Estimates of marine debris are often based on beach surveys. Few studies have documented the veracity of these observations and the factors that may affect accuracy. Our laboratory-scale experiment identified potential sources of error associated with visual identification of marine debris (1–2 cm long) during shoreline surveys of sand beaches. Characteristics of the survey site (beach characteristics), observer (personal characteristics), and debris (color and size) may be important factors to consider when analyzing data from shoreline surveys. The results of this study show that the ability of individuals to accurately identify plastic fragments depends on the plastic and sand color, and density of shell fragments. Most suggestively, the high accuracy of blue plastic counts (95%) and the under-counting of white (50%) and clear plastic counts (55%) confirmed the hypothesis that a significant amount of clear and white plastic fragments may be missed during shoreline surveys. These results highlight the need for further research and possible modifications of visual shoreline survey methodologies in order to optimize this cost-effective method of marine debris monitoring.

The diversity of free-living dinoflagellates in the coastal areas of the central Red Sea, Saudi Arabia, was studied from April 2016 to March 2017. A total of 106 dinoflagellates belonging to 36 genera, 20 families and 7 orders were identified and characterized using light microscopy. Of these, 47 taxa were potentially harmful, and 60 taxa were recorded for the first time from the Red Sea. The unexpectedly high species diversity, including new records, was due to the benthic species. The monthly variability of planktonic species records exhibited negative correlations with temperature and salinity, although in most cases, the links between them were insignificant. Subsequently, the dinoflagellates checklist for the entire Red Sea was updated and showed that there were currently 395 taxa and 66 genera. The results of this study provide a solid foundation for future studies of dinoflagellate biodiversity in the Red Sea, particularly for benthic and harmful species.

Concentration of organochlorine pesticides (OCPs) (α-, β-, γ- hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethane (DDD), dichlorodiphenyldichloroethylene (DDE)) in four species of Pacific salmon (pink, chum, chinook, and sockeye) are presented. OCPs in salmon organs increased in the following order: muscle < liver < eggs < male gonads. Concentrations of the OCP in salmon organs increased in following order: DDE < γ-HCH < α-HCH. The level of pollutants in salmon is compared with the sanitary and epidemiological norms of Russia and other countries. Cancer and noncancer hazard ratios through consumption of salmon in Russian Far East for both men and women also were summarized. Noncancer and cancer hazard ratio values were far below threshold values (<1.0).

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.

Plastic debris is a major global threat to marine ecosystems and species. However, our knowledge of this issue may be incomplete due to a lack of a standardized method for quantifying ingested ultrafine particles (1 μm – 1 mm) in wildlife. This study provides the first quantification of ultrafine plastic in seabirds using chemical and biological digestion treatments to extract plastic items from seabird gizzards. The alkaline agent, potassium hydroxide, outperformed the enzyme corolase, based on cost and efficiency (e.g., digestion time). Ultrafine plastics were observed in 7.0% of Flesh-footed Shearwater (Ardenna carneipes) gizzards collected from Lord Howe Island, Australia and accounted for 3.6% of all plastic items recovered (13 out of 359 items). Existing methods for extracting ingested plastic from seabirds do not account for ultrafine particles, therefore our results indicate current seabird plastic loads, and the associated physical and biological impacts, are underestimated.

Ecological risk assessment of metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in surface sediments from 31 small craft harbours (SCHs) in Nova Scotia, Canada was conducted using multiple risk assessment approaches. Approaches used were contamination factor, pollution load index, geoaccumulation index, potential ecological risk factor for individual metals, comprehensive potential ecological risk index, mean probable effect level quotient and mean effects range median quotient. Results indicated most SCHs exhibited low ecological risk from sediment metal concentrations, except for two harbours. Metal contamination was highest in Canso Harbour, followed by Clarks Harbour. SCH sediments were only slightly contaminated with low probability of pollution according to mean probable effect level and mean effects range median quotients. However, pollution load and geoaccumulation indexes indicated Cd and Hg had the highest metal contamination across SCH sediments. Cadmium and Hg had the highest potential ecological risk, respectively compared to other metals.

Mariculture is known to contribute to oxygen depletion, pH decline and accumulation of nutrients and organic matter in sediments. However, studies on the bacterial vertical distribution of mariculture area are very limited. The bacterial abundance in the non-culture site (3.8 ± 0.8 × 10⁹ copies g⁻¹) was significantly higher than that in the three mariculture sites (1.2 ± 0.2 × 10⁹ copies g⁻¹), and bacterial diversity in the non-culture site was significantly higher than that in fish cage-TF (p < 0.05). The vertical distribution profiles of bacteria in non-culture and oyster culture sites were similar but very different from that of fish cage-TF. In addition, significant downward trends in bacterial abundance and diversity were observed as sediment depth increased (p < 0.05), and the most relevant environmental factors were moisture content, total nitrogen, total organic carbon and carbon/nitrogen. The dominant bacterial phyla in sediment were Proteobacteria, Chloroflexi and Bacteroidetes.

Trace metal contamination in the European sardine and anchovy food web was investigated in the Gulf of Lions, NW Mediterranean Sea, including seawater and size fractions of plankton. The results highlighted: i) higher and more variable concentrations in the smaller plankton size classes for all metals except cadmium; ii) higher concentrations in anchovy versus sardine for all elements except lead; iii) different patterns of metal bioaccumulation through the food web: cobalt, nickel, copper, silver, lead and zinc displayed continuously decreasing concentrations (with the exception of increased zinc in fish only), while mercury concentrations dropped considerably in larger plankton size classes and rose significantly in fish. Lastly, cadmium concentrations were found to be highest in intermediate plankton size classes, with very low levels in fish. The need to efficiently characterize the biological composition of plankton in order to fully identify its role in the mobilization and transfer of metals was highlighted.

Polycyclic aromatic hydrocarbons (PAH) have been reported as acetylcholinesterase (AChE) inibitors, although in vitro studies on PAH effects on AChE activity are scarce and have only been performed using electric eel brain extracts. Thus, this study investigated PAH effects on brain AChE activity in a tropical fish species in Southeastern Brazil, mullet (Mugil liza). Mullet specimens were obtained from Guanabara Bay (N = 20), Rio de Janeiro, Brazil. Brain AChE was extracted and exposed to an environmentally relevant concentration of Pyrene, Chrysene, Phenanthrene, and Naphthalene, and PAH metabolites, 2-Naphthol and 1-OH-Pyrene. AChE activity inhibition was observed, although no difference was observed between high- and low- molecular weight PAH. 2-Naphthol was a less potent AChE inhibitor than Naphthalene, albeit non-significantly. Further studies are required, since only one PAH concentration was used herein. Mullet brain extracts seem to be adequate to assess possible neurotoxic PAH effects on fish AChE.

In this study, a system was established to perform an initial environmental risk assessment of hazardous and noxious substances (HNS) spill accidents. Initial environmental risk assessment was performed using exposure and hazard assessments. An integrated hydrodynamic and chemical fate model was used to predict HNS concentrations at harbors, taking into account local environmental conditions. To consider the worst case HNS spill accident, the spill amount of 10,000 tonnages, was used for this study. The results show that highly soluble HNS are fatal to marine organisms during the neap tide. The results were based on a hypothetical worst case HNS spill accident and, not any specific actual HNS spill accident. Nevertheless, the method and system developed in this study, which includes the physical/chemical properties of 158 priority HNS, can be readily used to perform an initial environmental risk assessment for future HNS spill accidents.