Complex Aquatic Environments Research Articles

Competitive adsorption of oxytetracycline and sulfamethoxazole by nanosized activated carbon in aquatic environments: Experimental analysis and DFT calculations

Nanosized activated carbon (NAC) is an emerging carbonaceous nanomaterial for water treatment, while oxytetracycline (OTC) and sulfamethoxazole (SMX) coexisting in aquatic environments may undergo competitive adsorption to influence its removal efficiency. This study investigated the competitive adsorption of OTC and SMX onto NAC under different interaction sequence, pH, electrolyte, and water matrix conditions, using experimental analysis and density function theory (DFT) calculations. Adsorption kinetics show that increasing concentration of one antibiotic inhibited the adsorption of another. Faster equilibrium was attained in binary systems than single systems due to competitive adsorption, with pseudo-second-order model providing the best fit in both systems. Adsorption isotherms suggest that NAC exhibited stronger affinity towards OTC (395.26 mg/g) than SMX (232.02 mg/g), with Langmuir model showing satisfactory fitting in both single and binary systems. Sequential adsorption of [NAC + OTC] + SMX was more favored than binary adsorption, aligning with the optimum configuration of SMX--[NAC-OTC±] with binding energy of −57.25 kcal/mol from DFT calculations. Competitive adsorption was preferred within pH 3.2–5.6, where electrostatic attraction existed between NAC and cationic antibiotics. Salting-out, charge screening, and complexation effects from Na+ and Ca2+ influenced competitive adsorption. Optimal removal of OTC and SMX by NAC was achieved in wastewater effluent among four water matrices in both single and binary systems. Hydrogen bonding, π − π electron donor–acceptor interactions, electrostatic interactions, and hydrophobic interactions contributed to adsorption. Sequential change in functional groups of NAC followed − OH → C − H → C − O → C = C and C = C → C − O → C − H → − OH in single and binary systems, respectively. The findings provide valuable insights into the competitive adsorption mechanisms of antibiotics on NAC, highlighting its potential for remediating mixtures of antibiotics in complex aquatic environments.

Effects of artemisinin sustained-release algaecides on in-situ cyanobacterial inhibition and microbes-floating plants dominated ecosystem functions in artificial landscape lake

The artemisinin sustained-release algaecides (ASAs) have been proven to be a safe and effective mean of inhibiting cyanobacteria in laboratory experiments. However, their effectiveness and impacts on ecosystem functions (EF) in natural waters are still unclear. In this study, the in-situ inhibitory effect of ASAs on cyanobacteria in natural waters was investigated over a period of 110 days to assess EF impacts dominated by microbes and floating plants. The results indicated that ASAs had a long-term inhibitory effect on cyanobacteria. ASAs did not affect sediment but increased TOC and TP in the water column in 2-10 days. Microbial diversity and network analyses indicated that ASAs enhanced bacterial diversity, network complexity, and hub-bacteria in networks. Metabolic pathway predictions and CCA analysis showed that ASAs maintained the stability of EF by enhancing the metabolic capacities of bacteria, and the relationships between metabolic microorganisms and environmental factors. PLS-PM revealed that ASAs primarily drove bacterial resistance to cyanobacteria, which was the key mechanism for its long-term inhibition of cyanobacteria. However, the early outbreak of floating plants was not conducive to the long-term inhibition of cyanobacteria by ASAs. This study provides new insights into the mechanisms and ecological impacts of cyanobacterial inhibition by ASAs in complex aquatic environments.

Two neglected contributors to water biosafety risks: The impacts of microbial co-existence and light on viral inactivation

Virus-induced risks to water quality persist, with the viability of viruses in complex aquatic environments impacted by various factors, including coexisting bacteria and exposure to light. This study investigated the disinfection efficacy of UV254 irradiation and free chlorine (FC) on Bacteriophage phiX174 in the presence of coexisting bacteria, specifically Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis). To elucidate the underlying mechanisms, this study examined the effects of bacterial compounds (i.e., E. coli lipopolysaccharide (LPS) and B. subtilis peptidoglycan (PGN)) on viral inactivation, thermal stability, and environmental persistence. The research results demonstrated that bacterial presence and their associated compounds significantly impaired viral inactivation, with greater concentrations of coexisting bacteria and their compounds exacerbating this effect. Additionally, the photoreactivation of phiX174 was explored following UV254 irradiation, indicating that high-dose UV254, coupled with low nutrient availability and minimal host bacteria levels, effectively suppressed viral photoreactivation. This study is the first to investigate the multifactorial effects on viral photoreactivation. The results offer novel insights into the challenges associated with virus-related pressures in water treatment, with potential implications for optimizing disinfection processes.

A-Star (A*) with Map Processing for the Global Path Planning of Autonomous Underwater and Surface Vehicles Operating in Large Areas

The global path planning system is one of the basic systems ensuring the autonomous operation of unmanned underwater vehicles (UUVs) and unmanned surface vehicles (USVs) in a complex aquatic environment. The A* path planning algorithm is one of the most well-known algorithms used to obtain an almost optimal path, avoiding obstacles even in a complex environment containing objects with specific shapes and non-uniform arrangements. The main disadvantage of this algorithm is the computational cost of path calculation. This article presents a new approach based on the image processing of the map before determining the path using A*. The results of numerical research based on a large-sized map expressing the port area confirm the proposed method’s effectiveness, which reduces the calculation time by over 500 times with a slight increase in the path length compared to the basic version of the A* algorithm. Based on the obtained results, the proposed approach also increases the path’s safety by designating narrow and risky areas as closed to vehicle movement. For this reason, the method seems suitable for use in global path planning for autonomous underwater vehicles (AUVs) and autonomous surface vehicles (ASVs) operating in large areas.

Current Trends in Biophysical Modeling of eDNA Dynamics for the Detection of Marine Species

ABSTRACTMarine pest introductions continue to occur and increase at accelerated rates, threatening the marine environment and blue economy. Environmental DNA (eDNA) is a tool for determining the presence of both indigenous and nonindigenous species, via the detection of genetic material that is shed into the local environment. Although eDNA approaches have gained widespread adoption in the last decade, fundamental knowledge gaps remain around factors that can influence the probability of detection, and how to optimize eDNA sampling in aquatic environments. Here, we partition eDNA research into four major research themes: eDNA concentration (shedding and decay), transport (advection and mixing), sampling design strategies, and the modeling of these dynamics. We review current developments and challenges in each theme with a focus on field sampling strategies and the use of biophysical models for understanding the movement of modeling eDNA in complex aquatic environments. We then introduce three modeling case studies from a large embayment where we (1) quantify the spatial and temporal variability of eDNA dispersion, (2) use biophysical models to inform a field sampling strategy, and (3) demonstrate a backtracking modeling technique to identify upstream DNA sources to an existing sample (monitoring) site. We conclude by identifying specific recommendations to help improve future eDNA studies. This work highlights how biophysical models can be applied to improve early detection and informing response and management decisions.

Electrocatalytic Selenate Transformation to Tunable Products Using Affordable Catalysts

Anthropogenic selenium (Se) pollution has profound ecosystem and human health impacts. Compared to selenite or Se(IV), selenate or Se(VI) is chemically inert and more challenging for selective removal from the complex aquatic environment.1 Current Se(VI) removal efforts seek intensive resource and energy input to drive Se(VI) transformation, and are subject to environmental and operating conditions.2 The potential solution for sustainable Se(VI) transformation involves catalytic reduction of Se(VI). In current catalytic approaches, the reduction of Se(VI) is achieved using either abiotic photocatalysts (e.g., TiO2) or biotic enzymes (e.g., nitrate reductase).3 Here, we explored the opportunities of electrified Se(VI) transformation with functionalized catalysts to manage aquatic selenate pollution. Se(VI) can be removed through phase transformation into solid Se(0) that could cover reactive surfaces and prevent further catalysis, or gaseous Se(-II) that is toxic and needs to be captured. Alternatively, the reduction of Se(VI) into reactive Se(IV) allows exposure of active interfaces for continuous electrochemcial transformation. Therefore, a controlled reduction of Se(VI) to Se(IV) would be ideal in aquatic Se(VI) management and potential Se recovery. To the best of our knowledge, controlled Se(VI) transformation has not been fully achieved in the literature. In this study, we evaluated five affordable catalysts on graphite cathodes, including TiO2,3 underpotentially deposited Cu (UPD Cu),4 underpotentially deposited Cd (UPD Cd), Co, and CuFe nanoarrays.5 Among these five candidates, characteristic Se(VI) reduction peaks were identified for TiO2, UPD Cu, and UPD Cd through cyclic voltammetry. Less than 5% of 1-mM Se was removed using UPD Cu and UPD Cd, based on 24-hour chronoamperometry tests at corresponding potentials. Unfortunately, ppm-level Cu or Cd were detected in the treated effluent. In contrast, more than 90% of Se(VI) was removed using TiO2 as the catalyst after 24 hours. TiO2 was more robust and stable in electrocatalytic reactions with minimal catalyst dissolution and, therefore, was selected for further electrocatalytic Se(VI) reduction studies.During the TiO2-catalyzed reduction, Se(VI) would first transform into Se(IV) at a relatively positive potential. A maximum of 97% Se(VI) was found to be converted to Se(IV) in a 6-hour electrocatalytic Se(VI) reduction at -0.18 V. Decreasing electrode potential to -0.35 V, solid deposits of Se(0) appeared on a TiO2-modified graphite cathode. With a more negative electrode potential, further Se(0) reduction to Se(-II) was identified. The findings spotlight the opportunities to control Se(VI) transformation and harvest tunable products per removal demand and strategies. The effect of operational conditions was investigated at various TiO2 loading and solution pH. Higher TiO2 loading and lower solution pH favored the electrocatalytic Se(VI) transformation. The removal kinetics and performance were then studied under optimal operational conditions at -0.45 V, where Se(0) was dominant among Se(VI) reduction products, and -0.70 V, where Se(-II) was abundant. Kinetics analysis revealed that electrocatalytic Se(VI) reduction at -0.70 V was roughly four times faster as compared to that at -0.45 V. A total of 88.7 ± 2.3% of Se(VI) was removed after 24 hours of electrocatalysis at -0.70 V. In contrast, 48.2 ± 9.3% of Se(VI) was removed after 24 hours of electrocatalysis at -0.45 V. These results warrant further evaluation of the regenerability and lifespan of TiO2-modified graphite electrodes, an optimized electrode/reactor design, and an integrated Se removal/recovery system.

Enhancing aggregation of microalgae on polystyrene microplastics by high light: Processes, drivers, and environmental risk assessment

Microplastics (MPs) are emerging pollutants, causing potential threats to aquatic ecosystems and serious concern in aggregating with microalgae (critical primary producers). When entering water bodies, MPs are expected to sink below the water surface and disperse into varying water compartments with different light intensities. However, how light influences the aggregation processes of algal cells onto MPs and the associated molecular coupling mechanisms and derivative risks remain poorly understood. Herein, we investigated the aggregation behavior between polystyrene microplastics (mPS, 10 µm) and Chlorella pyrenoidosa under low (LL, 15 μmol·m−2·s−1), normal (NL, 55 μmol·m−2·s−1), and high light (HL, 150 μmol·m−2·s−1) conditions from integrated in vivo and in silico assays. The results indicated that under LL, the mPS particles primarily existed independently, whereas under NL and HL, C. pyrenoidosa tightly bounded to mPS by secreting more protein-rich extracellular polymeric substances. Infrared spectroscopy analysis and density functional theory calculation revealed that the aggregation formation was driven by non-covalent interaction involving van der Waals force and hydrogen bond. These processes subsequently enhanced the deposition and adherence capacity of mPS and relieved its phytotoxicity. Overall, our findings advance the practical and theoretical understanding of the ecological impacts of MPs in complex aquatic environments.

Evaluation Method for Underwater Ultrasonic Energy Radiation Performance Based on the Spatial Distribution Characteristics of Acoustic Power.

In recent years, underwater wireless ultrasonic energy transmission technology (UWUET) has attracted much attention because it utilizes the propagation characteristics of ultrasound in water. Effectively evaluating the performance of underwater ultrasonic wireless energy transmission is a key issue in engineering design. The current approach to performance evaluation is usually based on the system energy transfer efficiency as the main criterion, but this criterion mainly considers the overall energy conversion efficiency between the transmitting end and the receiving end, without an in-depth analysis of the characteristics of the distribution of the underwater acoustic field and the energy loss that occurs during the propagation of acoustic waves. In addition, existing methods focusing on acoustic field analysis tend to concentrate on a single parameter, ignoring the dynamic distribution of acoustic energy in complex aquatic environments, as well as the effects of changes in the underwater environment on acoustic propagation, such as spatial variability in temperature and salinity. These limitations reduce the usefulness and accuracy of models in complex marine environments, which in turn reduces the efficiency of acoustic energy management and optimization. To solve these problems, this study proposes a method to evaluate the performance of underwater ultrasonic energy radiation based on the spatial distribution characteristics of acoustic power. By establishing an acoustic power distribution model in a complex impedance-density aqueous medium and combining numerical simulation and experimental validation, this paper explores the spatial variation of acoustic power and its impact on the energy transfer efficiency in depth. Using high-resolution spatial distribution data and actual environmental parameters, the method significantly improves the accuracy of the assessment and the adaptability of the model in complex underwater environments. The results show that, compared with the traditional method, this method performs better in terms of the accuracy of the acoustic energy radiation calculation results, and is able to reflect the energy distribution and spatial heterogeneity of the acoustic source more comprehensively, which provides an important theoretical basis and practical guidance for the optimal design and performance enhancement of the underwater ultrasonic wireless energy transmission system.

Synergistic activation of peroxymonosulfate by 3D CoNiO2/Co core-shell structure biochar catalyst for sulfamethoxazole degradation

In this study, a 3D CoNiO2/Co core–shell structure biochar catalyst derived from walnut shell was synthesized by hydrothermal and ion etching methods. The prepared BC@CoNi-600 catalyst exhibited exceptional peroxymonosulfate (PMS) activation. The system achieved 100 % degradation of sulfamethoxazole (SMX). The reactive oxygen species in the BC@CoNi-600/PMS system included SO4−, OH, and O2−. Density functional theory calculations explored the synergistic effects between nickel–cobalt bimetallic and carbon matrix during PMS activation. The unique 3D core–shell structure of BC@CoNi-600 features an outer nickel–cobalt bimetallic layer with exceptional PMS adsorption capacity, while protecting the zero-valence Co of the inner layer from oxidation. Based on the experimental-data, machine learning modeling mechanism, and information theory, a nonlinear modeling method was proposed. This study utilizes a machine learning approach to investigate the degradation of SMX in complex aquatic environments. This study synthesized a novel biochar-based catalyst for activated PMS and provided unique insights into its environmental applications.

The antimicrobial peptide Sparamosin26–54 exhibits antiviral activity against three aquatic enveloped viruses through lipid-binding-mediated virus lysis

The aquaculture industry is faced with huge economic losses caused by various enveloped virus infections, such as white spot syndrome virus (WSSV), Rana grylio virus (RGV), and Anguillid Herpesvirus 1 (AngHV). The urgent need for readily available broad-spectrum antiviral agents has led to the exploration of antiviral peptides (AVPs), among which antimicrobial peptides (AMPs) with antiviral activity have attracted increasing attention. Sparamosin26–54 (derived from Scylla paramamosain) is a promising antimicrobial agent. In this study, we found that Sparamosin26–54 significantly inhibited WSSV transcription and replication (as indicated by VP28 gene and protein levels), irreversibly inactivated virions, and impeded viral entry before binding to the cell. Transmission electron microscopy observations showed that Sparamosin26–54 had a direct destructive effect on WSSV virions. Lipidomic analysis and ELISA assay highlighted that Sparamosin26–54 had a potent affinity for phosphatidic acid (PA) and phosphatidylserine (PS) of WSSV. Liposome leakage assays further revealed a pronounced effect of Sparamosin26–54 on membrane lipid compositions, emphasizing its efficacy against the other two enveloped viruses (RGV and AngHV), but not against the non-enveloped virus, American eel adomavirus (AEAdov). Notably, in three animal models of viral infection, Sparamosin26–54 reduced viral loads in tissues, increased survival, or decreased infection rates in a concentration-dependent manner. Importantly, Sparamosin26–54 showed no animal toxicity under different modes of administration and could maintain antiviral activity in the complex aquatic environment. Taken together, Sparamosin26–54 was proved to be effective against three enveloped viruses, possibly inducing viral lysis via lipid-binding, providing an alternative approach for combating enveloped virus infections.

Novel Learning of Bathymetry from Landsat 9 Imagery Using Machine Learning, Feature Extraction and Meta-Heuristic Optimization in a Shallow Turbid Lagoon

Bathymetry data is indispensable for a variety of aquatic field studies and benthic resource inventories. Determining water depth can be accomplished through an echo sounding system or remote estimation utilizing space-borne and air-borne data across diverse environments, such as lakes, rivers, seas, or lagoons. Despite being a common option for bathymetry mapping, the use of satellite imagery faces challenges due to the complex inherent optical properties of water bodies (e.g., turbid water), satellite spatial resolution limitations, and constraints in the performance of retrieval models. This study focuses on advancing the remote sensing based method by harnessing the non-linear learning capabilities of the machine learning (ML) model, employing advanced feature selection through a meta-heuristic algorithm, and using image extraction techniques (i.e., band ratio, gray scale morphological operation, and morphological multi-scale decomposition). Herein, we validate the predictive capabilities of six ML models: Random Forest (RF), Support Vector Machine (SVM), CatBoost (CB), Extreme Gradient Boost (XGB), Light Gradient Boosting Machine (LGBM), and KTBoost (KTB) models, both with and without the application of meta-heuristic optimization (i.e., Dragon Fly, Particle Swarm Optimization, and Grey Wolf Optimization), to accurately ascertain water depth. This is achieved using a diverse input dataset derived from multi-spectral Landsat 9 imagery captured on a cloud-free day (19 September 2023) in a shallow, turbid lagoon. Our findings indicate the superior performance of LGBM coupled with Particle Swamp Optimization (R2 = 0.908, RMSE = 0.31 m), affirming the consistency and reliability of the feature extraction and selection-based framework, while offering novel insights into the expansion of bathymetric mapping in complex aquatic environments.

Interfacial effects of perfluorooctanoic acid and its alternative hexafluoropropylene oxide dimer acid with polystyrene nanoplastics on oxidative stress, histopathology and gut microbiota in Crassostrea hongkongensis oysters

The increasing interfacial impacts of polystyrene nanoplastics (PS) and per- and polyfluoroalkyl substances (PFAS) complex aquatic environments are becoming more evident, drawing attention to the potential risks to aquatic animal health and human seafood safety. This study aims to investigate the relative impacts following exposure (7 days) of Crassostrea hongkongensis oysters to the traditional PFAS congener, perfluorooctanoic acid (PFOA) at 50 μg/L, and its novel alternative, hexafluoropropylene oxide dimer acid (HFPO-DA), also known as GenX at 50 μg/L, in conjunction with fluorescent polystyrene nanoplastics (PS, 80 nm) at 1 mg/L. The research focuses on assessing the effects of combined exposure on oxidative stress responses and gut microbiota in the C. hongkongensis. Comparing the final results of PS + GenX (PG) and PS + PFOA (PF) groups, we observed bioaccumulation of PS in both groups, with the former causing more pronounced histopathological damage to the gills and intestines. Furthermore, the content of antioxidant enzymes induced by PG was higher than that of PF, including Superoxide Dismutase (SOD), Catalase (CAT), Glutathione Reductase (GR) and Glutathione Peroxidase (GSH). Additionally, in both PG and PF groups, the expression levels of several immune-related genes were significantly upregulated, including tnfα, cat, stat, tlr-4, sod, and β-gbp, with no significant difference between these two groups (p > 0.05). Combined exposure induced significant changes in the gut microbiota of C. hongkongensis at its genus level, with a significant increase in Legionella and a notable decrease in Endozoicomonas and Lactococcus caused by PG. These shifts led to beneficial bacteria declining and pathogenic microbes increasing. Consequently, the microbial community structure might be disrupted. In summary, our findings contribute to a deeper understanding of the comparative toxicities of marine bivalves under combined exposure of traditional and alternative PFAS.

New insights into microbial community for simultaneous removal of carbon and nitrogen via heterotrophic nitrification aerobic denitrification process

Heterotrophic nitrification aerobic denitrification (HNAD) process is considered to be a promising strategy for efficient removal of nitrogen and refractory organic pollutants from aquatic environments. However, isolated single strains or microbial communities of HNAD in most studies suffer from severe inadaptability in the face of complex aquatic environments. Therefore, the existence of fundamental microbial communities that is able to adapt to contaminants through shaping its structure and then remove the pollutants is a promising solution to this deficiency. Herein, we introduced three aromatic compounds (ACs) (2,4,6-Trinitrotoluene, Aniline, and Phenanthrene), and established HNAD microcosms containing the different ACs and nitrogen through aeration. Impressively, the removal efficiencies of aerobic microcosms were nearly 94.5%, 99.4% and 100% for 2,4,6-Trinitrotoluene, Aniline and Phenanthrene, respectively, and above 90% for total nitrogen (TN), demonstrating superior ACs and nitrogen elimination capabilities. Meanwhile, analysis of microbial community structure and symbiont networks exhibited that there are eight commonly dominant genera in different microcosms, namely Arthrobacter, Bacillus, Sphingobium, Massilia, Novosphingobium, Noviherbaspinrillum, Lysobacter and Azohydromonas. Notably, these core bacteria changed only in relative abundance with the microcosms, and had been proven that they all have laudable carbon and nitrogen conversion capabilities. This finding confirmed the existence of basic microbial communities whose dominant species coordinate with each other to adapt to different water environments for the purpose of water purification. Finally, the mechanism of nitrogen transformation at both gene and enzyme levels was revealed by KEGG enrichment analysis. Summarily, this study will provide valuable references for future development of water treatment technologies.

Detoxification of copper and zinc from anaerobic digestate effluent by indigenous bacteria: Mechanisms, pathways and metagenomic analysis

The presence of organic-complexed copper and zinc in anaerobic digestate effluent (ADE) poses persistent ecological toxicity. This study investigated the detoxification performance and biotic responses of indigenous bacteria against ethylene diamine tetraacetic acid (EDTA)-complexed Cu(II) and Zn(II). Heavy metals (HMs) stress induced reactive oxygen species (ROS) generation and enhanced extracellular polymeric substances (EPS) secretion. At a Cu(II) influent concentration of 20.0 mg·L−1, indigenous bacteria removed 88.2% of Cu(II) within nine days. The majority of copper and zinc sequestered by bacteria were stored in the cell envelope, with over 50% of copper and 60% of zinc being immobilized. Transmission electron microscopy mapping (TEM-mapping) revealed significant mineralization of copper and zinc on the cell wall. Proteins abundant in EPS, alongside humic acid-like substances, effectively adsorbed HMs. Indigenous bacteria exhibited the capacity to reduce cupric to the cuprous state and cupric is preferentially reduced to cuprous before reaching reducing capacity saturation. Sulfur precipitation emerges as a crucial pathway for Zn(II) removal. Metagenomic analysis indicated that indigenous bacteria upregulated genes related to HMs homeostasis, efflux, and DNA repair, enhancing its resistance to high concentrations HMs. This study provided theoretical guidance for employing bacterial consortia to eliminate HMs in complex aquatic environments.

Removal of per- and polyfluoroalkyl substances from water by plasma treatment: Insights into structural effects and underlying mechanisms

Non-thermal plasma emerges as a promising technology for per- and polyfluoroalkyl substances (PFAS) decomposition due to its notable efficacy and environmentally friendly characteristics. In this study, we demonstrated the efficacy of a falling film dielectric barrier discharge (DBD) system for the removal of 10 PFAS, including perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs) and hexafluoropropylene oxide (HFPO) oligomer acids. Results showed that compounds with fluoroalkyl chain length>4 were effectively decomposed within 100 min, with long-chain PFAS demonstrating more pronounced removal performance than their short-chain analogues. The superior removal but low defluorination observed in HFPO oligomer acids could be ascribed to their ether-based structural features. The integration of experimental results with density functional theory (DFT) calculations revealed that the synergistic effects of various reactive species are pivotal to their efficient decomposition, with electrons, OH•, and NO2• playing essential roles. In contrast, the degradation of PFSAs was more dependent on electron attack than that of PFCAs and HFPO oligomer acids. Significantly, the most crucial degradation pathway for HFPO oligomer acids was the cleavage of ether CO, whether through radical or electron attack. Furthermore, the demonstrated effective removal in various water matrices showed the potential of the plasma system for removing PFAS in complex aquatic environments. This study provided mechanistic insights into PFAS degradation behavior in plasma processes, and it underscored the vital influence of molecular structures on degradability, thereby contributing to the further development and regulation of plasma-based technologies for treating PFAS in water.

Single and combined effects of increased temperature and methylmercury on different stages of the marine rotifer Brachionus plicatilis

Rapid, anthropogenic activity–induced global warming is a severe problem that not only raises water temperatures but also shifts aquatic environments by increasing the bioavailability of heavy metals (HMs), with potentially complicated effects on aquatic organisms, including small aquatic invertebrates. For this paper, we investigated the combined effects of temperature (23 and 28 °C) and methylmercury (MeHg) by measuring physiological changes, bioaccumulation, oxidative stress, antioxidants, and the mitogen-activated protein kinase signaling pathway in the marine rotifer Brachionus plicatilis. High temperature and MeHg adversely affected the survival rate, lifespan, and population of rotifers, and bioaccumulation, oxidative stress, and biochemical reactions depended on the developmental stage, with neonates showing higher susceptibility than adults. These findings demonstrate that increased temperature enhances potentially toxic effects from MeHg, and susceptibility differs with the developmental stage. This study provides a comprehensive understanding of the combined effects of elevated temperature and MeHg on rotifers. Environmental implicationMethylmercury (MeHg) is a widespread and harmful heavy metal that can induce lethal effects on aquatic organisms in even trace amounts. The toxicity of metals can vary depending on various environmental conditions. In particular, rising temperatures are considered a major factor affecting bioavailability and toxicity by changing the sensitivity of organisms. However, there are few studies on the combinational effects of high temperatures and MeHg on aquatic animals, especially invertebrates. Our research would contribute to understanding the actual responses of aquatic organisms to complex aquatic environments.

Hydrodynamic performance of a biomimetic undulating fin robot under different water conditions

Inspired by the agile swimming behavior of the Black Ghost Knife Fish utilizing undulating propulsion in complex aquatic environments, this study investigates the locomotion principles and hydrodynamic performance of an undulating propulsion system under varying hydrodynamic conditions through numerical simulations and experiments. The influence of the fin aspect ratio on the thrust performance of the robot was explored, revealing a linear correlation between the aspect ratio and thrust generation. Furthermore, based on an aspect ratio of 0.3, the effects of frequency, amplitude, and wavenumber on the robot’s swimming performance were examined. The results indicated a quadratic relationship between frequency and thrust, a linear relationship between amplitude and thrust, and a trend where thrust initially increased and then decreased with wavenumber, reaching an optimal level around wavenumber 1. Using numerical simulations and experimental investigations, the thrust performance of the robot under wave conditions demonstrated a noticeable reduction in hydrodynamic performance compared to still water conditions. The effects of frequency, amplitude, and wavelength on thrust remained consistent with still water conditions, but the instantaneous thrust became unstable. The current conclusions provide valuable insights for designing and optimizing undulating propulsion robots, offering systematic guidance for selecting appropriate motion parameters to accomplish different tasks.

Re-identification and characterization of grass carp Ctenopharyngodon idella TLR20

Toll-like receptors (TLRs) play a crucial role in the recognition of microbial-associated molecular patterns in the innate immune system. Fish TLRs have undergone significant gene expansion to adapt to complex aquatic environments. Among them, TLR20 from the TLR11 family actively responds to viral and bacterial invasions. Previous studies have reported two TLR20s in grass carp (Ctenopharyngodon idella), and in this study, we revised this conclusion. Based on the latest grass carp genome, we identified a new TLR20 member. These three TLR20s are arranged in tandem on chromosome 9, indicating that they are generated by gene duplication events. They were renamed CiTLR20.1 to CiTLR20.3 based on their chromosomal positions. The CiTLR20s in C. idella exhibit higher similarities with those in Danio rerio, Cyprinus carpio, and Megalobrama amblycephala, and lower similarities with those in other distantly related fish species. Selective pressure analysis revealed low conservation and negative evolution of TLR20s during evolution. The 3D structures of the three TLR20s showed significant differences, reflecting functional variations and different downstream adaptor molecule recruitment. Transcriptome data revealed tissue distribution differences of TLR20s, with TLR20.1 showing relatively low expression levels in all the tissues, while TLR20.2 and TLR20.3 showed higher expression in the head kidney, spleen, and gill. Additionally, TLR20.2 and TLR20.3 actively responded to GCRV-II infection, with higher upregulation of TLR20.2 in response to Aeromonas hydrophila challenge. In conclusion, this study corrected the number of grass carp TLR20 members and analyzed TLR20 from an evolutionary and structural perspective, exploring its role in antiviral and antibacterial defense. This study provides reference for future research on fish TLR20.

Comprehensive analysis of bisphenol analogues in complex water using a group-targeting aptamer engineered by base mutation

Bisphenol analogues (BPs) are typical environmental hormones with endocrine-disrupting effects and reproductive toxicity requiring analysis and monitoring in complex aquatic environments. However, the presence of various co-existing contaminants makes the accurate determination of total BPs difficult. To address this challenge, there is a strong need to obtain a group-targeting binder to specifically detect a class of BPs. In this work, for the first time we have identified the group-targeting BPs-aptamer with similar affinities for multiple structurally and qualitatively similar BPs. Base mutations were introduced into an aptamer specific to bisphenol A (BPA) and utilized molecular docking calculations to identify a group-targeting aptamer capable of binding BPs, including BPA, bisphenol B (BPB), bisphenol E (BPE) and bisphenol F (BPF) with binding constants in the range of 2.0 × 106 ∼ 2.7 × 106 / M. In addition, an electrochemical aptamer-based sensor (aptasensor) was constructed for highly sensitive and comprehensive analysis of a class of BPs. This aptasensor demonstrated remarkable anti-interference performance against co-existing contaminants at concentrations up to 100-fold and achieved an impressive detection limit of 6.7 pM. This innovative approach of engineering a group-targeting BPs-aptamer is important for the comprehensive analysis of BPs, providing insights into identification and monitoring a class of pollutants.

Platform development and gliding optimization of a robotic flying fish with morphing pectoral fins

The aquatic-aerial robot with the free interface crossing can enhance adaptability in complex aquatic environments. However, its design is extremely challenging for the striking discrepancies in propulsion principles. The flying fish in nature exhibits remarkable multi-modal cross-domain locomotion capability, such as high-maneuvers swimming, agile water-air crossing, and long-distance gliding, providing extensive inspiration. In this paper, we present a unique aquatic-aerial robotic flying fish with powerful propulsion and a pair of morphing wing-like pectoral fins to realize cross-domain motion. Furthermore, to explore the gliding mechanism of flying fish, a dynamic model with a morphing structure of pectoral fins is established, and a double deep Q-network-based control strategy is proposed to optimize the gliding distance. Finally, experiments were conducted to analyze the locomotion of the robotic flying fish. The results suggest that the robotic flying fish can successfully perform the ‘fish leaping and wing spreading’ cross-domain locomotion with an exiting speed of 1.55 m s−1 (5.9 body lengths per second, BL/s) and a crossing time of 0.233 s indicating its great potential in cross-domain. Simulation results have validated the effectiveness of the proposed control strategy and indicated that the dynamical adjustment of morphing pectoral fins contributes to improving the gliding distance. The maximum gliding distance has increased by 7.2%. This study will offer some significant insights into the system design and performance optimization of aquatic-aerial robots.