Plastic pollution is one of the major issues impacting on the marine environment. Plastic polymers are known to leach industrial chemicals and associated contaminants. In this review, we focused on assessing the global distribution and concentration of two polystyrene-derived contaminants, hexabromocyclododecanes (HBCDs) and styrene oligomers (SOs), in marine sediments and seawater. Overall, most of the studies were carried out in Asia, North America, and Europe. Relatively high concentrations of these contaminants are generally attributed to the proximity of urban cities, plastic industries, polystyrene pollution, and aquaculture. Moreover, the concentrations in sediments are many times higher than in seawater. HBCDs were found to be a negligible risk to marine biota when compared to the ecotoxicological endpoints. However, realistic concentrations of SOs could compromise the wellbeing of certain species in highly polluted sites. The future perspectives and research were discussed.

A risk assessment framework for direct exposure of residual additives and monomers present in ingested plastic particles, including microplastics, in the Danish marine environment, was presented. Eight cases of different polymer types and product groups were defined that represent the most significant exposures, and thus potential high-risk cases, towards marine organisms. Risk Quotients (RQ) were calculated for three trophic levels, i.e. pelagic/planktonic zooplankton: copepod, benthopelagic fish: Atlantic cod and seabird: northern fulmar. European and Danish Environmental Quality Standard (EQS) values were used as Predicted No-Effect Concentrations (PNEC). RQ larger than unity, indicating potential risks, were found for copepod and cod (pelagic community) and the flame-retardant pentabromodiphenyl ether (PeBDE) used in polyurethane (PUR), the biocide tributyltin (TBT) present as impurity in polyvinylchloride (PVC) and PUR, and the flame-retardant hexabromocyclododecane (HBCDD) used in expanded polystyrene (EPS). A potential risk was found for fulmar (secondary poisoning) and PeBDE used in PUR.

Compared to open sea environments, there is still limited knowledge about microplastic levels in semi-enclosed systems such as coastal lagoons. This work aims to assess the levels of MPs in the waters of an urban lagoon (Bizerte lagoon, northern Tunisia) and to study the effects of environmental factors on their distribution and abundance. Average concentration of total MPs was found to be 453.0 ± 335.2 items m⁻³. The upper 25 cm water layer of the lagoon is most likely to contain ~16.99 × 10⁹ MPs items (which correspond to a total mass of 42.47 t). Fibers were the primary MPs types encountered, and most of MPs particles identified were white and clear-colored. Polyethylene and polypropylene were the predominant polymer types in Bizerte lagoon. Among the various potential plastic sources of MPs, unmanaged domestic plastic wastes are likely to be the major source of plastic pollution in the lagoon. Several environmental factors appeared to influence the distribution and density of MPs in the lagoon waters. These information contribute to better understand the dynamics of MPs in lagoons and to develop environmental management actions.

Marine litter is one of the most pressing problems of our time and a major threat to ocean health; much of it comes from land-based sources, including from beachgoer activities. This study investigates how product design could influence littering behaviors of beachgoers when applied to beach trash cans (TCs). Over the course of six weeks three differently designed TCs were placed on a Mediterranean Sea tourist beach in Israel while observers tracked the behavior of 536 nearby groups (“entities”) of beachgoers. Researchers analyzed: a) entities' locational choices; b) materials discarded in the TCs; and c) littering behaviors around the TCs. Based on the data collected, a “motivating” TC design performed best, encouraging the highest level of beachgoer interaction. Further research is needed in more and varied beach contexts, but this type of initial interdisciplinary research suggests how the design discipline could contribute to preventing marine litter from land-based sources.

Nitrogen fixation and its ecological regulation are poorly understood in the tropical estuaries, which are highly influenced by anthropogenic disturbances. In this study, we investigated the role of nutrient stoichiometry in the diversity, abundance and activity of N₂-fixing bacterial community and their seasonal variations in the water column of a tropical eutrophic estuary (Cochin estuary). The N₂ fixation rates in the estuary ranged from 0.1 to 2.0 nmol N₂ l⁻¹ h⁻¹, with higher activity during post-monsoon and lower during monsoon. The rates are appeared to be primarily controlled by dissolved inorganic nitrogen and phosphorous (N:P) ratio. Clone library analysis of nitrogenase (nifH) gene revealed that the major N₂ fixing phylotypes belong to Cluster I and Cluster III diazotrophs. The overall findings of this study suggest that monsoon induced seasonal changes in nutrient stoichiometry control the distribution and activity of diazotrophs in a tropical estuary.

The potential ecological impacts of elevated suspended sediments (SS) in coastal areas due to human activities remain unclear. In particular, physiological response of benthic fish to SS exposure in polluted environment has not been documented. We determined sub-lethal toxicity of polluted and non-polluted SS to olive flounder. Test organism was exposed to varying concentrations of SS (0–4000 mg L⁻¹) and real-time oxygen consumption rate (OCR) was measured for 12 h. The early-juvenile was sensitive to SS, particularly at >500 mg L⁻¹, but late-juvenile was tolerant up to 4000 mg SS L⁻¹. Metal polluted SS (HQₘₑₜₐₗ > 1) increased OCR in general, particularly at >1000 SS mg L⁻¹. Combined effect of copper and SS exposure on fish was either synergistic or antagonistic. Overall, potential adverse effect of polluted SS on fish greatly varied at different life stage and/or by metal pollution gradients.

In the present study, a modified water quality index (WQI) was used to evaluate the water quality in south coastal aquaculture area of Dalian, Liaoning Province, China. Four main culture areas with 40 sampling stations were covered. Ten variables were selected for principal component analysis/factor analysis (PCA/FA), and the major factors affecting water quality were identified. The PCA results showed that these factors were mainly associated with nutrients, natural conditions and organic matter. The modified WQI was calculated to identify the classes of water quality and to evaluate the spatial and temporal changes among the sampling areas. The results revealed that the water quality generally performed the worst in June, and the best in October. The modified WQI proved to be a useful method for water quality classification and characterizing spatial and temporal changes in Dalian aquaculture areas.

A study on the Rare Earth Element (REE) distribution in the bottom sediments of the Gulf of Tigullio (north-west Italy) was conducted. The results constitute a baseline for this zone of the Ligurian Sea and enabled the obtaining of valuable information on the origin and transport of sediments in the gulf. The distribution of REEs is controlled by phosphates, mainly monazite, and is generally homogeneous in the study area, reflecting the homogeneous distribution of the minerals. Some differences in REE and Sc distribution allow us to identify two sub-basins (Entella and Gromolo torrent sub-basins) characterised by slightly different geological frameworks. The “hat-shaped” observed patterns seem to indicate an overprinting of the original REE patterns due to exchanges between phosphates and seawater. REEs seem to be related with the rocks outcropping in the area, although an indirect effect of anthropic activity could be seen near a fish farm.

This research characterizes the temporal and spatial variability of the seawater carbonate chemistry on the near-shore waters of the northern Persian Gulf and Makran Sea. In general, normalized total alkalinity (nAT) showed a westward decrease along the coasts of Makran Sea and the Persian Gulf. Intertidal seawater was always supersaturated in terms of calcium carbonate minerals during the daytime. Rocky shore waters in the Persian Gulf were sinks for CO₂ in the winter during the daytime. The nAT decreased from Larak to Khargu Island by 81 μmol/kg. As expected, the two hypothetical drivers of bio-calcification, i.e., Ω and the [HCO₃⁻]/[H⁺] ratio, were significantly related at a narrow range of ambient temperature. However, as data were pooled over seasons and study sites, in contrast to ΩAᵣ, the [HCO₃⁻]/[H⁺] ratio showed a slight dependence on temperature, suggesting that the ratio should be investigated as a more reliable factor in future biocalcification researches.

Beaches are fundamental habitats that regulate the functioning of several coastal processes and key areas contributing to national and local budgets. In this study we provide the first large-scale systematic survey of anthropogenic litter on Brazilian beaches, covering a total of 35 degrees of latitude, recording the litter type, its use and size. Plastic comprised the most abundant litter type, followed by cigarette butts and paper. Small pieces (<5 cm) were dominant among litter size-classes and food-related use was associated to most litter recorded types. Generalized additive models showed that proximity to estuarine run-offs was the main driver to beach litter accumulation, reinforcing river drainages as the primary route of litter coastal pollution. Also, the Clean-Coast Index evidenced there was not a pattern of beach litter pollution among regions, which denotes that actions regarding marine pollution must be taken by all state governances of the country.