Microplastics pretreatment of prior to biodegradation is an efficient approach for their bioremediation. We isolated Achromobacter denitrificans from compost and used it for biodegradation of thermo-oxidative pretreated polyvinyl chloride (PVC) and low-density polyethylene (LDPE). About 12.3 % and 6.5 % weight loss, and 326.4 and 112.32 mg L⁻¹ extracellular protein were observed in bacterial flasks with PVC and LDPE, respectively. The pH in treated PVC reached to 5.12 and the thermal stability increased by 29 °C. The chemical modification in LDPE was demonstrated through oxidation of antioxidants (Phenol group), formation of new groups (Aldehyde group), and chain fracture in the main backbone by Fourier transform infrared spectroscopy. Formation of peaks at the range of 1700–1850 cm⁻¹ in LDPE attributed to formation of carbonyl groups as the degradation result. Scanning electron microscopy confirmed LDPE and PVC degradation by surface alterations. Consequently, thermo-oxidative pretreatment can be considered as a suitable strategy for improving microplastics biodegradation.

Microplastics (MPs) are a ubiquitous contaminant worldwide, damaging the environment and human health. These particles have been identified in important seafood species, which are a possible source of contamination for humans and must be investigated. This study therefore aimed to identify the concentrations of microplastics in four important species of bivalves commercialized in Brazilian markets. The presence of microplastics was identified in all bivalves, with an average concentration of 1.64 MPs/g and 10.69 MPs/ind. We concluded that bivalves are a source of microplastics for the Brazilian population. However, further studies must evaluate other species sold in different regions of the country, estimating microplastics ingested by this population through bivalves. Finally, this contamination must be controlled by regulations such as mandatory depuration, in which can effectively minimize this problem.

Aquatic ecosystems provide habitats for many organisms. Historically, riverbanks have always been inhabited and exploited for subsistence and navigation. The present study evaluates the contamination and ecological risks caused by potentially toxic elements in surface sediments of the Paraguaçu River, Bahia, Brazil. Seven sediments samples were collected, and eight heavy metals were determined employing inductively coupled plasma spectrometry mass (ICP-MS). The concentrations range as (mg kg⁻¹) found were 6.78–18.68 for lead, 14.21–42.16 for zinc, 27.61–48.63 for nickel, 2.03–6.50 for chromium, 6.06–12.90 for vanadium, 5.99–13.33 for cupper, 1.25–3.19 for cobalt, and 79.52–286.08 for manganese. Nickel showed significant enrichment (EF: 5.75; 7.62, and 14.11), followed by zinc, which showed moderate enrichment (EF: 2.16; 2.19, and 4.52). These enrichment levels are possible of anthropogenic origin. When the pollution index (PI) was evaluated, the elements V, Ni, Zn, Mn, Co, and Cu were strongly polluted (PI ≥3). In general, the pollution index (PI), geoaccumulation index (Igₑₒ), enrichment factor (EF), and potential ecological risk indices (Eᵣ and PERI) show that contaminated sediments have adverse effects on aquatic environments, especially for o Mn, Ni, Pb, V, and Zn.

Rhodamine water tracer (RWT) released during the 2021 Tracer Release Experiment in the St. Lawrence Estuary provides a proxy for the water-soluble fractions of contaminant spills. Measurements of total and size-resolved aerosols were taken onboard a research vessel throughout the experiment. Size-resolved aerosol measurements show airborne transmission of water-soluble RWT in a bimodal distribution peaking at 5.2 μm and 0.9 μm. Highest aerosol RWT (30.5 pg m⁻³) was observed in the 12-hour daytime period following the first dye release (Sept. 5), while the lowest (8.8 pg m⁻³) was observed in the subsequent nighttime sample. Available wind and RWT patch information were used to identify factors contributing to the factor-of-three variation in aerosol RWT concentrations. Negligible correlations were found between aerosol RWT and wind speed and sample time-of-day. Wind direction is isolated as the key variable for consideration in identifying the impact of contaminant spills on coastal and inland communities.

The long-term fate of plastics in the ocean and their interactions with marine microorganisms remain poorly understood. In particular, the role of sinking plastic particles as a transport vector for surface microbes towards the deep sea has not been investigated. Here, we present the first data on the composition of microbial communities on floating and suspended plastic particles recovered from the surface to the bathypelagic water column (0-2000 m water depth) of the North Pacific Subtropical Gyre. Microbial community composition of suspended plastic particles differed from that of plastic particles afloat at the sea surface. However, in both compartments, a diversity of hydrocarbon-degrading bacteria was identified. These findings indicate that microbial community members initially present on floating plastics are quickly replaced by microorganisms acquired from deeper water layers, thus suggesting a limited efficiency of sinking plastic particles to vertically transport microorganisms in the North Pacific Subtropical Gyre.

Aquaculture plays a crucial role in the global food security and nutrition supply, where China accounts for the largest market share. Although there are some studies that focus on large-scale extraction of coastal aquaculture ponds from satellite images, they have often variable accuracies and encounter misclassification due to the similar geometric characteristics of various vivid water bodies. This paper proposes an efficient and novel method that integrates the spatial characteristics and three biophysical parameters (Chlorophyll-a, Trophic State Index, and Floating Algae Index) to map coastal aquaculture ponds at a national scale. These parameters are derived from bio-optical models based on the Google Earth Engine (GEE) cloud computing platform and time series of high-resolution Sentinel-2 images. Our proposed method effectively addresses the misclassification issue between the aquaculture ponds and rivers, lakes, reservoirs, and salt pans and achieves an overall accuracy of 91 % and a Kappa coefficient of 0.83 in the Chinese coastal zone. Our results indicate that the total area of Chinese coastal aquaculture ponds was 1,039,214 ha in 2019, mainly distributed in the Shandong and Guangdong provinces. The highest aquaculture intensity occurs within the 1 km coastal buffer zone, accounting for 22.4 % of the total area. Furthermore, more than half of the Chinese coastal aquaculture ponds are concentrated in the 0–5 km buffer zone. Our method is of general applicability and thus is suitable for large-scale aquaculture ponds mapping projects. Moreover, the biophysical parameters we employ can be considered as new indicators for the classification of various water bodies even with different aquaculture species.

The association of heavy metals with plastics could represent a source of contamination, presenting acute metal exposure to ecosystems. Here, we aimed to evaluate the level of 20 metals on plastics employed in aquaculture areas and their surrounding water. All the selected metals were detected on six different polymers/types of plastics. Despite the difference in sampling sites, there was no significant difference among metal concentrations on plastics. However, some metals showed a significant difference in the surrounding seawater among sites or were not detected. Additionally, the median concentrations of all heavy metals were higher on plastic than in their surrounding water at all sites. Furthermore, multivariate analysis showed that metals accumulate on plastics in a similar pattern among sites but distinct from the surrounding water. This study contributes to understanding the accumulation of metals on plastics used in aquaculture areas.

Dissolved organic nitrogen (DON) from terrestrial input exacerbates eutrophication and induces harmful algal blooms. We investigated the effects of hydrophilic (Hic) and low molecular weight (LMW) DON on the phytoplankton community in Jiaozhou Bay during autumn (October 2017) and spring (May 2018). Our results showed DON additions significantly increased algal growth while decreasing community biodiversity and provide a competitive advantage for Skeletonema costatum. These situations were further intensified by increasing temperature in autumn. Additionally, Hic DON had a higher bioavailability than LMW DON. Based on emission-excitation matrix spectra, we identified protein-like components as the main components of Hic DON whereas humus-like components were the principal components of LMW. Correlation analysis confirmed a positive correlation between DON bioavailability and protein-like components. Therefore, our results indicate DON from terrestrial input disrupts the structural stability of the phytoplankton community and increases the risk of harmful algal blooms, which in turn threaten coastal ecosystems.

To better understand the spatial distribution and ecological risks of polycyclic aromatic hydrocarbons especially in low latitude coastal productive areas, PAHs in sea ice were examined for the first time in northern Liaodong bay of China in December 2020. Results showed ΣPAHs were dominated by 2- and 3-ring, with the mean concentration of 241.9 ng L⁻¹ and 202.8 ng L⁻¹ in sea ice and seawater, respectively, suggesting a moderate ecological risk based on Risk Quotients assessment. Ice enrichment factors were greater than 1 at 82% of the sampling sites, reflecting enrichment of PAHs in sea ice. The characteristic compounds ratios demonstrated PAHs mainly derived from petrogenic sources, while combustion was another crucial source for PAHs in sea ice via atmospheric deposition. This helps to better elucidate pollution status, potential sources and risk assessment of PAHs in productive coastal oceans especially during ice-covered period for contamination control and environmental management.

In this study, we conducted two cruises in the Bohai Bay (China) focusing on phytoplankton community and relation to water quality. The evaluation revealed that most of the open area was non-eutrophic, whereas the river inlet had severe eutrophication. Phytoplankton populations respond differently to different aquatic environments and are controlled by more than two factors, as revealed by aggregated boosted tree analysis. Notably, a shift in the phytoplankton community structure was observed during the seasonal transition, from the dominance of diatoms to the co-dominance of diatoms-dinoflagellates. However, the relative abundance of dinoflagellates increased by 14 % in autumn, when the harmful algae species Akashiwo sanguinea exclusively predominated; this was primarily linked to the nutrient ratios, temperature, and dissolved oxygen. The eutrophication and organic pollution had direct effects on phytoplankton abundance. Overall, our findings may provide further insights into the impacts of eutrophic environments on phytoplankton community structure in coastal systems.