Decade-long historical shifts in legacy and emerging per- and polyfluoroalkyl substances (PFAS) in surface sediments of China's marginal seas: Ongoing production and ecological risks.

Since the addition of perfluorooctane sulfonate (PFOS) to the Stockholm Convention in 2009, it became imperative to reassess the distribution and ecological risk of per- and polyfluoroalkyl substances (PFAS) in coastal sediments over the past decade as sediment records the history of pollutants from human activities. To achieve this, sediments were collected in 2009 and 2021 from China's coastal regions. Despite the consistent geographical pattern where the highest concentrations of ∑PFAS were found in the Yellow Sea, temporal changes have emerged. During the studied period, ∑PFAS levels experienced an increase in the East China Sea while concurrently witnessing a decrease in the South China Sea. Of significance, emerging PFAS compounds displayed not only rising concentrations but also a broader array, pointing towards their intensified production and utilization within China. Alarmingly, PFOS levels in sediments taken from the East China Sea maintained a consistently high ecological risk status over the last ten years. Significant correlations were found between long-chain PFAS and organic carbon content. Comparisons between datasets from 2009 to 2021 uncovered a shifting ecological risk landscape, with heightened concerns for PFOA in the East China Sea, while PFOS-associated risks appeared to diminish in the South China Sea-potentially reflecting the transition to alternative PFAS chemicals. The research reinforces the importance of continuous monitoring and emphasizes the urgent necessity for deeper exploration into the environmental implications and hazards posed by emerging PFAS.

Sediment organic matter predicts polycyclic aromatic hydrocarbon distribution in port sediments.

We evaluated the influence of organic matter in polycyclic aromatic hydrocarbons (PAHs) in port sediments using multiple linear regression (MLR) and prediction models. Total sediment PAHs ranged between 45 and 3230 ng/g dw (average: 557 ± 962 ng/g dw), with PAHs primarily originating from river inputs, confined to areas near the estuaries. Coal/biomaterial combustion and petroleum mainly contribute to the presence of PAHs along estuaries, with medium-high to high ecological risks. MLR TPAHs prediction model included variables, namely, the marine-derived total organic carbon (TOCmar), terrestrial fraction of organic matter (Fterr), and carbon-to­nitrogen ratio (CNR). Results indicate that mainly marine- followed by terrestrially-derived organic matter influenced sediment PAH distribution. Total organic nitrogen and CNR were variables in the toxic equivalent (TEQ) prediction model, demonstrating that terrestrial pollution sources primarily influenced TEQ. The study analyzes and predicts the impact of organic matter and its sources on the fate and transport of PAHs in port sediments.

Bio-Based Materials as a Sustainable Solution for the Remediation of Contaminated Marine Sediments: An LCA Case Study.

Contaminated sediments may induce long-term risks to humans and ecosystems due to the accumulation of priority and emerging inorganic and organic pollutants having toxic and bio-accumulation properties that could become a secondary pollution source. This study focused on the screening of novel bio-based materials to be used in the decontamination of marine sediments considering technical and environmental criteria. It aimed to compare the environmental impacts of cellulose-based adsorbents produced at lab scale by using different syntheses protocols that involved cellulose functionalization by oxidation and branching, followed by structuring of an aerogel-like material via Soxhlet extraction and freeze-drying or their combination. As model pollutants, we used 4-nitrobenzaldehyde, 4-nitrophenol, methylene blue, and two heavy metals, i.e., cadmium and chromium. When comparing the three materials obtained by only employing the Soxhlet extractor with different solvents (without freeze-dying), it was observed that the material obtained with methanol did not have a good structure and was rigid and more compact than the others. A Life Cycle Assessment (LCA) was conducted to evaluate the environmental performance of the novel materials. Apart from the hierarchical categorization of the materials based on their technical and environmental performance in eliminating organic pollutants and heavy metal ions, it was demonstrated that the cellulose-based material obtained via Soxhlet extraction with ethanol was a better choice, since it had lower environmental impacts and highest adsorption capacity for the model pollutants. LCA is a useful tool to optimize the sustainability of sorbent materials alongside lab-scale experiments and confirms that the right direction to produce new performant and sustainable adsorbent materials involves not only choosing wastes as starting materials, but also optimizing the consumption of electricity used for the production processes. The main results also highlight the need for precise data in LCA studies based on lab-scale processes and the potential for small-scale optimization to reduce the environmental impacts.

Preservation of Organic Carbon Associated with Iron on Continental Shelves Influenced by Hydrodynamic Processes.

Understanding the environmental fate of organic carbon associated with iron (OC-Fe) is critically important for investigating OC preservation in aquatic systems. Here, we first investigate 13C and 14C isotopes of OC-Fe within grain size-fractionated sediments retrieved from the East China Sea and estimate their sources and reactivities of OC-Fe through isotope-mixing models and thermal pyrolysis approaches in order to reveal the fate of OC-Fe on continental shelves influenced by hydrodynamic processes. Our results show that the OC-Fe proportion in total OC (fOC-Fe) in the sortable silt fractions (20-63 µm) is the highest among three grain size fractions, likely suggesting that hydrodynamics may enhance the iron protection on OC. In addition, Δ14COC-Fe values fall within the range of from -358.73 to -64.03‰, and both Δ14COC-Fe values and ancient OC-Fe% exhibit strong positive linear relationships with fOC-Fe. This emphasized that the hydrodynamic processes may cause the ancient OC to be tightly associated with Fe, accompanying OC-Fe aging. Our findings shed new light on the preservation of OC-Fe in marginal seas to advance the recognition of carbon "rusty sinks" in seafloor sediments.

Development of Multiplex RT qPCR Assays for Simultaneous Detection and Quantification of Faecal Indicator Bacteria in Bathing Recreational Waters.

In this study, we designed and validated in silico and experimentally a rapid, sensitive, and specific multiplex RT qPCR for the detection and quantification of faecal indicator bacteria (FIB) used as microbiological references in marine bathing water regulations (Escherichia coli and intestinal enterococci). The 16S rRNA gene was used to quantify group-specific enterococci and Escherichia/Shigella and species-specific such as Enterococcus faecalis and E. faecium. Additionally, a ybbW gene encoding allantoin transporter protein was used to detect E. coli. An assessment of marine coastal systems (i.e., marine water and sediment) revealed that intestinal enterococci were the predominant group compared to Escherichia/Shigella. The low contribution of E. faecalis to the intestinal enterococci group was reported. As E. faecalis and E. faecium were reported at low concentrations, it is assumed that other enterococci of faecal origin are contributing to the high gene copy number of this group-specific enterococci. Moreover, low 16S rRNA gene copy numbers with respect to E. faecalis and E. faecium were reported in seawater compared to marine sediment. We conclude that marine sediments can affect the quantification of FIBs included in bathing water regulations. Valuing the quality of the marine coastal system through sediment monitoring is recommended.

Swarm and UNOISE outperform DADA2 and Deblur for denoising high-diversity marine seafloor samples.

The performance of sequence variant resolution analytic tools for metabarcoding has not yet been adequately benchmarked for high-diversity environmental samples. We therefore evaluated the sequence variant tools DADA2, Deblur, Swarm, and UNOISE, using high-diversity seafloor samples, resulting in comparisons of 1800 sequence variant tables. The evaluation was based on 30 sediment grab samples, for which 3 replica samples were collected. Each replica sample was extracted using 5 common DNA extraction kits, resulting in 450 DNA extracts which were 16S rRNA gene sequenced (V3-V4), using Illumina. Assessments included variation across replica samples, extraction kits, and denoising methods, in addition to applying prior knowledge about alpha diversity correlations toward the cosmopolitan marine archaeon Nitrosopumilus with high diversity and the sulfide oxidizing Sulfurovum with low diversity. DADA2 displayed the highest variance between replicates (Manhattan distance 1.14), while Swarm showed the lowest variance (Manhattan distance 0.93). For the analysis based on prior biological knowledge, UNOISE displayed the highest alpha diversity (Simpson's D) correlation toward Nitrosopumilus (Spearman rho = 0.85), while DADA2 showed the lowest (Spearman rho = 0.10). Deblur completely eliminated Nitrosopumilus from the dataset. For Sulfurovum, on the other hand, all the methods showed comparable results. In conclusion, our evaluations show that Swarm and UNOISE performed better than DADA2 and Deblur for high-diversity seafloor samples.

Effective capping of dissolved sulfide generated in Ulva prolifera-rich marine sediments by iron-rich red soil.

Bloom-induced macroalgal enrichment on the seafloor can substantially facilitate dissolved sulfide (DS) production through sulfate reduction. The reaction of DS with sedimentary reactive iron (Fe) is the main mechanism of DS consumption, which however usually could not effectively prevent DS accumulation caused by pulsed macroalgal enrichment. Here we used incubations to investigate the performance of Fe-rich red soil for buffering of DS produced from macroalgae (Ulva prolifera)-enriched sediment. Based on our results, a combination of red soil additions (6.8 kg/m2) before and immediately after pulsed macroalgal deposition (455 g/m2) can effectively cap DS within the red soil layer. The effective DS buffering is mainly due to ample Fe-oxide surface sites available for reaction with DS. Only a small loss (4 %) of buffering capacity after 18-d incubation suggests that the red soil is capable of prolonged DS buffering in macroalgae-enriched sediments.

Remediation of sediments contaminated by harmful heavy metals using aluminum sulfate: Sustainable approach for practical applications.

Chemical washing could be suitable for the remediation of marine sediments contaminated with harmful heavy metals. Considering green and sustainable remediation (GSR), the application of aluminum sulfate (AS) is intended to reduce the costs and environmental impacts. We extracted harmful heavy metals from manganese nodules using an ion exchange mechanism that occurs when AS dissociates in water. AS in the range from 2 % to 5 % was used. The remediation efficiencies using 5 % AS were found to be the highest, at 91.8 % for Ni and ≥ 100 % for other harmful heavy metals. The Pearson's coefficient evaluation showed that increasing elapsed time did not significantly affect the extraction of harmful heavy metals. Pollutants in post-processing products may not cause secondary pollutions if solidification/stabilization and additional treatments are used. Our results can serve as fundamental data for the actual remediation processes using AS not only for deep-sea mining tailings but also contaminated marine sediments.

Single and Combined Effects of Phenanthrene and Silver Nanoparticles on Denitrification Processes in Coastal Marine Sediments.

The increasing production and utilization of polycyclic aromatic hydrocarbons (PAHs) and commercial silver nanoparticles (AgNPs) have raised concerns about their potential environmental release, with coastal sediments as a substantial sink. To better understanding the effects of these contaminants on denitrification processes in coastal marine sediments, a short-term exposure simulation experiment was conducted. We investigated the effects of single and combined contamination of phenanthrene (Phe) and AgNPs on denitrification processes in a coastal marine sediment. Results showed that all contaminated treatment groups had different degrees of inhibitory effect on denitrification activity, denitrifying enzyme activity, total bacteria count and denitrifying genes. The inhibitory effect sequence of each treatment group was combined treatment > AgNPs treatment > Phe treatment. Moreover, the inhibitory effects of denitrifying genes were much larger than that of total bacteria count, indicating that the pollutants had specific toxic effects on denitrifying bacteria. The sequence of sensitivity of three reduction process to pollutants was N2O > NO2- > NO3-. All contaminated treatment groups could increase NO3-, NO2- and N2O accumulation. Furthermore, according to the linear relationship between functional gene or reductase and denitrification process, we also found that the abundance of denitrifying genes could better predict the influence of Phe and AgNPs on sediment denitrification than the denitrifying bacterial diversity. In addition, at the genus level, the community structure of nirS- and nosZ-type denitrifying bacteria changed dramatically, while changes at the phylum level were comparatively less pronounced. Single and combined contamination of Phe and AgNPs could reduce the dominance of Pseudomonas, which may lead to a potential slow-down in the degradation of Phe and inhibition of denitrification, especially the combined contamination. Overall, our study revealed that combined contamination of Phe and AgNPs could lead to an increase in NO3-, NO2- and N2O accumulation in coastal sediment, which poses a risk of eutrophication in coastal areas, exacerbates the greenhouse effect and has adverse effects on global climate change.

Chemical-physical parameters and microbial community changes induced by electrodes polarization inhibit PCB dechlorination in a marine sediment.

Microbial reductive dechlorination of organohalogenated pollutants is often limited by the scarcity of electron donors, that can be overcome with microbial electrochemical technologies (METs). In this study, polarized electrodes buried in marine sediment microcosms were investigated to stimulate PCB reductive dechlorination under potentiostatic (-0.7 V vs Ag/AgCl) and galvanostatic conditions (0.025 mA·cm-2-0.05 mA·cm-2), using graphite rod as cathode and iron plate as sacrificial anode. A single circuit and a novel two antiparallel circuits configuration (2AP) were investigated. Single circuit polarization impacted the sediment pH and redox potential (ORP) proportionally to the intensity of the electrical input and inhibited PCB reductive dechlorination. The effects on the sediment's pH and ORP, along with the inhibition of PCB reductive dechlorination, were mitigated in the 2AP system. Electrodes polarization stimulated sulfate-reduction and promoted the enrichment of bacterial clades potentially involved in sulfate-reduction as well as in sulfur oxidation. This suggested the electrons provided were consumed by competitors of organohalide respiring bacteria and specifically sequestered by sulfur cycling, which may represent the main factor limiting the applicability of METs for stimulating PCB reductive dechlorination in marine sediments.

Speciation and distribution of arsenic in cold seep sediments of the South China Sea.

Arsenic (As) is an abundant metalloid in marine environments, while the biogeochemical cycling of As in cold seeps remains poorly understood. We characterized the speciation of As and investigated controls of As distribution in cold seeps of South China Sea. High methane concentrations (0.2-5.5 mmol/L) and rapid sulfate depletion were observed in the seepage. Dissolved inorganic arsenic (DIAs) was enriched in the porewater ranging from 7.5 to 23.5 µg/L. As in the solid phase ranged from 2.9 to 22.6 µg/g, and sulfide mineral-bound As dominated the total arsenic (TAs) pool, followed by iron (manganese, aluminum) oxide-bound As. The significant correlations between porewater Fe2+ and DIAs reflect the controls of iron on DIAs release. Incubation experiments showed that adsorption to the solid phase and sulfate reduction activity affected the bioavailability and removal of DIAs, suggesting that multiple processes regulate the speciation and transformation of As in seep sediments.

Impacts of cadmium accumulation on the diversity, assembly processes, and co-occurrence patterns of archaeal communities in marine sediments.

There is limited understanding regarding the changes in the ecological processes and the mechanisms of archaeal community in response to heavy metal contamination in the marine sediments. In this study, sediment samples were collected from 46 locations near harbors, and the concentration of heavy metals and the diversity of archaeal communities were investigated to understand the impact of Cd on archaeal communities. The results demonstrated a significant correlation between the diversity of archaeal community and Cd concentration, particularly showing a linear decrease in the species richness with rising Cd concentration. ANME-1b was identified as a significantly enriched archaeal taxon in the higher Cd environment. Null model and neutral community model indicated that the ecological assembly of archaeal communities in marine sediments was primarily governed by the stochastic processes, with dispersal limitation being the primary factor. The contribution of deterministic process to the assembly of archaeal communities in higher Cd environments increased clearly, accompanied by a notable reduction in species migration rates and widths of ecological niche of archaeal populations. Co-occurrence network analysis revealed an obvious increase in species interactions in higher Cd environments, with an apparent rise in the proportion of competitive relationships and an increase in the number of keystone species. Moreover, archaeal species formed a more complex and stable community to cope with Cd stress. This study provides new insights into the impacts of heavy metals on the ecological processes of marine microorganisms and the underlying mechanisms.

Plastic pollution in Moreton Bay sediments, Southeast Queensland, Australia.

The mounting issue of plastic waste in the aquatic ecosystem is a growing source of concern. Most plastic waste originates on land and a significant proportion of this eventually finds its way into the marine environment, which is widely regarded as a major repository for plastic debris. Currently, there exists a substantial gap in our understanding of how much plastic, the main polymer types, and the distribution of plastic in the marine environment. This study aimed to provide information on mass concentrations of a range of plastics in the surface sediments in the semi-enclosed Moreton Bay, just offshore the large city of Brisbane, Southeast Queensland, Australia. Surface sediment samples were quantitatively analysed for a suite of 7 common plastic polymer types (i.e., polystyrene (PS), polycarbonate (PC), poly-(methyl methacrylate) (PMMA), polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE) and polyvinyl chloride (PVC)) using a pressurized liquid extraction (PLE) followed by double-shot microfurnace pyrolysis coupled to gas chromatography mass spectrometry (Pyr-GC/MS). The advantage of this approach is that it can measure plastics below the limit of visual detection. The study revealed that Σ7plastics were consistently present in the samples, although the concentrations displayed a wide range of concentrations from 3.3 to 2194.2 µg/g across different sites. Among the polymers analysed, PE and PVC were found at the highest concentrations, ranging from 2.3 to 1885.9 µg/g and 3.0-979.5 µg/g, respectively. Based on the average concentrations of plastics measured, the dry bulk density and volume of sediments within the top 10 cm of the bay, it was estimated that there is a minimum of 7000 t of plastics stored in the surface sediments of the bay. This study is the first to report the mass concentrations of identified plastics and identify the main polymer types in Moreton Bay. This is important information to develop management plans to reduce the plastic waste entering the coastal marine environment.

Metagenomic analysis of carbohydrate-active enzymes and their contribution to marine sediment biodiversity.

Marine sediments constitute the world's most substantial long-term carbon repository. The microorganisms dwelling in these sediments mediate the transformation of fixed oceanic carbon, but their contribution to the carbon cycle is not fully understood. Previous culture-independent investigations into sedimentary microorganisms have underscored the significance of carbohydrates in the carbon cycle. In this study, we employ a metagenomic methodology to investigate the distribution and abundance of carbohydrate-active enzymes (CAZymes) in 37 marine sediments sites. These sediments exhibit varying oxygen availability and were isolated in diverse regions worldwide. Our comparative analysis is based on the metabolic potential for oxygen utilisation, derived from genes present in both oxic and anoxic environments. We found that extracellular CAZyme modules targeting the degradation of plant and algal detritus, necromass, and host glycans were abundant across all metagenomic samples. The analysis of these results indicates that the oxic/anoxic conditions not only influence the taxonomic composition of the microbial communities, but also affect the occurrence of CAZyme modules involved in the transformation of necromass, algae and plant detritus. To gain insight into the sediment microbial taxa, we reconstructed metagenome assembled genomes (MAG) and examined the presence of primary extracellular carbohydrate active enzyme (CAZyme) modules. Our findings reveal that the primary CAZyme modules and the CAZyme gene clusters discovered in our metagenomes were prevalent in the Bacteroidia, Gammaproteobacteria, and Alphaproteobacteria classes. We compared those MAGs to organisms from the same taxonomic classes found in soil, and we found that they were similar in its CAZyme repertoire, but the soil MAG contained a more abundant and diverse CAZyme content. Furthermore, the data indicate that abundant classes in our metagenomic samples, namely Alphaproteobacteria, Bacteroidia and Gammaproteobacteria, play a pivotal role in carbohydrate transformation within the initial few metres of the sediments.

Phosphorus mining from marine sediments adopting different carbon/nitrogen strategies driven by anaerobic reactors: The exploration of potential mechanism and microbial activities.

To investigate the possibility of phosphorus (P) recovery from marine sediment and explore the role of the carbon: nitrogen ratio in affecting the internal P release under anaerobic conditions, we experimented with the external addition of carbon (acetic acid and glucose) and ammonia nitrogen (NH4-N) to expose P release mechanisms. The 24-day anaerobic incubations were conducted with four different carbon: nitrogen dosing groups including no NH4-N addition and COD/N ratios of 100, 50, and 10. The P release showed that extra NH4-N loading significantly suppressed the decomposition of P (p < 0.05) from the marine sediment, the maximum P release was 4.07 mg/L and 7.14 mg/L in acetic acid- and glucose-fed systems, respectively, without extra NH4-N addition. Additionally, the results exhibited that the imbalance of carbon: nitrogen not only failed to induce the production of organic P mineralization enzyme (alkaline phosphatase) in the sediment but also suppressed its activity under anaerobic conditions. The highest enzyme activity was observed in the group without additional NH4-N dosage, with rates of 1046.4 mg/(kg∙h) in the acetic acid- and 967.8 mg/(kg∙h) in the glucose-fed system, respectively. Microbial data analysis indicated that a decrease in the abundance of P release-regulating bacteria, including polyphosphate-accumulating organisms (Rhodobacteraceae) and sulfate-reducing bacteria (Desulfosarcinaceae), was observed in the high NH4-N addition groups. The observed reduction in enzyme activity and suppression of microbial activity mentioned above could potentially account for the inhibited P decomposition in the presence of high NH4-N addition under anaerobic conditions. The produced P-enriched solution from the bioreactors may offer a promising source for future recovery endeavors.

Metagenome-assembled genomes of deep-sea sediments: changes in microbial functional potential lag behind redox transitions.

Hadal sediments are hotspots of microbial activity in the deep sea and exhibit strong biogeochemical gradients. But although these gradients are widely assumed to exert selective forces on hadal microbial communities, the actual relationship between biogeochemistry, functional traits, and microbial community structure remains poorly understood. We tested whether the biogeochemical conditions in hadal sediments select for microbes based on their genomic capacity for respiration and carbohydrate utilization via a metagenomic analysis of over 153 samples from the Atacama Trench region (max. depth = 8085 m). The obtained 1357 non-redundant microbial genomes were affiliated with about one-third of all known microbial phyla, with more than half belonging to unknown genera. This indicated that the capability to withstand extreme hydrostatic pressure is a phylogenetically widespread trait and that hadal sediments are inhabited by diverse microbial lineages. Although community composition changed gradually over sediment depth, these changes were not driven by selection for respiratory or carbohydrate degradation capability in the oxic and nitrogenous zones, except in the case of anammox bacteria and nitrifying archaea. However, selection based on respiration and carbohydrate degradation capacity did structure the communities of the ferruginous zone, where aerobic and nitrogen respiring microbes declined exponentially (half-life = 125-419 years) and were replaced by subsurface communities. These results highlight a delayed response of microbial community composition to selective pressure imposed by redox zonation and indicated that gradual changes in microbial composition are shaped by the high-resilience and slow growth of microbes in the seafloor.

Spatial patterns of sediment contamination and their influence on benthic infaunal communities in a highly tidal and industrial estuary in Atlantic Canada.

Sediment contamination can be elevated in ports, harbours, and estuaries with legacies of exploitation, negatively impacting infaunal invertebrate communities. Saint John Harbour (45.25° N, 66.05° W), New Brunswick, Canada, is an active harbour with strong tides and a long history of human activity. To examine spatial patterns of sediment contamination, samples were collected between 2011 and 2021 from subtidal sites near potential contaminant sources. Invertebrate data from the same samples were used to investigate potential effects on biological communities. Contaminant concentrations in the inner parts of the harbour were elevated compared to reference sites, but generally did not reach levels comparable to other highly contaminated harbours in the region. Effects on invertebrates were detectable, particularly at sites with higher contamination, although physical factors (depth, sediment grain size) were more important. Dynamic tidal conditions in the harbour may reduce the accumulation of contaminants in subtidal sediments and their impacts on infaunal communities.

Electrochemical remediation of synthetic and real marine sediments contaminated by PAHs, Hg and As under low electric field values.

To date, remediation, protection, and restoration of contaminated sites is a global concern. The current technologies to restore sediments characterized by heterogeneous characteristics, several pollutants, fine grains, and low hydraulic permeability are poorly effective; hence their remediation is still challenging. A promising approach for the sediment's remediation could be the electrochemical route since it is a not-expensive, effective and noninvasive in situ technology. Electrochemical remediation (ER) is commonly studied under relatively high electric fields (E ≥ 1 V cm-1) and using costly processing fluids in a three compartments cell aiming to desorb and transport the contaminants into the processing fluids (secondary dangerous effluent). In this work, contaminated marine sediments were electrochemically treated focusing on the insertion of electrodes directly in the sediments and adopting, for the first time for real sediments, low E values (≤ 0.25 V cm-1) for 4-days period. It was observed that PAHs can be simultaneously transported and degraded in situ preventing the production of a secondary dangerous effluent and reducing the energy consumption. Firstly, clay marine sediments dragged from Capo Granitola Coast (Trapani, Italy) spiked with five PAHs congeners (5PAHs), Hg and As were used as a simplified model matrix and treated to simulate a real case study. A total PAHs removal efficiency of 57% was reached after 96 h of treatment under 0.05 V cm-1. Then, real polluted marine sediments from Augusta Bay (Syracuse) and Bagnoli-Coroglio Bay (Naples) in the southern Italy were treated as real contaminated sediments to be restored, to validate the proposed approach for real cases. A quite good removal efficiency of PAHs was reached after 96 h of electrochemical treatment coupled with a low energetic consumption due to the rather E values adopted. In addition, it was observed that this approach, under the adopted conditions, is unsuitable for the remediation of Hg and As.

Antibiotics and antibiotic resistance change bacterial community compositions in marine sediments.

Emerging contaminants, including antibiotics, antibiotic-resistant bacteria (ARB), and extracellular antibiotic resistance genes (eARGs), have been detected in large numbers in the aquatic environment. The effects of emerging contaminants on bacterial communities in marine sediments are not well studied. In this study, the effects of emerging contaminants (antibiotics, ARB, and eARGs) on the variations of bacterial populations in marine sediments of the Bohai Sea, Yellow Sea, East China Sea, and South China Sea were investigated. The results showed that the abundance of the host bacterial phylum Probacteria in the marine sediments of the Bohai Sea was the lowest among the four seas after exposure to different antibiotics, ARB, and eARGs. The inputs of exogenous antibiotics and resistance genes significantly affected the community function, resulting in significant differences in community abundance at the genus level. The abundance of Halomonas, Sulfitobacter, and Alcanivorax in the four sea areas displayed noteworthy differences in response to the addition of exogenous antibiotics and eARGs. These findings contribute to a more comprehensive understanding of the intricate interplay between emerging contaminants and the dynamics of bacterial communities in natural ecosystems.

Effects of electron acceptors and donors on anaerobic biodegradation of PAHs in marine sediments.

Polycyclic aromatic hydrocarbons (PAHs) are typical organic pollutants accumulated in the environment. PAHs' bioremediation in sediments can be promoted by adding electron acceptor (EA) and electron donor (ED). Bicarbonate and sulfate were chosen as two EAs, and acetate and lactate were selected as two EDs. Six groups of amendments were added into the sediments to access their role in the anaerobic biodegradation of five PAHs, containing phenanthrene, anthracene, fluoranthene, pyrene, and benzo[a]pyrene. The concentrations of PAHs, EAs and EDs, electron transport system activity, and microbial diversity were analyzed during 126-day biodegradation in serum bottles. The HA group (bicarbonate and acetate) achieved the maximum PAH degradation efficiency of 89.67 %, followed by the SL group (sulfate and lactate) with 87.10 %. As the main PAHs degrading bacteria, the abundance of Marinobacter in H group was 8.62 %, and the addition of acetate significantly increased the abundance of Marinobacter in the HA group by 75.65 %.