Diversity and structure of pelagic microbial community in Kuroshio Extension.

Kuroshio Extension (KE) is the most active region of oceanic change in the North Pacific Ocean, which provides an essential place for the survival of marine microorganisms. However, Vertical changes in microbial communities in the Kuroshio Extension and the mechanisms by which environmental factors drive vertical changes in community structure remain unclear. In this work, microbial diversity, abundance, and community structure of 12 water layers (from surface to bottom) at five stations were uncovered by 16S rRNA gene high-throughput sequencing. Microbial diversity and richness decreased with increasing seawater depth. Microorganisms in the euphotic zone can be well separated from other zones based on NMDS analysis. Proteobacteria (65.20%), Bacteroidota (8.48%), Actinobacteriota (5.76%), and Crenarchaeota (4.49%) accounted for a relatively large proportion and their distribution is similar in four zones. Most of microorganisms were significantly (Spearman test, p < 0.05) correlated with salinity, density, pressure, and temperature. This work enhances our understanding of vertical microbial diversity and provides insights into the pelagic microbial community structure.

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.

An eco-friendly porous hydrogel adsorbent based on dextran/phosphate/amino for efficient removal of Be(II) from aqueous solution.

A novel environmentally-friendly porous hydrogel adsorbent (GHPN) is firstly designed and prepared using dextran, phosphate, and calcium hydroxide for the adsorption of Be(II). GHPN shows good adsorption selectivity for Be(II) (Kd = 1.53 × 104 mL/g). According the adsorption kinetics and thermodynamics, the theoretical adsorption capacity of GHPN to Be(II) is 43.75 mg/g (35 °C, pH = 6.5), indicating a spontaneous exothermic reaction. After being reused for 5 cycles, the adsorption and desorption efficiencies of Be(II) with GHPN are obtained to be more than 80 %, showing acceptable recycling performance. Both of the characterizations and theoretical calculations indicate that the phosphate group, hydroxyl group, and amino group own the affinity to form stable complexes with Be(II). Benefiting from the introduction of phosphate and amino, the adsorption effect of the hydrogel adsorbent on Be(II) can be greatly improved, and surface precipitation, complexation, and ligand exchange are the dominant mechanisms of beryllium adsorption. The results suggest that GHPN has great potential to be utilized as an eco-friendly and useful adsorbent of Be(II) from aqueous solution.

N-alkane shape distinctive microbial patterns in Kuroshio Extension.

Marine microorganisms are primary drivers of the elemental cycling. The interaction between heterotrophic prokaryotes and biomarker (n-alkane) in Kuroshio Extension (KE) remains unclear. Here, we categorize KE into three characteristic areas based on ocean temperatures and nutrient conditions: Cold Water Area (CWA), Mixed Area (MA), and Warm Water Area (WWA). A total of 49 samples were collected during two-year voyage to identify the source of n-alkane and associated degrading microorganisms. Total n-alkane concentrations (Σn-Alk) in surface water (SW) spanned from 1,308 ng L-1 to 1,890 ng L-1, it was significantly higher (Tukey-Kramer test, p < 0.05) in MA than CWA and WWA. The Σn-Alk in surface sediments (SS) gradually increased from north to south, ranging from 5,982 ng g-1 to 37,857 ng g-1. Bacteria and algae were the primary sources of n-alkane in both SW and SS. Proteobacteria was the most widely distributed among three areas. The presence of Rhodobacteraceae with alkB was the primary reason affecting n-alkane concentrations in SW. The Gammaproteobacteria with alkB and alkR chiefly affected n-alkane concentrations in SS. In summary, n-alkane s serve as an energy source for particular microorganisms, shaping the unique oceanographic patterns.

Porous durian shell biochar modified by KMnO4 (Mn-DSB) as a highly selective adsorbent for Be(II).

The mining of uranium-beryllium ores has resulted in substantial beryllium (Be) contamination. In this study, agricultural waste durian shells were utilized as raw materials to prepare biochar, which was further modified to enhance its adsorption capacity (Mn-DSB). The results effectively demonstrated Mn loading onto the DSB surface. Batch experiments were conducted to identify the optimal adsorption conditions of Mn-DSB for beryllium. At a temperature of 35 °C and pH 6, beryllium's maximum adsorption capacity (Qe) was 42.08 mg·g-1. The materials' internal structure was analyzed before and after adsorption via multiple techniques. Mn-DSB manifested potent selectivity towards beryllium in multicomponent mixed solutions, binary systems, and uranium-beryllium wastewater, as the beryllium removal rate exceeded 90%. The study investigated the recyclability of Mn-DSB and found that after five reuse cycles, the adsorption and desorption efficiencies were 90% and 85%, respectively. The strong ligand complexation (N-H, CO32-, -OH) and ion exchange mechanisms (with Mn7+ ions) of Mn-DSB explained its high adsorption capacity. Therefore, this study demonstrates the potential of Mn-DSB for treating uranium-beryllium tailing wastewater.

Spatial distribution characteristics of perfluoroalkyl substances in bulk and grain size fractionated sediments in Shenzhen Bay.

Understanding Perfluoroalkyl substances (PFASs) spatial distribution in natural environments is crucial due to their environmental persistence and potential bioaccumulation. However, limited research has investigated PFASs spatial distribution at a high resolution, especially in the Guangdong-Hong Kong-Macao Greater Bay Area. Here, we examined the composition and concentration of PFASs in 36 bulk surface sediments and grain-size fractionated sediments from 9 representative sites to determine the spatial distribution characteristics in Shenzhen Bay. We found that ΣPFASs decreased gradually from nearshore area to offshore area (0.680 and 0.297 ng g-1 dw, respectively). Furthermore, PFASs are easily adsorbed on fine-grained sediments, likely due to their chain length and hydrophobicity. We argue that the lateral movement of sediments may transport fine-grained sediments associated with ΣPFASs out of the bay, resulting in the spatial difference in ΣPFASs in Shenzhen Bay. Our findings provide important insights into explore the mechanisms associated with preservation and transport of PFASs.

Temporal variation of per- and polyfluoroalkyl substances (PFASs) abundances in Shenzhen Bay sediments over past 65 years.

We examined the vertical distribution of per- and polyfluoroalkyl substances (PFASs) and total organic carbon in sediment cores located in Shenzhen Bay area. We investigated the 210Pbex specific activity of the sediments and calculated the flux of PFASs to understand the temporal variation of PFASs in the past 65 years. The results showed that the concentrations of PFASs generally decreased with depth, ranging from 13 to 251 pg/g dw. The highest PFASs detected were perfluorobutanesulfonic acid, perfluorooctanoic acid, and perfluorohexanoic acid, which correspond to raw materials used in fire-fighting foam and food packaging industries. The flux of PFASs in Shenzhen Bay showed varying growth after 1978 when China's GDP entered a rapid growth stage. Our findings suggest that the vertical distribution of PFASs in Shenzhen Bay is fluctuating with the changes in industrial types and economic development, with implications for studying the fate of other persistent pollutants in the oceans.

A step closer to real practice: Integrated tandem photocatalysis-biofilm process towards degradation of crude oil.

Intimately coupled photocatalysis and biodegradation (ICPB) systems represent a promising wastewater treatment technology. The implementation of ICPB systems for oil spill treatment is a pressing concern. In this study, we developed an ICPB system comprising BiOBr/modified g-C3N4 (M-CN) and biofilms for the treatment of oil spills. The results demonstrate that the ICPB system achieved the rapid degradation of crude oil, outperforming the single photocatalysis and biodegradation methods by degrading 89.08 ± 5.36% within 48 h. The combination of BiOBr and M-CN formed a Z-scheme heterojunction structure, enhancing the redox capacity. The interaction between the holes (h+) and the negative charge on the biofilm surface promoted the separation of electrons (e-) and h+, thereby accelerating the degradation process of crude oil. Moreover, ICPB system maintained an excellent degradation ratio after three cycles and its biofilms progressively adapted to the adverse effects of crude oil and light. The microbial community structure remained stable throughout the degradation of crude oil, with Acinetobacter and Sphingobium identified as the dominant genera in biofilms. The proliferation of the Acinetobacter genus appeared to be the main factor contributing to the promotion of crude oil degradation. Our work demonstrates that the integrated tandem strategies perhaps represent a feasible pathway toward practical crude oil degradation.

Quantitative analysis of biosurfactants in water samples by a modified oil spreading technique.

The oil spreading technique relies on biosurfactant to reduce the surface tension of an oil film and form an oil spreading ring in the center, and then judges the content of biosurfactant according to the diameter of the spreading ring. However, the instability and large errors of the traditional oil spreading technique limit its further application. In this paper, we modified the traditional oil spreading technique by optimizing the oily material, image acquisition and calculation method, which improves the accuracy and stability of the quantification of biosurfactant. We screened lipopeptides and glycolipid biosurfactants for rapid and quantitative analysis of biosurfactant concentrations. By selecting areas by color done by the software to modify image acquisition, the results showed that the modified oil spreading technique has a good quantitative effect, reflected in the concentration of biosurfactant being proportional to the diameter of the sample droplet. More importantly, using the pixel ratio method instead of the diameter measurement method to optimize the calculation method, the region selection was more exact, and the accuracy of the data results was high, and the calculation efficiency was improved significantly. Finally, the contents of rhamnolipid and lipopeptide in oilfield water samples were judged by the modified oil spreading technique, the relative errors were analyzed according to the different substances as the standard, and the quantitative measurement and analysis of oilfield water samples (the produced water of Zhan 3-X24 and the injected water of the estuary oil production plant) were realized. The study provides a new perspective on the accuracy and stability of the method in the quantification of biosurfactant, and provided some theoretical and data support for the study of the microbial oil displacement technology mechanism.

The Role of Bacteria in the Formation and Migration of Oil-Particle Aggregates (OPAs) after Marine Oil Spills and the Associated Mechanism.

Oil spills interact with mineral particles to form oil-particle aggregates (OPAs), which promotes the oil's natural diffusion and biodegradation. We investigated the effect of bacteria on the formation and vertical migration of OPAs under different concentrations and types of particles and proposed and elucidated an oil-particle-bacteria coupling mechanism. The depth of particle penetration into oil droplets (13-17 µm) was more than twice that of the nonbacterial group. Oil that remained in the water column and deposited to the bottom decreased from 87% to 49% and increased from 14% to 15% at high/low concentration, respectively. Interestingly, the median droplet diameter showed a negative correlation (R2 = 0.83) and positive correlation (R2 = 0.60) at high/low concentration, respectively, with the relative penetration depth first proposed. We further demonstrated that bacteria increased the penetrating depth by a combination of reducing/increasing the interfacial tension, reducing the oil amount (C17-C38) in the OPAs, and increasing the particle width. These effects reduced the droplet size and ultimately changed the vertical migration of OPAs. Finally, we provided a simple assessment of the vertical distribution of OPAs in nearshore environments based on experimental data and suggested that the role of bacteria in increasing the depth of particles penetrating into the oil droplets should not be ignored. These findings will broaden the research perspective of marine oil spill migration.

An approach for carbon content measurement in marine sediment: Application of organic and elemental carbon analyzer.

Organic and Elemental Carbon (OEC) is widely applied in the atmospheric sciences for determining carbon content and distinguishing black carbon contents of aerosols, with an advantage that OEC-based approach can provide thermograms derived from carbonaceous material. It is potential to adopt the advantage to measure the content and composition of organic carbon (OC)% in marine sediments. Here, we utilized the OEC analyzer to measure the OC% in marine sediment based on the pyrolytic oxidation principle, and obtain the OC-derived carbon dioxide (CO2) thermograms. We examined marine sediments and reference materials to understand the stability and reproducibility of OC% measurements using our approach. The findings indicate that the OC% results (ranging from 1.44 to 1.59%, ave. 1.55 ± 0.03%, n = 64) based on this approach are accurate. In addition, CO2 concentration thermograms obtained by repeated measurements exhibit a strong reproducibility. Our approach can thus provide the concentrations of thermally-evolved CO2 with increasing heating temperature to deeply understand the reactivities of OC and the compositions in sediments. We suggest that the OEC-based OC% measurement is credible when samples preparation is well-performed (e.g., suitable sample mass and uniformly distributed loading). To sum up, we provide a means to accurately determine the OC% in marine sediments in terms of the ramped-pyrolysis principle.

Effect of fermentation pH on the structure, rheological properties, and antioxidant activities of exopolysaccharides produced by Alteromonas australica QD.

The pH value was essential for the growth and metabolism of microorganisms. Acidic pH exopolysaccharide (AC-EPS) and alkaline pH exopolysaccharide (AL-EPS) secreted by A. australica QD mediated by pH were studied in this paper. The total carbohydrate content and molecular weight of AC-EPS (79.59% ± 2.24% (w/w), 8.374 × 105 Da) and AL-EPS (82.48% ± 1.46% (w/w), 6.182 × 105 Da) were estimated and compared. In AC-EPS, mannose (3.78%) and galactose (3.24%) content was more, while the proportion of glucuronic acid was less in comparison to AL-EPS. The scanning electron microscopy revealed the structural differences among the AC-EPS and AL-EPS. Thermogravimetric analysis showed degradation temperatures of 272.8 °C and 244.9 °C for AC-EPS and AL-EPS, respectively. AC-EPS was found to exhibit better rheological properties and emulsifying capabilities, while AL-EPS had superior antioxidant activities. Overall, both AC-EPS and AL-EPS have the potential to be used as emulsifiers and biological antioxidants.

Characterization and protective effect against ultraviolet radiation of a novel exopolysaccharide from Bacillus marcorestinctum QDR3-1.

Although exopolysaccharide (EPS) has been applied to various fields, EPS for UVR-mediated oxidative stress repair still needs further exploration. In this study, a novel EPS was isolated from the fermentation medium of Bacillus sp. QDR3-1 and its yield was 4.8 g/L (pH 8.0, 12 % glucose, 30 °C and 6 % NaCl). The pure fraction (named EPS-M1) was purified by DEAE-cellulose and Sephadex G-100 column. EPS-M1 was a heteropolysaccharide composed of Man, Glc, Gal, and Fuc with a molecular weight of 33.8 kDa. Scanning electron microscopy (SEM) observed a rough surface and reticular structure of EPS-M1, and EPS-M1 formed spherical aggregates in aqueous solution observed in atomic force microscopy (AFM). Thermal analysis revealed that the degradation temperature of EPS-M1 was 306 °C. Moreover, methylation and NMR analysis determined that EPS-M1 was consisted of →3)-Manp-(1→, →2,6)-Manp-(1→, →4,6)-Glcp-(1→, →3)-Glcp-(1→, →4)-Galp-(1→, →4)-Fucp-(1→, and T-Manp-(1→. Furthermore, the cytotoxicity and the repair ability of UVR-mediated cell damage of EPS-M1 were studied with L929 cells. The results showed that EPS-M1 had good biocompatibility and it could mitigate UVR-mediated cell damage by regulating the levels of cellular reactive oxygen species (ROS), depolarization of mitochondrial membrane potential (MMP) and Caspase-3/7 activity. Overall, the structure analysis and the protective effects of EPS against L929 cells exposed to UVR provided an experimental basis for EPS in practical applications.

Mesoscale evaluation of oil submerging and floating processes during marine oil spill response: Effects of dispersant on submerging stability and the associated mechanism.

The migration of oil spills in marine environment is still not clear, especially the key processes of submerging and floating, which is an important concern for effective disposal of oil spills. In mesoscale wave tank (32 m × 0.8 m × 2 m), this study has evaluated the characteristics of oil submergence based on oil concentration and oil droplet size. The concept of effective submergence is put forward for the first time, utilized to analyze the effects of dispersant on submerging stability and associated mechanisms. The results indicate dispersants increase submerged oil concentration and promote homogeneous distribution and vertical penetration. Of concern is that dispersants increase the proportion of small oil droplets (2.5-70 µm), prolonging the residence time of oil droplets in water by delaying the floating process. Dispersants sharply reduce oil droplets size (VMD<44 µm) thus decreasing the coalescence probability. These contribute to better submerging stability. By contrast, the submerged oil, formed as oil patches, oil streamers, and large oil droplets (VMD>170 µm) when without dispersant, will float and reattach to oil slicks more quickly due to their large volume. These findings help to clarify spilled oil behaviors and provide a new idea for the research on oil submergence.

Biodegradation Potential of Bacillus sp. PAH-2 on PAHs for Oil-Contaminated Seawater.

Microbial degradation is a useful tool for inhibiting or preventing polycyclic aromatic hydrocarbons (PAHs) widely distributed in marine environment after oil spill accidents. This study aimed to evaluate the potential and diversity of bacteria Bacillus sp. PAH-2 on Benzo (a) anthracene (BaA), Pyrene (Pyr), and Benzo (a) pyrene (BaP), their composite system, aromatic components system, and crude oil. The seven-day degradation rates against BaA, Pyr, and BaP were 20.6%, 12.83%, and 17.49%, respectively. Further degradation study of aromatic components demonstrated PAH-2 had a high degradation rate of substances with poor stability of molecular structure. In addition, the degradation of PAHs in crude oil suggested PAH-2 not only made good use of PAHs in such a more complex structure of pollutants but the saturated hydrocarbons in the crude oil also showed a good application potential.

Solid inoculants as a practice for bioaugmentation to enhance bioremediation of hydrocarbon contaminated areas.

Vacuum freeze-drying is a scientifically advanced method to prepare solid inoculants from oil degrading bacterium. The introduction of oil-degrading microbes or bioaugmentation can be an efficient way to bioremediate oil spills in marine areas, where oil-degrading bacteria are deficient. The purpose of this study is to evaluate the potential use of solid inoculants of LZ-2 bacteria to enhance the degradation rate of crude oil. In this study, response surface methodology (RSM) was incorporated into the experimental design to optimize a response, which is influenced by different protectants. Our results showed that five factors have interactive and synergistic protective effects on the growth of LZ-2. Optimal growth of freeze-dried LZ-2 (63.8%) was observed with a 10.5% solution of skim milk supplemented with 14.3% sucrose, 14.4% of trehalose, 4.9% of glycerin and 14.7% of ß-cyclodextrin. The culture grew in medium containing crude oil (3 g L-1) at 37 °C at 150 rpm for 30 d, GC and GC-MS analysis showed biodegradation of 44.2 and 21.6% for total saturate and aromatic hydrocarbons respectively. These results indicated that the solid inoculants of LZ-2 bacteria had the potential to be used for ex-situ bioremediation of hydrocarbon pollutants associated with crude oil.

The interaction between dispersed crude oil droplets and particulate matter.

In this study, the effect of particulate matter type, temperature, oil type and weathering degree on the interaction between dispersed crude oil droplets and particulate matter was investigated. The increase of total petroleum hydrocarbon (TPH) percentage in oil-particle aggregates (OPAs) could be attributed to the increase of oil polarity or viscosity. For small size particulate matter, there was a fine dependence relationship between the TPH percentage in OPAs and the oil viscosity and the content of polar components, respectively (R2 > 0.7502). And the total organic carbon content also played an important role in the formation of OPAs. The petroleum hydrocarbon extracts of OPAs showed a decrease in short-carbon-chain components and a relative increase in long-carbon-chain compounds. Petroleum hydrocarbon compounds trapped by three types of particulate matter exhibited a similar change tendency, but there was no apparent difference in the residual TPH percentage in water.

Regulation of different electron acceptors on petroleum hydrocarbon biotransformation to final products in activated sludge biosystems.

The types and concentrations of electron acceptor are the significant factors influencing the oxidation and biotransformation of organic matter in the process of pollutant biodegradation. Regulation of O2, SO42- and NO3- as electron acceptors on petroleum hydrocarbon biotransformation to final products was studied using the multiple methods including mesoscale biodegradation experiments, thermodynamic theoretical calculations and stoichiometric analyses. Petroleum hydrocarbon biodegradation ratio (PHBR) rose from 64.7 to 82.4% with dissolved oxygen (DO) (3-5 mg L- 1). PHBR increased from 57.4 to 66.1% in SO42--reducing biosystems and rose from 65.0 to 77.9% in NO3--reducing biosystems. Carbon balance was verified in different cultures. The shared functional microorganisms in different biosystems included Candida, Rhodococcus, Pseudomonas, Ochrobactrum, Marinobacter, Bacillus, Azoarcus, Alcanivorax, Acinetobacter. Pandoraea, Enterobacter and Burkholderia in anaerobic biosystems preferred to use NO3- and SO42- as electron acceptors for metabolism, and order of availability followed: NO3- > SO42-. Thermodynamic constraint showed that potentials of alkanes biotransformation to methane through hydrogenotrophic and acetoclastic methanogenesis in NO3--reducing biosystems were 7.27-7.73 and 7.25-7.70 times larger than those of SO42--reducing biosystems, respectively. Metabolism equations of microorganisms proved that anabolism and catabolism on alkanes were feasible. This work provides a support for studying the biochemical process of petroleum hydrocarbon biotransformation and lays a foundation for the realization of oil-containing wastewater bioremediation.

Petroleum hydrocarbon release behavior study in oil-sediment aggregates: turbulence intensity and chemical dispersion effect.

This study investigated the effects of turbulence and oil dispersants on release of petroleum hydrocarbons in oil-sediment aggregates. A kinetic study showed that the static oil release process could be fitted to the first-order kinetics model. The oil concentration increased with increasing temperature and salinity, while remaining independent of pH. The dispersant desorption ability of petroleum hydrocarbons followed the sequence of: Tween 80 > Tween 85 > Span 80 > DOSS. In the presence of turbulence, the maximum release ratio was 40.28%. However, the combination of dispersants and turbulence had a smaller effect than turbulence alone. Furthermore, residual n-alkanes and PAHs in the sediments were analyzed. The results showed higher proportions of C15-C35 and 2-3 ring PAHs in residual oil. These results can help assess the fate and distribution of oil spills in marine environments.

Biodegradation of hydrolyzed polyacrylamide by the combined expanded granular sludge bed reactor-aerobic biofilm reactor biosystem and key microorganisms involved in this bioprocess.

An investigation was carried out to study the performance of a combined expanded granular sludge bed reactor-aerobic biofilm reactor (EGSB-ABR) biosystem and key microorganisms involved in this bioprocess. When the concentration of hydrolyzed polyacrylamide (HPAM) was 500 mg/L, the maximum removal rate of HPAM reached 64.36%, among which the contribution of the EGSB reactor was 24.35%. Scanning electron microscope (SEM) images and gel permeation chromatography (GPC) analysis showed that macromolecular HPAM was degraded into oligomer with lower molecular weight. Among the key enzymes involved in the degradation of HPAM, laccase had the best tolerance to HPAM. Microbial community structure was analysed by Illumina MiSeq Sequencing, which revealed that Firmicutes, Proteobacteria and Bacteroidetes were the most prevalent bacterial phyla, Trichococcus, Brooklawnia, Bacillus and Pseudomonas were the predominant functional genera, and Methanosaeta was the dominant archaeal genus in the bioprocess. Furthermore, hypothesis about the mechanisms of HPAM biodegradation was proposed.