High Salinity Environment Research Articles

Post-Modification of a Robust Covalent Organic Framework for Efficient Sequestration of 99 TcO4 - /ReO4.

Nuclear industry spent fuel reprocessing and some radioactive contamination sites often involve high acidity and salinity environments. Currently developed and reported sorbents in 99 TcO4 - sequestration from the nuclear waste are unstable and show low adsorption efficiency in harsh conditions. To address this issue, we developed a post-synthetic modification strategy by grafting imidazole-based ionic liquids (ILs) onto the backbone of covalent organic framework (COF) via vinyl polymerization. The resultant COF-polyILs sorbent exhibits fast adsorption kinetics (<5 min) and good sorption capacity (388 mg g-1 ) for ReO4 - (a nonradioactive surrogate of 99 TcO4 - ). Outstandingly, COF-polyILs composite shows superior ReO4 - removal even under highly acidic conditions and in the presence of excess competing ions of Hanford low-level radioactive waste stream, benefiting from the stable covalent bonds between the COF and polyILs, mass of imidazole rings, and hydrophobic pores in COF.

Insight into the effect of rice-straw ash on enhancing the anaerobic digestion performance of high salinity organic wastewater

Anaerobic digestion is an economic method for treating high salinity organic wastewater (HSOW), but performance enhancement is needed because of the inhibitory effect of high salinity. In this study, rice-straw ash (RSA) was applied to alleviate the inhibitory effect during HSOW anaerobic digestion. The results showed that, when the NaCl content increased from 0% to 3.0%, the methane production decreased by 87.35%, and the TOC removal rate decreased to 34.12%. As a K+ and alkalinity source, RSA addition enhanced the anaerobic digestion performance, and the optimal dosage was 0.88 g/L. Under this dosage, the methane production increased by 221.60%, and TOC removal rate reached 66.42% at 3.0% salinity. The addition of RSA increased the proportion of living cells in the high salinity environment, and enhanced the activity of key enzymes and electron transfer efficiency in the anaerobic digestion process. The addition of RSA with a dosage of 0.88 g/L promoted the accumulation of acetoclastic methanogen Methanothrix. The abundance of substrate transporters, ion transporters and electron transfer related functional genes were enriched, which might be key for promoting HSOW anaerobic digestion performance. The results also showed that RSA addition played an important role in maintaining the stability of the anaerobic digestion system, and it could be a potential strategy for enhancing the anaerobic digestion performance under high salinity conditions.

Establishment of a halotolerant bioremediation platform from Halomonas cupida using synthetic biology approaches

At present, the vast majority of organic pollutants-degrading microbes are unable to grow and lose their degradation capability under high-salt conditions owing to lack of resistance to high osmotic pressure imposed by salt stress. To overcome the bottleneck, in this study, a halotolerant bioremediation platform is established from a halophilic chassis Halomonas cupida J9. As a proof of concept, we chose a typical environmental pollutant p-nitrophenol (PNP) to validate the feasibility of engineering H. cupida J9 for efficient mineralization of environmental pollutants in high saline environments. Firstly, four strong promoters including P3, P15, P16 and P22 were screened from H. cupida J9 by transcriptome analysis and promoter strength characterization. Subsequently, the constructed strain J9U-P15-AB and J9U-P8KT-AB with a chromosome-borne P15- and P8KT-pnpAB expression cassette could rapidly degrade and tolerate 200 mg/L PNP. Furthermore, a pathway for PNP biodegradation was functionally assembled in the genome of H. cupida J9 and optimized by enhanced expression of all PNP degradation genes with P15 and P8KT promoter, resulting in two stable genetically engineered strains J9U-P15PNP and J9U-P8KTPNP capable of metabolizing the only carbon source PNP to support cell growth in high-salinity media. Eventually, stable isotope analysis for elucidating the degradation pathway of 13C6-PNP indicated that the finally constructed strains were capable of converting PNP into CO2 in high saline media. These results suggest that promoter engineering may serve as a useful strategy for significantly improving the mineralization efficiency of organic pollutants. The engineered strains could degrade 25 mg/L PNP in seawater within 6 h, suggesting good potential of these degraders for in situ bioremediation. The gfp-labeled degraders also can be tracked during bioremediation. More importantly, this study underscores the value of H. cupida J9 as a promising chassis for the establishment of a halotolerant bioremediation platform using synthetic biology approaches.

Substrate quality overrides soil salinity in mediating microbial respiration in coastal wetlands

AbstractAs productive and essential ecosystems, coastal wetlands have experienced increased environmental impacts such as saltwater intrusion and eutrophication, resulting in significant shifts in microbially mediated ecosystem functions, such as carbon sequestration and nutrient transformations. The soil microbial respiration, a primary process in the transfer of carbon from soil to the atmosphere, is susceptible to environmental changes. However, studies on how salinity affects soil microbial respiration in coastal wetlands have not been fully explored. Soil samples were systematically collected from divergent sampling sites covering medium‐ and extremely‐saline wetlands along a river‐estuary‐coast continuum to investigate mechanisms controlling soil microbial respiration in coastal wetlands. According to the results, the microbial biomass and carbon‐related extracellular enzyme activities were significantly lower in extremely saline (ECe &gt;15 ds m−1, ES) than medium and highly saline soils (ECe &lt;15 ds m−1, MHS) (p &lt; 0.05), indicating a suppressive effect of salinity on soil microbiota. Meanwhile, high‐salinity soils had lower vector length and soil microbial respiration rates, suggesting that soils with low carbon limitation might cause less carbon loss under higher salinity environments. Moreover, it was showed that increased available phosphorus could alleviate microbial carbon limitations. Changes in the microbial functional community demonstrated that the microbial community in favor of metabolic mediates and secondary metabolites substrates (regarded as labile substrates) were more sensitive to salinity. The partial least square path modeling further confirmed that microbial nutrient limitation and microbial biomass contribute more directly to promoting soil microbial respiration. These results have substantial implications for elucidating carbon dynamics in coastal wetlands ecosystems under increased nutrient discharge and sea‐level rise.

Interaction of electrolyzed nanomaterials with sandstone and carbonate rock: Experimental study and DLVO theory approach

The utilization of nanoparticles (NPs) in various applications, such as water pollution treatment, CO2 geological storage enhancement, and enhanced oil recovery, holds great promise. However, the instability of NPs in fluidic environments severely limits their potential applications. Moreover, NPs tend to adsorb onto the surfaces of sandstones and carbonate rocks in high-saline environments, leading to formation damage. To enable large-scale implementation of NPs, comprehensive research is crucial to understand their stable behavior in harsh saline environments. This study focuses on investigating the interaction of electrolyzed synthesized nanomaterials, specifically titanium dioxide (TiO2), manganese oxide (Mn2O3), and graphene oxide (GO), with the surfaces of carbonate rock and sandstone. To characterize the nanomaterials, various techniques were employed, including Fourier transform-infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), Brunauer−Emmett−Teller (BET), x-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). TiO2, Mn2O3, and GO were synthesized using sol-gel, co-precipitation, and modified Hummer's methods, respectively. The stability of nanofluids was assessed through zeta potential and particle size measurements. The results revealed that the inner-sphere complexes formed by Ca2+ on GO NPs were more effective in neutralizing negative surface charges compared to Mg2+, resulting in a shift of the zeta potential towards lower absolute values. CaCl2 and MgCl2 were found to reverse the charges of Mn2O3 and TiO2 NPs (towards positive values), thus enhancing their stability at higher salt content. SEM images and ultraviolet–visible (UV–vis) spectroscopy measurements demonstrated that Mn2O3 and GO NPs were more prone to adsorption on rock surfaces when Ca2+ and Mg2+ ions were present in the nanofluids, respectively. To assess the interaction energies between NPs and surfaces and investigate the reversibility of NP adsorption, Derjaguin-Landau-Verwey-Overbeek (DLVO) analysis was conducted. The outcomes of this analysis were found to be consistent with the data obtained through SEM and UV–vis spectroscopy.

Deep learning-enabled discovery and characterization of HKT genes in Spartina alterniflora.

Spartina alterniflora is a halophyte that can survive in high-salinity environments, and it is phylogenetically close to important cereal crops, such as maize and rice. It is of scientific interest to understand why S. alterniflora can live under such extremely stressful conditions. The molecular mechanism underlying its high-saline tolerance is still largely unknown. Here we investigated the possibility that high-affinity K+ transporters (HKTs), which function in salt tolerance and maintenance of ion homeostasis in plants, are responsible for salt tolerance in S.alterniflora. To overcome the imprecision and unstable of the gene screening method caused by the conventional sequence alignment, we used a deep learning method, DeepGOPlus, to automatically extract sequence and protein characteristics from our newly assemble S. alterniflora genome to identify SaHKTs. Results showed that a total of 16 HKT genes were identified. The number of S. alterniflora HKTs (SaHKTs) is larger than that in all other investigated plant species except wheat. Phylogenetically related SaHKT members had similar gene structures, conserved protein domains and cis-elements. Expression profiling showed that most SaHKT genes are expressed in specific tissues and are differentially expressed under salt stress. Yeast complementation expression analysis showed that type I members SaHKT1;2, SaHKT1;3 and SaHKT1;8 and type II members SaHKT2;1, SaHKT2;3 and SaHKT2;4 had low-affinity K+ uptake ability and that type II members showed stronger K+ affinity than rice and Arabidopsis HKTs, as well as most SaHKTs showed preference for Na+ transport. We believe the deep learning-based methods are powerful approaches to uncovering new functional genes, and the SaHKT genes identified are important resources for breeding new varieties of salt-tolerant crops.

Superhydrophobic melamine sponges with high performance in oil/organic solvent sorption

The severe adverse impacts of the frequently occurring marine oil spills call for the urgent development of an efficient approach for oil spill restoration. Here, we prepared a superhydrophobic melamine sponge with water contact angle of 151.6° via a one-step dip-coating process by simply reacting the melamine sponge with stearic anhydride. The as-prepared sponge, MS-4, demonstrates excellent sorption capacities for various organic solvents such as hexane, toluene and chloroform, as well as oils including diesel, mineral oil, and crude oil, with sorption capacities ranging from 78 to 160 times its own mass. Moreover, MS-4 exhibits good recyclability with retention rate of over 93% even after 50 sorption/squeezing cycles, remarkable stability when exposed to challenging conditions such as strong acidic (pH = 1.0) and alkaline (pH = 13.0) environments, as well as high salinity environments. Additionally, MS-4 displays superb selectivity, enabling the continuous oil/water separation when assisted by a vacuum pump, achieving a high flux of approximately 106 L•m−2•h−1, while maintaining a low water content of as minimal as 30 ppm. Notably, through a facile filtration process, MS-4 achieves an exceptional demulsification efficiency of up to 99.7% for water-in-oil emulsions.

Insights into saline adaptation strategies through a novel halophilic bacterium isolated from solar saltern of Yellow sea

Solar salterns were placed along the coast and were frequently left unattended after use. While many studies have isolated and identified microorganisms from hypersaline environments, their role and adaptation mechanisms are still unclear. Herein, we elucidated the role of halophiles in salt-polluted areas through the recently reported Halomonas getboli YJPS3-2 from the abandoned saltern. We analyzed the expression levels of genes in the YJPS3-2 strain to identify its adaptation mechanisms to high salinity environments, by representing the process from tidal flats to abandoned salterns with varying salinity gradients. The YJPS3-2 strain primarily overexpresses genes associated with ABC transport to adapt to hypersaline environments. Interestingly, the cheA gene, which recognizes changes in the surrounding, was the most upregulated, and it was also associated with the overexpression of the MS ring and T3SS mechanisms relating to the flagellar activity. The YJPS3-2 recognized the high salt concentration in its surroundings and attempted to accumulate compatible solutes that could withstand high osmotic pressure inside the cell to adapt to the high salinity environment. Furthermore, during this process, the YJPS3-2 strain removed surrounding pollutants and secreted secondary metabolites that could be utilized by neighboring organisms. Our results suggested that this halophilic bacterium has the potential to serve as a pioneering species for thriving the surrounding while adapting to saline environments.

Co-inoculation of Bacillus velezensis and Stenotrophomonas maltophilia strains improves growth and salinity tolerance in maize (Zea mays L.)

Limiting factors for plant growth, such as low nutrient availability and intolerance to high salinity, may impair the production of several crops. Plant growth-promoting bacteria (PGPB) present a potential solution to mitigate these limitations by stimulating plant growth and development. This study aimed to identify the strains LGMB12, LGMB319, and LGMB426 (Bacillus velezensis) and LGMB417 (Stenotrophomonas maltophilia), and to assess single and co-inoculation effects of these bacteria on the growth promotion of maize (Zea mays L.) plants under normal conditions and in high salinity environments. These strains were identified through Bayesian inference multilocus analysis using 16 S rRNA, gyrA, recA, and rpoB genes. Antibiosis analysis revealed that the strains did not inhibit each other's growth. Thirteen inoculation conditions were tested in greenhouse experiments including controls, inoculation of each strain separately and in the six pairs of combinations to evaluate growth promotion and salinity tolerance, using 75 and 100 mM NaCl in the irrigation water. The results revealed that co-inoculation yielded the best outcomes, highlighting the synergistic effects of combining the strains. Overall, this study emphasizes the potential of co-inoculation with Bacillus velezensis and Stenotrophomonas maltophilia strains as a strategy to enhance plant growth and improve salinity tolerance in maize cultivation. Further investigations are warranted to explore their application as bioinputs in agricultural settings.

Development of eco-friendly chitosan-g-polyacrylamide preformed particle gel for conformance control in high-temperature and high-salinity reservoirs

Oil and gas extraction has become challenging nowadays due to the accompanying amount of excess produced water that results in poor recoverability of hydrocarbon, besides other environmental and economic isues. A recent and efficient technology for conformance control is the injection of preformed particle gels (PPGs), which results in a more practical production process. Nevertheless, existing treatments fail in high-temperature reservoirs, are extremely sensitive to salinity, and are hazardous. The characteristics of the designed PPG, such as mechanical strength and thermal durability, is mainly depend on their crosslinking method. Polysaccharides-based gels prepared by physical crosslinking are weaker than the ones crosslinked by strong covalent bonding. This paper uses one of the polysaccharides and proposes an environmentally friendly PPG for water shutoff applications in reservoirs of high temperature (≤130 °C) and high salinity (200,000 ppm), named chitosan grafted polyacrylamide crosslinked with N, N′-methylene bisacrylamide, synthesized chemically by microwave assisted method. The PPG's chemical compositions, grafting and crosslinking mechanism have been investigated by FTIR spectroscopy and SEM techniques. Swelling kinetics, swelling capacity, and mechanical strength measurements were conducted in different conditions to evaluate the influence of the reservoir conditions, such as salinity, temperature, and pH, on the PPG stability. TGA experiments were also performed to examine the thermal stability. Results have shown that the grafting method has produced a PPG with improved mechanical strength, thermal durability, and salt insensitivity. These results are consistent with the testing observations, where the swelling capacities and the storage modulusof Cs/PAMBA samples, with different MBA content, in deionized water were 2.72–11.64 g/g and 4272.1–22,687 Pa, respectively, while they are 2.52–13.82 g/g and 3699.6–22,910, respectively, in saline solution of TDS 67.2976 g/L. The PPGs are thermally stable and resist temperatures up to 130 °C. Besides being eco-friendly, the Cs/PAMBA showed good long-term thermal stability in high-temperature and high-salinity environments.

Exploring the Physiological and Molecular Mechanisms of Halophytes' Adaptation to High Salinity Environments: Implications for Enhancing Plant Salinity Tolerance

Exploring the Physiological and Molecular Mechanisms of Halophytes' Adaptation to High Salinity Environments: Implications for Enhancing Plant Salinity Tolerance

Deterministic processes dominate archaeal community assembly from the Pearl River to the northern South China Sea.

Archaea play a significant role in the biogeochemical cycling of nutrients in estuaries. However, comprehensive researches about their assembly processes remain notably insufficient. In this study, we systematically examined archaeal community dynamics distinguished between low-salinity and high-salinity groups in water and surface sediments over a 600-kilometer range from the upper Pearl River (PR) to the northern South China Sea (NSCS). Neutral community model analysis together with null model analysis showed that their C-score values were greater than 2, suggesting that deterministic processes could dominate the assembly of those planktonic or benthic archaeal communities at both the low-salinity and high-salinity sites. And deterministic processes contributed more in the low-salinity than high-salinity environments from the PR to the NSCS. Furthermore, through the co-occurrence network analysis, we found that the archaeal communities in the low-salinity groups possessed closer interactions and higher proportions of negative interactions than those in the high-salinity groups, which might be due to the larger environmental heterogeneities reflected by the nutrient concentrations of those low-salinity samples. Collectively, our work systematically investigated the composition and co-occurrence networks of archaeal communities in water as well as sediments from the PR to the NSCS, yielding new insights into the estuary's archaeal community assembly mechanisms.

Experimental Evaluation of Blends Containing Lineal Alkylbenzene Sulfonates for Surfactant Flooding in Carbonate Reservoirs

Summary About one-half of the proven conventional oil reserves are in carbonate reservoirs. However, conducting surfactant flooding in these reservoirs presents several challenges, including formation heterogeneities, surfactant retention, high temperature and salinity, and oil-wet/mixed-wet conditions. Linear alkylbenzene sulfonates (LASs) are low-cost anionic surfactants that tend to precipitate in high-salinity environments and show high adsorption values in carbonate material. In this paper, the possibility of using petrochemical LASs of different alkyl chain lengths and isomer content to extract oil from carbonate reservoirs was tested using blends with the ionic liquid cocosalkylpentaethoximethylammonium methylsulfate (C1EG). Phase behavior, stability in the presence of divalent ions, and interfacial tension (IFT) measurements were the criteria used to design several optimal formulations containing 36–45% LASs. The structure-performance relationship was further assessed via static adsorption and wettability tests. LASs enriched in isomers with the benzenesulfonic group in external positions of the alkyl chain resulted in lower IFT but significantly higher adsorption, so those surfactants were discarded for the application. Additional oil recoveries achieved with tested formulations ranged from 36.7% to 43.5% of the residual oil in place. The longer the alkyl chain length, the higher the oil recovery. The main mechanism associated with improved oil recovery is IFT reduction. The use of a cost-effective ionic liquid derived from natural raw materials, the stability of the blends, the low adsorption of the chemical, and a significant oil recovery ensure the overall feasibility of the proposal.

An Anti-Fracture and Super Deformable Soft Hydrogel Network Insensitive to Extremely Harsh Environments.

Design of hydrogels with superior flexible deformability, anti-fracture toughness, and reliable environment adaption is fundamentally and practically important for diverse hydrogel-based flexible devices. However, these features can hardly be compatible even in elaborately designed hydrogels. Herein soft hydrogel networks with superior anti-fracture and deformability are proposed, which show good adaption to extremely harsh saline or alkaline environments. The hydrogel network is one-step constructed via hydrophobic homogenous cross-linking of poly (sodium acrylate), which is expected to provide hydrophobic associations and homogeneous cross-linking for energy dissipation. The obtained hydrogels are quite soft and deformable (tensile modulus: ≈20kPa, stretchability: 3700%), but show excellent anti-fracture toughness (10.6kJm-2 ). The energy dissipation mechanism can be further intensified under saline or alkaline environments. The mechanical performance of the hydrophobic cross-linking topology is inspired rather than weakened by extremely saline or alkaline environments (stretchability: 3900% and 5100%, toughness: 16.1 and 17.1kJm-2 under saturated NaCl and 6molL-1 NaOH environments, respectively). The hydrogel network also shows good performance in reversible deformations, ion conductivity, sensing strain, monitoring human motions, and freezing resistance under high-saline environments. The hydrogel network show unique mechanical performance and robust environment adaption, which is quite promising for diverse applications.

A Gemini viscoelastic surfactant stabilized by steric hindrance group on its spacer to construct wormlike micelle structure in concentrated brines

To overcome the disordered aggregation of viscoelastic surfactant (VES) molecules in high concentrated brines resulting in phase separation, a steric hindrance group was modified onto the spacer of a Gemini VES for stabilization in brine, and then a novel Gemini novel VES, named VES-BC, with double erucicamide tails, was synthesized successfully. Molecular dynamic simulation showed that the benzoic acid as a steric hindrance group effectively inhibited the disordered aggregation of VES-BC in concentrated brine, and RDF between the oxygen on the spacer and water varied slightly with increase salinity. Comparably, the Gemini cationic VES without steric hindrance group aggregated excessively and disorderly in high salinity environments, and the counterpart RDF varied significantly. VES-BC exhibits superior stabilization in brines, its salinity cloudy point reaches over 10 wt%. The surface tension, DLS, and fluorescent probe were carried out to explain stabilization mechanism of VES-BC in brine. The wormlike micelle (WLM) construction by VES-BC was studied through viscosity measurement, oscillatory measurement and microstructure observation, which proves the WLM networks can be formed with salinity between 3 wt% and 10 wt%, and 6 wt% is optimal. The steric hindrance group imparts VES-BC an insensitivity to salinity realizing the stabilization in high concentrated brines, and the salinity for WLM-driving is comparably high. Thus, VES-BC is an excellent clean thickener under extremely concentrated brine environment, especially for the preparing of clean fracturing fluid to save freshwater resources.

Anti-swelling P(DAC-co-NaSS-co-VDT) polyampholyte hydrogel with solvent displacement and salinity enhanced wet strength and adhesion

Polyampholyte (PA) hydrogels in general possess excellent mechanical properties, but their underwater applications are largely limited due to swelling induced dramatically reduced strength and poor wet adhesion, especially in high salinity environments. Here, we report our approach to fabricating an anti-swelling poly(acryloyloxyethyltrimethyl ammonium chloride (DAC)-co-sodium p-styrenesulfonate (NaSS)-co-2-Vinyl-4,6-diamino-1,3,5-triazine (VDT), or P(DAC-co-NaSS-co-VDT), PA hydrogel by introducing multi-hydrogen bonding capable functional VDT moieties into the DAC/NaSS coexisting and cation/anion ratio easily tunable PA network. The mechanical properties of the P(DAC-co-NaSS-co-VDT) hydrogel in bulk and at interface were controllable with dimethyl sulfoxide (DMSO)/H2O solvent displacement and Hofmeister effect in a wide salinity range, exhibiting maximum tensile strength, Young's modulus, and wet adhesion toughness of 7.6 MPa, 200 MPa, and 350 J m−2, respectively. The anti-swelling and strong P(DAC-co-NaSS-co-VDT) PA hydrogel developed in this work may find great potential in underwater sensing and sewage treatment as well as for many biomedical applications.

On developing accurate prediction models for residual tensile strength of GFRP bars under alkaline-concrete environment using a combined ensemble machine learning methods

GFRP (Glass-fiber reinforced polymer) bars are recognized as a structural material enabling replace existing steel rebar. However, GFRP bars exhibit a decrease in tensile strength under severe conditions such as strong alkalinity, high salinity, and humid environment. Thus, a predictive model for such GFRP tensile strength deterioration attempts to be developed, but model accuracy still needs improvement. Therefore, this paper proposes a more enhanced ensemble machine learning model to predict the residual tensile strength of GFRP bars accurately. For this end, tensile strength retention (TSR) experiment results of GFRP bars are utilized. Critical parameters for GFRP TSR are diameter, fiber volume fraction, pH, temperature, and exposure time. Regarding the TSR prediction model of GFRP bar, single machine learning models such as multiple linear regression, nonlinear regression, support vector machine, artificial neural network, and Gaussian process regression show 0.482–0.894 for training and 0.412–0.813 for testing, based on the accuracy of coefficient of determination (R2). Individual ensemble learning machine learning models of bagging and stacking show an accuracy of about 0.897 for training and 0.816 for testing. The proposed model shows an accuracy of about 0.912 for training and 0.834 for testing, which improves about 4–22% compared to previous study model performances.

Electrocatalytic and green system coupling strategy for simultaneous recovery and purification of uranium from uranium-containing wastewater

The recycling of uranium in wastewater is not only beneficial to the protection of ecological safety but also has great significance for the sustainable development of nuclear energy. However, there is no satisfactory method to recover and reuse uranium efficiently up to now. Here, we have developed an efficient and economical strategy that can achieve uranium recovery and direct reuse in wastewater. The feasibility analysis verified that the strategy still had good separation and recovery ability in acidic, alkaline, and high-salinity environments. The purity of uranium recovered from the separated liquid phase after electrochemical purification was up to about 99.95%. Ultrasonication could greatly increase the efficiency of this strategy, and 99.00% of high-purity uranium could be recovered within 2 h. We further improved the overall recovery rate by recovering the residual solid-phase uranium, and the overall recovery of uranium was increased to 99.40%. Moreover, the concentration of impurity ions in the recovered solution met the World Health Organization guidelines. In summary, the development of this strategy is of great importance for the sustainable use of uranium resources and environmental protection.

Picoplankton diversity in an oligotrophic and high salinity environment in the central Adriatic Sea

By combining qualitative 16S metabarcoding and quantitative CARD-FISH methods with neural gas analysis, different patterns of the picoplankton community were revealed at finer taxonomic levels in response to changing environmental conditions in the Adriatic Sea. We present the results of a one-year study carried out in an oligotrophic environment where increased salinity was recently observed. We have shown that the initial state of community structure changes according to environmental conditions and is expressed as qualitative and quantitative changes. A general pattern of increasing diversity under harsh environmental conditions, particularly under the influence of increasing salinity at the expense of community abundance was observed. Considering the trend of changing seawater characteristics due to climate change, this study helps in understanding a possible structural change in the microbial community of the Adriatic Sea that could affect higher levels of the marine food web.

Nocturnal sap flow as compensation for water deficits: an implicit water-saving strategy used by mangroves in stressful environments.

As part of the plant water-use process, plant nocturnal sap flow (Q n) has been demonstrated to have important ecophysiological significance to compensate for water loss. The purpose of this study was to explore nocturnal water-use strategies to fill the knowledge gap in mangroves, by measuring three species co-occurring in a subtropical estuary. Sap flow was monitored over an entire year using thermal diffusive probes. Stem diameter and leaf-level gas exchange were measured in summer. The data were used to explore the different nocturnal water balance maintaining mechanisms among species. The Q n existed persistently and contributed markedly over 5.5%~24.0% of the daily sap flow (Q) across species, which was associated with two processes, nocturnal transpiration (E n) and nocturnal stem water refilling (R n). We found that the stem recharge of the Kandelia obovata and Aegiceras corniculatum occurred mainly after sunset and that the high salinity environment drove higher Q n while stem recharge of the Avicennia marina mainly occurred in the daytime and the high salinity environment inhibited the Q n. The diversity of stem recharge patterns and response to sap flow to high salinity conditions were the main reasons for the differences in Q n/Q among species. For Kandelia obovata and Aegiceras corniculatum, R n was the main contributor to Q n, which was driven by the demands of stem water refilling after diurnal water depletion and high salt environment. Both of the species have a strict control over the stomata to reduce water loss at night. In contrast, Avicennia marina maintained a low Q n, driven by vapor pressure deficit, and the Q n mainly used for E n, which adapts to high salinity conditions by limiting water dissipation at night. We conclude that the diverse ways Q n properties act as water-compensating strategies among the co-occurring mangrove species might help the trees to overcoming water scarcity.