Aquatic Systems Research Articles

Metal bioavailability in aquatic systems— beyond complexation and competition

Metal bioavailability in solution is mostly driven by two factors: complexation and competition. The first factor, complexation, contributes to decrease the overall reactivity of the metal by reducing the activity of the free metal ion, which is known as the common denominator of metal reactions involving either dissolved ligands or surface functional groups (abiotic or biotic). Ubiquitous in natural ecosystems, natural organic matter is, for several metals, the most important metal complexing ligand. The second factor, competition, contributes to decrease the availability of biotic ligands involved in the membrane transport of metals from the bulk solution to the intracellular medium. In freshwater systems, proton and hardness cation concentrations are the main parameters potentially modulating metal bioavailability. The above reflects the current accepted paradigm. In this paper, two knowledge gaps are identified: i) the role of natural organic matter other than metal complexation that may lead to an increase in metal bioavailability; and ii) the effects of multiple metals other than competition that may trigger biological feedback mechanisms which may, in turn, alter biotic ligand binding properties. More research efforts are needed to decipher the extent of these overlooked potential effects and to improve the predictability of metal bioavailability.

Distribution and risk assessment of pesticide pollution in small streams adjoining paddy fields

The present investigation was planned to bridge the knowledge gap on spatiotemporal variations of pesticide pollution in small streams adjacent to paddy fields, and to visualize the associated risks in the aquatic ecosystems. We screened 106 pesticides using GCMSMS and LCMSMS from 10 small streams (n = 212, surface water samples) adjacent to paddy fields over seven months. Fifty-five pesticides were detected across different streams and months. The highest mean concentration was detected for fenobucarb (272 ng L−1), followed by thiamethoxam (199 ng L−1). The highest maximum concentration was detected for thiamethoxam ( 13,264 ng L−1), followed by triflumezopyrim ( 11,505 ng L−1). The highest detection frequency was recorded for fenobucarb (80.00%), followed by pretilachlor (79.00%). Out of the ten streams, Attabira stream had the highest mean number of pesticides detected in each sample. Maximum number of pesticides were detected in October followed by September. Pesticides namely, hexaconazole, pretilachlor, tricyclazole, fenobucarb and thiamethoxam were consistently detected across all streams. The risk assessment against the fishes, micro-invertebrates and algae were measured by risk quotient index (RQ). Twenty-five pesticides out of the detected pesticides (n = 55) had risk quotient values greater than 1. The highest RQmax values were observed in case of fenpropathrin followed by cyfluthrin-3. The highest RQmean value was observed in case of cyfluthrin, indicating its higher toxicity to fishes. The present study reveals that small streams are polluted with pesticides and there is a need to develop strategies and policy interventions in regularizing the pesticide uses for reducing the pesticide pollution in aquatic systems.

Assessment of Microplastics in Hanumante River of Kathmandu Valley

Plastic debris is one of the most significant organic pollutants in the aquatic environment. Researchers are currently focusing on the impact of micro and nano-scale plastic waste on aquatic systems. In this study, we investigated the distribution of plastic pellets and fragments present in the freshwater ecosystem. The goal was to assess microplastic (MP) abundance in the Hanumante River, a tributary of the Bagmati River, and analyze their properties. Sample collection involved the bottle sampling method. Filtration, wet peroxide oxidation, density separation, gravimetric analysis, and microscopic examination were performed to study the characteristics of microplastics. The study was conducted by following the guidelines of the National Oceanic and Atmospheric Administration (NOAA) protocol. Gravimetric analysis was applied to calculate the reduced mass of the sample after total organic carbon reduction. Results showed that the maximum amount of reduced sample was obtained from the sample taken from sample taken from Madhyapur Thimi area (~3.593g) and the minimum amount of reduced sample was obtained from the sample taken from the Shiva temple Jagati area (~2.130g). Microscopic inspection showed that samples taken from different locations were composed of an average of 14–23 microplastics per liter of sample. FT-IR analysis was performed to analyze the characteristics of microplastics and the type of polymers present in the sample which showed the abundance of polymer materials like polyethylene, polypropylene, and polycarbonates. The findings imply that appropriate plastic waste management measures be implemented in the communities to safeguard the ecosystem benefits derived from the river.

Exposure to nanopolystyrene and phoxim at ambient concentrations causes oxidative stress and inflammation in the intestines of the Chinese mitten crab (Eriocheir sinensis)

Nanopolystyrene (NP) and phoxim (PHO) are common environmental pollutants in aquatic systems. We evaluated the toxic effects of exposure to ambient concentrations of NP and/or PHO in the intestines of the Chinese mitten crab (Eriocheir sinensis). Our study showed that histopathological changes were observed in the intestines. Specifically, NP and/or PHO exposure increased intraepithelial lymphocytes. Furthermore, NP and/or PHO exposure induced oxidative stress, as evidenced by a significant decrease in superoxide dismutase activity (SOD), peroxidase activity (POD), and total antioxidant capacity (T-AOC). Pro-inflammatory gene expression and transcriptome analysis demonstrated that NP and/or PHO exposure induced the intestinal inflammatory response. Transcriptome results showed that NP and/or PHO exposure upregulated the NF-κB signaling pathway, which is considered a key pathway in the inflammatory response. Additionally, the expression of pro-inflammatory genes significantly increased after a single exposure to NP or PHO, but it exhibited a significant decrease after the co-exposure. The downregulation of these genes in the co-exposure group likely suggested that the co-exposure mitigated intestinal inflammation response in E. sinensis. Collectively, our findings mainly showed that NP and/or PHO exposure at ambient concentrations induces oxidative stress and inflammatory response in the intestines of E. sinensis.

Effect of UV-LED Wavelength on Reactive Species Photogeneration from Dissolved Organic Matter

The photogeneration of reactive species from dissolved organic matter (DOM) plays a crucial role in the photochemical and photobiochemical processes in natural aquatic systems. However, the impact of the ultraviolet (UV) wavelength on the photogeneration of reactive species by different sources of DOM remains unclear. In this study, UV light at four wavelengths (365 nm, 310 nm, 280 nm, and 260 nm) provided by UV-LEDs were irradiated onto three types of DOM: humic acid (HA), fulvic acid (FA), and effluent organic matter (EfOM). Three reactive species produced by DOM, including excited triplet-state DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radicals (•OH), were determined. UV365 proved to be the most efficient wavelength for generating 1O2 and •OH, with formation rates of 3.47 × 10−6 M s−1 and 1.67 × 10−8 M s−1, respectively, with the addition of FA and EfOM. The highest steady-state concentrations of all three reactive species were also generated under UV365, reaching 3.00 × 10−13 M (3DOM*) and 1.64 × 10−11 M (1O2) with the FA addition, and 1.44 × 10−10 M (•OH) with the EfOM. Across the different DOM sources, UV365 obtained the maximum quantum yields of reactive species, indicating the stronger effect of UV365 on inducing the photosensitization of DOM compared to the other shorter wavelengths. This study expands our understanding of the photochemistry of DOM in aquatic environments.

Storm-induced nitrogen transport via surface runoff, interflow and groundwater in a pomelo agricultural watershed, southeast China

The storm-induced export of nitrogen (N) from agricultural watersheds significantly impacts aquatic ecosystems, yet the mechanisms of source supply and transport behind N species remain unclear. Here, we investigated the hydrological factors influencing the timing and magnitude of river N species export in a Chinese pomelo agricultural watershed. We conducted continuous observations of watershed hydrology, N species, and their isotopic ratios along a soil-groundwater-river continuum during two storm events in 2018–2019. We found the export flux of river NO3–N covers ∼80% of the total N flux during storms, and the rest for other N species. Our results further revealed distinct pathways and timing of N transport among different N species, especially between ammonium N (NH4–N) and nitrate N (NO3–N). NH4–N in stormflow predominantly originates from sewage and soil leachate, rapidly transported via surface runoff and interflow. Orchard fertilization (contributed 41–56% based on SIAR analysis) was the major source of river NO3–N, which underwent initial dilution via surface runoff and subsequently became enriched through delayed discharge of soil leachate and groundwater. The variations in timing and magnitude of N transport between storms can be explained by antecedent conditions such as precipitation, soil N pools, and storm size. These findings emphasize the hydrological controls on N export from agricultural watersheds, and highlight the variations in source supply and transport pathways among different N species. The insights gained from this study hold significance for managing agricultural pollution and restoring impaired aquatic systems.

Degradation of the strobilurin fungicide mandestrobin in illuminated water-sediment systems.

The degradation behavior of mandestrobin (1) was investigated in aerobic aquatic water-sediment systems exposed to continuous artificial sunlight (λ>290 nm). [14C]mandestrobin uniformly labeled at the phenoxy or benzyl ring was individually applied to the overlying water of the system at a rate equivalent to 262.5 g a.i./ha. The transformation of 1 was mainly proceeded via photoinduced bond cleavage at the benzyl phenyl ether and the subsequent rearrangement reaction. Interestingly, some of the photodegradates and microbial metabolites of 1 observed in the aquatic photodegradation and water-sediment (dark) studies, respectively, were never detected. Furthermore, the observed photoproducts were less formed and were steadily degraded or metabolized to carbon dioxide or strongly adsorbed to bottom sediment. The fate of 1 and its degradates in illuminated water-sediment systems was considered to reflect realistic conditions more precisely, as it accounts for various effects attributed to sunlight.

Effects of hydrological dynamics in controlling phosphorus bioavailability in intermittent rivers and implications for estuaries

Several studies on intermittent rivers and ephemeral streams (IRES) have focused on the ecology of populations and communities, and very few explored the biogeochemistry and bioavailability of key elements, such as phosphorus (P) and nitrogen (N). In this study, we aimed to explore the role of environmental seasonality on P bioavailability in an intermittent river in Northeastern Brazil and the implications for nutrient dynamics to downstream ecosystems, such as the estuaries. The study was performed at the Cruxati River, located in the Litoral Hydrographic Basin on the coast of Ceará State, Brazil. We sampled riverine sediments during three hydroperiods (i.e., dry, rewetting, and flow) according to the theoretical model for research in intermittent rivers. We performed a geochemical fractionation of different P forms and determined the physicochemical parameters, particle size distribution, mineralogy, and total organic carbon of the sediments. Mean values were compared using the Kruskal–Wallis non-parametric statistical test (p-value < 0.05) and by discriminant function analysis. We observed that the predominant fractions of P were associated with Fe-oxides, silicates, and refractory organic matter, but there were no statistical differences among these fractions for all hydroperiods. The exchangeable-P form was higher in the dry and flow periods than in the rewetting period. On the opposite side, P associated with humic acids and carbonates was lower in the dry and flow periods but higher in the rewetting period. We concluded that seasonality influences the bioavailability of P in intermittent rivers, being strongly influenced by the organic fraction, including the humic acid fraction and the refractory organic matter, which are important sources of P in the aquatic system. Furthermore, the IRES may act as a source or a sink of nutrients throughout the cycles of wetting and drying, which may release P from the sediments to the aquatic environment. Hence, IRES plays an important role in transporting nutrients to estuaries and maintaining their ecosystem services.

Recent advances in heavy metal/metalloid ion treatment from wastewater using nanocomposites and bionanocomposites

Wastewater remediation is of paramount importance for the water-stressed modern civilization from the perspective of sustainable development and the management of limited freshwater resources. Contaminants such as heavy metal and metalloid ions, toxic dyes, and pathogenic microbes present in the aquatic ecosystem have adverse effects not only on the environment but also on human health. Traditional wastewater remediation processes are costly, energy-consuming, and have less efficiency in removing pollutants from wastewater. Multi-phasic nanomaterials or nanocomposites have enormous potential for removing contaminants from water bodies. These materials have an enormous tunable surface area for interacting with the target toxicants and are extremely stable in the aquatic system, but they readily agglomerate. Many research groups have exploited biosorption, bioleaching, and bioprecipitation capacities of fungal hyphae for wastewater remediation. Recently, researchers have attempted to explore the synergistic effect of the bionanocomposite of fungal hyphae and nanomaterials for removing pollutants from wastewater. This bionanocomposite has already shown promise as a superior material for wastewater treatment and can easily be separated from the polluted water for reuse over several cycles. The bionanocomposite-mediated decontamination of water can lead to a total paradigm shift in wastewater management strategies.

Comparative Investigation of Phosphate Adsorption Efficiencies of MOF-76 (Ce) and Metal Oxides Derived from MOF-76 (Ce).

Phosphate pollution is a very challenging problem for the water environment. Phosphate mixed with water in various ways causes eutrophication. To sustain life in aquatic systems, phosphate ions must be cleaned. Therefore, it is very important to remove phosphate in wastewater. Here, an adsorption method has been tried for the removal of phosphate. MOF-76 (Ce), a cerium-based metal-organic framework, was synthesized by a hydrothermal method. Since metal oxides are known to be successful in phosphate adsorption, CeO2 nanoparticles were also obtained by pyrolysis of this MOF structure. The phosphate adsorption efficiencies of both adsorbents were compared. The characterization methods (SEM, FTIR, XRD, and TGA) were applied to adsorbents. The kinetic, isotherm, and thermodynamics studies were applied to experimental results. At 298 K, the adsorption capacity of MOF-76 (Ce) is higher than that of CeO2, according to Langmuir isotherm qm values. The qm values are 72.97 and 55.71 mg/g, respectively. Both adsorbents follow the pseudo second-order kinetic model. It has been found that MOF-76 (Ce) has a pH-selective property in phosphate adsorption. No change was observed in the phosphate adsorption capacity of CeO2 with pH. In terms of thermodynamics, the endothermic reaction is valid for both adsorbents.

Energy recovery and clean water remediation using antibiofouling polysaccharide coated PAN hollow fiber membrane obtained via green route synthesis

Biofouling is an important biological constrain in the water treatment process, and the control or management strategies using green principles have gained recent attention. Antibiofouling agents based on the biological source are now extensively studied due to their high efficacy and are environmentally friendly. In this present study, Poly Acrylo Nitrile (PAN)/Ulvan hollow fibre membranes of four different modules were fabricated for water treatment studies by testing against B. subtilis and E. coli along with separation efficiency studies on proteins such as albumin, pepsin, and clay. Ulvan (Ulv), green seaweed sulfated polysaccharide extracted from Ulva fasciata, was coated on PAN hollow fibres, fabricated using a wet-spinning process. Ulvan was dip-coated on membrane surface followed by cross-linking and resultant changes in terms of performance and morphology. PAN/Ulv hollow fibre membranes were examined for the pure water flux and protein separation analysis to analyse the membrane efficiency. SEM was used to analyse the membrane structure and ATR- FTIR for the determination of functional groups. Ulvan coated (310 C) hollow fibre membrane showed better performance than the other three membranes with a flux of 398.1 L m−2 h−1. Higher sample concentration of suspended solids paved simpler route for enhanced COD sequestration efficacy. Pepsin, albumin, and clay particles were rejected by the 310C Ulvan adorned membranes at rates greater than 80%. By incrementing suspended particles beyond 3200 mg/L, the greatest power recovery was reduced that portrays an adverse influence of bio-fouling process on membrane operation. Experimental results demonstrated that synthesised 310 C membrane possessed better separation performance and antifouling characteristics for aquatic water systems.

Screening and characterization of novel biosorbent for the removal of Cadmium from contaminated water

Presence of trace metal pollutants in the aquatic system is a worldwide foremost concern. The present investigation was an attempt to find out the novel biosorbent for the removal of Cadmium(CdII) from contaminated water. The leaf of Sesbania bispinosa was screened out as a potential Cd(II) removing biosorbent from thirty different natural biomasses by physico-chemical and sorption process characterizations. Biosorption capacity of S. bispinosa was determined by batch mode biosorption method with the functions of solution pH, contact time, biosorbent dose and initial Cd(II) concentration. Obtained results were analyzed for isotherm and kinetic study. The S. bispinosa biosorbent exhibited the biosorption equilibrium of Cd(II) uptake in 30 min. At pH 4, biosorbent dose of 1 g/L was sufficient for maximum Cd(II) uptake. Scanning Electron Microscopy (SEM) images and Fourier Transform Infrared Spectroscopy (FTIR) spectra confirmed the favourable sorption surface characteristics. The data also demonstrated that Freundlich isotherm (R2=0.998) is the better fitted model compared to Langmuir model and the maximum sorption capacity was found to be 33.33 mg/g. Suitabilty of pseudo second order reaction pathway was observed during the kinetic study. Most especially, The selected biosorbent is ascertained effective in removing multimetals [Cd(II) - 67.51 %, Cr(VI) – 40.36 %, Pb(II) – 100 % and Cu(II) – 59.01 %] from a quaternary aqueous solution of Cd(II), Cr(VI), Pb(II) and Cu(II) mixture and spent biosorbent can be easily regenerated by applying 0.1 M HCl solution as a desorbing agent. It, therefore, could be concluded that leaves of S.bispinosa might be a low-cost and environmentally sound novel biosorbent for the treatment of Cd(II) contaminated water.

Investigation of alkyl, aryl, and chlorinated OPFRs in sediments from estuarine systems: Seasonal variation, spatial distribution and ecological risks assessment

Estuaries in South Africa are very important for biodiversity conservation and serve as focal points for leisure and tourism activities. The organophosphate flame retardants (OPFRs) levels in these aquatic systems haven't been documented in any studies as of yet. Due to the negative effects of persistent organic pollutants in South African estuaries, we examined the occurrence of eight OPFRs in sediments of two estuaries by studying their spatiotemporal distribution, season variation, and ecological risks. The Sundays Estuary (SDE), a semi-urbanized agricultural surrounding system, recorded an ∑8OPFR concentration in sediments that ranged from 0.71 to 22.5 ng/g dw, whereas Swartkops Estuary, a largely urbanized system, recorded a concentration that ranged from 0.61 to 119 ng/g dw. Alkyl-OPFRs were the prevalent homologue in both estuaries compared to the chlorinated and aryl groups. While TBP, TCPP, and TCrP were the most abundant compounds among the homologue groups. There was no distinct seasonal trend of ∑8OPFR concentration in either estuary, with summer and autumn seasons recording the highest concentrations in SDE and SWE, respectively. Ecological risks in the majority of the study sites for the detected compounds were at low (RQ < 0.1) and medium levels (0.1 ≤ RQ < 1) for certain species of fish, Daphnia magna and algae. However, the cumulative RQs for all the compounds had ∑RQs ≥1 for most sites in both estuaries, indicating that these organisms, if present in both estuaries, may be exposed to potential ecological concerns due to accumulated OPFR chemicals. The scope of future studies should be broadened to include research areas that are not only focus on the bioaccumulation patterns of these compounds but also find sustainable ways to reduce them from these estuarine environments.

Existing evidence on the use of environmental DNA as an operational method for studying rivers: a systematic map and thematic synthesis

BackgroundEnvironmental DNA (eDNA) is the DNA that can be extracted from an environmental sample, enabling the monitoring of whole biological communities across a large number of samples, at a potentially lower cost, which can significantly benefit river conservation. A systematic mapping protocol was designed to investigate the use of eDNA in rivers, specifically in terms of research topics, geographic and taxonomic biases, as well as information gaps. Furthermore, the potential research opportunities of eDNA in rivers and possible paths to find this kind of information on available platforms are identified.MethodsA published systematic map protocol was applied, consisting of a search for published articles and gray literature in two bibliographic databases and one search engine. All search results were submitted to a 2-stage screening for relevance and pertinence in accordance with pre-defined eligibility criteria. Data extraction and codification regarding country of study, year, taxonomic group, sequencing platform, and type of technique employed resulted in a publicly available database.ResultsFrom 7372 studies initially obtained by the search, 545 met the inclusion criteria spanning a period from 2003 to 2022. The five countries with most studies are: USA (134), Japan (61), China (54), Brazil (29) and the UK (25). The most used fragments to analyze DNA are 16S and COI, whilst 26S and 23S are the least used. Only 84 (15%) of the studies reported hypervariable regions, among which the most used are V4 and V5. Regarding taxonomic groups, fishes are most often studied (176), followed by bacteria (138) and virus (52), while fungi is the least studied group (3). Concerning data availability, 229 (42%) studies provided access to sequencing data.ConclusionsThis study presents a comprehensive analysis of the available evidence regarding the implementation of the eDNA methods in rivers. The findings indicate that since the year 2003, this approach has been applied to aquatic lotic systems, and their recent increase can be attributed to the development of Next-Generation-Sequencing technologies and their reduced costs. However, there is a bias towards high-income countries, particularly USA and Europe. Widespread use and applications of this approach at a global level would allow for the generation of a large amount of information that can be compared between countries to understand if responses of aquatic systems follow similar patterns worldwide.

Impact of Chlorella vulgaris Bioremediation and Selenium on Genotoxicity, Nephrotoxicity and Oxidative/Antioxidant Imbalance Induced by Polystyrene Nanoplastics in African Catfish (Clarias gariepinus)

Contamination of the environment with nano- and microplastic particles exerts a threatening impact on the aquatic ecosystems and sustainable catfish aquaculture. The presence of nanoplastics has been found to have a detrimental impact on both aquatic and terrestrial ecosystems. The present study examines the effect of polystyrene nanoplastics (PS NPs) on the DNA, erythrocytes, oxidative status and renal histology of catfish, in addition to the potential protective effects of Chlorella vulgaris bioremediation and selenium to hinder this effect. Six equal groups of fish were used as follows: Group 1 served as a control group and received water free from PS NPs; Group 2 was exposed to PS NPs at a concentration of 5 mg/L; Group 3 was exposed to PS NPs (5 mg/L) + selenium (1 mg/kg diet); Group 4 was exposed to PS NPs (5 mg/L) + C. vulgaris (25 g/kg diet); Group 5 was supplemented with C. vulgaris (25 g/kg diet); and Group 6 was supplemented with selenium (1 mg/kg diet). The exposure period was 30 days. The results indicated that PS NPs induced oxidative stress by significantly elevating malondialdehyde activities and slightly reducing antioxidant biomarkers, resulting in DNA damage, increased frequency of micronuclei, erythrocyte alterations, and numerous histopathological alterations in kidney tissue. Selenium and C. vulgaris significantly ameliorated the oxidative/antioxidant status, reducing DNA damage, micronucleus frequency, erythrocyte alterations, and improving the morphology of kidney tissue. Nevertheless, further research is needed for a profound understanding of the mechanism behind the toxicity of nano-microplatics in aquatic systems.

Exposure to environmentally relevant concentrations of Bisphenol-A linked to loss of visual lateralization in adult zebrafish (Danio rerio)

Weak, but environmentally relevant concentrations of contaminants can have subtle, yet important, impacts on organisms, which are often overlooked due to the lack of acute impacts and the timing of exposure. Thus, recognizing simple, non-invasive markers of contamination events is essential for early detection and addressing the effects of exposure to weak environmental contaminants. Here, we tested whether exposure to an environmentally relevant concentration of Bisphenol-A (BPA), a common and persistent contaminant in aquatic systems, affects the lateralization of adult zebrafish (Danio rerio), a widely used model organism in ecotoxicology. We found that 73.5% of adult zebrafish displayed a left-side bias when they approached a visual cue, but that those exposed to weak BPA (0.02 mg/L) for 7 days did not exhibit laterality. Only 47.1% displayed a left-side bias. We found no differences in activity level and visual sensitivity, motor and sensory mechanisms, that regulate lateralized responses and that were unaffected by weak BPA exposure. These findings indicate the reliability of laterality as a simple measure of contaminant exposure and for future studies of the detailed mechanisms underlying subtle and complex behavioral effects to pollutants.

Instream barriers contribute to population isolation of a small‐bodied, benthic, headwater‐specialist fish (Percidae)

AbstractGenetic differentiation in aquatic systems is often driven by geographic distance (isolation by distance) due to the linear and hierarchical distribution of populations, but habitat fragmentation often exacerbates this effect by decreasing population connectivity, leading to isolation by resistance. Stronghold populations of the Kentucky Arrow Darter (Etheostoma spilotum) in the South Fork Kentucky River system within the Daniel Boone National Forest of eastern Kentucky, USA have a high population structure not explained by distance alone. Higher than expected levels of genetic differentiation among proximate populations were hypothesized to be driven by land‐use change, but this was not previously tested. Here we use a riverscape genetics approach to test for the effects of natural landscape features including slope, elevation and stream size, and anthropogenically altered habitat features, including specific conductance (conductivity), culverts and forest cover, on population connectivity and genetic diversity of E. spilotum. We found isolation of populations among all tributary systems and a strong, positive relationship between genetic and geographic distances as expected. However, high conductivity levels due to surface coal mining best explain the population structure observed. We also found signatures of low genetic diversity overall and indicators that culverts may limit upstream movements of E. spilotum. This study provides a novel fine‐scale view of the effects of instream and landscape features on connectivity among, and genetic diversity within populations of an imperilled, small‐bodied, benthic fish.

TJ-FlyingFish: An Unmanned Morphable Aerial–Aquatic Vehicle System

In this paper, we present in this work a fairly complete process for developing an unmanned aerial–aquatic vehicle system, TJ-FlyingFish, which includes an innovative design methodology of the aerial–aquatic platform and the cross-medium localization, dynamics modeling, and flight control systems. The development faces the challenge how to manipulate locomotion effectively in both water and air which presents substantial differences in fluid properties. Additionally, there are difficulties in perception and navigation because of the discontinuity of mediums. To cope with these challenges, we designed an innovative unmanned aerial–aquatic vehicle with an optimized dual-speed and tilting propulsion configuration. The rotors/propellers operate in different ranges of rotating speed in the two different mediums, providing sufficient thrust and ensuring output efficiency. Besides, thrust vectoring is achieved by rotating each propulsion unit around its mounted arm, facilitating agile underwater cruising. Another key component of our approach is a sophisticated multi-sensor-based cross-medium localization system that combines SLAM, sensor synchronization, and data capture mechanisms, enabling seamless transitions between aerial and aquatic environments, and supporting autonomous operations. The results are fully validated through actual flight experiments.

Effects of water quality on palladium-induced olfactory toxicity and bioaccumulation in rainbow trout (Oncorhynchus mykiss).

Through emission processes, palladium (Pd) particulates from industrial sources are introduced into a range of ecosystems including freshwater environments. Despite this, research on Pd-induced bioaccumulation, uptake, and toxicity is limited for freshwater fishes. Unlike other metals, there are currently no regulations or protective guidelines to limit Pd release into aquatic systems, indicating a global absence of measures addressing its environmental impact. To assess the olfactory toxicity potential of Pd, the present study aimed to explore Pd accumulation in olfactory tissues, olfactory disruption, and oxidative stress in rainbow trout (Oncorhynchus mykiss) following waterborne Pd exposure. Olfactory sensitivity, measured by electro-olfactography, demonstrated that Pd inhibits multiple pathways of the olfactory system following 96 h of Pd exposure. In this study, the concentrations of Pd for inhibition of olfactory function by 20% (2.5 μg/L; IC20) and 50% (19 μg/L; IC50) were established. Rainbow trout were then exposed to IC20 and IC50 Pd concentrations in combination with varying exposure conditions, as changes in water quality alter the toxicity of metals. Independent to Pd, increased water hardness resulted in decreased olfactory perception owing to ion competition at the olfactory epithelium. No other environmental parameter in this study significantly influenced Pd-induced olfactory toxicity. Membrane-associated Pd was measured at the olfactory rosette and gill following exposure; however, this accumulation did not translate to oxidative stress as measured by the production of malondialdehyde. Our data suggest that Pd is toxic to rainbow trout via waterborne contamination near field-measured levels. This study further demonstrated Pd bioavailability and uptake at water-adjacent tissues, adding to our collective understanding of the toxicological profile of Pd. Taken together, our results provide novel insights into the olfactory toxicity in fish following Pd exposure. Integr Environ Assess Manag 2024;00:1-13. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Turbidity drives plasticity in the eyes and brains of an African cichlid.

Natural variation in environmental turbidity correlates with variation in the visual sensory system of many fishes, suggesting that turbidity may act as a strong selective agent on visual systems. Since many aquatic systems experience increased turbidity due to anthropogenic perturbations, it is important to understand the degree to which fish can respond to rapid shifts in their visual environment, and whether such responses can occur within the lifetime of an individual. We examined whether developmental exposure to turbidity (clear, <5 NTU; turbid, ∼9 NTU) influenced the size of morphological structures associated with vision in the African blue-lip cichlid Pseudocrenilabrus multicolor. Parental fish were collected from two sites (clear swamp, turbid river) in western Uganda. F1 broods from each population were split and reared under clear and turbid rearing treatments until maturity. We measured morphological traits associated with the visual sensory system (eye diameter, pupil diameter, axial length, brain mass, optic tectum volume) over the course of development. Age was significant in explaining variation in visual traits even when standardized for body size, suggesting an ontogenetic shift in the relative size of eyes and brains. When age groups were analyzed separately, young fish reared in turbid water grew larger eyes than fish reared in clear conditions. Population was important in the older age category, with swamp-origin fish having relatively larger eyes and optic lobes relative to river-origin fish. Plastic responses during development may be important for coping with a more variable visual environment associated with anthropogenically induced turbidity.