Seawater Conditions Research Articles

Effect of laser shock peening on tribological properties of WC-Ni under seawater conditions: Anomalous behavior and solutions

This research investigated the effect of laser shock peening (LSP) on the tribological properties of WC-Ni under seawater lubrication. The experimental findings revealed an anomalous behavior, contrary to the existing literature, indicating that the LSP treatment actually deteriorated the tribological properties of WC-Ni. The mechanism and solutions for anomalous behavior were also examined, and the results indicated that the enhancement of material properties through LSP treatment cannot counterbalance the detrimental effects of increased surface roughness. For improved processes, the sample treated with LSP + Polish exhibits the highest residual compressive stress and the lowest surface roughness, thereby yielding the best comprehensive performance. Therefore, the experimental results demonstrate that LSP + Polish treatment can improve material performance and hydrodynamic effect, leading to reductions in friction and wear.

Water mass influence on spatial and seasonal distributions of diatoms, dinoflagellates and coccolithophores in the western Barents Sea

Arctic phytoplankton are highly sensitive to seawater physical and chemical conditions, especially in the context of rapid climate change and sea ice loss. We studied the spatial and seasonal distributions of diatoms, dinoflagellates and coccolithophores, and clarified their associations with light, temperature and nutrients in the western Barents Sea in late summer 2017, and winter, spring and early summer 2018. Diatoms, composed mainly of Chaetoceros, Fragilariopsis and Thalassiosira, bloomed in spring at the southern border of the marginal ice zone with mean abundance of 1.1 × 106 cells L−1 and biomass of 119.5 µg C L−1, and were observed to follow the retreat of sea ice in the Arctic water to the north at the shelf break near Nansen Basin, contributing to the progression of the summer situation. Dinoflagellates flourished in surface waters south of Svalbard in summer, with maxima of 2.2 × 105 cells L−1 and 78.2 µg C L−1. High abundances and calcite mass of coccolithophores were detected in the southern Barents Sea and southwest of Svalbard in summer, with maxima of 3.3 × 105 cells L−1 and 4.7 µg C L−1. Two distinct phytoplankton assemblages, closely linked with Atlantic water and Arctic water, were geographically separated by the Polar Front in two summers, with a percent similarity below 11.9%, suggesting great influence of the two water masses on large-scale distributions of phytoplankton. Redundancy analysis revealed that temperature was one of the most important factors in shaping the seasonal distributions of diatoms, while irradiance showed positive correlation with dominant dinoflagellates of each season. From the perspectives of phytoplankton composition and carbon biomass, our findings highlight the governing effect of physical seawater conditions on driving seasonal patterns of phytoplankton biogeography, as well as the pivotal role of nutrients in supporting the phytoplankton growing seasons in the western Barents Sea.

Does climate change increase the risk of marine toxins? Insights from changing seawater conditions.

Marine toxins produced by marine organisms threaten human health and impose a heavy public health burden on coastal countries. Lately, there has been an emergence of marine toxins in regions that were previously unaffected, and it is believed that climate change may be a significant factor. This paper systematically summarizes the impact of climate change on the risk of marine toxins in terms of changes in seawater conditions. From our findings, climate change can cause ocean warming, acidification, stratification, and sea-level rise. These climatic events can alter the surface temperature, salinity, pH, and nutrient conditions of seawater, which may promote the growth of various algae and bacteria, facilitating the production of marine toxins. On the other hand, climate change may expand the living ranges of marine organisms (such as algae, bacteria, and fish), thereby exacerbating the production and spread of marine toxins. In addition, the sources, distribution, and toxicity of ciguatoxin, tetrodotoxin, cyclic imines, and microcystin were described to improve public awareness of these emerging marine toxins. Looking ahead, developing interdisciplinary cooperation, strengthening monitoring of emerging marine toxins, and exploring more novel approaches are essential to better address the risks of marine toxins posed by climate change. Altogether, the interrelationships between climate, marine ecology, and marine toxins were analyzed in this study, providing a theoretical basis for preventing and managing future health risks from marine toxins.

Efficient and durable seawater electrolysis with a V2O3-protected catalyst.

The ocean, a vast hydrogen reservoir, holds potential for sustainable energy and water development. Developing high-performance electrocatalysts for hydrogen production under harsh seawater conditions is challenging. Here, we propose incorporating a protective V2O3 layer to modulate the microcatalytic environment and create in situ dual-active sites consisting of low-loaded Pt and Ni3N. This catalyst demonstrates an ultralow overpotential of 80 mV at 500 mA cm-2, a mass activity 30.86 times higher than Pt-C and maintains at least 500 hours in seawater. Moreover, the assembled anion exchange membrane water electrolyzers (AEMWE) demonstrate superior activity and durability even under demanding industrial conditions. In situ localized pH analysis elucidates the microcatalytic environmental regulation mechanism of the V2O3 layer. Its role as a Lewis acid layer enables the sequestration of excess OH- ions, mitigate Cl- corrosion, and alkaline earth salt precipitation. Our catalyst protection strategy by using V2O3 presents a promising and cost-effective approach for large-scale sustainable green hydrogen production.

Impacts of microplastic and seawater acidification on unicellular red algae: Growth response, photosynthesis, antioxidant enzymes, and extracellular polymer substances

Microplastics (MPs) pollution and seawater acidification have increasingly become huge threats to the ocean ecosystem. Their impacts on microalgae are of great importance, since microalgae are the main primary producers and play a critical role in marine ecosystems. However, the impact of microplastics and acidification on unicellular red algae, which have a unique phycobiliprotein antenna system, remains unclear. Therefore, the impacts of polystyrene-MPs alone and the combined effects of MPs and seawater acidification on the typical unicellular marine red algae Porphyridium purpureum were investigated in the current study. The result showed that, under normal seawater condition, microalgae densities were increased by 17.75-41.67 % compared to the control when microalgae were exposed to small-sized MPs (0.1 μm) at concentrations of 5-100 mg L-1. In addition, the photosystem II and antioxidant enzyme system were not subjected to negative effects. The large-sized MPs (1 μm) boosted microalgae growth at a low concentration of MPs (5 mg L-1). However, it was observed that microalgae growth was significantly inhibited when MPs concentration increased up to 50 and 100 mg L-1, accompanied by the remarkably reduced Fv/Fm value and the elevated levels of SOD, CAT enzymes, phycoerythrin (PE), and extracellular polysaccharide (EPS). Compared to the normal seawater condition, microalgae densities were enhanced by 52.11-332.56 % under seawater acidification, depending on MPs sizes and concentrations, due to the formed CO2-enrichment condition and appropriate pH range. PE content in microalgal cells was significantly enhanced, but SOD and CAT activities as well as EPS content markedly decreased under acidification conditions. Overall, the impacts of seawater acidification were more pronounced than MPs impacts on microalgae growth and physiological responses. These findings will contribute to a substantial understanding of the effects of MPs on marine unicellular red microalgae, especially in future seawater acidification scenarios.

Implementation of a Far-Field Water Quality Model for the Simulation of Trace Elements in an Eastern Mediterranean Coastal Embayment Receiving High Anthropogenic Pressure

Water quality modeling is a key element for the support of environmental protection and policymaking. The aim of this work is to describe the application of a far-field water quality model for the simulation of marine pollution occurring from heavy metals (cadmium, lead, nickel, copper, and zinc). The highly stressed marine area of the Saronikos Gulf (Aegean Sea, Eastern Mediterranean) was chosen for investigation. Major pollution sources were identified, loads were estimated, and the model was parameterized to reproduce the local seawater conditions. The distribution of the pollutants between the dissolved and particulate phases was examined. The performance of the model set-up was evaluated using field concentration measurements. The described implementation succeeded in reproducing the observed levels of pollution and therefore can be used as a baseline configuration to examine the cumulative impact of future pollution sources; for example, accidental pollution events.

Characterization of a novel root-associated diazotrophic rare PGPR taxa, Aquabacter pokkalii sp. nov., isolated from pokkali rice: new insights into the plant-associated lifestyle and brackish adaptation

Salinity impacts crop growth and productivity and lowers the activities of rhizosphere microbiota. The identification and utilization of habitat-specific salinity-adapted plant growth-promoting rhizobacteria (PGPR) are considered alternative strategies to improve the growth and yields of crops in salinity-affected coastal agricultural fields. In this study, we characterize strain L1I39T, the first Aquabacter species with PGPR traits isolated from a salt-tolerant pokkali rice cultivated in brackish environments. L1I39T is positive for 1-aminocyclopropane-1-carboxylate deaminase activity and nitrogen fixation and can promote pokkali rice growth by supplying fixed nitrogen under a nitrogen-deficient seawater condition. Importantly, enhanced plant growth and efficient root colonization were evident in L1I39T-inoculated plants grown under 20% seawater but not in zero-seawater conditions, identifying brackish conditions as a key local environmental factor critical for L1I39T-pokkali rice symbiosis. Detailed physiological studies revealed that L1I39T is well-adapted to brackish environments. In-depth genome analysis of L1I39T identified multiple gene systems contributing to its plant-associated lifestyle and brackish adaptations. The 16S rRNA-based metagenomic study identified L1I39T as an important rare PGPR taxon. Based on the polyphasic taxonomy analysis, we established strain L1I39T as a novel Aquabacter species and proposed Aquabacter pokkalii sp nov. Overall, this study provides a better understanding of a marine-adapted PGPR strain L1I39T that may perform a substantial role in host growth and health in nitrogen-poor brackish environments.

NiS modified SrTiO3:Al bifunctional photocatalyst for H2 generation and cathodic protection

Developing low-cost and high-efficiency non-precious metal cocatalysts is the key to the practical application of photocatalysis technology. Here, nickel sulfide (NiS) nanoparticles were synthesized on the surface of strontium titanate (SrTiO3) via a hydrothermal method, identifying the optimal loading molar concentration of NiS as 10 %. The solar-to-hydrogen efficiency (STH) of 10%NiS/SrTiO3:Al was enhanced by 97 times compared to SrTiO3:Al and by 1.62 times compared to RhCrCoOx/SrTiO3:Al. This improvement is primarily attributed to the metallic-like properties of NiS, which enhance the photocatalyst's light absorption capacity and charge transfer capability. Additionally, the STH value of samples loaded with both NiS and RhCrCoOx reached 0.436 %, indicating a positive synergistic effect in photocatalysis between NiS and RhCrCoOx. Their photocathodic protection capability was also studied in simulated seawater conditions, showing a reduced self-corrosion potential (−0.31V) and a low interface charge impedance (5962 KΩ). This work reveals the potential of NiS as an alternative to precious metal cocatalysts, offering new possibilities for developing cost-effective and high-performance materials for photocatalytic water splitting and photocathodic protection.

Toxicity of Ammonia Stress on the Physiological Homeostasis in the Gills of Litopenaeus vannamei under Seawater and Low-Salinity Conditions.

Ammonia is a major water quality factor influencing the survival and health of shrimp, among which the gill is the main effector organ for ammonia toxicity. In this study, we chose two types of Litopenaeus vannamei that were cultured in 30‱ seawater and domesticated in 3‱ low salinity, respectively, and then separately subjected to ammonia stress for 14 days under seawater and low-salinity conditions, of which the 3‱ low salinity-cultured shrimp were domesticated from the shrimp cultured in 30‱ seawater after 27 days of gradual salinity desalination. In detail, this study included four groups, namely the SC group (ammonia-N 0 mg/L, salinity 30‱), SAN group (ammonia-N 10 mg/L, salinity 30‱), LC group (ammonia-N 0 mg/L, salinity 3‱), and LAN group (ammonia-N 10 mg/L, salinity 3‱). The ammonia stress lasted for 14 days, and then the changes in the morphological structure and physiological function of the gills were explored. The results show that ammonia stress caused the severe contraction of gill filaments and the deformation or even rupture of gill vessels. Biochemical indicators of oxidative stress, including LPO and MDA contents, as well as T-AOC and GST activities, were increased in the SAN and LAN groups, while the activities of CAT and POD and the mRNA expression levels of antioxidant-related genes (nrf2, cat, gpx, hsp70, and trx) were decreased. In addition, the mRNA expression levels of the genes involved in ER stress (ire1 and xbp1), apoptosis (casp-3, casp-9, and jnk), detoxification (gst, ugt, and sult), glucose metabolism (pdh, hk, pk, and ldh), and the tricarboxylic acid cycle (mdh, cs, idh, and odh) were decreased in the SAN and LAN groups; the levels of electron-transport chain-related genes (ndh, cco, and coi), and the bip and sdh genes were decreased in the SAN group but increased in the LAN group; and the level of the ATPase gene was decreased but the cytc gene was increased in the SAN and LAN groups. The mRNA expression levels of osmotic regulation-related genes (nka-β, ca, aqp and clc) were decreased in the SAN group, while the level of the ca gene was increased in the LAN group; the nka-α gene was decreased in both two groups. The results demonstrate that ammonia stress could influence the physiological homeostasis of the shrimp gills, possibly by damaging the tissue morphology, and affecting the redox, ER function, apoptosis, detoxification, energy metabolism, and osmoregulation.

Design of Magnetic Coupler for AUV Wireless Charging and Its Electromagnetic Field Simulation

The magnetic coupler is one of the important components of wireless charging system, and its coupling coefficient directly influences the energy transmission efficiency. This paper designs a magnetic coupler for Autonomous Underwater Vehicle(AUV) wireless charging in the marine environment. Firstly, the eddy current effect during energy transmission of the magnetic coupler under seawater conditions is analyzed, and the equivalent model of the wireless charging system is compensated and corrected. Then, the genetic-BP neural network algorithm is used to determine the relevant structural parameters of the magnetic coupler. Finally, the electromagnetic field simulation analysis of the offset phenomenon between the transmitting and receiving sides of the magnetic coupler is carried out based on ANSYS MAXEWLL software.The results show that the coupling coefficient of the magnetic coupler under normal operation is 0.87, and if there is a 10mm radial offset (or 5 ° circumferential offset), the coupling coefficient will decrease to 0.74 (or 0.78), which provides a reference basis for the subsequent offset fault-tolerant design of the AUV wireless charging system.

Tribocorrosion behavior of GCr15 steel in water–glycol fire-resistant hydraulic fluids (HFC) containing seawater

With the development of deep-sea exploration technology, the technology of fire-retardant hydraulic fluid (HFC) has played an important role in the power transmission of exploration equipment. However, the mechanism of the influence of seawater content on the tribocorrosion behavior of HFC remains unclear. In this study, the effects of different seawater contents on the tribological and corrosive properties of HFC were systematically investigated. The results showed that when the seawater concentration exceeds 30 wt%, a soft Mg-containing reaction film is formed in the friction contact area owing to seawater corrosion, thus effectively improving the sintering load and wear resistance to some extent. By contrast, with increasing seawater concentration, the lubricity declines, the wear intensifies, and the extreme pressure characteristics decrease significantly. The comparative analysis shows that the composition of the wear and corrosion reaction films significantly differs under high-concentration seawater conditions, which is also a key factor affecting the friction and corrosion behavior of HFC. This study provides a direction for the research and development of wear- and corrosion-resistant materials and coatings on the surface of deep-sea exploration equipment.

Energetic Comparison of Flow-Electrode Capacitive Deionization and Membrane Technology: Assessment on Applicability in Desalination Fields.

Flow-electrode capacitive deionization (FCDI) is a promising technology for sustainable water treatment. However, studies on the process have thus far been limited to lab-scale conditions and select fields of application. Such limitation is induced by several shortcomings, one of which is the absence of a comprehensive process model that accurately predicts the operational performance and the energy consumption of FCDI. In this study, a simulation model is newly proposed with initial validation based on experimental data and is then utilized to elucidate the performance and the specific energy consumption (SEC) of FCDI under multiple source water conditions ranging from near-groundwater to high salinity brine. Further, simulated pilot-scale FCDI system was compared with actual brackish water reverse osmosis (BWRO) and seawater reverse osmosis (SWRO) plant data with regard to SEC to determine the feasibility of FCDI as an alternative to the conventional membrane processes. Analysis showed that FCDI is competent for operation against brackish water solutions under all possible operational conditions with respect to the BWRO. Moreover, its distinction can be extended to the SWRO for seawater conditions through optimization of its total effective membrane area via scale-up. Accordingly, future directions for the advancement of FCDI was suggested to ultimately prompt the commercialization of the FCDI process.

Dynamic analysis of a drilling string for deepwater riserless drilling with vortex-induced vibration considered

Riserless drilling will become the mainstream technology for deepwater drilling in the future owing to its operational characteristics. At present, researchers only analyze the seawater section or formation section but do not analyze the whole drill string to study the dynamics of riserless drilling. In fact, the ocean load affects not only the vortex-induced vibration characteristics of the drill string in seawater but also the load distribution of the drill string in the formation. Ignoring the formation or ocean load will lead to inaccurate prediction results. On this basis, in addition to the traditional drilling string boundary condition of seawater and formation, a new boundary condition of drilling string at mud line for riserless drilling is proposed. Considering vortex-induced vibration, a full-well drilling string dynamic model without riser drilling is established by the finite element method, and the dynamic characteristics of the full-well drilling string under multiple loads are analyzed. In addition, the effects of WOB, surface flow rate, and drilling fluid density on the dynamics of riserless drilling string in seawater and formation sections are discussed. This study provides theoretical guidance for the safety of riserless drilling in complex marine environments.

Effects of Temperature and Salinity on the LMS (Lysosomal Membrane Stability) Biomarker in Clams Donax trunculus and Chamelea gallina

Population of clams Donax trunculus and Chamelea gallina have been declining significantly in recent decades, and environmental pollution and accelerated global warming have been proposed as contributing factors to this decline, in addition to overfishing. Lysosomal membrane stability (LMS) is a sensitive indicator of health status of the organisms. In this study, we investigate the LMS in these species after exposure for 21 days to nine combined conditions of water temperature (12, 20, and 27.5 °C) and salinity ranges (27–28, 32–33, and 37–38). LMS was assessed in living hemocytes by using the neutral red retention assay. Mortality and the condition index of the organisms were evaluated as supporting parameters. The results indicated interspecies differences in the LMS under similar environmental conditions. Overall, LMS was found to be more sensitive to temperature than to salinity changes. Although both species can tolerate changes in either salinity or temperature seawater conditions, the tolerance range is narrower for D. trunculus, showing a significant cytotoxicity (NRRT < 50 min) at temperatures above 27.5 °C and salinities above 32, and 100% mortality at 27.5 °C and a low salinity range (27–28). This study is the first to assess the combined effect of temperature and salinity on the LMS in C. gallina and D. trunculus, and provide necessary information before using LMS as contaminant-related biomarker in field studies with these species.

Mechanical behavior of glass fiber‐reinforced hollow glass particles filled epoxy composites under moisture environment

AbstractThe utilization of hollow glass particle‐filled fiber‐reinforced composites in marine applications necessitates a proper understanding of their behavior when exposed to moisture environments. In this study, the glass fiber‐reinforced composites reinforced with 0%–30% volume fraction of glass microspheres were fabricated and immersed in seawater and distilled water conditions for monotonic tensile and flexural testing. The degradation mechanisms were analyzed by dynamic mechanical analysis (DMA), Fourier transform infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). Moisture absorption results showed an increasing trend with the inclusion of glass microspheres. A decline in glass transition temperature and storage modulus was observed as a result of moisture absorption. The tensile results of the specimens exhibited a decrease of 13% and 9% in distilled water and seawater solution, respectively when compared with unaged samples, respectively. The flexural results of the aged composite specimens demonstrated a reduction of 24% and 11% in distilled water and seawater solution, respectively when compared with unaged samples. The findings also show that the influence of moisture on the modulus is less pronounced compared to its effect on strength under both environmental conditions. The micrograph results revealed a notable deterioration of the glass microsphere and the fiber/matrix interface in the moist environment.Highlights Water absorption increases with the addition of glass microspheres. Microsphere degradation and fiber/matrix debonding are the governing mechanism. Retained 89% of tensile strength of their initial properties after exposed in sea water. Increase in microsphere contents decreases the tensile and flexural strength.

Laboratory Investigations of Iceberg Melting under Wave Conditions in Sea Water

Changes in the masses of icebergs due to deterioration processes affect the drift of icebergs and should be taken into account when assessing iceberg risks in the areas of offshore development. In 2022 and 2023, eight laboratory experiments were carried out in the wave tank of the University Centre in Svalbard to study the melting of icebergs in sea water under calm and rough conditions. In the experiments, the water temperatures varied from 0 ℃ to 2.2 ℃. Cylindrical iceberg models were made from columnar ice cores with a diameter of 24 cm. In one experiment, the iceberg model was protected on the sides with plastic fencing to investigate the iceberg’s protection from melting when towed to deliver fresh water. The iceberg masses, water temperatures, and ice temperatures were measured in the experiments. The water velocity near the iceberg models was measured with an acoustic Doppler velocimeter. During the experiments, time-lapse cameras were used to describe the shapes and measure the vertical dimensions of the icebergs. Using experimental data, we calculated the horizontal dimensions of icebergs, latent heat fluxes, conductive heat fluxes inside the iceberg models, and turbulent heat fluxes in water as a function of time. We discovered the influence of surface waves and water mixing on the melt rates and found a significant reduction in the melt rates due to the lateral protection of the iceberg model using a plastic barrier. Based on the experimental data obtained, the ratio of the rates of lateral and bottom melting of the icebergs and lateral melting of the icebergs under wave conditions was parametrized depending on the wave frequency.

Cost-based optimization, feasibility study, and sensitivity analysis of forward osmosis/crystallization/reverse osmosis with high-temperature operation for high-salinity seawater desalination

Seawater desalination plants using reverse osmosis (RO) in high temperature and high-salinity conditions, such as in the Middle East, face challenges such as limited achievable recoveries and high energy costs. This study evaluated the economic feasibility under seawater and high-salinity conditions by introducing a forward osmosis/crystallization/reverse osmosis (FO/Cry/RO) hybrid process. The optimization results were then used to compare the specific water cost (SWC), specific energy consumption (SEC), recovery, and permeate quality of the hybrid process with two different draw solutes and a conventional seawater RO process. In addition, a sensitivity analysis was conducted to determine how individual process parameters and operating conditions affect the economic feasibility of the proposed process under seawater and high-salinity conditions. The FO/Cry/RO hybrid process achieved a higher recovery with a lower SWC and SEC as the feed concentration increased compared to the conventional RO process. Utilizing waste heat further increased the economic advantages of the proposed process. In addition, much higher permeate quality can be obtained depending on the type of draw solute. The results of this study revealed that the proposed hybrid system outperformed the conventional RO process in terms of both energy efficiency and cost-effectiveness for seawater desalination under high-temperature and high-salinity conditions.

Salinity stress in the black-chinned tilapia Sarotherodon melanotheron.

Physiological and morphological acclimation capacities of black-chinned tilapia, Sarotherodon melanotheron were studied from fish to gill cell level when fish are maintained in freshwater, seawater, and hypersaline conditions. Fish osmoregulatory capacity, gill ionocyte morphology, osmo-respiratory compromise, O2 consumption rate, branchial antioxidative defense, and cell apoptosis were considered. Captive juvenile tilapias were maintained in controlled freshwater conditions (FW: 0.4 ppt; 12 mOsm kg-1) or gradually transferred to seawater (SW: 32 ppt; 958 mOsm kg-1) and concentrated SW (cSW: 65 ppt; 1920 mOsm kg-1). After 15 days in these conditions, blood osmolality and chloride ion concentration were determined. Gill ionocyte density and morphology were measured using immunolabelled histological sections to specifically detect the sodium pump (NKA). Gill osmo-respiratory compromise was also calculated along with oxygen consumption rates from normoxic to hypoxic conditions from excised gills (indirect respirometry). Finally, catalase and caspase 3/7activities were recorded from gill extracts. Results indicate that elevated salinity induces an osmotic imbalance and a profound morphological change with proliferating and hypertrophied ionocytes. This thickening of the gill interlamellar cell mass and the shortening of the lamellae induce a reduced osmo-respiratory ratio and reduced respiratory capacity under both normoxic and hypoxic conditions. Although salinity changes do not affect one of the major antioxidative defense mechanism, it strongly affects apoptosis that appears the most elevated in SW. However, in freshwater condition, fish can maintain their osmotic balance with a low ionocyte density, a low apoptotic level and a drastically reduced O2 consumption in normoxic condition that is maintained in hypoxia. Therefore, S. melanotheron presents the typical functional remodeling due to environmental salinity changes ranging from FW to SW. However, elevated seawater induces major cellular stress inducing a profound gill morphofunctional dysfunctioning. While cell apoptosis is reduced, ionocyte proliferation is massively increased with impaired osmotic regulation and reduced O2 consumption both in normoxic and hypoxic conditions.

Microenvironment-Modulating Adsorption Enables Highly Efficient Lithium Extraction under Natural pH Conditions.

Ion-sieve adsorbents are effective materials in practical applications for extracting liquid lithium. However, it is greatly suppressed in adsorption capacity and selectivity (Li/Mg) under natural near-neutral conditions of seawater or salt lakes, due to the interference of in situ released H+ and Mg2+ impurity. This paper proposes an adsorbent with a microenvironment-modulating function as a solution. The introduction of quaternary ammonium groups into the carrier accelerates the migration of H+, while preventing the diffusion of Mg2+ by electrostatic repulsion. Besides, it can also prestore OH-, effectively consuming the generated hydrogen ions in situ. Based on the rational design, the alkali consumption of the microenvironment-modulating strategy is dramatically reduced to 1/144 of the traditional alkali-adding method. Additionally, adsorption performance is significantly promoted under natural pH conditions, with a maximum 33 times higher separation factor (selectivity) and 4 times higher adsorption capacity than commercial ion-sieve adsorbents. This development indicates the feasibility of using microenvironment modulation for effective lithium extraction and inspires the development of next-generation high-performance adsorbents.

Rich microbial and depolymerising diversity in Antarctic krill gut.

With almost a quadrillion individuals, the Antarctic krill processes five million tons of organic carbon every day during austral summer. This high carbon flux requires a broad range of hydrolytic enzymes to decompose the diverse food-derived biopolymers. While krill itself possesses numerous such enzymes, it is unclear, to what extent the endogenous microbiota contribute to the hydrolytic potential of the gut environment. Here we applied amplicon sequencing, shotgun metagenomics, cultivation, and physiological assays to characterize the krill gut microbiota. The broad bacterial diversity (273 families, 919 genera, and 2,309 species) also included a complex potentially anaerobic sub-community. Plate-based assays with 198 isolated pure cultures revealed widespread capacities to utilize lipids (e.g., tributyrin), followed by proteins (casein) and to a lesser extent by polysaccharides (e.g., alginate and chitin). While most isolates affiliated with the genera Pseudoalteromonas and Psychrobacter, also Rubritalea spp. (Verrucomicrobia) were observed. The krill gut microbiota growing on marine broth agar plates possess 13,012 predicted hydrolyses; 15-fold more than previously predicted from a transcriptome-proteome compendium of krill. Cultivation-independent and -dependent approaches indicated members of the families Flavobacteriaceae and Pseudoalteromonadaceae to dominate the capacities for lipid/protein hydrolysis and to provide a plethora of carbohydrate-active enzymes, sulfatases, and laminarin- or porphyrin-depolymerizing hydrolases. Notably, also the potential to hydrolyze plastics such as polyethylene terephthalate and polylactatide was observed, affiliating mostly with Moraxellaceae. Overall, this study shows extensive microbial diversity in the krill gut, and suggests that the microbiota likely play a significant role in the nutrient acquisition of the krill by enriching its hydrolytic enzyme repertoire.IMPORTANCEThe Antarctic krill (Euphausia superba) is a keystone species of the Antarctic marine food web, connecting the productivity of phyto- and zooplankton with the nutrition of the higher trophic levels. Accordingly, krill significantly contributes to biomass turnover, requiring the decomposition of seasonally varying plankton-derived biopolymers. This study highlights the likely role of the krill gut microbiota in this ecosystem function by revealing the great number of diverse hydrolases that microbes contribute to the krill gut environment. The here resolved repertoire of hydrolytic enzymes could contribute to the overall nutritional resilience of krill and to the general organic matter cycling under changing environmental conditions in the Antarctic sea water. Furthermore, the krill gut microbiome could serve as a valuable resource of cold-adapted hydrolytic enzymes for diverse biotechnological applications.