There are many toxicological studies on microplastics, but little is known about the effect of nanoplastics (NPs). Here, we evaluated the oxidative stress responses induced by NPs (10, 10⁴ and 10⁶ particles/l) in juvenile Larimichthys crocea during 14-d NPs exposure followed by a 7-d recovery. After exposure, the activities of antioxidant enzymes (SOD, CAT, GPx) and MDA levels increased in the liver of fish at the highest NPs concentration. SOD and CAT activities remained elevated above the baseline after recovery under high-concentration NPs but returned to the baseline in two other NP treatments. Although lipid peroxidation in liver was reversible, juvenile fish in NPs treatments exhibited a lower survival rate than the control during both exposure and recovery. Furthermore, IBR value and PCA analysis showed the potential adverse effects of NPs. Considering that NPs can reduce the survival of fish juveniles, impacts of NPs on fishery productivity should be considered.

The pollution characteristics, sources, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in surface sediment samples from the river networks and outlets of the Pearl River Delta (PRD) were investigated. The total PAH concentrations were in the range of 69.1–1297 ng g⁻¹ in river networks and 56.6–617 ng g⁻¹ in river outlets. The results of source identification showed that PAHs in sediments were mainly derived from combined sources of coke tar and liquid fossil fuel combustion, coal/wood combustion, and petroleum contamination. The ecological risks of PAHs were evaluated based on sediment quality guidelines (SQG), mean probable effects levels quotient values (PEL-Q), and the toxicity equivalence factor (TEQBₐP) method. The ecological risks of PAHs in sediments were at moderate levels in the Pearl River Delta. Although no high risk was found, regular and continuous monitoring of PAHs in sediments needs to be performed.

Decades after a ban on hunting, and despite focused management interventions, the endangered St. Lawrence Estuary (SLE) beluga (Delphinapterus leucas) population has failed to recover. We applied a population viability analysis to simulate the responses of the SLE beluga population across a wide range of variability and uncertainty under current and projected changes in environmental and climate-mediated conditions. Three proximate threats to recovery were explored: ocean noise; contaminants; and prey limitation. Even the most optimistic scenarios failed to achieve the reliable positive population growth needed to meet current recovery targets. Here we show that predicted effects of climate change may be a more significant driver of SLE beluga population dynamics than the proximate threats we considered. Aggressive mitigation of all three proximate threats will be needed to build the population's resilience and allow the population to persist long enough for global actions to mitigate climate change to take effect.

The distribution, congener patterns, possible sources, and ecological risks of polybrominated diphenyl ethers (PBDEs) were investigated in the surface sediments of 20 fishing ports along the coast of Bohai Sea. PBDEs are widespread pollutants in fishing ports, and the total concentrations of 14 PBDEs (∑₁₄PBDEs) are 4.23–20.59 ng/g with a mean value of 12.56 ng/g. BDE-209 was the dominant congener. The fishing ports with high PBDE concentrations were located near Liaohe River, Haihe River, manufacturing plants of BFRs near Laizhou Bay, and tipping areas of marine garbage. BDE-209 and BDE-47 were the most important congeners that discriminate PBDE pollution. The possible sources of PBDEs included the input of commercial mixtures of penta-BDE, octa-BDE, and deca-BDE, the debromination of BDE-209, and the atmospheric transport of the low brominated diphenyl ethers. The ecological risks in surface sediments were attributed to the congeners of tetra-BDE, penta-BDE, and deca-BDE with low or medium levels.

The Vina del Mar - Concón Coastal strip is well known for its urban beaches, which play an essential role in the national economy. With extreme urban development, these beaches have become more polluted by litter. This paper evaluates the abundance, spatio-temporal distribution, typology, and sources of beach litter in 14 sectors located inside this coastal strip. A total of 19,886 litter items were collected and grouped into 50 different categories (11 litter typologies). Overall average litter abundance was 0.21 items/m² while during the fall and winter averages were 0.25 items/m² and 0.17 items/m². Values changed along the area and between seasons. Plastics, cigarette butts and paper-cardboard typologies dominated the samples with 42% (0.088 items/m²), 25.4% (0.053 items/m²) and 20.8% (0.043 items/m²).

This study evaluated microplastic pollution in beaches that have served as historical nesting grounds for green turtles in Hainan Island, China and explored the sources of microplastic pollutants to conduct habitat restoration for sea turtles. The average abundance of the microplastics in the beach surface sediments was 2567.38 ± 2937.37 pieces·m⁻² or 641.85 ± 734.34 thousand pieces·m⁻³, foam and plastic block were the main microplastics identified. Microplastic size was predominantly within the 0.05–1 mm category (small microplastic particles), and most microplastic particles were white. Polystyrene and polyethylene were the dominant plastic compositions. The type and compositions of microplastics indicate that most microplastics in this study were broken from large plastic blocks and foam. To reduce the threat of microplastic pollution to marine life, including sea turtles, we suggested removing plastic litter, especially small plastic on beaches, and replacing and recovering the foam used in aquaculture before it ages and fragments.

To understand the role of submarine groundwater discharge (SGD) in a mangrove combined aquaculture ecosystem, groundwater samples and timeseries observations (27 h) of ²²⁴Ra, ²²³Ra, and nutrients were obtained during wet and dry seasons in Zhenzhu Bay, a typical mangrove and aquaculture ecosystem along the Beibu Gulf in China. The SGD rates in Zhenzhu Bay were estimated to be 22.3–44.5 cm/d in the wet season and 41.1–58.1 cm/d in the dry season, which were 0.8–1.6 and 9.8–14.1 times higher than the corresponding river water discharge values, respectively. Furthermore, SGD-driven dissolved inorganic nitrogen, dissolved inorganic orthophosphate, and dissolved inorganic silicate accounted for 72%, 56%, and 60% of the total nutrient input, respectively, during wet season, which increased to 93%, 98%, and 89% during dry season. The findings highlight that SGD plays an important role in the dissolved inorganic nutrient sources of Zhenzhu Bay, and that the effective utilization and management of the bay should consider SGD.

Assessment of microplastics (MPs) in sediment cores is necessary to unveil global plastic pollution since most of the plastic litter might have been stored in sediment columns. In the current study, MPs inventory was determined in a 105 cm sediment core, collected in the Golden Horn Estuary, Sea of Marmara. Radiodating of sediment profile by using naturally occurring ²¹⁰Pb and fission product ¹³⁷Cs allowed us to couple the retrospective of global MP production to sediment MPs inventory. More than 90% of total MPs inventory was found in the deep layer of the sediment column (below 15 cm). Small MPs (20–200 μm) were more abundant than large ones (200–4000 μm). Elevated concentrations of MPs were attributed to industrial and municipal effluent of Istanbul metropolitan. On a local scale, this study suggests that the Golden Horn Estuary was polluted with MPs before the 1950s, and the abundance of MPs reached a maximum in the 1980s. We also propose on a global scale that “the missing” plastics might have been buried in deep sediment and radiodating of sediment is useful to reveal their historical input records.

There is a paucity of information on the levels of PAHs and PCBs in the deep-sea (≥200 m). In this study, the body-burdens of 16 PAHs and 29 PCBs were measured in: Actinaria (sea anemones), Holothuroidea (sea cucumber), Pennatulacea (sea pens), and Crinoidea (sea lilies) in the deep Gulf of Mexico. All epibenthic species were collected at depths of approximately 2000 m. The PAH and PCB congener profile displayed a similar pattern of bioaccumulation across all four taxa. The high molecular weight PAH, dibenz[a,h]anthracene, was the most abundant PAH in all organisms, ranging from 36 to 53% of sum total PAHs. PCBs 101 and 138 exhibited the highest levels at 20–25% of total congener concentrations in all taxa. The exposure to PAHs and PCBs is likely attributed to contaminated particulate organic matter that is consumed by the deposit and filter feeding epibenthic megafauna sampled in this study.