Divergent marine anaerobic ciliates harbor closely related Methanocorpusculum endosymbionts.

Ciliates are a diverse group of protists known for their ability to establish various partnerships and thrive in a wide variety of oxygen-depleted environments. Most anaerobic ciliates harbor methanogens, one of the few known archaea living intracellularly. These methanogens increase the metabolic efficiency of host fermentation via syntrophic use of host end-product in methanogenesis. Despite the ubiquity of these symbioses in anoxic habitats, patterns of symbiont specificity and fidelity are not well known. We surveyed two unrelated, commonly found groups of anaerobic ciliates, the Plagiopylea and Metopida, isolated from anoxic marine sediments. We sequenced host 18S rRNA and symbiont 16S rRNA marker genes as well as the symbiont ITS region from our cultured ciliates to identify hosts and their associated methanogenic symbionts. We found that marine ciliates from both of these co-occurring, divergent groups harbor closely related yet distinct intracellular archaea within the Methanocorpusculum genus. The symbionts appear to be stable at the host species level, but at higher taxonomic levels, there is evidence that symbiont replacements have occurred. Gaining insight into this unique association will deepen our understanding of the complex transmission modes of marine microbial symbionts, and the mutualistic microbial interactions occurring across domains of life.

Assessment of the level and risk of radioactive hazards in coastal sediments in northern Vietnam.

Radioactivity in coastal sediments in northern Vietnam was examined using data from five sediment cores to assess radioactivity concentrations and radiation risk indices. Radiation risk indices included radium equivalent activity (Raeq), the absorbed dose rate (ADR), the annual effective dose equivalent (AEDE), the activity utilization index (AUI), the external hazard index (Hex), the representative level gamma index (Iγr), and the annual gonadal effective dose rate (AGDE). The radioactivity concentrations of 40K, 232Th, 226Ra, 238U, and 137Cs were 567, 56.1, 35.1, 37.9, and 1.18 Bq/kg, respectively. The average concentrations of 40K, 232Th, 226Ra, and 238U were above the global average at five sites, except for 137Cs, which was low. The Raeq, Hex, and AUI indices were below the recommended values, while the AEDE, ADR, AGDE, and Iγr indices were above the recommended values. Moreover, 40K, 232Th, 226Ra, and 238U had significant impacts on the radiation hazard indices Raeq, ADR, AEDE, Iγr, AUI, Hex, and AGDE. There are three coastal sediment groups on the northern coast of Vietnam: Group 1 has a higher radioactivity and radiation risk index than Group 2 but a lower value than Group 3. Group 3 had the highest radioactivity and radiation risk index. The values of 40K, 232Th, 226Ra, and 238U and the ADR, AUI, Iγr, and AGDE indices in the sediment threaten the living environment.

Microbial diversity and oil biodegradation potential of northern Barents Sea sediments.

The Arctic, an essential ecosystem on Earth, is subject to pronounced anthropogenic pressures, most notable being the climate change and risks of crude oil pollution. As crucial elements of Arctic environments, benthic microbiomes are involved in climate-relevant biogeochemical cycles and hold the potential to remediate upcoming contamination. Yet, the Arctic benthic microbiomes are among the least explored biomes on the planet. Here we combined geochemical analyses, incubation experiments, and microbial community profiling to detail the biogeography and biodegradation potential of Arctic sedimentary microbiomes in the northern Barents Sea. The results revealed a predominance of bacterial and archaea phyla typically found in the deep marine biosphere, such as Chloroflexi, Atribacteria, and Bathyarcheaota. The topmost benthic communities were spatially structured by sedimentary organic carbon, lacking a clear distinction among geographic regions. With increasing sediment depth, the community structure exhibited stratigraphic variability that could be correlated to redox geochemistry of sediments. The benthic microbiomes harbored multiple taxa capable of oxidizing hydrocarbons using aerobic and anaerobic pathways. Incubation of surface sediments with crude oil led to proliferation of several genera from the so-called rare biosphere. These include Alkalimarinus and Halioglobus, previously unrecognized as hydrocarbon-degrading genera, both harboring the full genetic potential for aerobic alkane oxidation. These findings increase our understanding of the taxonomic inventory and functional potential of unstudied benthic microbiomes in the Arctic.

Distribution of 137Cs specific activity in river sediments of the Barents Sea basin (Nenets Autonomous Okrug, Russian Arctic).

This article focuses on the study of the distribution of 137Cs in the bottom sediments of Arctic rivers of the Barents Sea basin (using the example of the Nenets Autonomous Okrug, Russian Arctic). This research is relevant due to the poorly studied region and the significant number of radiation-hazardous facilities in the Arctic zone of Russia, both those currently in operation and those that are "nuclear heritage sites". The study of 137Cs specific activity in bottom sediments was carried out in the period from 2020 to 2023 in the rivers Chizha, Nes, Vizhas, Oma, Pechora (river delta), as well as the rivers Kolva and Usa (first and second order tributaries, respectively, of the Pechora River). A total of 199 samples were collected. In addition to 137Cs specific activity, the samples were analysed for sediment particle size distribution, organic matter content, carbonate content and ash content. The 137Cs specific activity mainly ranged from the minimum detectable specific activity to 5.4 ± 0.8 Bq·kg-1. In the Nes River basin (Kaninskaya tundra), the 137Cs content in bottom sediments reached 36.0 ± 3.2 Bq·kg-1 (in the case of lake sediments) and 22.9 ± 3.7 Bq·kg-1 (in the case of river sediments), values that are higher than those of the North-West of Russia. Considering the large area of the study area (Kaninskaya tundra, Pechora river delta, southern part of Bolshezemelskaya tundra) and the similarity of physical and chemical parameters of the studied rivers, it is possible to assume the existence of a zone of increased radionuclide content in the Nes river basin. This may be due to the runoff from the Nes River catchment area, its hydrological features, and the accumulation of 137Cs in the small fractions of bottom sediments. The results confirm the conclusions of previous soil studies in the Nes river basin. The main sources of elevated 137Cs content are global atmospheric deposition and the Chernobyl Nuclear Power Plant accident.

A novel assessment of potentially toxic elements (PTEs) in water and sediment samples from the Indus River, Pakistan: An ecological risk assessment approach.

Pakistan, a country with limited water resources and highly vulnerable to the adverse effects of climate change, faces numerous challenges in managing its water supply. In this sense, this study assessed potentially toxic elements (PTEs) in the surface water and sediments of Pakistan's Indus River and its tributaries. Key water quality parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) were determined, with respective average values of 7.1, 40 µS/cm, and 208 mg L-1. The concentrations of Cd, Cr, Cu, Ni, and Zn in surface water samples averaged 26 µg L-1, 0.9 µg L-1, 1.4 µg L-1, 22 µg L-1, and 2.1 µg L-1, respectively. The general sediment PTE profile was Ni > Cd > Zn > Cu > Cr. Certain PTE levels exceeded recommended thresholds, indicating the establishment of environmental pollution. Calculated geo-accumulation index values suggested moderate to heavy pollution levels in sediment, with PERI (404) values reinforcing the ecological risk posed by elevated PTE concentrations. Furthermore, significant correlations were observed between specific PTE pairs in both water and sediment samples. This study contributes with novel insights into the distribution and ecological implications of PTE contamination in the Indus River and its tributaries, paving the way for ecological risk management efforts.

Bottom sediments as an indicator of the restoration potential of lakes-a case study of a small, shallow lake under significant tourism pressure.

The study covered a small, shallow lake, intensively used for recreation (sailing, tourist services and port infrastructure). This study aimed to determine the spatial differentiation of bottom sediments and the potential for phosphorus release in five zones, differing mainly in the type of recreation, depth, direct catchment management, shoreline management and macrophyte presence. The results were used to propose protective and restoration measures to improve the water quality of the studied lake. The innovation in the study was the detailed analysis of bottom sediments, which can be a significant source of pollution besides the external load from the catchment and tourist pressure, in the planned management of this ecosystem. Examination of the physicochemical properties of the bottom sediments showed a clear variation in both composition and potential for internal phosphorus loading. The sediments from the profundal zone, where the most boating activity was observed, together with the sediments from the shallow zone where the boats dock (mooring zone), had the highest potential to supply phosphorus to the bottom waters. This fact was demonstrated by the highest total phosphorus (TP) concentrations in sediments (up to 1.32 mgPg-1 DW) and the content of the most mobile fractions (up to 33%). The other zones associated with the marina, fuel zone, tributary and canal were not significant sources of phosphorus to the ecosystem. Based on the above results, a restoration method involving the removal of bottom sediments from the bottom zone was proposed, supported, of course, by protective measures in the catchment (maintaining a buffer zone around the lake and limiting the inflow of pollutants with tributary waters). The proposed measures with sustainable tourist pressure should improve water quality and thus contribute to protecting this valuable natural landscape.

Study on the diversity and germination of dinoflagellate cysts in the sediments of foreign ships in Shanghai Port.

The dinoflagellate cysts present in the ballast water sediment of foreign ships in Shanghai Port have not been previously studied. Therefore, sediment samples were collected from the ballast water of 16 foreign ships in Shanghai Port, and the types of dinoflagellate cysts were identified and their abundance was calculated, with a specific focus on the analysis of toxic and harmful dinoflagellates. Moreover, simulations of temperature and salinity conditions throughout the year in the Shanghai port waters were conducted to carry out dinoflagellate cyst germination experiments, with analyze and compare the germinated dinoflagellate cysts under different conditions. Dinoflagellate cysts were found in 100 % of the ship sediment samples, including a total of 9 species of toxic and harmful dinoflagellate cysts. In the germination experiment, 15 °C was found to be the optimal temperature for the germination of dinoflagellate cysts in ballast water sediment, and high salinity is more favorable for cyst germination.

Dewatering and valorizing lake sediments by electroosmotic dewatering for lakes restoration.

Dredging eutrophic lake sediments can improve water quality, but it also requires dewatering and valorizing the dredged material to avoid wasting resources like phosphorus. This study experimentally investigated the basic mechanism and performance of electroosmotic dewatering of 1-L dredged sediments using different electric currents (20 mA, 40 mA, and 60 mA) after gravity filtration. The dewatering performance, moisture content and distribution, effect of electrochemical reaction on dewaterability, energy consumption, and changes in metals and phosphorus (P) distribution and pH values were analyzed. The results indicated that electroosmotic dewatering effectively decreased sediment mass by predominantly eliminating free and a portion of interstitial water, with reductions ranging from 7 to 20%. The optimal duration and current should, however, be considered to balance water removal and energy consumption. Higher moisture removal occurred with 40 mA for 24 h and 60 mA for 6 h, while the energy consumption obtained with 60 mA (0.201 kWh/kg water removed) was significantly lower than that of applying 40 mA for 24 h (0.473 kWh/kg water removed), with the assistance of ohmic heating, resulting in reduced viscosity and water release from capillaries. The tested conditions did not significantly extract heavy metals or P from the sediments, which may facilitate the disposal of the removed water back into the lake and the utilization of the treated sediments for different purposes. This technology is easy to operate and suitable for the treatment of dredged sediments, and the dewatering result is comparable to low pressurized filtration but at low energy consumption.

Relationship between human activities and environmental changes in the southern Tibetan Plateau since the Little Ice Age.

The Tibetan Plateau (TP) is one of the most challenging areas for human long-term settlement due to its extreme living environment. Understanding the relationship between human activities and environmental changes in this extreme environment is important and can provide a historical reference for adapting to future climate change. In this study, we took the Angren Basin in the southern TP as a case study to elucidate the relationship since Little Ice Age (LIA). Using fecal stanol in feces, lake and river surface sediments, surface soils, and sediment core, we found that specific indices S1 and S2 from the composition of coprostanol, epicoprostanol, 5ß-ethylcoprostanol and 5ß-ethylepicoprostanol can reflect changes in human population and herbivores, respectively. Through the comparison between environmental changes determined by grain size, elements, sedimentation rate, and other climate records, the relationship between human activities and environmental changes was interpreted. Our results indicate that: (i) during 1480-1820 CE, the fecal stanols in lake sediments mainly originated from livestock, and the human population was low. In contrast, during 1820-2021 CE, the proportion and flux of S1 have been continuously increasing, indicating significant population growth. (ii) During the middle LIA, the cold-dry climate inhibited the development of agriculture and farming. However, the increased precipitation during the late LIA promoted that development, resulting in an increase in human population and livestock in a short term. (iii) Since 1951, people have reclaimed wasteland and developed husbandry, leading to increased soil erosion. (iv) Over the past 40 years, with a warm-humid climate and good policy support, human activities, such as agriculture and husbandry, have rapidly increased, but soil erosion has declined in the recent 20 years due to good soil-water conservation efforts. This study sheds light on the relationship between human activities and environmental changes and provides insights into future climate change responses.

Utilities of environmental radioactivity tracers in assessing sequestration potential of carbon in the coastal wetland ecosystems.

Demand for accurate estimation of coastal blue carbon sequestration rates in a regular interval has recently surged due to the increasing awareness of nature-based climate solutions to alleviate adverse impacts stemming from the recent global warming. The robust estimation method is, however, far from well-established. The international community requires, moreover, to quantify its effect of "management." This article tries to provide the environmental isotope community with basic biophysical features of coastal blue carbon ecosystems to identify a suitable set of environmental isotopes for promoting coastal ocean-based climate solutions. This article reviews (i) the primary biophysical characteristics of coastal blue carbon ecosystems and hydrology, (ii) their consequential impact on the accumulation and preservation of organic carbon (OC) in the sediment column, (iii) suitable environmental isotopes to quantifying the sedimentary organic carbon accumulation, outwelling of the carbon-containing byproducts of decomposition of biogenic organic matter and acid neutralizing alkalinity produced in situ sediment to the offshore. Above-ground biomass is not cumulative over the years except for mangrove forests within coastal blue carbon systems. Non-gaseous carbon sequestration and loss occur mainly as a form of sediment organic carbon (SOC) and dissolved carbon in an intertidal and subtidal bottom sediment body in a slow, patchy, and dispersive way, on which this article focuses. Investigating environmental radionuclides is probably the most cost-effective effort to contribute to defining the offshore spatial extent of coastal blue carbon systems except for seagrass beds (e.g., Ra isotopes), to quantify millimeter per year scale carbon accretion and loss within the systems (e.g., 7Be, 210Pb) and a liter per meter of coastline per a day scale water movement from the systems (Ra isotopes). A millimeter-scale spatial and an annual (or less) time-scale resolution offered by the use of environmental isotopes would equip us with a novel tool to enhance the carbon storage capacity of the coastal blue carbon system.

Comparison of sediment bioavailable methods to assess the potential risk of metal(loid)s for river ecosystems.

A heavily impacted river basin (Caudal River, NW Spain) by Hg and Cu mining activities, abandoned decades ago, was used to evaluate the environmental quality of their river sediments. The obtained results compared with reference values established by the US EPA and the Canadian Council of Ministers of the Environment for river sediments, have shown that the main elements of environmental concern are arsenic (As), mercury (Hg) and, to a lesser extent, copper (Cu), which reach concentrations up to 1080, 80 and 54 mg kg-1, respectively. To understand the role that river sediments play in terms of risk to ecosystem health, a comparison has been made between the total content of metal(oid)s in the sediments and the bioavailable contents of the same elements in pore water, passive DGT (Diffusive Gradients in Thin films) samplers and the sediment extractant using acetic acid. A good correlation between the As and Cu contents in the DGTs and the pore water was found, resulting in a transfer from the pore water to the DGT of at least 47 % of the Cu and more than 75 % of the As when the concentrations were low, with a deployment time of 4 days. When As and Cu concentrations were higher, their transfer was not so high (above 23.6 % for As and 19.3 % for Cu). The transfer of Hg from the pore water to the DGT was practically nil and does not seem to depend on the content of this metal. The fraction extracted with acetic acid, conventionally accepted as bioavailable, was clearly lower than that captured by DGTs for As and Cu (≤5 % and ≤8.5 % of the total amount, respectively), while it was similar for Hg (0.2 %).

Distribution, sources and ecological risks of PAHs and n-alkanes in water and sediments of typically polluted estuaries: Insights from the Xiaoqing River.

Seasonal water and sediment samples were collected from the Xiaoqing River estuary and the neighboring sea to study the spatial and temporal distributions, sources and ecological risks of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes. The results showed significant spatial and temporal differences in the concentrations of PAHs and n-alkanes under the influence of precipitation, temperature, and human activities. The concentrations of PAHs in water were lower in the wet season than in the dry season, and those in sediments were higher in the wet season than in the dry season. The concentrations of n-alkanes were higher in the rainy season than in the dry season for both water and sediments. The spatial distributions of PAHs and n-alkanes were estuarine > offshore. The concentration ranges of ∑PAHs in water and sediments were 230.66-599.86 ng/L and 84.51-5548.62 ng/g, respectively, in the wet season and 192.46-8649.55 ng/L and 23.39-1208.92 ng/g, respectively, in the dry season. The proportion of three-ring PAHs in water (57.03% and 78.27% in the wet and dry seasons, respectively) was high, followed by two-ring PAHs (27.31% and 13.59% in the wet and dry seasons, respectively). The proportion of four-ring PAHs was higher in sediments (24.79% and 32.20% in the wet and dry seasons, respectively). The ecological risk of PAHs assessed using the toxicity equivalent quotient and risk quotient was at moderate to moderately high risk levels. The high concentration of n-alkane fraction C16 (611.65-75594.58 ng/L) in the water is indicative of petroleum or other fossil fuel inputs. The main peaks of n-alkanes in river sediments were C27, C29 and C31, indicating higher inputs of plant sources. The sediments in the estuary showed dominance of both short-chain C16 and long-chain C25-C31, indicating a combined input of higher plants and petroleum. The diagnostic ratios of PAHs and n-alkanes indicated that their sources were mainly oil/coal/biomass combustion and petroleum spills attributed to frequent vehicular, vessel and mariculture activities. Given the potential ecological risks of PAHs and n-alkanes in water and sediments, future studies should focus on their bioaccumulation and biotoxicity.

A review of the pollution signatures of polycyclic aromatic hydrocarbons in the sediments of the East China Sea.

Marine sediments serve as crucial reservoirs for polycyclic aromatic hydrocarbons (PAHs), and their PAH signatures offer valuable historical pollution records. This article provides a comprehensive review of the pollution status of 16 priority PAHs in more than 1000 sediments from the East China Sea (ECS). It focuses on the PAH sources, spatiotemporal distributions, driving factors, and ecological risks, with information derived from peer-reviewed papers published between 2003 and 2023. The results revealed that vehicular emissions, mixed combustion sources of coal, biomass, and coke, as well as petrogenic sources, were the primary contributors to PAH pollution in the ECS sediments, accounting for 50%, 34%, and 16%, respectively. Human activities, hydrodynamic mechanisms, and environmental variables such as particle size and organic matter, collectively influenced the distribution of PAHs. Additionally, the population size and economic development played a key role in the temporal distribution of PAHs in the ECS sediments. The ecotoxicity assessment of PAHs in sediments indicated a low risk level. These outcomes are expected to provide environmentalists with detailed and up-to-date insights into sedimentary PAHs in the ECS, helping to develop suitable monitoring plans and strategies for promoting better management of ECS environment.

Human and ecological risk assessments of potentially toxic elements in sediments around a pharmaceutical industry.

Potentially toxic elements (PTEs) in sediment can be highly hazardous to the environment and public health. This study aimed to assess the human and ecological risks of PTEs in sediments around a pharmaceutical industry in Ilorin, Nigeria. Physicochemical parameters and the concentrations of lead (Pb), chromium (Cr), cadmium (Cd), cobalt (Co), arsenic (As), and nickel (Ni) were analyzed in sediment samples collected from seven locations in the wet and dry seasons. Standard two-dimensional principal component analysis (PCA) and risk assessments were also conducted. The concentrations of Pb, Co, Ni, Cr, Cd, and As in the sediments ranged from 0.001 to 0.031 mg/kg, 0-0.005 mg/kg, 0.005-0.012 mg/kg, 0.001-0.014 mg/kg, 0.005-0.024 mg/kg, and 0.001-0.012 mg/kg, respectively. The mean concentrations of the total PTEs content were found in decreasing order of concentration: Pb > Cd > Ni > Cr > As > Co. PCA showed that some of the PTEs were highly concentrated in samples obtained at other locations as well as at the discharge point. The Hazard Index was mostly <1 across locations, indicating little to no probable non-cancerous effect. However, the incremental lifetime cancer risk for arsenic and nickel was high and required attention. The ecological risk assessment showed that lead and arsenic were the major PTEs pollutants in all locations. The study identifies PTEs profiles in sediments and emphasises the necessity of continual monitoring and action to stop long-term negative impacts on the local environment and public health.

Development of High Surface Area Organosilicate Nanoparticulate Thin Films for Use in Sensing Hydrophobic Compounds in Sediment and Water.

The scope of this study was to apply advances in materials science, specifically the use of organosilicate nanoparticles as a high surface area platform for passive sampling of chemicals or pre-concentration for active sensing in multiple-phase complex environmental media. We have developed a novel nanoporous organosilicate (NPO) film as an extraction phase and proof of concept for application in adsorbing hydrophobic compounds in water and sediment. We characterized the NPO film properties and provided optimization for synthesis and coatings in order to apply the technology in environmental media. NPO films in this study had a very high surface area, up to 1325 m2/g due to the high level of mesoporosity in the film. The potential application of the NPO film as a sorbent phase for sensors or passive samplers was evaluated using a model hydrophobic chemical, polychlorinated biphenyls (PCB), in water and sediment. Sorption of PCB to this porous high surface area nanoparticle platform was highly correlated with the bioavailable fraction of PCB measured using whole sediment chemistry, porewater chemistry determined by solid-phase microextraction fiber methods, and the Lumbriculus variegatus bioaccumulation bioassay. The surface-modified NPO films in this study were found to highly sorb chemicals with a log octanol-water partition coefficient (Kow) greater than four; however, surface modification of these particles would be required for application to other chemicals.

Biotic regulation of phoD-encoding gene bacteria on organic phosphorus mineralization in lacustrine sediments with distinct trophic levels.

Organic phosphorus (Po) mineralization hydrolyzed by alkaline phosphatase (APase) can replenish bioavailable P load in the sediment water ecosystem of lakes. However, the understanding about the interaction between P load and bacteria community encoding APase generation in the sediment are still limited. Different P pools in the sediments from Taihu Lake, China were measured using sequential extraction procedure. The APAase activity (APA) were obtained accompanying with enzymatic dynamical parameters Vmax and Km. The abundances and diversity of gene phoD-harboring bacterial communities were assessed using high throughput sequencing. The analysis results showed the decrease of potentially bioavailable P fractions including MgCl2-P and Fe-P along sampling gradient southwards together with active P concentrations in the water. Conversely, increasing APA and absolute abundance of phoD gene were found with the decreasing of P loads southwards. Positive correlation (p < 0.05) between absolute abundance and APA indicated that phoD-encoding bacteria manipulated the APA and Po mineralization. Negative correlation (p < 0.01) suggested that the APA was restrained by high P load and was promoted under low P condition. However, higher Vmax and Km values suggested that high mineralization potential of Po maintained the high concentrations of potentially bioavailable P even the APA was restricted. The abundance increase of predominant genus Cobetia (from 15.51 to 24.34 %) mirrored by the reduced Calothrix abundance (from 24.65 to 1036 %) was speculated to be responsible for the APA promotion under low P condition. Higher diversity indices in the high P scenario suggested that high P load stimulated the ecological diversity of gene phoD-encoding bacteria community. Generally, rare taxa such as Burkholderia having high connected degrees in bacterial communities together with abundant genera synergistically manipulated the phoD gene abundance and APase generation. Interaction between P fractions and bacteria encoding phoD gene determined the eutrophication status in the lacustrine ecosystem.

Compound- and element-specific accumulation characteristics of persistent toxic substances and metals in sediments of the Yellow Sea.

This study investigated the large-scale distributions of persistent toxic substances (PTSs) and heavy metals in sediments of the Yellow Sea, collected from six transects between latitudes 32 and 37 degrees north (n = 35). Elevated concentrations of polychlorinated biphenyls (PCBs) were detected near the mainland, with a predominance of low-chlorinated congeners (di to tetra, ∼60%), indicative of atmospheric deposition. Analysis of traditional and emerging polycyclic aromatic hydrocarbons (t-PAHs and e-PAHs) revealed notable enrichment in the Central Yellow Sea Mud Zone (CYSM), attributing fossil fuel combustion as the significant source. Styrene oligomers and alkylphenols exhibited notable accumulation near the Han River Estuary in South Korea and the Yangtze River Estuary in China, respectively. The accumulation of heavy metals was predominantly observed in the CYSM, with element-specific distribution patterns. Cluster analysis revealed distinct distribution patterns for PTSs and metals, highlighting their source-dependent and grain size-dependent behaviors. In addition, the distribution and accumulation of PTSs tended to depend on their partitioning coefficients, such as the octanol-air partition coefficient (log KOA) and octanol-water partition coefficient (log KOW). This study offers valuable insights into the sources, transport, and fate of hazardous substances in the Yellow Sea, emphasizing the necessity for targeted environmental management strategies.

Vertical transfer of microplastics in nearshore water by cultured filter-feeding oysters.

Microplastics (MPs) are widely distributed in the sea, but the vertical transfer of MPs by marine organisms in coastal area is still poorly understood. In this study, we used laser direct infrared (LDIR) spectroscopy to determine the number and characteristics of MPs deposited by cultured oyster Crassostrea gigas and further compared the differences between MPs of natural deposit and biodeposit in field environments. The amounts of MPs found in the biodeposit of cultured oysters were 3.54 times greater than that in the natural deposition. The polymer types of biodeposit MPs also differed from those of natural deposition. It was estimated that a single oyster can deposit 15.88 MPs per day, which is a figure much higher than the initial results, and hotspots of MPs deposition may be formed within the oyster aquaculture area. We used generalized linear mixed model (GLMM) to further infer the sources of MPs in sediments and found that distance to shore, cultured zone and urban center were important predictors of MPs abundance in sediments of aquaculture area. The above results suggest that cultured bivalves have an important capacity for MPs biodeposition and will further change the vertical distribution pattern of MPs in coastal environments.

Effects of microplastics on sedimentary greenhouse gas emissions and underlying microbiome-mediated mechanisms: A comparison of sediments from distinct altitudes.

Microplastics (MPs) are emerging contaminants in aquatic ecosystems that can profoundly affect carbon and nitrogen cycling. However, the impact mechanisms of MPs on sedimentary greenhouse gas (GHG) emissions at distinct altitudes remain poorly elucidated. Here, we investigated the effects of polyvinyl chloride (PVC) and polylactic acid (PLA) on sedimentary CO2, CH4, and N2O emissions at distinct altitudes of the Yellow River. PVC increased the relative abundance of denitrifiers (e.g., Xanthobacteriaceae, Rhodocyclaceae) to promote N2O emissions, whereas PLA reduced the abundance of AOA gene and denitrifiers (e.g., Pseudomonadaceae, Sphingomonadaceae), impeding N2O emissions. Both PVC and PLA stimulated the growth of microbes (Saprospiraceae, Aquabacterium, and Desulfuromonadia) associated with complex organics degradation, leading to increased CO2 emissions. Notably, the concurrent inhibition of PLA on mcrA and pmoA genes led to its minimal impact on CH4 emissions. High-altitude MQ sediments, characterized by abundant substrate and a higher abundance of functional genes (AOA, AOB, nirK, mcrA), demonstrated higher GHG emissions. Conversely, lower microbial diversity rendered the low-altitude LJ microbial community more susceptible to PVC, leading to a more significant promotion on GHG emissions. This study unequivocally confirms that MPs exacerbate GHG emissions via microbiome-mediated mechanisms, providing a robust theoretical foundation for microplastic control to mitigate global warming.

Effects of acid mine drainage and sediment contamination on soil bacterial communities, interaction patterns, and functions in alkaline desert grassland.

Acid mine drainage and sediments (AMD-Sed) contamination pose serious ecological and environmental problems. This study investigated the geochemical parameters and bacterial communities in the sediment layer (A) and buried soil layer (B) of desert grassland contaminated with AMD-Sed and compared them to an uncontaminated control soil layer (CK). The results showed that soil pH was significantly lower and iron, sulfur, and electroconductivity levels were significantly higher in the B layer compared to CK. A and B were dominated by Proteobacteria and Actinobacteriota, while CK was dominated by Firmicutes and Bacteroidota. The pH, Fe, S, and potentially toxic elements (PTEs) gradients were key influences on bacterial community variability, with AMD contamination characterization factors (pH, Fe, and S) explaining 48.6 % of bacterial community variation. A bacterial co-occurrence network analysis showed that AMD-Sed contamination significantly affected topological properties, reduced network complexity and stability, and increased the vulnerability of desert grassland soil ecosystems. In addition, AMD-Sed contamination reduced C/N-cycle functioning in B, but increased S-cycle functioning. The results highlight the effects of AMD-Sed contamination on soil bacterial communities and ecological functions in desert grassland and provide a reference basis for the management and restoration of desert grassland ecosystems in their later stages.