Sinking experiments were conducted using irregularly shaped polyamide (PA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET) particles sized 6 to 251 μm. Certified PS spheres were used to validate experiments and showed that the effect of particle size on terminal sinking velocity is well reproduced by the method. As expected sinking velocities of irregularly shaped particles were considerably lower than theoretical values for spheres of the same size range calculated via several approximations available in the literature. Despite the influence of particle shape, the dependence of terminal sinking velocity on particle size can reasonably well be described by a quadratic linear regression, with an average determination of 63%. To generalize results we present a model that predicts terminal sinking velocity as a function of particle size and particle excess density over the fluid. Improving the predictive power of this model requires further experiments with a range of particle characteristics.

Ten pharmaceutically active compounds (PhACs) were determined in northern Taiwan estuarine waters and Taiwan Strait (TS) seawater. The ecological risk of these PhACs was assessed using risk quotient (RQ), which is the ratio of the measured maximum concentration to the predicted no-effect concentration. Six PhACs were detected within the estuarine waters. Caffeine concentration (130–718 ng l⁻¹) was the highest among the analyzed PhACs. The distribution of PhACs in the Danshuei River Estuary generally exhibited addition behavior, except that caffeine showed conservative behavior. Carbamazepine, gemfibrozil, caffeine, and ketoprofen were detected in TS seawaters. Their concentrations follow the sequence: gemfibrozil > ketoprofen > caffeine > carbamazepine. The caffeine concentrations in TS seawaters were 2–3 orders of magnitude lower than those in Danshuei estuarine waters. With few exceptions for caffeine, erythromycin, and sulfadiazine posing low risk in some estuarine waters, most of the RQ values were <0.01, suggesting no adverse effects on aquatic organisms.

Discharge of effluents loaded with phosphorus (P) from anthropogenic activities constitutes serious eutrophication risks in marine and terrestrial ecosystems, including mangroves. Three mangroves in NE-Brazil were studied to evaluate the impact of P-rich-effluents from shrimp farming and domestic sewage, in relation to a control area (natural mangrove). Soil phosphorus fractionation and water chemical analysis were performed to assess potential pollution. We observed the most labile P forms increased gradually and significantly from control to sewage to shrimp farm impacted mangroves as observed by increasingly dissolved orthophosphate (PO₄³⁻) content in water and the exchangeable/soluble P (Exch-P) extracted from soils, which is supported by the discriminant analysis. Exch-P results were correlated to Humic-Acid-P, which can release more labile P forms when mineralized. Our results demonstrate a substantial impact of aquiculture and sewage effluents in mangroves at both organic and inorganic P fractions, raising important concerns regarding pollution for these marine ecosystems.

We aimed to show how the predicted pH decrease in the ocean would alter the toxicity, bioconcentration and dietary transfer of trace metal copper on seagrass ecosystems, on a short-term basis. Seagrass Zostera noltei was exposed to two pH levels (8.36 and 8.03) and three copper levels (nominal concentrations, <3, 30 and 300 μg Cu L⁻¹) in a factorial design during 21 days, while Gammarus locusta amphipods were continuously fed with the treated seagrass leaves. We found that the toxicity and bioconcentration of copper in seagrasses were not affected by pH, yet complex copper-pH interactions were observed in the seagrass photosynthesis. We demostrated that seagrasses can act as a copper source in the food web via direct consumption by herbivores. Future research need to investigate the interactive effects on a long-term basis, and to include biochemical and molecular endpoints to provide additional insights to the complex phisiological interactions observed.

Increased plastic consumption and poor waste management have resulted in litter representing an ever-increasing threat to the marine environment. To identify sources and evaluate mitigation measures, beach litter has been monitored. Using data from two citizen science protocols (CSPs) and OSPAR monitoring of Norwegian beaches, this study 1) identifies the most abundant litter types, 2) compares OSPAR to citizen science data, and 3) examines how to improve the management relevance of beach litter data. The dominant litter types were; food and drink- and fishery related items, and unidentifiable plastic pieces. Data from CSPs are consistent with OSPAR data in abundance and diversity, although few OSPAR beaches limit verification of CSP data. In contrast to OSPAR, the CSPs estimate the weight of the litter. CSPs lack important variables which could explain why some litter types are abundant in some particular areas. The latter could be improved by recording GPS positions.

Guanabara Bay (southeastern Brazil) is located in the metropolitan region of the Rio de Janeiro State and is being affected by high levels of anthropization. This work analyzes not only the concentrations of potentially toxic elements (PTEs), but also Pb stable isotopes to trace possible anthropogenic and natural sources of pollutants in the northern region of Guanabara Bay and the Suruí and Magé rivers. The Governador Island Channel, the regions to the north of Governador Island, north and west of Paquetá Island, and the Magé coast are most affected by PTEs. In the study area, high PTE concentrations result from both natural and anthropogenic sources. The main sources of metals include municipal solid waste incineration, atmospheric aerosols, and ore lead tailings, as indicated by Pb isotopes. This work shows that Pb stable isotopes, associated with metal contamination, can improve the assessment of estuarine environment quality.

An interlaboratory comparison exercise was conducted to assess the consistency of microplastic quantification across several laboratories. The test samples were prepared by mixing one liter seawater free of plastics, microplastics made from polypropylene, high- and low-density polyethylene, and artificial particles in two plastic bottles, and analyzed concurrently in 12 experienced laboratories around the world. The minimum requirements to quantify microplastics were examined by comparing actual numbers of microplastics in these sample bottles with numbers measured in each laboratory. The uncertainty was due to pervasive errors derived from inaccuracies in measuring sizes and/or misidentification of microplastics, including both false recognition and overlooking. The size distribution of microplastics should be smoothed using a running mean with a length of >0.5 mm to reduce uncertainty to less than ±20%. The number of microplastics <1 mm was underestimated by 20% even when using the best practice for measuring microplastics in laboratories.

Understanding the fate of spilled oil in cold environments is essential for oil spill response in Arctic areas. The potential for oils to adhere to sea ice and mechanical skimmers can significantly impact the success of oil spill response and influence the fate of oil in the marine environment. Therefore, the affinity of oil to sea ice and skimmer material was quantified experimentally for three different types of oils at various degrees of weathering. Contact angle measurements of crude oil droplets were performed on the top of and under sea ice and polyethylene-based skimmer material, being submerged in seawater (−2 °C). In addition, “dip- and refloat” tests were performed to quantify the adhesion and study the re-floating process of oil from sea ice at −2 °C (moist ice) and −20 °C (cold dry ice), and from a skimmer material prior to and subsequently to its submersion in seawater (−2 °C). The results indicated limited interaction of oils with sea ice submerged in seawater, but a strong affinity of oils towards polyethylene-based skimmer material.

The main objectives of the present study were to measure the concentration of mercury in Alosa spp. muscle tissue and to assess the health risk to consumers. For this purpose, fish samples were collected from four regions of the southern coast of the Caspian Sea. Mean concentrations of mercury in the regions of Bandar Torkaman, Feridonkenar, Chalos and Bandar Anzali were 264.10, 73.74, 161.90, and 183.80 μg g−1 dw, respectively. The mercury averages obtained in all four regions were below the standards recommended by the World Health Organization (WHO), the Food and Agriculture Organization (FAO), the Standardization Administration of China (SAC) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The values of hazard quotient also showed no potential health risk for consumer. However, the assessment of other contaminants is recommended for more accurate conclusions about the health risks of consumers through the consumption of the fish.

Riverine input is an important source of contaminants in the marine environments. Based on a hydrodynamic model, the dilution characteristics of riverine contaminants in the Seto Inland Sea and their controlling factors were studied. Results showed that contaminant concentration was high in summer and low in winter. Contaminant concentration decreased with the reduction of its half-life period, and the relationship between them followed power functions. Sensitivity experiments suggested that the horizontal current and vertical stratification associated with air-sea heat flux controlled the seasonal cycle of contaminant concentration in the water column; however, surface wind velocity was the dominant factor affecting the surface contaminant concentration. In addition, contaminant concentration in a sub-region was likely controlled by the variations in river discharges close to the sub-region. These results are helpful for predicting contaminant concentrations in the sea and are expected to contribute to assessing the potential ecological risks to aquatic organisms.