A bleached kraft pulp mill operating in Nova Scotia, Canada has discharged effluent into a former tidal estuary known as Boat Harbour since 1967. After treatment in Boat Harbour, effluent is discharged into Northumberland Strait. Contaminated sediments in Boat Harbour are slated for remediation following cessation of effluent discharge. A review of historical documents to identify contaminants in marine biota in Northumberland Strait found insufficient data to properly assess baseline conditions prior to remediation. This study measured metal, methylmercury, dioxin and furan concentrations in surficial sediments and American lobster (Homarus americanus), rock crabs (Cancer irroratus) and blue mussels (Mytilus edulis) in Northumberland Strait. When compared to Canadian Council of Ministers of the Environment sediment quality guidelines and Canadian Food Inspection Agency tissue guidelines results indicated limited contamination in sediments and biota, posing low risk to marine biota. Long-term monitoring is recommended to verify effectiveness of remediation.

Health risks of human exposures to 12 Polycyclic aromatic hydrocarbons (PAHs) in coastal soils of Koh Samed Island (KSI), Thailand, were evaluated after the coastal areas were cleaned up of the 2013 oil-spill contamination. The risk assessment quantified both total cancer and non-cancer risks for four groups of receptors using average PAHs concentrations. Two exposure pathways (incidental ingestion and dermal contact) were selected to evaluate the risks, and three methods were used to calculate the total cancer risks to determine an appropriate assessment method. The non-cancer risk was represented by the total Hazard Index (HI). The contributions of each PAH to the total cancer risk and total HI were also investigated. The total cancer risk (3.53×10⁻¹⁰ to 9.12×10⁻⁸) and total HI (4.35×10⁻⁶ ᵗᵒ ².¹³×¹⁰⁻³) from this work were relatively lower than the USEPA baselines (10⁻⁶ for the cancer risk and 1 for the HI) and were quite low when compared with other works in the literature. Benzo(a)pyrene made the highest contribution to the total cancer risk (61.82%), while benzo[g,h,i]perylene made the highest contribution to the total HI (62.41%). In regard to the contributions of the two exposure routes, dermal contact contributed the most to the total cancer risk, while incidental ingestion contributed the most to the total HI.

In this study, heavy metals (Cd, Co, Cu, Ni, Pb, Zn, V) and ²¹⁰Pb analyses have been performed in the marine biota (scaldfish, sea lettuce, crab). Samples were collected from 5 different parts of the Marmara Sea and Western Black Sea in January 2020. The results indicated that the highest Cu and Zn content was found in algae samples, but it was observed that heavy metal concentrations such as Co, Cu, Cd and V were generally low and under permissible limit. Also, ²¹⁰Pb (radioactive isotope of Pb) activity levels were determined to vary from 23.20 Bq kg⁻¹ to 52.67 Bq kg⁻¹ dry weight. It was clearly seen that there was a linear correlation between the toxic and radioactive Pb when the obtained data were compared.

Ten surface sediments collected from Joanes River, Bahia, Brazil in rainy and drought periods in 2019 were evaluated according to the enrichment factor (EF), potential ecological risk index (RI), potential contamination index (PCI), pollution load index (PLI), and index of geoaccumulation (Igₑₒ). Initially the dry sediment was subjected to granulometric analysis and determination of the concentration of organic matter. Then, the samples were digested in HNO₃ and analyzed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) to determine the metals cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb) and zinc (Zn). Zn and Cu were classified in that order as the most contaminated elements in most sediment. Comparison of the total metal concentrations with the threshold (TELs) and probable (PELs) effect levels in sediment quality guidelines suggested a more worrisome situation for Zn (648.83–1415.90 μg g⁻¹; PELZₙ = 315 μg g⁻¹), of which concentrations were occasionally associated with adverse biological effects in four sediments, followed by Cu in five sediments during dry and rainy periods; while adverse effects were rarely associated with Cd, Cr, Ni, and Pb. In another evaluation, Cd, Cu, Cr, and Zn could be considered the most dangerous in the entire river, as they were classified in the high levels of contamination by the PCI, associated with serious adverse effects in most samples. In an assessment regarding the ecological risks in the study environment, the sediment samples remained below the limit established by the risk index (IR). The Zn presented moderately severe enrichment (6.78–11.83) in all the collection stations in the dry and rainy periods, followed by the Cd that presented moderate enrichment (2.23–4.17), whose values exceeded almost 1000 times the background at one site. Through the PCA it was possible to evidence the existing correlation between metals, organic matter, and silt and clay fraction. The results obtained in the PCA represented more than 80% of the variance between the data. The environmental risk assessment revealed a significant increase in the risk associated with metals during the rainy season. This is probably due to the greater supply of organic matter from the leaching of the margins.

Swordfish (Xiphias gladius) is a major marine resource of high economic value to industrial and artisanal fisheries. As a top predator with a long lifespan, it is prone to accumulate high levels of contaminants. The bioaccumulation of a wide range of both legacy and emerging persistent organic contaminants was investigated in the muscle, liver and gonads of swordfish collected from the Seychelles, western Indian Ocean. The detection of all target contaminants, some at frequencies above 80%, highlights their widespread occurrence, albeit at low levels. Mean concentrations in muscle were 5637, 491 and 331 pg g⁻¹ ww for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and perfluoroalkyl substances (PFASs), respectively. ∑BFR mean concentrations were far below, i.e. 47 pg g⁻¹ ww. The data are among the first obtained for such a high diversity of contaminants in an oceanic top predator worldwide and constitute a benchmark of the contamination of Indian Ocean ecosystems.

Microplastic pollution is an increasing problem in the marine environment. This study had three objectives: 1) determine if seagrass beds and adjacent sand flats in the Florida Keys differed in microplastics concentration, 2) determine if sea cucumbers from the Florida Keys and sand dollars from the panhandle of Florida contain microplastics, and 3) conduct a laboratory experiment on the sand dollar Mellita tenuis to determine if it will ingest plastic microbeads contained in sediment. Both seagrass beds and sand flats in the Florida Keys contained microplastics. Sediment near Pensacola Beach and in St. Joseph Bay contained microplastics. Sea cucumbers from the Florida Keys and sand dollars from the panhandle of Florida contained microplastics in their gut contents. In the laboratory, M. tenuis ingested microbeads in slightly lower proportions compared to surrounding sediment. Both sea cucumbers and sand dollars may make useful animals for monitoring sandy environments for microplastics pollution.

The 3D dispersion of marine litter (ML) over the Mediterranean basin has been simulated using the velocity fields from a high resolution circulation model as base to run a 3D Lagrangian model. Three simulations have been performed to mimic the evolution of ML with density lower, similar, or higher than seawater. In all cases a realistic distribution of ML sources was used. Our results show that the accumulation/dispersion areas of the floating and buoyancy neutral particles are practically the same, although the latter are distributed in the water column, 80% of them found in the photic layer (average depth of 35m). Regarding to the densest particles, they rapidly sink and reach the seafloor close to their source. The regions of higher temporal variability mostly coincide with the ML accumulation regions. Weak seasonal variability occurs at a sub-basin scale as a result of the particles redistribution induced by the seasonal variability of the current field.

Large amounts of crude oil were found along Brazil's northeast and southeast seaboard from August 2019 to January 2020. Petroleum companies and oil tankers reported no accidents previously or during this period. The stranded oil on Brazilian beaches looks like tar; it has solid aspect and is denser than seawater. Chemical characterization of this oil showed that light hydrocarbons were still present, increasing the probability of negative effects to coastal organisms and ecosystems upon release in the water column. Diagnostic ratios, chromatogram pattern, and percentage-weathering plots proved that the oil samples share the same oil source. This work provides data for future comparison with oil samples that will likely be found stranded along the Brazilian shoreline in the years to come, helping to understand long term issues associated with the mysterious oil spill that made landfall in late 2019.

Marine particle-attached (PA) and free-living (FL) microbes play important roles in the biogeochemical cycling of organic matter along the water column. Deep-sea cold seeps are highly productive and chemosynthetic ecosystems, their continuous emission of CH₄, CO₂, and H₂S can reach up to 100 m in the above water, therefore would influence the distribution and potential metabolic functions of deep-sea prokaryotes. In this study, the vertical distribution profiles of both PA and FL microbes in the water column above two cold seeps of the South China Sea were investigated using Illumina sequencing and quantitative PCR (qPCR) based on 16S rRNA gene. Photosynthetic and heterotrophic prokaryotes were predominant in respective surface and deep layers below the photic zone. The typical cold seep chemosynthetic microbes, such as methanotrophs and sulfate-reducing bacteria were observed with low proportions in the two cold seeps as well. Distinct PA and FL microbial fractions were found in terms of abundance and diversity. FL fraction exposed to the bulk water was significantly affected by temperature and inorganic nutrients, whereas PA fraction relied more on the organic matter of the particles and less susceptible to the environmental variability. Our study highlights the importance of vertical geochemical gradients on the distribution and potential metabolic choice of marine microbes and extends our current knowledge of depth-associated microbial distribution patterns.

The ribbed mussel has been demonstrated to tolerate high levels of urban pollution and inhabits intertidal regions of the New York City estuary. The ability of this bivalve to filter bacteria raises the question of whether it can remove from the water column the fecal bacteria introduced to urban waterways by septic system leakage or sewer overflow. The study here addresses the hypothesis that ribbed mussel filters bacteria introduced by combined sewer overflow (CSO) discharge. Mussels and water were collected from a highly polluted region of the NYC estuary in order to conduct two sets of five trials for filtration of coliform and coccoid fecal indicator bacteria, respectively, Escherichia coli and Enterococcus species. Mussels and water samples were collected in proximity to a major CSO outfall within 1–2 days of a rainfall event to ensure high baseline values of bacterial contamination for filtration trials. For any given Enterococcus or E. coli trial, equal volume water samples were serially distributed across aerated tanks either containing a mussel or not. Comparison of with-mussel versus no-mussel tank water contamination across pooled trials showed significant (P < 0.05) reduction in water exposed to mussel filtration for both, Enterococcus and E. coli trials. For Enterococcus trials, measures of turbidity (suspended particle density) were taken concurrently with measures of bacterial contamination. Regression of contamination against turbidity, with measures standardized across trials, yielded a significant positive association (n = 50, P < 0.0001) across all tank water with a mussel. Thus, contamination reduction was associated with particle removal by mussel filtration.