visible debris including macroplastics. Polyethylene (53%) and polypropylene (43%) were the most abundant polymers observed. The majority of the non-plastic particles were classified as particulate natural organic matter (82% of non-plastics). Particles from samples collected during 2022 (N = 864) also had color, morphology, and two size dimensions recorded. MP particle size was significantly associated with sampling site, with the coastal ocean sampling site generally having the smallest MPs. A correlation between total post-extraction particles and total plastic particles was observed. Aspect ratios for the plastics ranged from one to 40.7, with larger ratios for fibers, with a mean (±standard deviation) of 3.39 ± 4.72 (unitless). These aspect ratios can be used to select shape factors used to estimate the total volume of MP in the studied size range. Overall, these results can help inform fate, transport, and risk assessments related to estuarine plastic pollution., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Robert Chant reports financial support was provided by National Oceanic and Atmospheric Administration Marine Debris Program (Grant number: NA19NOS9990083). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

A baseline survey for floating microplastics (MPs) in the vicinity of a marine protected area and semi-enclosed bay of northern Peru was carried out. An average concentration of 0.22 MPs/L was estimated, primarily dominated by blue polyethylene terephthalate fibers. The distribution of floating MPs suggests that they tend to accumulate within the semi-enclosed Sechura Bay regardless of the sampling season. This behavior may be explained by local surface currents in the bay, which flow inwards and exhibit vorticities that could entrap MPs. Future studies are suggested to investigate the trajectory and fate of floating MPs within semi-enclosed areas. On the other hand, the impact of floating MPs on the trophic chain of coastal marine protected areas requires further research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study aimed to evaluate the concentration, distribution, along with the environmental and human health impact of eight heavy metals-Pb, Cr, Cu, Cd, Zn, Mn, Ni, and As-on St. Martin's Island in the northeastern Bay of Bengal, and in doing so to help implement new legislations to protect the island. Focusing on the island's significance as a tourist destination, with seafood being a prominent dietary component, three sample types (sediment, seawater, and crustaceans) were selected for a comprehensive assessment, considering seasonal variations. Concentration of metals was observed to be lower than the established standards in sediment samples, but in seawater samples, Pb, Cr, Cd and Zn were higher than US-EPA values for natural marine water. The metals displayed a decreasing trend of Zn > Ni > Pb > Cu > Mn > As > Cd > Cr in crustacean samples for both seasons. Crustacean samples displayed higher metal concentrations in winter than in monsoon. Pb exceeded the maximum allowable limit for crustaceans with a concentration of about 3 and 4 mg kg -1 in monsoon and winter respectively; being more than 6-8 times the standard for Bangladesh which is only about 0.5 mg kg -1 . Health indices displayed that although adults may suffer less from carcinogenic/non-carcinogenic health effects, the risks are far greater for children. For both age groups, As and Ni displayed possibilities of developing cancer. Principal Component Analysis (PCA)shed light on the sources of metals and showed that most of them were from anthropogenic sources. Overall, this study found that the quality of the environment of the island was better in comparison to previous studies made before the pandemic, and so, if the trend continues, it may lead to a better environment for the organisms around the island and help to keep the negative physiological impacts from the consumption of these organisms to a minimal., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Plastic particles have emerged as a growing threat to both ecosystems and human well-being, as they are being ingested and accumulate at different trophic levels. However, microplastic and mesoplastic contamination and its risk to coastal and marine water fish have not been well studied, particularly in the northern Bay of Bengal. In this study, the presence of small-scale plastic particles (micro- and meso-sized) in the gastrointestinal tract (GIT) and muscles of six edible fish species from the northern Bay of Bengal Coast were identified and analyzed. The overall range of microplastics was 1.74 ± 0.23-3.79 ± 2.03items/g in muscle and 0.54 ± 0.22-5.96 ± 3.16 items/g in the GIT, with 16.38 ± 8.08-31.88 ± 12.09 items/individual. No mesoplastics were found in muscle tissue, but they were present in the GIT at concentrations ranging from 0.33 ± 0.27 to 0.03 ± 0.02 items/g and from 0.51 ± 0.05to 1.38 ± 1.01 items/individual. Lepturacanthus savala accumulated the most microplastics in muscle, and Harpadon nehereus had the least. In addition, the highest levels of mesoplastics were detected in the GIT of Polynemus paradiseus and the lowest was detected in the GIT of Lutjenus sanguineus. Omnivorous fish showed higher plastic concentrations than carnivorous fish, which was linked to dietary habits, feeding strategies and digestive processes. Plastic material predominantly accumulated in the GIT rather than in the muscle. The majority of ingested plastic particles were fibres (95.18 %), were violet in color (34 %), and were < 0.5 mm in size (87 %). The dominant microplastic polymers included 38 % PE, 15 % PP, 33 % PU, and 14 % CES. In contrast, the prevalent mesoplastic polymers comprised 45 % PE, 19 % PP, 13 % PS, 16 % PA, and 7 % PET. Subsequently, a hazard analysis using the polymer hazard index (PHI) revealed that plastic contamination was of distinct hazard categories for different polymer types, ranging from grade I (<1) to grade IV (100-1000). The assessment of the contamination factor (1 < CF < 3) and pollution load index (PLI > 1) indicated moderate contamination of fish by the ingestion of plastic debris. This study provides the foremost evidence for the presence of mesoplastics and microplastics in coastal and marine fish in the study region, paving the way for future investigations and policy implementation., Competing Interests: Declaration of competing interest There are no known conflicts of interest., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Sansha and Luoyuan Bay are influenced by different industrial structure, but the sources and pollution status of polycyclic aromatic hydrocarbons (PAHs), especially alkylated PAHs, are poorly understood. We studied 25 PAHs in surface sediments from the two bays. The results showed that PAHs concentrations in Sansha and Luoyuan Bay sediment range from 6.54 to 479.28 ng/g and 118.82 to 2984.09 ng/g, respectively. Alkylated PAHs dominated in Sansha (48.86 % of Σ 25 PAHs), while 3-ring PAHs dominated in Luoyuan (36.32 % of ∑ 25 PAHs). Results of sources analysis indicated oil spills as the main PAHs source in Sansha, and domestic emissions and fossil fuel combustion in Luoyuan. Ecological risk assessment of showed low sediment risk, but in Luoyuan was higher than in Sansha. Compared with Luoyuan Bay, Sansha Bay emits less industrial pollutants, so the pollution is lower than Luoyuan Bay. Increased attention to protecting Luoyuan Bay is recommended., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Coastal estuaries are often heavily subject to riverine influences by the inputs of sediment from terrestrial sources. Hangzhou Bay (HZB) is threatened by the riverine derived trace metals from two large rivers of Qiantang River (QTR) and Yangtze River (YZR). However, previous studies mainly focused on the incidental transport from the largest river in China (YZR) and failed to simultaneously evaluate the contributions of these two rivers, especially the directly flowing river of QTR, by their trace elemental geochemical composition and distribution. Herein, a comprehensive study identified the river-derived sources of multiple trace metals in surface sediments which transported from both of the rivers. The sampling stations were separated into three regions of YZR, HZB, and QTR based on their spatial distributions of sediment grain size and components. The significant variations for most of the trace metals concentrations, except for Cd, Th, and U, were found among three regions (χ 2  ≥ 8.22, p ≤ 0.016). The highest concentrations in HZB were mainly resulted from the grain size effect (68.82% of the total variance), while the highest concentrations of Sr, Cd, and Ba in YZR and Zr and Hf in QTR were attributed to the anthropogenic source (11.90%) and mineral composition (6.21%) of river basins. After normalized the diversity of multiple trace metals concentrations and the influence of grain size by ratios of I geo and EF Li , three regions were effectively distinguished. It was indicated that As, Cd, and Sb were enriched in the sediments of rivers by anthropogenic source (EF Li  > 1.5 and/or I geo > 1). The results evidenced that, after removing the influence of grain size, elemental geochemical composition of the surface sediments confidently identified the river-derived anthropogenic sources of the enriched trace metals from two major rivers, and largely from YZR., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

In the aquatic environment around the world, microplastic contamination has been a common and ongoing issue. Particularly, the ability of microplastics to absorb persistent organic pollutants (POPs) and then transmit these POPs to aquatic creatures has attracted a lot of interest. A stereomicroscope was used to detect the size, shape, and color of the microplastics (MPs), and Fourier Transform Infrared (FTIR) spectroscopy was used to identify the polymer composition of the MPs. To address MP transit, destiny, and mitigation, a study of MP pollution coastal areas is required. In the current study, MP pollution in the collected sample from upper layer of water and sediment of the Digha and Puri beaches along the coast of BOB was evaluated. The average concentration with SD of MPs observed in water was 5.3 ± 1.8 items/L whereas, in sediments, it was 173.4 ± 40.1 items/kg at Digha beach. The mean MPs abundance in the Puri beach was 6.4 ± 1.7 items/L in the water and 190.4 ± 28.0 items/kg in the sediments. The investigated total 16-PAHs concentrations were 164.7 ng/g, 121.9 ng/g, 73.6 ng/g, and 101.3 ng/g on the MPs surface of foam, fragment, fibers, and film respectively in the studied MPs sample. Smaller than 1000 µm size of MPs are distributed in the largest concentration. Fibers, films, fragments, and foam were the most common shapes of MPs. The molecular structure of MPs in water and sediment samples was analysed i.e., polyesters (PEs), polypropylene (PP), polyethylene (PE), polymethyl methacrylate (PMMA), polystyrene (PS), polyamide (PA), polycarbonates (PC), and polyurethane (PU). The obtained result offers an accurate assessment of the PLI, and the investigated polymer facilitates determining the polymer hazard levels, which emphasizes the risk associated with it., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Microplastics (MPs) as hazardous contaminants has drawn the rapid attention of the general public due to their omnipresence and adverse impacts on ecosystems and human health. Despite this, understanding of MPs contamination levels in the estuarine ecosystems along the Bay of Bengal coast remains very limited. This research focused on the presence, spatial distribution, morpho-chemical characteristics and ecological implications of MPs in water and sediment from five key estuaries (Meghna, Karnaphuli, Matamuhuri, Bakkhali, and Naf rivers) within the Bengal delta. Out of the five estuaries, the Meghna exhibited the least amount of MPs in both surface water (150.00 ± 65.62 items/m 3 ) and sediment (30.56 ± 9.34 items/kg). In contrast, the highest occurrence of MPs was recorded in Karnaphuli river water (350.00 ± 69.22 items/m 3 ) and Matamuhuri river sediment (118.33 ± 26.81 items/kg). ANOVA indicated a statistically significant distinction (p < 0.01) among the examined estuaries. Most identified MPs were fibers and < 0.5 mm in size in both water and sediment samples. Transparent MPs were dominant in both water (42.28%) and sediment (45.22%). Besides violet, red, blue, pink and green colored MPs were also observed. Various polymer types, including PE, PP, PET, PS, Nylon, EVA, and ABS, were detected, with PE being the dominant one. Based on the polymer risk index (PHI), the estuaries were classified as hazard level V, signifying a severe level of MP contamination. However, the potential ecological hazardous index (PHI), potential ecological risk index (RI), and pollution load index (PLI) indicated moderate pollution levels. This study offers initial insights into the pollution caused by MPs in major estuaries of Bengal delta, which policymakers can utilize to implement suitable management strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The Sepetiba Bay (Southeast Brazil) is a known Cd- and Zn-contaminated site that received spills of a large slag pile leachate from a Zn smelter. With important harbors, Sepetiba Bay demands periodic dredging operations which affect the mobility of the metals. The main goal of this work was to assess metal mobility in sediments and its associated toxicity in a fictive dredging area, to evaluate the risks of the operation. To achieve this goal, 18 superficial sediment samples were collected and characterized for pH and Eh. Sediments were analyzed for grain size, organic carbon, and total nitrogen, and metal mobility was evaluated with a sequential extraction procedure, proposed by the European Community Bureau of Reference (BCR). The results demonstrate that Cd and Zn are mainly associated with the exchangeable fraction (mean concentrations 1.4 mg kg -1 and 149.4 mg kg -1 , respectively) and reducible fractions (mean concentrations 0.3 mg kg -1 and 65.5 mg kg -1 , respectively), while Fe, Cr, Cu, Ni, and Al were associated with the residual fraction. Metals in the residual fraction are probably associated with the mineral lattice of the sediment and should not represent an environmental risk for the biota. The application of the enrichment factor and three risk assessment indexes (Risk Assessment Code, Risky Pollution Index, and Bioavailability Risk Assessment Index) show that the sediments are considerably enriched in metals that constitute a relevant risk for the sediment biota. In the case of dredging operations, Cd and Zn should be released to the overlying waters and be available to organisms, threatening the whole ecosystem. The proposed approach was shown to be much more precise than what is frequently presented in the Environmental Impact Assessments that only consider the threshold limits of the legislation., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Due to their extremely toxic properties, 226 Ra and it daughters ( 222 Rn, 210 Pb, and 210 Po) in drinking groundwater require monitoring. Recent studies have reported exceptionally high levels of natural 210 Po (up to 10,000 Bq/m 3 ), 226 Ra, and 222 Rn isotopes in groundwater. This study aims to provide background data on 226 Ra and its daughter radionuclides in the typical agricultural-industrial Dongshan Bay (DSB) before the construction of Zhangzhou Nuclear Power Plant (Zhangzhou NPP). The measurement results indicate that no abnormally high activities of 210 Po and 210 Pb were detected in the investigated wells. Strong positive correlations between 210 Pb and 210 Po, as well as between 222 Rn and 210 Pb activities, suggest that the origins of 210 Pb and 210 Po in groundwater are strongly influenced by the decay of the parent radionuclides 222 Rn and 210 Pb, respectively. In the DSB coastal zone groundwater, significant deficiencies of 210 Po relative to 210 Pb and 210 Pb relative to 222 Rn were observed, providing further evidence that 210 Po and 210 Pb are also effectively scavenged due to their geochemical properties (specifically particle affinity) within the groundwater-aquifer system. A systematic comparison among all relevant water bodies in the DSB revealed that the activity concentrations of 210 Pb and 210 Po in groundwater were the highest, except for rainwater. Based on the evaluation of 210 Pb sources, the results imply that submarine groundwater discharge (SGD) is an important pathway for transferring radionuclides (such as 210 Pb) from land to the nearshore marine environment, even though the study area has a lower 210 Pb background groundwater. By considering all the 210 Pb's sources in the DSB, we found low 210 Pb background groundwater discharge still needs to be taken into account for small-scale bays. This is because SGD was calculated to be one of the most important 210 Pb sources in the bay during observation season. Regardless of whether the system is in a normal state or a nuclear accident emergency state, greater attention should be paid to the groundwater discharge of radionuclides into the ocean., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Qatar's rapid industrialization, notably in its capital city Doha, has spurred a surge in land reclamation projects, leading to a constriction of the entrance to Doha Bay. By reducing and deflecting the ocean circulation, land reclamation projects have reduced the effective dispersion of wastewater introduced into the bay and hence degraded the water quality. Here, we assess fluctuations in water residence time across three distinct eras (1980, 2000, and 2020) to gauge the impact of successive land reclamation developments. To do this, we couple the multi-scale ocean model SLIM with a Lagrangian model for water residence time within Doha's coastal area. We consider three different topographies of Doha's shoreline to identify which artificial structures contributed the most to increase water residence time. Our findings reveal that the residual ocean circulation in Doha Bay was predominantly impacted by northern developments post-2000. Between 1980 and 2000, the bay's residence time saw a modest rise, of about one day on average. However, this was followed by a substantial surge, of three to six days on average, between 2000 and 2020, which is mostly attributable to The Pearl mega artificial island development. Certain regions of the bay witnessed a tripling of water residence time. Given the ongoing population expansion along the coast, it is anticipated that the growth of artificial structures and coastal reclamation will persist, thereby exacerbating the accumulation of pollutants in the bay. Our findings suggest that artificial offshore structures can exert far-reaching, non-local impacts on water quality, which need to be properly assessed during the planning stages of such developments., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright: © 2024 Lecart et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Hanauma Bay's coral reef system is threatened by sunscreen pollution. Understanding the hydrodynamic nature of the bay is crucial for understanding the transport and fate of pollutants within the bay. This study conducted a comprehensive hydrodynamic analysis, revealing significant aspects of current patterns and their influence on sunscreen pollutant behavior. The analysis demonstrated the formation of flows that drive currents parallel to the shoreline, resulting in increased pollutant retention time over sensitive reef areas. Direct flushing currents were identified as playing a role in reducing pollution buildup. Particle dynamics analysis highlighted the importance of considering temporal dynamics and their implications for pollutant pathways, particularly through the swash zone during high tide phases. The study identified primary current patterns near the reef area and emphasized the circular behavior within the water body, affecting corals' susceptibility to bleaching in the southwestern part of Hanauma bay. To understand where oxybenzone concentrations were a threat to wildlife, we created a geographic model that integrated ecological risk assessment with hydrodynamic behavior in a given system, which we designate the Risk Quotient Plume - the geographic area where the concentration is above the threat level for a chemical. The study found high oxybenzone concentrations throughout the bay, threatening coral, fish, and algae populations. Oxybenzone's distribution indicated a serious threat to the entire back reef habitat and a hinderance to coral restoration efforts. The study also emphasizes the need to consider the hydrodynamic behavior of pollutants and their interaction with microplastics in the bay. Overall, the findings provide insights into hydrodynamics and pollutant dispersion in Hanauma Bay, supporting effective pollution management and conservation strategies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Heavy metals play a significant role in marine ecosystems, exerting notable impacts on the environment and human health. In this study, water, sediment, and aquatic organism samples from Jiaozhou Bay were investigated to comprehensively assess the distribution, temporal-spatial variations, and ecological risks of heavy metals. The results indicate that pollution from industrial wastewater discharge contributes to regional differences in the distribution of heavy metals, possibly being a major source of Zn, Cr, Cd, and Hg (r > 0.7, p < 0.05). Biological and physicochemical processes influence the distribution of Zn, Cr, and Pb in the water and sediment. Hg exhibits a polluted state in both the water and sediment, with As and Hg being the two highest-risk heavy metals in water and sediment, respectively. Among the organisms, crustaceans show significantly higher levels of heavy metal content and accumulation compared to mollusks and fish (p < 0.05), and the bioamplification of heavy metals occurs in the sediment-Rapana venosa-Portunus trituberculatus biological pathway. Portunus trituberculatus, Charybdis japonica, Oratosquilla oratoria, and Octopus ocellatus could pose risks to human health, especially for children and vulnerable populations. This study aims to enhance our understanding of the current status of heavy metal pollution in Jiaozhou Bay and to provide a scientific basis and favorable support for the ecological environmental protection and prevention of ecological risks associated with heavy metal pollution in Jiaozhou Bay and other bays in China., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Bay ecosystem has garnered significant attention due to the severe threat posed by organic pollutants, particularly polycyclic aromatic hydrocarbons (PAHs). However, there is a dearth of information regarding the extent of PAHs pollutant risk and its impact on microbial communities and metabolism within this environment. In this study, the distribution, sources, ecological risk, and microbial community and metabolic response of PAHs in Jiaozhou Bay, Aoshan Bay, and Lingshan Bay in Qingdao, China were investigated. The results showed that the average concentration of ∑PAHs ranged from 120 to 614 ng/L across three bays, with Jiaozhou and Aoshan Bay exhibiting a higher risk than Lingshan Bay due to an increased concentration of high-molecular-weight PAHs. Further analysis revealed a negative correlation between dissolved organic carbon concentration and ∑PAHs concentration in water. Metagenomic analysis demonstrated that higher levels of PAHs can lead to decreased microbial diversity, while the abundance of PAHs-degrading bacteria is enhanced. Additionally, the Erythrobacter, Jannaschia and Ruegeria genera were found to have a significant correlation with low-molecular-weight PAH concentrations. In terms of microbial metabolism, higher PAH concentrations were beneficial for carbohydrate metabolic pathway but unfavorable for amino acid metabolic pathways and membrane transport pathways in natural bay environments. These findings provide a foundation for controlling PAHs pollution and offer insights into the impact of PAHs on bacterial communities and metabolism in natural bay environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Mussels were collected from four coastal sites around Port Phillip Bay, Australia in Mar and Apr 2021). Body burdens of Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) were measured and the possible sources of toxicants discussed. In addition, a gas chromatography-mass spectrometry (GC-MS) based untargeted metabolomics analysis was performed using the mantle tissues of mussels. Correlations between the results of contaminant body burdens and metabolic variations were investigated. The results demonstrated that high accumulations of low-molecular-weight PAHs were found in mussels. High body burdens of PCBs and OCPs were only found at mussels from the site close to the river mouth. Some of the metabolic pathways were correlated with the accumulation of PAHs. No correlations were found between PCB and OCP accumulations and metabolic abundances. According to the food and environmental standards of the European Union (EU), the PAH, PCB, and OCP accumulation in mussels in this study are a serious food safety concern., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Heavy metal contamination has been the focus of many studies owing to its potential risk on the health of coastal ecosystems. The Bohai Bay (BHB) is the second largest bay of Bohai Sea and subjected to serious anthropogenic perturbations. The aim of this study was to evaluate the distribution and pollution status of toxic heavy metals in seawater with two fractions (dissolved and suspended particulate phases) and surface sediments of this coastal system. Therefore, several hydrochemical parameters and concentration of seawater metals and sediment metals were measured at two cruises of 2020 summer and autumn. The spatial distribution and potential ecological risks were examined and their inter-element relationships were analyzed to identify potential geochemical processes. By comparing historical data since 1978, we find declining trends in contents of most trace metals in seawater and sediments, suggesting that recent pollution control in BHB have an effect on diminishing metal pollution. Dissolved metals showed no significant dependence on their particulate phase. The seawater posed a moderate to high level of ecological risk. The hydrochemical factors mainly had a greater impact on dissolved metals during summer, whereas they influenced suspended metals more significantly during autumn. These results provide fundamental information to support environmental quality management and ecological protection in coastal systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

This study identified and quantified microplastics in the Bay of Asunción, Paraguay, and its main tributaries. Surface water samples were sieved in duplicate at six locations using stainless-steel sieves (0.3-4.75 mm range), digested employing the Fenton's reaction (Fe-catalysed H 2 O 2 digestion), and floated using NaCl and NaI. Particles were inspected using a microscope and characterized by IR spectrometry. Microplastics were found in all samples; more abundant (p < 0.05) in water from the bay (13.2 ± 13.4 items·m -3 ) than from the tributaries (1.0 ± 0.5 items·m -3 ). Most microplastics were common polymers and their abundance was in the order polypropylene > high-density polyethylene > low-density polyethylene, transparent and white. The results were similar to other regional studies and suggested that their main source was single-use packaging, disposed inadequately due to poor garbage collection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

A large number of aquaculture facilities produced during the farming process are made of plastics. These plastics can be a distinct habitat for bacteria due to their unique materials. Therefore, this paper focuses on plastic aquaculture facilities and investigates the impact of bacterial accumulation on plastic surfaces. In this study, the high-throughput sequencing of 16S rRNA was conducted to investigate bacterial community profiling associated with the pearl culture facilities (cultured net cages and foam buoys) and surrounding water of Liusha Bay. Alpha diversity analysis showed that the richness and diversity indexes of bacterial communities in pearl culture facilities were higher than those in the aquatic environment. The richness and diversity indexes of bacterial communities were different between cultured net cages and foam buoys. Spatially influenced bacterial communities attached to pearl culture facilities varied between aquaculture areas. Thus, plastic has become a habitat for bacteria, floating in the marine environment and providing a favorable living environment for marine microorganisms and specific preferences for different substrate types. The relative abundance of certain functions on the attached bacterial community of the culture facility was high, which suggested that plastics did not only alter community structure but also influenced bacterial function. In addition, we detected small amounts of pathogenic bacteria, such as Vibrio and Bruegeria, in pearl culture facilities and surrounding seawater, suggesting that plastics can act as vectors for potentially pathogenic bacteria that may have an impact on the development of aquaculture. Our understanding of plastic ecology has been enriched by the discovery of the various microbial assemblages that can occur in aquaculture facilities., Competing Interests: Declaration of competing interest No conflicts of interest, financial or otherwise, are declared by the authors., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Domoic acid (DA), a natural marine phytotoxin produced by toxigenic algae, is harmful to fishery organisms and the health of seafood consumers. In this study, we performed a whole-sea area investigation of DA in seawater, suspended particulate matter (SPM), and phytoplankton of the Bohai and Northern Yellow seas to clarify the occurrence, phase partitioning, spatial distribution, potential sources, and environmental influencing factors of DA in the aquatic environment. DA in different environmental media was identified using liquid chromatography-high resolution mass spectrometry and liquid chromatography-tandem mass spectrometry. DA was found to be predominantly in a dissolved phase (99.84 %) in seawater with only 0.16 % in SPM. Dissolved DA (dDA) was widely detected in nearshore and offshore areas of the Bohai Sea, Northern Yellow Sea, and Laizhou Bay with concentrations ranging from < limits of detection (LOD) to 25.21 ng/L (mean: 7.74 ng/L), < LOD to 34.90 ng/L (mean: 16.91 ng/L), and 1.74 ng/L to 38.20 ng/L (mean: 21.28 ng/L), respectively. dDA levels were relatively lower in the northern part than in the southern part of the study area. In particular, the dDA levels in the nearshore areas of Laizhou Bay were significantly higher than in other sea areas. This may be due to seawater temperature and nutrient levels exerting a crucial impact on the distribution of DA-producing marine algae in Laizhou Bay during early spring. Pseudo-nitzschia pungens may be the main source of DA in the study areas. Overall, DA was prevalent in the Bohai and Northern Yellow seas, especially in the nearshore aquaculture zone. Routine monitoring of DA in the mariculture zones of the northern seas and bays of China should be performed to warn shellfish farmers and prevent contamination., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Vanadium is a component of different natural and industrial products and a widely used metal, which, nonetheless, has only garnered attention in recent years owing to its potential risks. Six sampling trips were conducted over different seasons and years, collecting 108 samples from rivers and 232 from the bays and analyzed using high-precision inductively coupled plasma mass spectrometry. This study investigated the sources, spatiotemporal characteristics, and risks of vanadium in the aquatic ecosystems of two typical bays of the Northwest Pacific that have strong links with vanadium-related industries. Likewise, the health and ecological risks were assessed using probabilistic and deterministic approaches. Overall, vanadium concentrations were higher in Jiaozhou Bay (JZB: 0.41-52.7 μg L -1 ) than in Laizhou Bay (LZB: 0.39-17.27 μg L -1 ), with concentrations higher than the majority of the worldwide studies. Vanadium-realted industries significantly impacted (p < 0.05) the metal concentrations in the rivers with 54.22% (40.73-150%) and 54.45% (27.66%-68.87%) greater concentrations in JZB and LZB rivers. In addition, vanadium exhibited significant seasonal variation, and higher values were quantified during the monsoon period at LZB owing to the greater catchment area. Impacted by smaller freshwater inputs, the post-monsoon period had substantial impacts on JZB, and vanadium in the rivers and bays was significantly higher during the winter. Despite some concentrations being higher than that indicated in the drinking water guidelines established by China, vanadium presents low to null risks to the population as per both approaches. Last, species with limited resilience are likely to face medium to high risks, with an incidence of 65-93% using the probabilistic method and 52-97% using the deterministic assessment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Land-based transport from nearshore areas is a key pathway of microplastic (MP) pollution in the oceans. Therefore, transport, fate, and intervention on MPs necessitate an investigation of MP contamination in coastal regions. Here, MP pollution in the surface waters of Xiamen Bay and Jiulong River estuary was evaluated in 2021 after the outbreak of COVID-19. The abundance of MPs in Xiamen Bay ranged from 0.20 to 5.79 items m -3 with an average of 1.03 items m -3 , whereas that in the Jiulong River estuary spanned from 0.55 to 2.11 items m -3 with a mean of 1.30 items m -3 . A yearly decreasing trend in the abundance of MPs in surface waters in both regions was observed. The particle sizes of MPs were concentrated in the range of 2.50-5.00 mm, and the colors were mainly white, transparent, and green. The micro-Raman spectroscopic results showed that MP polymer types were predominantly polyethylene, polypropylene, and polystyrene. A lower abundance of MPs in Xiamen Bay with no obvious pattern was observed, while that in the Jiulong River estuary showed a wavelike distribution from upstream to downstream. Ecological risk assessment of MP pollution in surface waters of two regions was performed using the pollution load index (PLI), giving the risk level in descending order: wastewater discharge area > aquaculture area > sloughs > estuary mouth > estuarine rivers > shipping lane. The average risk level of Xiamen Bay (I) was lower than that in Jiulong River estuary (II). The MP pollution in the Jiulong River estuary appeared heavier than that in Xiamen Bay, which may be due to the combined effects of COVID-19 and marine governance. This study provided insights into the prevention and management of MP pollution in nearshore semi-enclosed bays., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Due to the widespread use of organophosphate esters (OPEs), the occurrence and trophic transfer of OPEs have attracted attentions in ecosystems. However, as the final sink for these chemicals, the bioaccumulations and trophodynamics of OPEs in marine ecosystems are still not clear. In this study, seawater, sediment and marine organisms collected from Bohai Bay (BHB), Laizhou Bay (LZB), and Liaodong Bay (LDB) in Bohai Sea (BS), China were analyzed to investigate the occurrence, bioaccumulation and trophic transfer of typical OPEs. Total concentration of OPEs (∑ 9 OPEs) in surface water in LZB (255.8 ± 36.44 ng/L) and BHB (209.6 ± 35.61 ng/L) was higher than that in LDB (170.0 ± 63.73 ng/L). Marine organisms in LZB accumulated the highest concentrations of OPEs among the 3 bays (∑ 10 OPEs, 70.56 ± 61.36 ng/g ww). Average bioaccumulation factor (BAF) of OPEs in marine organism in BHB, LZB, and LDB was ranged from -2.48 to 0.16, from -2.96 to 1.78, and from -2.59 to 0.59. We also found that trophic magnification factors (TMF) are generally <1, which suggested trophic dilutions of OPEs in BS, China. Nevertheless, the relatively high OPEs levels in BS still may bring potential risks to ecosystem and human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Microplastics (MPs) are widely distributed in marine environments. The pollution characteristics and risk assessment of MPs in estuarine sediments are still insufficient. In this study, the MPs pollution characteristics in surface sediments of the Liao Estuary and Daliao Estuary were investigated. The characteristics of MPs in sediments were determined by stereo microscopy and micro-Fourier transform infrared spectroscopy. The results showed that the average MPs abundance ranged from 32.33 to 49.91 items·kg -1 d.w. The MPs were mainly composed of 500-2000 μm black and blue fibers. Five polymer types were identified, including rayon (RA) (87.46 %), polyethylene terephthalate (PET) (6.81 %), polyamide (PA) (2.94 %), polypropylene (PP) (2.17 %) and polyethylene (PE) (0.62 %). The pollution load index (PLI) risk assessment showed that all sampling sites were at Hazard Level I. Our results can provide useful information for assessing the environmental risks of MPs in coastal areas of China., Competing Interests: Declaration of competing interest There is no conflict of interest with respect to our manuscript, (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Hudson Bay is a small arctic inland shelf sea which receives large amounts of freshwater from riverine discharges, with marine flow from the north and the Atlantic. A warming climate has resulted in an expanded open water season which will result in an increase in shipping of fuel oil and petroleum to communities and mines on the western shore, increasing the risk of hydrocarbon releases. To evaluate the status of hydrocarbons, surface sediments were collected at 34 locations in the transportation route and offshore and analysed for several types of hydrocarbons. Total hydrocarbons varied by over 25 times between sites, reaching a maximum of 1116 μg/g OC (organic carbon basis) in Hudson Strait due to low molecular weight n-alkanes from marine primary production. The gross mean for all sites was 344 μg/g OC (GSD = 173-682), roughly equivalent to other remote sites in the Canadian Arctic with no known local hydrocarbon source. n-alkanes accounted for >90 % of residues. Diagnostic ratios (e.g., Carbon Preference Index (CPI), Odd-Even Predominance (OEP)) indicated mixed sources of n-alkanes, likely due to the input from vascular plants and ombrotrophic peat in northern and western watersheds, and primary production within the Bay. The elevated proportion of high molecular weight n-alkanes at deep water sites is consistent with lotic particulate organic matter deposited in the nearshore environment and redeposited offshore. Ʃ 36 PAHs were a small fraction (1.9 %) of hydrocarbons, with a gross mean of 5.68 μg/g OC (GSD = 3.30-9.79). PCA separated deep water sediments from nearshore and community samples due to 4 alkylated naphthalenes which usually indicate a petrogenic source but probably indicates a natural source due to the lack of other petrogenic markers. Priority PAHs (i.e., Ʃ 16 PAH) varied from 31.5 % to 56.6 % of the Ʃ 36 PAH residues. The concentrations of individual PAHs were well below the Interim Sediment Quality Guidelines recommended by the Canadian Council of Ministers of the Environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Heavy metal pollution associated with human activity is of big concern in tropical bays. Microorganisms may be highly sensitive to heavy metals. Nonetheless, little is known about effects of heavy metals on microbial structure in tropical bay sediments. In this study, 16S rRNA gene sequencing and potential ecological risk index analysis were used to analyze the relationships between nine metals (arsenic, lead, cadmium, cobalt, chromium, copper, zinc, manganese, and nickel) and bacterial communities in the sediments of Bamen Bay, China. Our results showed that Bamen Bay was under a considerable ecological risk and cadmium had the highest monomial potential ecological risk. In addition, individual metal contamination correlated with bacterial community composition but not with bacterial α-diversity. Arsenic was the metal influencing bacterial community structure the most. Our findings provide a novel insight into the monitoring and remediation of heavy metal pollution in tropical bays., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

Antibiotics have been detected in aquatic environment around the world. Understanding internal concentrations of antibiotics in organisms could further improve risk governance. In this study, we investigated the occurrence of seven sulfonamides, four tetracyclines, five fluoroquinolones, and five macrolides antibiotics in six fish, four crustaceans, and five mollusks species collected from Qinzhou Bay, an important part of the Beibu Gulf in the South China Sea in 2018. 19 of all the 21 target antibiotics were detectable in biota. The total concentrations of the antibiotics ranged from 15.2 to 182 ng/g dry weight in all marine organisms, with sulfonamides and macrolides being the most abundant antibiotics. Mollusks accumulated more antibiotics than fish and crustaceans, implying the species-specific bioaccumulation of antibiotics. The pH dependent partition coefficients of antibiotics exhibited significantly positive correlation with their concentrations in organisms. The ecological risk assessment suggested that marine species in Qinzhou Bay were threatened by azithromycin and norfloxacin. The annual mass loading of antibiotics from Qinzhou Bay to the coastal land area for human ingestion via marine fishery catches was 4.02 kg, with mollusks being the predominant migration contributor. The estimated daily intakes of erythromycin indicated that consumption of seafood from Qinzhou Bay posed considerable risks to children (2-5 years old). The results in this study provide important insights for antibiotics pollution assessment and risk management., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

With the rapid marine economic development, the problem of the marine ecological environment has become progressively prominent. Mariculture monitoring plays an essential role in sustaining ecological stability, rational planning, and green economic development of sea areas. Using the Landsat image, the raft-mariculture area information of Haizhou Bay and its adjacent southern waters were extracted by the object-oriented classification method based on remote sensing techniques. Landscape pattern index and principal component analysis were used to analyze the spatiotemporal expansion and structural changes of mariculture areas, and to quantify the effects of natural, socio-economic factors on the spatiotemporal variations of mariculture areas. This study discusses the correlation between the mariculture area and the outbreak scale of Enteromorpha Enteromorpha green tide. Results show that the object-oriented classification method has the highest accuracy, with total classification accuracy and Kappa coefficient of more than 90% and 0.79, respectively. The total area, patch density, and landscape shape index of mariculture areas in Haizhou Bay increase yearly, which demonstrates that the heterogeneity and fragmentation increase with the expansion of the mariculture area. The landscape pattern changes in the mariculture area are predominantly impacted by annual mean sea surface temperature (SST), annual average wind speed, social development level, and population density, etc. The larger the area of raft-aquaculture, the wider the outbreak scale of the Enteromorpha prolifera disaster. Study results can provide scientific references for the further development of mariculture in Haizhou Bay and marine environmental protection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The nutrient status in Laizhou Bay has changed in composition and structure as a result of anthropogenic activities and climate change, which has led to several environmental problems (e.g., eutrophication, organic pollution and red tides). To better understand the spatiotemporal variations in dissolved inorganic nitrogen (DIN), dissolved inorganic phosphorus (DIP), and eutrophication in the Laizhou Bay, we collected historical research data and conducted four cruises in 2021. The highest surface DIN was found to occur in autumn and predominantly concentrated in the southwestern bay. The highest surface DIP content was found in winter and distributed in the northwestern bay. Surface organic pollution showed estuaries as the most polluted areas. In the past 40-60 years, the DIN, DIP, and eutrophication have shown an inverted U-shaped trend, and the bay has changed from N limitation to P limitation. Economic development, phytoplankton absorption, and bottom mineral release are factors influencing the content and distribution of nutrient in the bay., Competing Interests: Declaration of competing interest The authors declare that this article was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

An analytical framework was proposed for analyzing long-term chemical pollution in a coastal region with limited environmental data. The framework consists of compiling and synthesizing the available knowledge including the chemical's properties and the environmentally relevant data, as well as the data obtained by past monitoring studies. The gathered data is analyzed to assess multimedia fate of the pollutant by using fugacity-based intermedia transport calculations. Uncertainty analysis by applying Monte Carlo simulations is an integrated part of the framework. Dispersion factor (k) values were adopted, enabling a unified and intuitive way to define lognormal uncertainty distributions. The proposed framework was applied to polycyclic aromatic hydrocarbon (PAH) pollution in Izmit Bay, a coastal region in Turkey, impacted by industrialization and population growth. The analysis showed the importance of atmospheric pollution as a PAH source and indicated that Izmit Bay sediments may be at steady state for most PAHs., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Based on a three-dimensional hydro-biogeochemical model, the compound and individual impacts of two types of human activities, i.e., land reclamation and land-based pollutant input, on coastal water quality were studied. In Qinzhou Bay (QZB), China, a total of 38.90 km 2 of tidal flat was reclaimed between 2004 and 2019, and the Chemical Oxygen Demand (COD) in the wastewater was reduced by over 40%. However, the Dissolved Inorganic Nitrogen (DIN) was increased by above 40%, and the Dissolved Inorganic Phosphorus (DIP) was increased by about 17%, leading to the continuous deterioration of water quality in QZB. Correspondingly, the model results show that the bay's average COD decreased by 6.86%, but the DIN and DIP increased by 57.53% and 17.39%, respectively. Considering the individual effects, land reclamation contributed 72.73%, 75.38%, and 25.01% to the changes in the COD, DIN, and DIP concentrations in QZB, respectively; and the remainder was caused by the variations in the land-based pollutant input. By considering the compound effect of these two types of human activities, it was found that land reclamation can hinder the water quality improvement induced by the decrease in land-based pollutant input; and it can intensify the water quality deterioration induced by the increase in land-based pollutant input. These results indicate that the impact of land-based pollutant input on coastal water quality was modulated by land reclamation. However, the modulation did not affect the DIP since the phosphorus was the restrictive element in QZB. The comparison of different experimental results revealed that restoring hydrodynamics to enhance the bay-shelf exchange would be a more effective method of ecological restoration than solely reducing the pollutant input., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The history of metal pollution in the semi-enclosed and human-influenced marine system of the Boka Kotorska Bay (Southern Adriatic) was studied considering geological composition of the surrounding catchment, the sedimentation rate and the mineralogical and early diagenetic processes in the recent sediments. The determination of background concentrations of metals, undertaken for the first time in this environment, proved to be particularly important for Ni and Cr, which are naturally enriched in the sediments of the southern Adriatic. The results showed widespread moderate contamination with Pb and Sn since the 1970s, while the upper layers of sediments near shipyards, marinas and urban areas were more contaminated with Sn, Cu, Pb, Zn, Cd, As, Sb and Mo. The transport of material through the narrow straits separating different parts of Boka Kotorska Bay resulted in a different geochemical composition of the smaller bays and a limited distribution of contaminated sediments from local sources., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The concentrations of metals in the waters of Brunei Bay, Malaysia were determined to define the current level and changes of its distribution. Discriminant analysis showed that metals distribution was spatially influenced by anthropogenic activities, whereas the distribution of cadmium (Cd) and zinc (Zn) was temporally influenced by the seasonal changes. High concentration of particulate metals in the coastal region during the wet season was presumably affected by freshwater intrusion and strong current disturbance. Generally, the enrichment factor of the aluminium (Al), Cd, copper (Cu), lead (Pb), and Zn proved enrichment by anthropogenic sources, except for iron (Fe). Furthermore, Cd has the highest enrichment factor value, signifying the potential risk of Cd on the Brunei Bay waters even at a low level. However, the Malaysia Marine Water Quality Criteria and Standard have classified the Brunei Bay waters as unpolluted., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Microplastic (MP) was investigated in Zhanjiang Bay, a semi-enclosed bay in south China and famous for considerable mariculture industry, to evaluate whether mariculture activities accelerated MP pollution. The MP abundances ranged from 0 to 2.65 n/m 3 (number/m 3 ), showing seasonal variances with higher levels in May and September and lower levels in January. In the inner part of the bay, a significantly high MP abundance and predominance of foam were found during the oyster breeding period, and pollution sources were prone to be single and extensive. This suggested that MPs were strongly influenced by the intensive plastic products for oyster culturing, especially during breeding. Moreover, plastic cages used for culturing were the main source of MPs in the central part of the bay. By conducting statistical analysis for eight representative bays, the economic growth, social development, agriculture structure, and aquaculture development were supposed to influence the local MP pollution level., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Present study explains the disparity in biological production (primary and secondary) with respect to two distinct monsoonal regimes in the western Bay of Bengal, viz., deficit monsoon (DM) and normal monsoon (NM). A combination of in situ and satellite data during the years 2002 (DM) and 2003 (NM) was used to address the physico-chemical and biological responses. The basin was relatively warm (ΔSST = 0.55 °C) and fresh (ΔSSS =  -0.55) during DM than NM. Physical processes such as coastal upwelling and cyclonic eddy were prominent during NM. Variations of hydrography between DM and NM were reflected in the biological production as well. Chlorophyll a concentration (0.05 to 5.2 mg m -2 ) was almost similar during both the periods; however, column production showed higher values during DM. Mesozooplankton standing stock was relatively less during DM than NM. Composition of zooplankton also showed pronounced variation between the periods. This can be attributed to the variability in biological response of the region to the varying environmental condition. Relatively high chlorophyll a and primary productivity observed during DM may be due to the increased light availability (less cloud cover) and extended euphotic depth. In addition, the low mesozooplankton standing stock (low grazing) observed during the period also might have helped in maintaining a relatively high rate of production. The seasonal production of the basin is influenced by duration and intensity of various atmospheric as well as oceanic processes., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Globally, the conditions and time scales underlying coastal ecosystem recovery following disturbance remain poorly understood, and post-disturbance examples of resilience based on long-term studies are particularly rare. Here, we documented the recovery of a marine foundation species (turtlegrass) following a hypersalinity-associated die-off in Florida Bay, USA, one of the most spatially extensive mortality events for seagrass ecosystems on record. Based upon annual sampling over two decades, foundation species recovery across the landscape was demonstrated by two ecosystem responses: the range of turtlegrass biomass met or exceeded levels present prior to the die-off, and turtlegrass regained dominance of seagrass community structure. Unlike reports for most marine taxa, recovery followed without human intervention or reduction to anthropogenic impacts. Our long-term study revealed previously uncharted resilience in subtropical seagrass landscapes but warns that future persistence of the foundation species in this iconic ecosystem will depend upon the frequency and severity of drought-associated perturbation.

The impact of the trace elements on selected marine fishes/crustacean in Kuwait (Sheam, Lobster, Speatty, and Nagroor) were investigated (As, Cd, Ni, Pb, and V) using the element concentrations in marine water and sediments. The toxic elements concentrations were measured in water samples (As, Cd, Cr, Cu, Hg, Ni, Pb, V, and Zn) for estimation of toxic levels, heavy metal evaluation index (84-360), and the degree of contamination (77-353). Similarly, sediment samples were analyzed for As, Cd, Cr, Cu, Ni, Pb, V and estimated for contamination factor, I geo index, and ecological risk factor with respect to each element analyzed in the sample. The modified degree of contamination (0.25-3.67), risk index (6.5-282.27), metal pollution index (5.95-18.21), and pollution load index (0.27-1.2) were calculated for the samples. This study demonstrated that the water was medium to high contaminated with Cd, Hg, Pb, and V. The sediment analyses showed that most of the metals were within the toxic limits except for Cd, Cu, and Pb in few samples. Most samples were in between the effect range low-effect range medium and threshold effect level-probable effect level range of most metals, except for Cr, Cu, and Ni. Average trace elements concentration in fishes varieties investigated in this study indicated high As in all varieties irrespective of the season and high Ni in all fish during summer. The bioaccumulation factor showed that the trace elements in sediments contributed more to the fish than water. Concentrations of trace elements were greater in fish sampled in winter than that sampled in summer due to variations in the planktonic population in the sea. The estimated daily intake and the chronic daily intake for the Kuwaiti male and female were calculated. The hazards studied revealed that the consumption of Lobster and Speatty may lead to cancer and non-cancer hazards, in both male and female, Speatty having higher probability. The major sources of toxic elements contamination of Kuwait Bay water and sediment appear to be oil-based contamination, urban sewage, brine from desalination, and the trace elements released due to the natural oxidation-reduction processes.

Microplastic (MP) pollution has spurred a wide range of concerns due to its ubiquity and potential hazards to humans and ecosystems, yet studies on MP abundance, distribution, and ecological impacts on the small-scale local estuarine systems are insufficient. We conducted the first study of MP pollution in surface water of Dongshan Bay in southern China. A total of six water samples were collected using a Manta trawl (length = 3 m, width = 1 m, height = 0.6 m, and mesh size = ∼330 μm). The abundance, type, shape, color, and size, were measured using light microscopy and micro-Raman spectroscopy. Our results showed that MPs spanned from 0.23 to 4.01 particles m -3 with an average of 1.66 particles m -3 . 75% of the MPs were PP, PE, and PS that may be explained by the widespread application of PE, PP, and PS foam in local fishing and aquaculture within the bay. Foam, white, and 1.0-2.5 mm were dominant shape, color, and size of MPs, respectively. Both indices of MPs-induced risk (H estuary  = 13.7) and pollution load (PLI estuary  = 14.2) yielded a Hazard Level II for MPs pollution in the Dongshan Bay. The potential ecological risk from combined MPs polymers (RI estuary  = 21.5) ended up at a minor risk. Our findings established the first set of baseline data on MPs pollution in Dongshan Bay and provided preliminary quantitative measures on the scale of ecological risk, which would improve the understanding of MP fate, transport, and ecological impacts in the estuarine environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Submarine groundwater discharge and associated trace element fluxes from the Coleroon River estuary to south bay, India, has been attempted, because increasing trace elements could result in harmful algal blooms and eutrophication. Trace elements (Al, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Mo, Ba, Pb, Th, and U) in surface water, pore, and groundwater samples were monitored for 10 days in three locations (A, B, and C) by considering tidal fluctuations. The trace elements Al, Cr, Fe, Ni, Zn, Sr, Mo, Pb, Th, and U were greater and found to be influenced by processes, such as fresh groundwater discharge and seawater intrusion. Lower Mn, Cu, and Ba signifies impact due to sediment adsorption, mixing, and elemental exchange during fresh groundwater and seawater mixing. Salinity versus trace element plot infers greater trace element mobility with cumulative salinity influenced by the conformist behavior of freshwater, seawater, and mixing. The calculated submarine groundwater discharge supported dissolved trace elements fluxes were 107,047.8 n mol d -1  m -1 for location A, 183,520.2 n mol d -1  m -1 for location B, and 181,474.4 n mol d -1  m -1 for location C, respectively. Variations in dissolved trace elements fluxes are attributed to variations in pH, free redox environment in the aquifer, adsorption or desorption by sediments, and the environmental cycle of marine organisms.

The cycling and fate of polycyclic aromatic hydrocarbons (PAHs) is not well understood in estuarine systems. It is critical now more than ever given the increased ecosystem pressures on these critical coastal habitats. A budget of PAHs and cycling has been created for Galveston Bay (Texas) in the northwestern Gulf of Mexico, an estuary surrounded by 30-50% of the US capacity of oil refineries and chemical industry. We estimate that approximately 3 to 4 mt per year of pyrogenic PAHs are introduced to Galveston Bay via gaseous exchange from the atmosphere (ca. 2 mt/year) in addition to numerous spills of petrogenic PAHs from oil and gas operations (ca. 1.0 to 1.9 mt/year). PAHs are cycled through and stored in the biota, and ca. 20 to 30% of the total (0.8 to 1.5 mt per year) are estimated to be buried in the sediments. Oysters concentrate PAHs to levels above their surroundings (water and sediments) and contain substantially greater concentrations than other fish catch (shrimp, blue crabs and fin fish). Smaller organisms (infaunal invertebrates, phytoplankton and zooplankton) might also retain a significant fraction of the total, but direct evidence for this is lacking. The amount of PAHs delivered to humans in seafood, based on reported landings, is trivially small compared to the total inputs, sediment accumulation and other possible fates (metabolic remineralization, export in tides, etc.), which remain poorly known. The generally higher concentrations in biota from Galveston Bay compared to other coastal habitats can be attributed to both intermittent spills of gas and oil and the bay's close proximity to high production of pyrogenic PAHs within the urban industrial complex of the city of Houston as well as periodic flood events that transport PAHs from land surfaces to the Bay., Competing Interests: The authors have declared that no competing interests exist

The impacts of microplastics (MPs) and phthalates (PAEs), a class of MP-associated contaminants, on the marine environment are not thoroughly understood despite concern over their adverse effects on humans and ecosystems. Field studies linking MPs and PAEs in seawater have not yet been reported. We investigate for the first time the correlation between MPs contamination and the presence of PAEs in the surface seawater of Jiaozhou Bay (JZB), a semi-enclosed metropolitan bay in northern China heavily impacted by human activity. The abundance of MPs, dominated by polyethylene and polyethylene terephthalate mostly smaller than 2 mm, ranged between 24.44 items/m 3 and 180.23 items/m 3 , with the majority being black and transparent fibers and fragments. Concentrations of PAEs varied from 129.96 ng/L to 921.22 ng/L. Relatively higher abundances of MPs and higher concentrations of PAEs were generally found in areas near riverine inputs and sewage treatment plants. There was a strong correlation between PAEs concentration and MPs abundance, suggesting that they are closely linked. In a risk assessment combining PAEs and MPs, the risk quotients (RQs) indicated that the ecological risk of di-n-butyl phthalate in JZB was relatively high (0.046JZB  = 11.76), and mainly due to polyvinyl chloride., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Xiangshan Bay provides most of the seafood for residents from the southeast coast of China. However, information on the safety of local seafood was not well known. In this study, we investigated the residue, spatial distribution and potential health risks of ten polychlorinated biphenyls (PCBs) in seafood and surface sediment samples during six years (2011-2016). The results indicated the level of PCBs in 9 types of seafood from Xiangshan Bay ranged between ND and 25.3 ng·g -1 . The highest average concentration of PCBs (14.2 ng·g -1 ) was observed in Ostreidae. The average PCB concentrations in the surface sediments was 1.58 ng·g -1 (ND to 15.2 ng·g -1 ). The biota-sediment accumulation factors of the PCBs in most seafood indicated that the seafood was readily subjected to the bioaccumulation of PCBs from sediments. The carcinogenic risks were all within the safe ranges of 9 types of seafood for adults., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

To date, the impact of air-sea exchange on spatial distribution of atmospheric methane (CH 4 hereafter) remains less understood in the coastal areas of China. Here we measured the dissolved and atmospheric CH 4 in the Dalian Bay and adjacent area in July and August 2014, respectively. Results showed that the study area was a net significant source of atmospheric CH 4 , with a mean sea-to-air CH 4 flux of 170.6 ± 149.5 μmol/(m 2 ·day). We optimized a method to accurately quantify the elevated atmospheric CH 4 mole fraction (△CH 4 hereafter) caused by air-sea exchange. The calculated △CH 4 in the study area ranged from 15.4 to 102.1 nmol/mol, 1.5-10.2 nmol/mol, and 0.03-0.22 nmol/mol at the mixing height of 1, 10, and 471 m, respectively. The △CH 4 mole fractions caused by air-sea exchange were positive with sea-to-air CH 4 flux and in situ observed atmospheric CH 4 mole fraction, while negative with altitude. Under the standard conditions, we defined 50.8 μmol/(m 2 ·day) as the criteria value of sea-to-air CH 4 flux which could result in a detectable elevation atmospheric CH 4 mole fraction at a height of 10 m., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Environmental monitoring is important to the health management of an ecosystem. Biomarkers are particularly relevant because they are direct indicators of any toxic effects on organisms and are cheaper to use compared with chemical indicators, especially for extremely low-level organic contaminants. Fish can be significantly affected by pollutants, given their high trophic levels in aquatic food chains. Their immune function is closely related to their survival. The present study compared immune function-related parameters of wild mullet (Liza haematocheila) samples from low (Jinzhou) and high (Yingkou) polluted sites during the pre-winter (PW) and pre-breeding (PB) periods in Liaodong Bay, to evaluate the effect of water pollution on fish health and to explore potential biomarkers of coast water pollution. Compared with Jinzhou mullet, there was a significantly higher level of hematocrit in Yingkou mullet, but a significantly lower serum lysozyme level (P < 0.001), indicating that these fish were immunosuppressed. Significant differences occurred in the spleen between the two site populations. The abnormal: normal fish ratio in Yingkou L. haematochila was significantly higher than that of Jinzhou L. haematochila (2.5 times of that of Jinzhou during PB and nine times during PW). The splenic index of male Yingkou L. haematochila was 47.2% higher than that of Jinzhou L. haematochila in PW (P = 0.001). Moreover, histological observations showed that the spleen of the former was more congestive, with increased numbers (39.6% more) of melanomacrophage centers (MMCs) and changes in pigments (hemosiderin 8.3% higher and melanin 29.4% higher), compared with the latter. The splenic MMC area of Yingkou L. haematochila was significantly smaller than that of Jinzhou L. haematochila (P < 0.05) in PB, but showed no clear difference in PW (P > 0.05). Splenic MMC number was significantly higher in individual Yingkou L. haematochila with abnormal livers compared with normal Yingkou L. haematochila during both sampling periods. The splenic MMC area in abnormal livers was approximately four times those of normal individuals during PB in Yingkou L. haematochila. The number of splenic melanomacrophages (MM) in abnormal livers was approximately nine times those of the normal livers during PW. There were also differences in pigments in normal Yingkou individuals compared with normal Jinzhou samples during PW (melanin 29.4% higher and hemosiderin 8.3% higher). Based on these results, we suggest that serum lysozyme activity, splenic MM number and MMC (both number and area), and melanin of local fish have potential as sensitive biomarkers for the assessment of coastal water pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

We aimed to determine the temporal variation of trace metals concentrations in surface water and surface sediment samples at Kutubdia Channel, Bangladesh. Trace metals of samples were detected using energy dispersive X-ray fluorescence (Energy-dispersive X-ray spectroscopy) method. The lowest concentration of metals was found in water samples during post-monsoon season and the highest during pre-monsoon season (Cu: 0.030 ± 0.001 μg/L in pre-monsoon and 0.026 ± 0.002 μg/L in post-monsoon, Zn: 0.087 ± 0.003 μg/L in pre-monsoon and 0.073 ± 0.002 μg/L in post-monsoon, Fe: 0.080 ± 0.001 μg/L in pre-monsoon and 0.055 ± 0.001 μg/L in post-monsoon). In contrast, metal concentration in surface sediment samples were higher in post-monsoon than in pre-monsoon season i.e. Cr 11 mg/kg in pre-monsoon and 12 mg/kg in post-monsoon, Mn 571 mg/kg in pre-monsoon and 606 mg/kg in post-monsoon, As (8 mg/kg in pre-monsoon and 10 mg/kg in post-monsoon, Pb (22 mg/kg in pre-monsoon and 24 mg/kg in post-monsoon, and Fe 2317 mg/kg in pre-monsoon and 2435 mg/kg in post-monsoon. We found a spatial gradient of high to medium to low in trace metal concentration from river to river mouth to offshore area. Considering the sources of metals, land erosion by waves and tidal action, an influx of water and sediment from the surrounding rivers, agricultural waste, industrial effluent and sewage are the most likely sources of metal pollution in the study area. We conclude that proper management strategies should be adopted to control the pollution and conserve the ecosystem health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The contributions of contaminant sources are difficult to resolve in the sediment record using concentration gradients and flux reconstruction alone. In this study, we demonstrate that source partitioning using lead isotopes provide complementary and unique information to concentration gradients to evaluate point-source releases, transport, and recovery of metal mining pollution in the environment. We analyzed eight sediment cores, collected within 24 km of two gold mines, for Pb stable isotopes, Pb concentration, and sediment chronology. Stable Pb isotope ratios ( 206 Pb/ 207 Pb, 208 Pb/ 204 Pb) of mining ore were different from those of background (pre-disturbance) sediment, allowing the use of a quantitative mixing model. As previously reported for some Arctic lakes, Pb isotope ratios indicated negligible aerosol inputs to sediment from regional or long-range pollution sources, possibly related to low annual precipitation. Maximum recorded Pb flux at each site reached up to 63 mg m -2 yr -1 in the period corresponding to early years of mining when pollution mitigation measures were at a minimum (1950s-1960s). The maximum contribution of mining-derived Pb to these fluxes declined with distance from the mines from 92 ± 8% to 8 ± 4% at the farthest site. Mining-derived Pb was still present at the sediment surface within 9 km of Giant Mine more than ten years after mine closure (5-26 km, 95% confidence interval) and model estimates suggest it could be present for another ∼50-100 years. These results highlight the persistence of Pb pollution in freshwater sediment and the usefulness of Pb stable isotopes to quantify spatial and temporal trends of contamination from mining pollution, particularly as concentrations approach background., (Crown Copyright © 2020. Published by Elsevier Ltd. All rights reserved.)

Cartagena Bay (CB) is an industrialized site in the Caribbean. The aim of this study was to evaluate contamination patterns by trace elements in sediments from CB. Sediment samples from twelve sites in CB, and three at the Grand Marsh of Santa Marta (GMSM), a reference site, were collected during dry and rainy seasons. Forty-four trace elements were evaluated employing ICP-MS, and mercury (Hg) was measured using a Hg analyzer. Most contaminated sites corresponded to stations related to repair and maintenance of ships, with high concentrations of Cr, Cu, As and Cd; as well as in areas where cargo transshipment centers and cruise ship terminals operate, which showed elevated levels of Ba. Stations receiving inputs from petrochemical and fertilizer plants displayed high content of Pb. At the station where an extinct chlor-alkali plant was located, a high total Hg level was found, highlighting its persistence. At least 70% of the samples presented Cr, Cu, and As concentrations that were ≥ Threshold Effect Level, < Probable Effect Level, ≥ Effects Range Low and < Effects Range Medium, suggesting adverse biological effects could occur occasionally. Potential Ecological risk values revealed that only Hg and Cd may generate deleterious effects to the aquatic life. However, with few exceptions, sediment samples from CB can be considered as moderately to heavily contaminated, as shown by the I geo . In short, the principles of ecosystem-based management should be implemented along Cartagena Bay to guarantee safe levels of trace elements in sediments and a better quality of this estuary., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Lipophilic phycotoxins (LPs) pose significant threats to the health of marine mammals, birds, and human beings. The distribution and components of lipophilic phycotoxins contamination in subtropical area in the South China Sea are rarely known. This study systematically assessed the composition, concentration, and distribution of typical LPs in a typical subtropical bay, Daya Bay located in the South China Sea. Phytoplankton, seawater, suspended particulate matter, sediments, and shellfish samples were simultaneously collected from Daya Bay, and analyzed using liquid chromatography with tandem mass spectrometry. Okadaic acid, dinophysistoxins-1, pectenotoxins-2, yessotoxin and its derivate homo-yessotoxin, azaspiracid-2, 13-desmethyl spirolide C and gymnodimine were widely spread in multiple media in Daya Bay. Pectenotoxins-2 was the most widely distributed and highly concentrated toxin in the marine environments of Daya Bay. Toxin homo-yessotoxin was only detected in sediments and shellfish samples, and none of yessotoxin group components were found in phytoplankton and seawater, indicating that sediments were the major source of yessotoxin in shellfish. The study strongly demonstrated the lipophilic phycotoxins accumulated in shellfish are multisource, not only derived from toxigenic algae, but also from other marine media containing lipophilic phycotoxins. This study systematically distinguished multi-pathways of bioaccumulation of LPs in the marine shellfish., (Copyright © 2019 Elsevier Ltd. All rights reserved.)