Ongoing global changes such as increasing sea-surface temperatures, decreasing acidity levels, and expanding oxygen-minimum zone may impact on the biogeochemical cycles of trace metals in ocean systems. Each trace metal has unique characteristics and a distinctive distribution pattern controlled by chemical, biological, and physical processes that occur in ocean systems. The correlations of variability drivers in trace metals are interesting topics for investigation. Following up on ocean research in the coastal and estuary area, we specifically review the distribution of trace metals in seawater and suspended and surface sediment. The marginal seas usually feature significant terrestrial inputs accompanied by several active water-mass currents. The purpose of this review is to provide an overview of variability related to trace-metal distribution in coastal and estuary systems and to specifically describe the distribution, profile and drivers that affect trace metals variability.

This study aimed to evaluate the microplastics abundance, composition and distribution in Bandon Bay's surface seawater, in southern Thailand. Samples of microplastics were collected from 48 transects using a surface manta trawl at four different estuaries that support human activities. The results showed that the highest microplastic abundance occurred in the fishery and aquaculture areas with a mean abundance of 0.33 particles/m³. Fragments were the dominant form at all stations. Microplastics with <1 mm were the dominant size, and white was the colour most found in all stations. Polypropylene was the major type of microplastic, accounting for 57% overall. This study is an important reference for understanding the microplastics status in the surface seawater of Bandon Bay, as it will allow relevant agencies to accurately assess the pollution level of microplastics in the bay. It is of practical significance to understand the sources and sinks of microplastics.

In this paper, the distribution, degree of pollution and sources of Cu, Pb, Zn, Cd, Cr, As, Co, Ni and Hg in the surface sediment of Sanmen Bay were studied. The average concentrations of the identified potentially toxic elements (PTEs) were in the following order: Zn > Ni > Cr > Cu > Pb > Co > As>Cd > Hg. Almost all PTEs had a significant positive correlation with TOC, clay and Al; Cr had no significant correlations. Apart from Hg, the contamination levels of 8 PTEs were at those considered to be low-to-no pollution. Comparatively, the contamination level of Hg was much higher than the background value, which indicated moderate pollution. The source of this pollution may have included industrialization, urbanization and/or transport of industrial waste materials. Both geoaccumulation index (Igₑₒ) and potential ecological risk (RI) values suggested that Hg was the major contributor to the ecological risk posed by the selected PTEs.

Industrial and commercial port activities are widely recognized worldwide as an important source of pollution to proximal estuaries. In this study, we analysed geochemical and sedimentological parameters including major and trace elements, organic matter and sediment texture in surface sediments from the estuarine environment of Southampton Water, U.K. Using these data, and multivariate statistical tools [correlation, factor and cluster analysis and pollution indices such as Enrichment Factor (EF), Pollution Load Index (PLI) and the Adverse Effect Index (AEI)], we examine sedimentary trace metal and metalloid contamination, contamination sources, and potential biological impacts of the contamination present. The geochemical data, multivariate statistical analysis and pollution indices indicate that the spatial distribution of trace metals and metalloids is influenced by both sediment composition (and mixing) and anthropogenic activities. Most trace metal and metalloid concentrations are close to local geological background levels, except for Cu, Zn and Pb. The spatial distribution of these elements indicates that the Exxon oil refinery, Southampton port, local marinas and runoff from domestic and industrial activities act effectively as point sources of these elements. Pollution indices calculations highlight a degraded environment as a result of these pollutants, and further work is needed to assess the current impact of trace metals and metalloids on local ecology.

Biocides used in offshore oil and gas operations could be present in water discharges, and thus identifying such chemicals and their hazard could help address concerns regarding non-target organisms. Aquatic toxicity data, queried from different sources and augmented with predictive models, were used to develop species sensitivity distributions and their corresponding 5th percentile hazard concentrations (HC5s). Curated data, including over 1000 empirical records for 137 species, indicated no evidence of bias when comparing sensitivity between marine and freshwater species, even when predicted data were used. HC5s facilitated estimation of an acute-to-chronic ratio (ACR = 10), appropriate for most chemicals and useful in filling data gaps. Comparison of chronic-HC5s with the default approach for deriving predicted no effect concentrations showed that the latter systematically overstates aquatic hazard. The present approach shows promise of using acute-to-chronic HC5 ratios for defining assessment factors for different chemical classes, instead of the use of generic assessment factors.

The concentrations of 23 polycyclic aromatic hydrocarbons (PAHs; 16 parent PAHs and 7 alkyl-PAHs) were determined in 45 surface sediment and 7 basal sediment box core samples retrieved from the Estuary and Gulf of St. Lawrence in eastern Canada. The concentration sums of 16 priority PAHs (Σ₁₆PAHs) in the surface sediments (representing modern times or at least younger than the last decade) ranged from 71 to 5672 ng g⁻¹. Σ₁₆PAHs in the basal sediments ranged from 93 to 172 ng g⁻¹ among the pre-industrial samples (pre-1900 common era or CE) and from 1216 to 1621 ng g⁻¹ among the early post-industrial samples (~1930s and ~1940s CE). The highest Σ₁₆PAH values occurred in samples retrieved from the Baie-Comeau-Matane area, an area affected by intense industrial anthropogenic activities. Source-diagnostic PAH ratios suggest a predominance of pyrogenic sources via atmospheric deposition, with a minor contribution of petrogenic seabed pockmark sources. The PAH concentrations in the sediments from the study areas reveal low ecological risks to benthic or other organisms living near the water-sediment interface.

We present seasonal variation of four metals (Cd, Cu, Pb, and Zn) in nine pelagic and three benthic fish species from the highly polluted Cuddalore coast in Tamil Nadu, India. Metals were assessed using atomic absorption spectrometry and detected in all fish species, in at least one season, except Iniistius cyanifrons where cadmium was not detected throughout. In both benthic and pelagic fish, order of metal concentration was Zn > Cu > Pb > Cd. Multivariate statistical analysis revealed that metals may have originated from both natural and anthropogenic sources. Health risk assessment revealed that consumption of fish from Cuddalore coast does not pose health risk for now; however, hazard index values (pelagic = 0.97; benthic = 0.90) are in borderline. Even a slight increase in metal concentration in fish can prove hazardous for human consumption. Sooner or later, eating fish from Cuddalore coast may pose a considerable health risk to humans if metal pollution is not held at Bay.

Baseline marine litter abundance and distribution on Saint Martin Island, Bay of Bengal, were assessed. Seventy-two transects (100–150 m) along 12 km of coastline were surveyed for litter items every two weeks for two months. The most abundant items were polythene bags, food wrappers, plastic bottles/caps, straws, styrofoam, plastic cups, plastic fragments, fishing nets, clothes, and rubber buoys. Tourism, local markets, hotels, domestic waste, and fishing activities were primary sources of marine litter. According to the mean clean coast index (CCI), all transects were clean, of which 11.3 % and 14.1 % of sandy beaches and rocky shores with sandy beaches were reported dirty, respectively. Northern Saint Martin Island comprised sandy beaches (2.8 %) and was extremely dirty. In addition, plastic abundance index (PAI) analysis showed that 24 % of sites, out of 72 sites, were under “very high abundance”, 33 % were “high abundance”, 33 % showed “moderate abundance”, and 4 % were classified as “low abundance”. Establishing baseline results of marine litter abundance and distribution on Saint Martin Island may help improve island conservation and mitigation strategies (e.g., improved waste management, beach cleaning activities to raise public awareness, local government litter reduction policies, and increase local pro-environmental behavioral change).