The seasonal shift in the homogeneity of the periphytic protozoan fauna was studied based on a four-season baseline survey in the coastal waters of the Yellow Sea, northern China. Samples were collected using glass microscope slides as an artificial substratum at a depth of 2 m after the immersion time of 14 days during each of the four seasons (winter, spring, summer, and autumn, 2017). The protozoan fauna showed a clear seasonal shift in species composition and a significant variation in homogeneity in terms of both compositional and community structure during four seasons. The dispersion measures and β-diversity index represented an increase in the trend from spring to winter. These findings suggest that the homogeneity of the periphytic protozoan fauna was subject to a significant variability shaped mainly by species composition during a four-season cycle in marine ecosystems.

The objective was to establish possible temporal patterns in the microplastics (MPs) abundance in the water and in the intertidal sediment in an urbanized location of the Río de la Plata estuary (Argentina), in relation to environmental factors. The site was sampled monthly for a year (February 2019–January 2020). The presence of MPs was recorded, being more abundant in February in the water (110 MPs m⁻³) and in April in the sediment (613 MPs m⁻²). The types of MPs found were fibers, fragments, pellets, film and foam; while the polymers identified were polyethylene (PE) and polypropylene (PP). Regarding the environmental variables, the predominance of wind from the NE direction was related to a greater accumulation of MPs in the sediment, while wind from the NO direction was associated with a lower abundance of MPs in the water. Also, MPs abundance was negatively related to the larger sizes of sediment particles.

Pearl farming sustainability in South Central Pacific (SCP) atolls strongly depends on water quality and renewal. These factors are partly controlled by the wave conditions that impact the lagoon circulation. To characterize the wave conditions around 83 SCP atolls including those hosting pearl farming activities, we used 18 years of WaveWatchIII simulation with a grid refined from 50 to 5 km resolution. Three regional wave regimes are statistically identified: two associated with long distant swells originating from mid-latitude storms, and one with local trade winds. All regimes occur with a relatively high frequency (22–44%), but with a marked seasonality. Wave conditions are also strongly modified locally during their propagation between the archipelagoes. Western and southern isolated atolls generally have a single regime all around their rims. In contrast, central Tuamotu atolls experience different regimes depending on their levels of protection. These results help understanding atoll hydrodynamics, which has implications for their management.

The potentially toxic elements (PTEs) concentrations in water and sediments were measured in the Hoor Al-Azim wetland to evaluate the spatial distribution, pollution rate, fate, partitioning, and ecological risk and also to recognize the PTEs sources in sediments using MLR-APCs (multiple linear regression-absolute principal component scores) receptor model. The human health risk was investigated based on the seven fish species consumed in the study area. Based on the results, water and sediment contamination was observed at some stations in the southern part of the wetland where agricultural water drains. Also, the sediments of oil well drilling disposal site was polluted by PTEs. Based on the MLR-APCs model, 80.8% of Mo and 81.5% of Se originated from agricultural source. Total target hazard quotients (TTHQ) values suggested that the children could experience adverse health effects due to consumption of Coptodon zillii, Aspius vorax, Carassius auratus and Carasobarbus luteus.

Microplastics (MPs) are ubiquitous in marine environment. The prevalence of MPs in coastal and lagoon sediments, and water were studied in two Marine Protected Areas (MPAs); Bundala National Park (BNP) and Hikkaduwa Marine National Park (HNP) in Sri Lanka. Both areas are important for turtles, birds and coral ecosystems, all of which are particularly threatened by MPs. Abundance of MPs was generally higher in both coastal sediments and waters in HNP (111±29 MPs/m² for sediments and 0.515±0.054 MPs/m³ for water) than in the BNP (102±16 MPs/m² for sediments and 0.276±0.077 MPs/m³ for water). The most common shape and polymer type of MPs were fragments and Polyethylene respectively. This research is the first to survey MPs in MPAs in Sri Lanka and provides a baseline of MPs pollution in these environments for future research and management.

Products coal tar-based are largely used as concrete structures as protective coatings but some questions about leaching and potential toxic effects remain unclear. A laboratory experiment exposing oysters to miniaturized concrete pillars painted with Lackpoxi N1761 over time was performed and trace elements and 17 PAH were monitored in seawater exposure media, and oyster tissues. The original paint composition was also analyzed, and high concentrations of trace elements and PAH were detected. Sharp increases in PAH concentrations were observed after 6–96 h in exposure media and oyster tissues, suggesting that these compounds were leached from the painted structures. In parallel, the integrity of the hemocytes lysosomal membranes of exposed organisms has been damaged. Based on the response of this biomarker, the use of Lackpoxi N1761 is potentially harmful to the environment and it is required that coal tar-based paints be evaluated according to the environmental risk assessment protocols.

A two-dimensional hydrodynamic model that couples hydrology and water quality processes was developed to simulate the concentrations of PAH in water phase and sedimentation rates of PAHs in marine environment. The kinetic processes of the model included atmospheric exchange, transportation, deposition, etc. Taking Liaodong Bay as an example, the pollution level, spatial distribution of PAHs in sediments were analyzed and the transport, transformation and sedimentation processes of PAHs were simulated. The results show that PAHs concentrations in sediments are at a “moderate risk” level, and the distribution has a conspicuous spatial variation. According to the results of simulation, the PAHs in sediments are easily accumulated with weak hydrodynamic conditions. Thus, hydrodynamic is one of the important factors affecting the spatial distribution characteristics of PAHs in the sediments. The PAHs numerical calculation model established in this paper and its evaluation results have important research value for PAHs pollution prevention and control.

Microscopic plastic particles (microplastics) are widespread anthropogenic contaminants that are impacting aquatic ecosystems. Among the five most prevalent types of microplastics (polystyrene, polyamide, polyvinyl chloride, polyethylene, and polypropylene) in aquatic environments, the impact of polystyrene, polyethylene, and polypropylene has drawn more attention due to their high transportability. A lack of reliable inexpensive methods to accurately replicate the realistic microplastic samples extracted from environmental matrixes with the desired size and geometry is one of the main challenges in the design of experiments for systematic studies. In this work, a novel print-and-release technique to prepare colored microplastic (polystyrene) particles with a desired size and shape by using an office-grade laserjet printer is introduced. Microplastics ranging from 125 μm to 500 μm could be prepared with an average dimensional error of less than 5%. Their physical and chemical characteristics were obtained by SEM, FTIR, and XPS analyses.

The mercury (Hg) cycle in estuaries has been globally discussed, although Holocene deposition in mangrove sediments remains unknown. Herein, a sediment core from a mangrove system in southeastern Brazil was ¹⁴C-dated to evaluate millennial Hg deposition. The highest Hg concentrations (1010–2540 ng g⁻¹) in surface sediments were explained by emissions from a chlor-alkali industry (1964 CE). However, Hg levels were also high in pre-industrial periods, associated to fine grain-size and algal organic deposition. Less anomalous Hg concentrations in bottom sediments indicate Holocene ages (~1940–3324 cal yr BP), potentially associated to Serra do Mar mountains weathering. This study reveals the capacity of mangrove to retain Hg over millennial time scales, acting as significant and long-term Hg sinks. Therefore, the use of Hg as an Anthropocene marker must be considered cautiously in coastal systems that act as Hg sinks in times when environmental changes were not caused by human activities.

Since 2007, the outbreak of green tides has become the most serious ecological problem in the Yellow Sea. In this study, a new method was used to identify green tides in multi-source satellite data from 2007 to 2020, and the relationship between the conditions necessary for green tide dissipation and other environmental factors was discussed. We found a “wavy” trend of green tide scales over the 14-year dissipation period. The dissipation direction was influenced by sea surface wind (SSW) and sea surface circulation (SSC). Under the action of northeast moving SSW and SSC, green tides move away from the shore and drift northward; under the action of northwest or southwest moving SSW and SSC, they moved towards the shore and drift southward. The date of dissipation was influenced by sea surface temperature (SST) and precipitation, and high SST accelerated the process of green tide dissipation, while precipitation slowed it down.