A crucial step towards understanding potential impacts of the Deepwater Horizon oil spill to marsh ecosystems was to quantitatively determine the toxicity of oil remaining in the sediment. The objective of this study was to assess the potential injury to benthic species using standardized toxicity bioassays. Sediments were collected from locations with differing degrees of oiling based on previous assessments. Less than 13% of the 315 toxicity tests resulted in toxicity to amphipods, mysid shrimp, or sea urchins. There was no relationship among toxicity test results, oiling category or measured total polycyclic aromatic hydrocarbons (PAHs). Equilibrium partitioning sediment benchmarks and additive toxic units (ESBTUs) were applied as an additional line of evidence to evaluate the potential adverse effects based on PAH concentrations in field sediments. The ∑ESBTUs based on 34 PAHs at the 64 nearshore sampling locations were <1, indicating PAHs in sediments were unlikely to cause adverse impacts.

The ubiquitous presence of contaminants in the marine environment is considered a global threat to marine organisms. Heavy metals and microplastics are two distinct classes of pollutants but there are interactions between these two stressors that are still poorly understood. We examined the potential relationship between heavy metals (Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd, Ba, Hg, Pb) and microplastic particles in oysters sampled along the Paranaguá Estuarine System. The results suggested high levels of As and Zn in the bivalves, which are destined for human consumption. Microplastic particles were found in oysters from all sampled locations, demonstrating the spread of this pollutant in the marine environment and its ability to bioaccumulate in oysters. However, our data did not demonstrate a direct relationship between microplastics and heavy metals, suggesting that these particles are not the main route for heavy metal contamination of oysters in the Paranaguá Estuarine System.

The present study aimed to reveal correlations between environmental events and geochemistry variation and ecological risks of the coastal Tajan River. Sediment quality indices (Cf, Cd, Er, and RI) were applied to achieve the research objectives based on the concentration of toxic metals (As, Cd, Cr, Cu, Ni, Pb, Zn). The probably effective level is based on the concentration of As, Cr, and Ni observed. The coastal zone and the urban sector of the river have experienced a moderate ecological risk since 1975, especially during wet seasons (1988–1997) with a mean sedimentation rate of 2 cm/year. A significant correlation (r=0.439–0.633, p-values < 0.0001) between the toxic metal concentration and the Caspian Sea level fluctuation was obtained. The lowest concentration of toxic metals coincided with the high stand water level. Management practices recommend controlling toxic metals (As, Cd, Ni, Cr, Pb) from the sources and dredging of retention pounds along the Tajan River.

Plastics are the most important component in marine debris. In turn, within plastics, microplastics (<5 mm) are those that most affect marine biota. Thus, this review has as its main objective to show the current state of studies of microplastics, as well as to determine the groups of vertebrates most affected by microplastics, and the type and predominant color of microplastics. For this research, we review a total of 132 articles, from 2010 to May of 2020. Our results show that the group more affected are turtles with 88% of the specimens contaminated by microplastics and median of 121.73 particles/individue. The predominant type is fibers (67.3%), polymer is polyethylene (27.3%), size is less than 2 mm (73.6%), and color is blue (32.9%).

Large quantities of coal are transported through tropical regions; however, little is known about the sub-lethal effects of coal contamination on tropical marine organisms, including fish. Here, we measured aerobic metabolism and gill morphology in a planktivorous coral reef damselfish, Acanthochromis polyacanthus to elucidate the sub-lethal effects of suspended coal particles over a range of coal concentrations and exposure durations. Differences in the standard oxygen consumption rates (MO₂) between control fish and fish exposed to coal particles (38 and 73 mg L⁻¹) were minimal and generally not dose dependent; however, the MO₂ of fish exposed to 38 mg coal L⁻¹ (21 days) and 73 mg coal L⁻¹ (31 days) were both significantly higher than the MO₂ of control fish. Chronic coal exposure (31 days) altered gill structure in the higher coal treatments (73 and 275 mg L⁻¹), with fish exposed to 275 mg L⁻¹ exhibiting significant reductions in gill mucous and thinning of lamellar and filament epithelium. These findings contribute to our limited understanding of the potential impacts of coal on tropical reef species; however, most of the observed effects occurred at high coal concentrations that are unlikely under most coal spill scenarios. Future studies should investigate other contamination scenarios such as the impacts of chronic exposures to lower concentrations of coal.

Marine debris is widespread worldwide, from coastal areas to remote protected oceanic islands. We assessed marine macro-debris on the shores of Fernando de Noronha, an archipelago 360 km off Brazil that encompasses no-take and multiple-use areas. The windward uninhabited coast, more exposed to oceanic currents and winds and inside a no-take area, presented higher abundance of plastic debris. The leeward coast, within the multiple-use urban area, presented more disposable plastics and cigarette butts. These patterns may be explained by the marine debris transportation by ocean currents to the windward side and by locally generated debris by the high quantity of beach users in the leeward coast. These results indicate that oceanographic characteristics and tourism infrastructure play important roles in the accumulation of marine debris in a protected archipelago. They also serve as a baseline for future monitoring initiatives and to improve strategies to tackle plastic pollution within this remote archipelago.

Pollution of marine environments with microplastic particles has increased rapidly during the last few decades and its impact on marine lives have recently gained attention in both public and scientific community. Scleractinian corals are the foundation species of coral reef ecosystems that are greatly affected by the microplastics (MPs), yet little is known about the effects of microplastics on the coral azooxanthellate. In the present study, effects of the exposure and ingestion of polyvinyl chloride (PVC), polyethylene (PE), polyethylene terephthalate (PET), and polyamide 66 (PA66) were studied on the physiological responses of Tubastrea aurea. Our results shows that coral ingested microplastics in four treatment groups and the exposure of microplastics inhibited the antioxidant capacity, immune system, calcification and energy metabolism of the coral Tubastrea aurea. Superoxide dismutase (SOD), catalase (CAT), alkaline phosphatase (AKP), and total antioxidant capacity (TAC) were reduced by 29.4%, 35.5%, 73.9%, and 52.2% in the corals exposed to PVC, respectively. PET microplastics impacted more severely on pyruvate kinase (PK), Na, K-ATPase (Na, K-ATP), Ca-ATPase (Ca-ATP), Mg-ATPase (Mg-ATP), Ca-Mg-ATPase (Ca, Mg-ATP), and glutathione (GSH). Activity of these enzymes decreases to 89.6%, 66.7%, 63.6%, 60.4%, 48.4%, and 50.5% respectively. We anticipate that this work will provide important preliminary data for better understanding the effects of MPs on stony corals azooxanthellate.

Methylmercury concentrations in Minamata Bay are high, but the cause is unclear. We conducted a basic study on the behavior of methylmercury in Minamata Bay seawater; the findings suggest that mercury methylation may occur throughout the year in Minamata Bay. Seawater temperature, salinity, and concentrations of dissolved organic carbon were the environmental factors that affected methylation, and the degree of methylation was closely related to bacterial community structure. The concentration of methylmercury in suspended particulate matter was highest 10 m below the surface and decreased with greater depths. We did not observe a correlation between methylmercury concentrations in suspended particulate matter and concentrations of dissolved methylmercury.

Microplastics are emerging contaminants with a wide environmental distribution and potential to elicit adverse impacts on organisms. Despite this lack of consistency among reports, data obtained from different investigations are often compared, resulting in the potential for misrepresentation of global microplastic contamination. Major interlaboratory variability in quantification of microplastic levels stem from size-related differences in sampling and analysis with different density solutions to separate microplastics. Herein, we propose a nomenclature that provides key information relating to the microplastics abundance in samples. That is, the proposed nomenclature, MPscᵃ, ᵇ, informs on mesh or filter size used in sampling, the density of flotation solution used to separate the microplastics, and the detection limit during the analysis progress of microplastics. This proposed nomenclature would facilitate comparisons among studies to avoid over- or under-estimation of global microplastic levels. Moreover, it would also facilitate the interpretation of meta-data in future assessments.

The distribution of trace elements in sediments and five commercially important fish species of the Oman Sea were assessed using an atomic absorption spectrometer to determine ecological and human health risk assessment. The ranges of trace elements concentration in sediments were: Cr: 5.42-68.94, Zn: 5.22-18.11, Cu: 1.44-4.87, As: 18.07-79.96, Cd: 0.10-1.27, Ni: 43.0-65.34 and Pb: 8.92-30.53 mg/kg dry weight. Cr, Zn, Cu, Cd and Pb were below the ERL (effects range low) and TEL (threshold effect level) values at all the sampling stations with rarely biological effects. Whereas, As and Ni were higher than ERL and TEL with occasionally biological effects. The patterns of trace elements bioaccumulation in the tissues of all species were: liver> skin> gill> muscle. A significant positive correlation suggests that trace elements accumulation in fish is determined by trace elements in sediments. Estimated Daily Intake (EDI) was significantly lower than the tolerable daily intake (TDI) value. Target Hazard quotient (THQ), total target hazard quotient (TTHQ) and target carcinogenic risk (TR) values indicated no hazard risk from fish consumption. Hence, the consumption of concerned species to people in the Oman Sea is safe.