Characteristics and driving factors of antibiotic resistance genes in aquaculture products from freshwater ponds in China Yangtze River Delta

Antibiotic resistance genes (ARGs) are widespread in aquaculture and pose a huge threat to aquaculture organisms and human health. In this study, occurrences and relative abundances of ARGs were analysed in the guts of products cultured in freshwater ponds in the Yangtze River Delta region in China. A total of 29 ARGs were found in the gut samples, with detection frequencies ranging from 4.8% to 81%, and the relative abundances (ARGs/16S rRNA) ranging from 10-7 to 1. In addition, the human dietary intake of ARGs via aquaculture products was assessed, where the daily intake of most ARGs via aquaculture products was higher than those via PM2.5 and drinking water, but lower than that via vegetables. The relative abundances of MGE (IS613, Tp614, tnpA and int1) were significantly correlated with those of multiple ARGs, indicating the horizontal gene transfer (HGT) of ARGs among gut microorganisms. Proteobacteria, Firmicutes and Actinobacteria were the dominated microbial communities found in the guts of aquaculture products. In addition, significant correlations were found between Cyanobacteria and int1, between Nitrospira and tetE, and between sul2 and aadA2, indicating potential same hosts of these genes. In addition, results from co-correlation indicated both HGT (dominated by MGEs) of ARGs and the enrichment of ARGs in bacteria. MGEs, mostly int1, were more effective than bacteria in increasing the ARG abundance. This study could provide a better understanding of the transmission of ARGs in the aquaculture environment and improve the quality of aquaculture products and the ecology.

Model of shrimp pond-mediated spatiotemporal dynamic distribution of antibiotic resistance genes in the mangrove habitat of a subtropical gulf

Aquacultures are the main reason for the environmental selection of antibiotic resistance genes (ARGs), resulting in the enrichment of ARGs. As a filter, a marine mangrove ecosystem can reduce antimicrobial resistance (AMR) or eliminate ARGs; however, its elimination mechanism remains unclear. This study investigated the spatiotemporal dynamic distribution of ARGs in two different types of mangrove habitats (shrimp ponds and virgin forests), within a subtropical gulf located in the Beibu Gulf, China, during dry and wet seasons by using metagenomics and real time quantitative polymerase chain reaction (RT-qPCR) analysis. As the key environmental factors, sulfide, salinity, and mobile genetic elements significantly were found to contribute to ARGs distribution, respectively. Wet and dry seasons influenced the dispersal of ARGs but did not affect the microbial community structure. Three potential biomarkers, TEM-116, smeD, and smeE, played key roles in seasonal differences. The key different genes in the biological relevance of absolute abundance were demonstrated by RT-qPCR. Co-occurrence network analysis indicated that high-abundance ARGs were distributed in a modular manner. For the first time, a risk index weighted by risk rank (RIR) was proposed and used to quantify the human risk of ARGs in the mangrove metagenome. The shrimp ponds during the wet season showed the highest RIR detected. In addition to offering a perspective on reducing AMR in mangrove wetlands, this study constructed the first spatiotemporal dynamic model of ARGs in the Beibu Gulf, China and contributed to revealing the global spread of ARGs. Meanwhile, this study proposes a new pipeline for assessing the risk of ARGs, while also exploring the concept of "One Health."

Sunlight Induces the Production of Atmospheric Volatile Organic Compounds (VOCs) from Thermokarst Ponds

Ground subsidence caused by permafrost thawing causes the formation of thermokarst ponds, where organic compounds from eroding permafrost accumulate. We photolyzed water samples from two such ponds in Northern Quebec and discovered the emission of volatile organic compounds (VOCs) using mass spectrometry. One pond near peat-covered permafrost mounds was organic-rich, while the other near sandy mounds was organic-poor. Compounds up to C10 were detected, comprising the atoms of O, N, and S. The main compounds were methanol, acetaldehyde, and acetone. Hourly VOC fluxes under actinic fluxes similar to local solar fluxes might reach up to 1.7 nmol C m-2 s-1. Unexpectedly, the fluxes of VOCs from the organic-poor pond were greater than those from the organic-rich pond. We suggest that different segregations of organics at the air/water interface may partly explain this observation. This study indicates that sunlit thermokarst ponds are a significant source of atmospheric VOCs, which may affect the environment and climate via ozone and aerosol formation. Further work is required for understanding the relationship between the pond's organic composition and VOC emission fluxes.

A highly sensitive surface-enhanced Raman scattering sensor with MIL-100(Fe)/Au composites for detection of malachite green in fish pond water

Concerns about food safety have been arisen due to the improper use of chemicals in aquaculture. Malachite green (MG) has attracted attention because of its illegal usage and its potential negative impacts on the environment and public health. Surface-enhanced Raman scattering (SERS) platforms coupled with different SERS substrates have been employed for rapid analysis of MG residues in food. However, the most commonly used SERS substrates were non-reusable and showed limited detection sensitivity. In this study, a novel SERS substrate with a good recyclability and a high sensitivity was prepared by electrostatically assembling together a metal-organic framework material called materials of institute lavoisie-100(Fe) (MIL-100(Fe)) and Au NPs. The lowest detectable concentration of MG was 10^-13 M based on the optimal substrate. The SERS sensor was applied for the detection of the trace MG in fish pond water, which was accomplished with the correlation coefficients R² = 0.991-0.996 in a concentration range of 10^-6-10^-13 M. Moreover, MIL-100(Fe)/Au was recycled at least five times, realizing a "detection to degradation", showing great potential for food contamination monitoring due to its distinguished performance.

Ecological and health risk assessment and quantitative source apportionment of dissolved metals in ponds used for drinking and irrigation purposes

In this study, dissolved metal levels of 10 different ponds used as irrigation and drinking water sources in the north of Saros Bay (Türkiye) were evaluated using multivariate statistical methods, contamination and ecological risk indices, and absolute principal component score-multiple linear regression (APCS-MLR). The mean levels of metals in the ponds ranged from 0.045 µg/L (Cd) to 127 µg/L (Mn). Pond 7 used for drinking water source had the lowest total metal level. Only Mn levels in two ponds (P1 and P2) slightly exceeded the critical value set by EU Drinking Water Directive. However, the levels of all metals in all ponds were lower than the critical values set for irrigation water and aquatic life. According to the heavy metal pollution index (HPI), five ponds showed low metal pollution in terms of drinking water quality, four ponds showed moderate metal pollution, and one pond (P1) showed moderate to heavy pollution. According to the Nemerow pollution index (NPI) values (0.26-1.82), ponds P1 and P2 showed slight metal pollution, while other ponds showed insignificant metal pollution. Contamination degree (CD) values of ponds varied between 0.95 and 3.33, indicating that all ponds showed low pollution. In terms of irrigation water quality, all ponds showed low or insignificant metal pollution according to the HPI, NPI, and CD values. According to the ecological risk index (ERI) values, metals in all ponds posed low ecological risks for both drinking and irrigation purposes. Factor analysis identified two potential sources: mixed sources and natural sources. The APCS-MLR model results revealed that mixed sources and natural sources contributed 78.99% and 21.01% to dissolved metals in the ponds, respectively. Health risk assessment results indicated that both individual and combined metals in the ponds would not cause non-carcinogenic risks to both adults and children. Similarly, it was found that Cr and As would not cause carcinogenic risks to the residents of the region.

Enrofloxacin-induced transfer of multiple-antibiotic resistance genes and emergence of novel resistant bacteria in red swamp crayfish guts and pond sediments

Antibiotic resistance genes (ARGs) can be transferred from environmental microbes to human pathogens, thus leading to bacterial infection treatment failures. The aquaculture polluted by over-used antibiotics is considered as a notorious reservoir of ARGs. However, the origin, diachronic changes, and mobility of ARGs under antibiotic exposure in aquaculture systems remain elusive. Our findings showed that enrofloxacin application also increased the relative abundance of various ARGs in addition to quinolone-resistance genes and induced ARG dissemination in crayfish gut and sediment bacteria. Further investigation indicated that the transposase-mediated recombination was the major driver of horizontal gene transfer (HGT) of ARGs under antibiotic stress. Notably, enrofloxacin application also induced the generation of some metagenome-assembled genomes (MAGs) carrying multiple ARGs, which were identified as novel species. Additionally, Enterobacteriaceae constituted a mobile ARG pool in aquaculture. Therefore, aquaculture provides potential wide environmental pathways for generation and spread of antibiotic resistance. Our findings of ARG temporal variations and dissemination pattern in aquaculture with artificial use of antibiotics are critical to the management of antibiotic resistance, which is of great ecosystem and health implications.

Characterization of Dissolved Organic Matter in Solar Ponds by Elemental Analysis, Infrared Spectroscopy, Nuclear Magnetic Resonance and Pyrolysis-GC-MS

The abundance and chemical composition of dissolved organic matter (DOM) in the brine of solar ponds affect the efficiency of mineral extraction and evaporation rates of the brine, and cause undesired odor and color of the products. Here, we report an investigation into the composition and changes of DOM in solar ponds from Salt Lake brine with multiple complementary analysis techniques. The results showed that the DOM derived from Salt Lake brine was primarily composed of carbohydrates, aliphatic and aromatic compounds. The concentrations of dissolved organic carbon in solar ponds increased with exposure time by up to 15−fold (from 23.4 to 330.8 mg/L) upon evaporation/irradiation of Salt Lake brine. Further qualitative analyses suggest that the relative abundance of aliphatic compounds (including functionalized ones) increased from 49.5% to 59.2% in the solar pond process, while the opposite was observed for carboxylic acid moieties, aromatics and carbohydrates, which decreased from 15.7%, 7.1% and 26.1% to 13.4%, 5.3% and 23.0%, respectively. The pyrolysis–gas chromatography–mass spectrometry results reveal that the presence of some sulfur-containing organics implied some anaerobic biotic decay, but microbiological processes were probably subordinate to photo-induced DOM transformations. In the Salt Lake brine, exposure-driven decay decreased the abundance of polysaccharides and increased that of mono- and polyaromatic pyrolysis products. Our results here provide new insights for better understanding the changes of DOM chemical composition in the solar ponds of Salt Lake brine.

Evaluation of occurrence, fate and removal of priority phthalate esters (PAEs) in wastewater and sewage sludge by advanced biological treatment, waste stabilization pond and constructed wetland

Phthalate Esters (PAEs), detected in high concentrations generally in treated wastewater discharged from wastewater treatment plants (WWTPs), are important pollutants that restrict the reuse of wastewater. Investigating the fate of these endocrine-disrupting chemicals in WWTPs is crucial in order to protect both receiving environments and ecosystems. For this purpose, di(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP) and benzyl butyl phthalate (BBP) in the group of PAEs were monitored in simultaneously both in wastewater and sludge lines of selected two nature-based WWTPs and one advanced biological WWTP. Although it was frequently stated that phthalates were significantly removed in WWTPs in many studies found in literature, negative removal efficiencies of selected phthalates in investigated WWTPs during the sampling period were observed generally in this study. One of the reasons for this concentration increase could be releasing of phthalates from microplastics in wastewater during the treatment process or the desorption of PAEs from treatment sludge. DNOP was the compound with the highest concentration increase at almost each treatment unit of the three WWTPs. On the other hand, total PAEs load was 1997 g d^-1 in advanced biological WWTP and adsorption onto sludge of PAEs were determined as 90%. The side-stream total load returned from the decanter supernatant was 0.02% of the total PAEs load coming to advanced biological WWTP from the sewer system. As a result of detailed statistical analysis, the correlation between raw wastewater and primary clarifier (PC) effluent was determined as an increasing linear relation for DEHP and DNOP. On the other hand, moderate and strong correlations were observed both between septic tank and constructed wetland (CW) processes with raw wastewater. In the waste stabilization pond (WSP), while a significant correlation was not found between the sludge line data, homogeneous variance, strong and moderate correlations were obtained in the wastewater line data. However, while mean differences for all investigated PAEs were not significant (p > 0.05) in the wastewater line, mean differences of DEHP (p < 0.05) were significant in the sludge line according to ANOVA analysis.

Assessment of the effectiveness of a field-scale combined ecological treatment system at removing water pollutants, after optimization using a system dynamic model: a case study of rural inland ponds in China

Field-scale combined ecological treatment systems (FCETS) are designed to remove nutrients from aquaculture wastewater in ponds according to the characteristics of the nutrients present. We designed and established a numerical model based on the system dynamic (SD) method, to optimize the parameters of FCETS. Results showed that the mean removal rates of TSS, TN, NO₃^--N, NH₄⁺-N, TP, DP, and COD_Mn ranged from 83.3 to 125.8%, 41.1 to 49.1%, 44.8 to 56.2%, 49.3 to 55.6%, 80.0 to 88.2%, 52.6 to 65.0%, and 52.0 to 61.5%, respectively. The SD model provided satisfactory estimates of water quality at the outlet throughout both the validation and calibration periods. In addition, we conducted a sensitivity analysis to determine the key parameters of the SD model. This also involved optimization of the N and P removal capacity of FCETS, and their corresponding discharge (Q), and concentration (C) at the inlet. This made it possible to use R and MATLAB to simulate seasonal differences in the removal of N and P. Our results indicate that a FCETS can be used to efficiently remove nutrients from rural wastewater in ponds. In addition, we demonstrated that the SD-based numerical model is a useful management support tool to ensure that decisions are made which result in the stable operation of a FCETS. This illustrates that contamination-free aquaculture from rural inland ponds is a feasible goal.

Ecological response to antibiotics re-entering the aquaculture environment with possible long-term antibiotics selection based on enzyme activity in sediment

Antibiotics are frequently applied in aquaculture to control infectious diseases and promote aquaculture production. The long-term application of antibiotics can lead to antibiotic resistance within an ecosystem. Herein, we assessed the ecological responses to two antibiotics (oxytetracycline (OTC) and sulfadiazine (SD)) at three concentrations (0 mg/kg (control), 10 mg/kg, and 1000 mg/kg) re-entering the aquaculture sediments of shrimp ponds with an approximately long-term drug application history (5, 15, and more than 30 years) for 2 and 4 months. For the newly reclaimed aquaculture ponds (approximately 5 years), the re-entered OTC significantly promoted urease activity (UA) and peroxidase activity (POA), while inhibited dehydrogenase activity (DHA) and fluorescein diacetate esterase activity (FDA). Meanwhile, the re-entered SD showed promotional effects on POA and DHA, and inhibitory effects on UA and FDA. For ponds with 15 years of aquaculture history, re-entered OTC promoted POA, inhibited FDA, and changed the influencing effects of UA and DHA with exposure time. The re-entered SD showed promotional effects on UA, POA and DHA, and inhibitory effects on FDA. For long-term aquaculture ponds (more than 30 years of aquaculture history), re-entered OTC promoted POA, DHA, and FDA, while it inhibited UA. Meanwhile, SD promoted all four enzyme activities. Pearson correlation analysis indicated that the variances of enzyme responses to the re-entry of antibiotics in the three sediment environments were related with the type, concentration, and exposure time of antibiotics, as well as the sediment properties and aquaculture history. The enzyme activities in the sediment environment from newly reclaimed aquaculture ponds were more sensitive to the re-entered antibiotics, while the enzyme activities displayed a clear tolerance in the sediment environment with more than 30 years of aquaculture history. However, in the sediment environment with 15 years of aquaculture history, the response of the enzyme activities to re-entered antibiotics demonstrated time processes of antibiotic adaptation during antibiotic resistance selection. This study has illustrated the effects of re-entered antibiotics on enzyme activities in the aquaculture environment with long-term antibiotic resistance/tolerance profiles, and further establishes the possible effects on ecosystem functioning in continuous antibiotic selection pressure.

Effect of enzymatic pre-treatment on thermophilic composting of shrimp pond sludge to improve ammonia recovery

In recent years, attempts have been made to develop a thermophilic composting process for organic sludge to produce ammonia gas for high value-added algal production. However, the hydrolysis of non-dissolved organic nitrogen in sludge is a bottleneck for ammonia conversion. The aim of this study was to identify enzymes that enhance sludge hydrolysis in a thermophilic composting system for ammonia recovery from shrimp pond sludge. This was achieved by screening useful enzymes to degrade non-dissolved nitrogen and subsequently investigating their effectiveness in lab-scale composting systems. Among the four hydrolytic enzyme classes assessed (lysozyme, protease, phospholipase, and collagenase), proteases from Streptomyces griseus were the most effective at hydrolysing non-dissolved nitrogen in the sludge. After composting sludge pre-treated with proteases, the final amount of non-dissolved nitrogen was 46.2% of the total N in the control sample and 22.3% of the total N in the protease sample, thus increasing the ammonia (gaseous and in-compost) conversion efficiency from 41.5% to 56.4% of the total N. The decrease in non-dissolved nitrogen was greater in the protease sample than in the control sample during the pre-treatment period, and no difference was observed during the subsequent composting period. These results suggest that Streptomyces proteases hydrolyse the organic nitrogen fraction, which cannot be degraded by the bacterial community in the compost. Functional potential analysis of the bacterial community using PICRUSt2 suggested that 4 (EC:3.4.21.80, EC:3.4.21.81, EC:3.4.21.82, and EC:3.4.24.77) out of 13 endopeptidase genes in S. griseus were largely absent in the compost bacterial community and that they play a key role in the hydrolysis of non-dissolved nitrogen. This is the first study to identify the enzymes that enhance the hydrolysis of shrimp pond sludge and to show that the thermophilic bacterial community involved in composting has a low ability to secrete these enzymes.

Flexible and reusable carbon dot decorated natural microcline membrane: a futuristic probe for multiple heavy metal induced carcinogen detection

A flexible nano-engineered natural mineral (carbon dot doped natural microcline) based membrane (MCPV) has been developed, which can efficiently detect the presence of hexavalent chromium (Cr⁶⁺) and trivalent iron (Fe³⁺) ions in water by altering its fluorescence emission. Detailed characterization of the membrane was carried out using XRD, FT-IR spectroscopy, FESEM, TEM, and UV-Vis spectroscopy. Mechanical and temperature stabilities were also investigated. This new-generation sensor membrane is designed in such a way that it does not dissolve in water, keeping the water quality unaffected. The fluorescence studies were conducted at 414 nm and "turn-off" response was observed specifically for Fe³⁺ at 489 nm. A prominent red shift (530 nm) of the fluorescence maxima takes place when it comes to Cr⁶⁺. Figures of merit, such as LOD (8.7 μM for Cr⁶⁺ and 18.4 μM for Fe³⁺) and LOQ (29.1 μM for Cr⁶⁺ and 61.6 μM for Fe³⁺), were evaluated from the linear range (0-60 μM for Cr⁶⁺ and 0-30 μM for Fe³⁺) of the calibration curve (Stern-Volmer plots) showing high sensitivity of this sensing probe toward Cr⁶⁺ and Fe³⁺. Recovery and RSD calculations were done in various real-life water samples on intraday-interday basis to determine the accuracy of the sensor. This work validates the fact that the synthesized sensor membrane is capable of detecting these heavy metals in glutathione environment as well, which could be beneficial for early-stage carcinogen detection in living cells.

Greenhouse gases emissions from duckweed pond system treating polyester resin wastewater containing 1,4-dioxane and heavy metals

Phytoremediation of polyester resin wastewater containing 1,4-dioxane and heavy metals using Lemna gibba (L.gibba) was enhanced by incorporation of perforated polyethylene carrier materials (PCM) onto the duckweed pond (DWP) system. The DWP module was operated at a hydraulic retention times (HRTs) of 2, 4 and 6 days and as well as 1,4-dioxane loading rate of 16, 25 and 48 g/m³.d. The maximum removal efficiency of 54 ± 2.5% was achieved for 1,4-dioxane at an HRT of 6 days and loading rate of 16 g1,4-dioxane/m³.d. Similarly, the DWP system provided removal efficiencies of 28.3 ± 2.1, 93.2 ± 7.6, 95.7 ± 8.9 and 93.6 ± 4.9% for Cd²⁺, Cu²⁺, Zn²⁺ and Ni²⁺ at influent concentration of 0.037 ± 0.01, 1.2 ± 0.9, 27.2 ± 4.7 and 4.6 ± 1.2 mg/L respectively. The structural analysis by Fourier-transform infrared spectroscopy (FTIR) clearly displayed a reduction of 1,4- dioxane in the treated effluent. A strong peak was detected for L. gibba plants at frequency of 3417.71 cm^-1 due to N-H stretching, which confirm the proposed mechanism of partially conversion of 1,4-dioxane into amino acids. Glycine, serine, aspartic, threonine and alanine content were increased in L. gibba by values of 35 ± 2.2, 40 ± 3.2, 48 ± 3.7, 31 ± 2.8, and 56 ± 4.1%, respectively. The contribution of DWP unit as a greenhouse gases (GHG) emissions were relatively low (1.65 gCO₂/Kg BOD_removed.d., and 18.3 gCO₂/Kg _biomass.d) due to photosynthesis process, low excess sludge production and consumption of CO₂ for nitrification process (1.4 gCO₂/kgN _removed.d). Based on these results, it is recommended to apply such a technology for treatment of polyester resin wastewater containing 1,4-dioxane and heavy metals at a HRT not exceeding 6 days.

Spread of resistance genes from duck manure to fish intestine in simulated fish-duck pond and the promotion of cefotaxime and As

Integrated culture is a widespread culture mode in South China, in which resistance genes (RGs) also spread in the circulation system with nutrients. Accordingly, the aim of the present study was to investigate the spread of RGs in a fish-duck pond and the RGs and bacterial community of fish intestines. Five fish tanks, including a control tank and four experimental tanks (duck manure, duck manure + cefotaxime, duck manure + As, and duck manure + cefotaxime + As), were tested for 100 days. The results showed that duck manure increased both the diversity and relative abundance of RGs in fish intestines, and the addition of stress factors (cefotaxime, As) increased the relative abundance of RGs by one to two orders of magnitude. The stress-inducing effect of cefotaxime was greater than that of As. Tetracycline resistance genes were more sensitive to stress factors and were the predominant RGs in fish intestines. RGs in duck manure preferentially spread from the water to biofilm and then to fish intestines, whereas co-stress of cefotaxime and As obviously promoted the spread of RGs to fish intestines. In comparison to the control tank, duck manure and stress factors significantly changed the bacterial community of fish intestines. Correlation analysis also revealed that arsB, MOX, tetA and sul1 were significantly correlated with intI1 (P < 0.01), which hinted a potentially dissemination risk of RGs in fish intestines. These findings provide a theoretical basis for further investigating the dissemination of RGs in integrated culture systems and for evaluating the ecological risk of antibiotic and As use in aquaculture.

Effects of sunlight, microbial activity, and temperature on the declines of antibiotic lincomycin in freshwater and saline aquaculture pond waters and sediments

The residues of lincomycin (LIN), an antibiotic administered to aquatic animals, are often detected in aquatic environments. This study investigated effects of three environmental factors, sunlight, microbial activity, and temperature, on declines of spiked LIN in waters and sediment slurry samples collected from freshwater tilapia (Oreochromis mossambicus) and marine shrimp (Litopenaeus vannamei) culture ponds. The results showed that sunlight, temperature, and microbial activity all accelerated LIN transformation in the water and slurry samples. In matrixes of all water and slurry samples, LIN transformation was significantly faster under light conditions [half-life (t_1/2) = 24-53 days] than under dark conditions (t_1/2 = 154-2897 days). Microbial activity also accelerated LIN transformation; the t_1/2 of LIN was shorter after nonsterile treatment (t_1/2 = 12-809 days) than after sterile treatment (t_1/2 = 154-2897 days). Moreover, LIN transformation was faster at 28 °C (t_1/2 = 18-38 days) than at 20 and 12 °C (t_1/2 = 34 and 462 days, respectively) in both slurry samples. The results revealed that LIN transformation in aquaculture pond water and sediment was either slow or stagnant. Sunlight, microbial activity, and temperature can accelerate LIN transformation to reduce LIN residue levels.

Glassy carbon electrodes modified with reduced graphene oxide-MoS2-poly (3, 4-ethylene dioxythiophene) nanocomposites for the non-enzymatic detection of nitrite in water and milk

The detrimental effect of (NO₂^-) on environment, a sensitive and selective detection of nitrite (NO₂^-) ions with point-to-care device is need to be fabricated. Herein, we report the non-enzymatic nitrite sensor using a novel reduced graphene oxide/molybdenum disulfide/poly (3, 4-ethylene dioxythiophene) (rGO/MoS₂/PEDOT) nanocomposite electrode. The rGO/MoS₂/PEDOT nanocomposite was synthesized using facile and cost-effective hydrothermal and polymerization approaches. The characteristics of rGO-MoS₂-PEDOT nanocomposite was investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Raman, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses. The rGO-MoS₂-PEDOT nanocomposite modified glassy carbon electrode (GCE) was directly used for electrocatalytic detection of nitrite ions present in the solution. TEM images show the PEDOT nanoparticles with an average size of 100-120 nm are uniformly covered on the outer face of rGO-MoS₂ nanosheets. The interaction between the PEDOT and rGO-MoS₂ is evidenced in the FTIR, XRD and XPS studies, and they produced synergistic effect, resulting enhanced electrocatalytic performance activity towards oxidation of nitrite. Under optimized conditions, the fabricated electrode exhibited remarkably good sensitivity (874.19 μA μM^-1 cm^-2), low detection limit (LOD) (0.059 μM, S/N = 3), wide linear range (0.001-1 mM) of nitrite with desirable selectivity, long-term stability and reproducibility. Furthermore, the practical feasibility of the fabricated sensor is validated by the successful detection of nitrite ion in some water and milk samples with excellent correlation. Thus, feasible easier synthesis method was adopted first time to fabricate rGO-MoS₂-PEDOT nanocomposite nitrite sensor in the milk and water samples with enhanced selectivity, sensitivity and LOD.

Prokaryotic Diversity and Distribution in Different Habitats of an Alpine Rock Glacier-Pond System

Rock glaciers (RG) are assumed to influence the biogeochemistry of downstream ecosystems because of the high ratio of rock:water in those systems, but no studies have considered the effects of a RG inflow on the microbial ecology of sediments in a downstream pond. An alpine RG-pond system, located in the NW Italian Alps has been chosen as a model, and Bacteria and Archaea 16S rRNA genes abundance, distribution and diversity have been assessed by qPCR and Illumina sequencing, coupled with geochemical analyses on sediments collected along a distance gradient from the RG inflow. RG surface material and neighbouring soil have been included in the analysis to better elucidate relationships among different habitats.Our results showed that different habitats harboured different, well-separated microbial assemblages. Across the pond, the main variations in community composition (e.g. Thaumarchaeota and Cyanobacteria relative abundance) and porewater geochemistry (pH, DOC, TDN and NH₄⁺) were not directly linked to RG proximity, but to differences in water depth. Some microbial markers potentially linked to the presence of meltwater inputs from the RG have been recognised, although the RG seems to have a greater influence on the pond microbial communities due to its contribution in terms of sedimentary material.

Salino-alkaline lime of anthropogenic origin a reservoir of diverse microbial communities

This paper presents study on the microbiome of a unique extreme environment - saline and alkaline lime, a by-product of soda ash and table salt production in Janikowo, central Poland. High-throughput 16S rDNA amplicon sequencing was used to reveal the structure of bacterial and archaeal communities in the lime samples, taken from repository ponds differing in salinity (2.3-25.5% NaCl). Surprisingly abundant and diverse bacterial communities were discovered in this extreme environment. The most important geochemical drivers of the observed microbial diversity were salinity, calcium ions, nutrients, and water content. The bacterial and archaeal communities in saline, alkaline lime were similar to those found in natural haloalkaline environments. Although the archaeal contribution to the whole microbial community was lower than 4%, the four archaeal genera Natronomonas, Halorubrum, Halobellus, and Halapricum constituted the core microbiome of saline, alkaline lime - a set of OTUs (> 0.1% of total archaeal relative abundance) present in all samples under study. The high proportion of novel, unclassified archaeal and bacterial sequences (not identified at 97% similarity level) in the 16S rRNA gene libraries indicated that potentially new genera, especially within the class of Thermoplasmata inhabit this unique environment.

Distribution, Toxic Potential, and Influence of Land Use on Conventional and Emerging Contaminants in Urban Stormwater Pond Sediments

This study examined the distribution and toxic potential of conventional and emerging contaminants in composite sediment samples from 15 stormwater ponds in the Minneapolis-St. Paul, MN metropolitan area. Previously, coal tar-based sealants were shown to be a major source of polycyclic aromatic hydrocarbons to these ponds, and concentrations of carcinogenic benzo[a]pyrene (B[a]P) equivalents were influencing management options about pond maintenance. For the second component of this study, a complex mixture of 13 metal(loid)s, 4-nonylphenols, 8 brominated diphenyl ethers (BDEs), and total polybrominated diphenyl ethers (PBDEs) were detected in all surficial samples. Contaminants with detection frequencies ≥ 20% included: silver (46.7%), beryllium (20.0%), chloride (60.0%), bis(2-ethylhexyl)phthalate (60.0%), 10 per- and polyfluoroalkyl substances (PFASs; 26.7-80.0%), 4-nonylphenol monoethoxylate (66.7%), 4-nonylphenol diethoxylate (40.0%), bifenthrin (20.0%), total permethrins (33.3%), and 24 other BDE congener groups (20.0-93.3%). Five stormwater ponds had contaminants exceeding benchmarks likely to be associated with harmful effects to benthic organisms. Ponds with watersheds dominated by either commercial and/or industrial land uses had significantly higher (p < 0.05) concentrations of zinc, 4-nonylphenol, six BDEs (28 + 33, 47, 99, 100, 154, and 209), and total PBDEs than those dominated by residential land uses. Multivariate statistical analyses verified that updated B[a]P equivalents were an effective chemical proxy for making management decisions about excavated pond sediment. Jurisdictions that do not test their stormwater pond sediments prior to maintenance dredging should consider the environmental ramifications of applying this potentially contaminated material to land.

Effects of conversion of mangroves into gei wai ponds on accumulation, speciation and risk of heavy metals in intertidal sediments

Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] - [AVS])/f_oc, and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

Hydraulic conditions affect pollutant removal efficiency in distributed ditches and ponds in agricultural landscapes

Distributed ditches and ponds in agricultural landscapes can retain agricultural pollutants (such as nutrients and pesticides) like wetlands while facilitating crop field drainage. Their complex hydraulic conditions affect pollutant transport and degradation processes, but the existing lump-sum method for estimating pollutant removal treats the total area simply as one unit without considering their specific hydraulic conditions (HCs). In this paper we proposed an analytical method for evaluating pollutant removal efficiencies of distributed ditches and ponds by considering their different HCs explicitly. A realization factor (RF) was used to compare pollutant removal rates with and without considering specific HCs. Application of the method was demonstrated with a case study based on field investigations in an intensively farmed area in southeastern China. The total area of ditches and ponds accounts for 15% of drained crop fields; and the calculated RFs were 0.70-0.84% for various removal rate constants. The difference was mainly caused by the uneven distribution of ditches and ponds along different drainage paths. For pollutants with small values of removal rate constants, the calculated concentration reductions along different flow paths were proportional to their wetland sizes, making the pollutant removal as area limited. For pollutants with larger values of removal rate constant, however, the calculated pollutant removal became concentration limited when the wetland to farmland area ratio was high. Large ponds and ditches were major contributors (85-94%) of pollutant removal in the whole system, while the field ditches contributed to less than 10% of the total removal due to their small dimension and shallow water depth. The distributed nature of ditches and ponds poses some inherent limitations to their water quality functions due to variable hydraulic conditions; understanding such underlying constraints may help guide proper evaluation and conservation of the existing ditches and ponds in agricultural landscapes.

Trace elements and microbiological parameters in farmed Nile tilapia with emphasis on muscle, water, sediment and feed

Fish may bioaccumulate contaminants from the aquatic environment and extend them to the food chain provoking risks to human health. This study evaluated the microbiological parameters of the pond´s water and trace elements concentrations in samples of water, sediment, feed and muscle of farmed Nile tilapia used for human consumption in southern Brazil. A total of 240 fish were collected from 12 tilapia farms. Sediment, tank water and dry ration used in the animals' diet were collected for analysis. Analysis were performed by Energy Dispersion X-ray Fluorescence (EDXRF), Inductively Coupled Plasma Mass Spectrometer (ICP-MS), Induced Coupled Plasma Optical Emission Spectrometer (ICP-OES), and Atomic Absorption Spectrometer (AAS-VGA). In addition, the microbiological analysis of the water was carried out. The concentrations of Se, I, Fe, Cu and Zn in fish muscle were higher than the recommended by the Brazilian legislation, considering the advised daily intake for adults. The arsenic element had concentrations above the limit stipulated by the present Brazilian legislation, observed in all samples of muscle, sediment and tank water highlighting a possible environmental and fish contamination by the toxic element. Moreover, the arsenic concentration in the water presented a positive correlation (ρ = 0.33) with arsenic in the muscle, suggesting that tilapia is a good environmental bioindicator, once they properly reflect the levels of arsenic in the water. It is suggested to perform an arsenic speciation for quantification of the inorganic form and accurate assessment of the degree of toxicity in the muscle samples and risks it can bring to human health. Regarding the other potentially toxic elements (Hg, Pb and Cd), and microbiological analysis of water it was verified that the consumption of the fish in question does not raise risks, since the values are within a quality benchmark established by law. The concentration of total and fecal coliforms in pond´s water in the facilities was in agreement with the microbiological indexes required by the legislation of CONAMA class II. Western region presented the lowest concentrations of fecal coliforms when compared to the other regions. There was no significant difference in the microbiological counts of total heterotrophic bacteria, Vibrio spp. and Pseudomonas spp. among the regions.

Monitoring the morphological integrity of neotropical anurans

Amphibians are considered to be excellent bioindicators to their morphophysiological characteristics and life cycle. In this context, the present study investigated the morphological integrity of anuran larvae collected in preserved environments in the Emas National Park, in the municipality of Mineiros (Goiás state, Brazil), and in environments representative of the agricultural matrix of the Rio Verde region, also in Goiás, where there is a long history of the use of agricultural pesticides. Samples of water from temporary ponds, permanent dams, and veredas were analyzed for the presence of pesticides and, especially atrazine (5350 μg/L), found at significantly higher concentrations in the agricultural matrix. We observed a high percentage (approximately 10%) of morphological malformations including alterations of the fins in Boana albopunctatus and Scinax fuscovarius; alteration in oral structures in B. albopunctatus, Dematonotus muelleri, Physalaemus centralis, Physalaemus cuvieri, and Leptodactylus fuscus mainly in the tadpoles collected in the agricultural environment in comparison with those from the protected area (3.5%; P < 0.0001, χ² 31.75). However, changes in the eyes, mouth, intestines, and nostrils, as well as amelia were observed only in the agricultural environment. The vast majority of the observed malformations were associated with the tail and oral disc, which suggests that these anatomical parameters may be used as sensitive morphological biomarkers. Given these findings, we reinforce that areas of agricultural land may have a deleterious effect on the morphological integrity of the tadpoles and consequently, on their development, and that these features may be used as indicators of environmental quality and health.

Unexpected consequences of bombing. Community level response of epiphytic diatoms to environmental stress in a saline bomb crater pond area

The spatial response of epiphytic diatom communities to environmental stress was studied in a moderately saline wetland area located in the plain of Danube-Tisza Interfluve, Hungary. The area is characterised by World War II bomb crater ponds and can be regarded as an excellent ecological model system where the dispersion of species is slightly limited by distance. To study the effect of environmental variables on the communities, canonical correspondence analysis was applied. Salinity, pH, total suspended solids, total phosphorous and depth proved to be significant environmental drivers in this analysis. The ecological status of the ponds was assessed with Ziemann’s halobity index, as the trophity-depending metric cannot be applied to these habitats (due to the naturally high phosphorus content). Ponds in “good” ecological status significantly differed from those appertaining to water quality category of “not-good” ecological status considering characteristic of natural astatic soda pans (e.g. salinity, pH, ammonium, total phosphorous concentration, nitrogen:phosphorous ratio and turbidity). The differences between epiphytic diatom communities inhabiting the ponds were detected using non-parametric multidimensional scaling. The samples formed three groups according to the types of ponds (“transparent”, “transitional” and “turbid”) based on the width of the macrophyte belt around them. Indicator species related to the ecological status of the ponds and diatom communities contributing to the separation of groups of ponds were identified. One of the indicator species differed from species already described. Light and scanning electron microscopy features and phylogenetic analyses based on three genes (18S and 28S rRNA genes, rbcL) proved that it was a new species of Nitzschia genus, closely related to Nitzschia frustulum and Nitzschia inconspicua. Therefore, description of a new species, Nitzschia reskoi Ács, Duleba, C.E.Wetzel & Ector is proposed. We concluded that the increasing abundance of Nitzschia reskoi was a signal of the degradation of the intermittent saline wetlands.

Optimization process of organic matter removal from wastewater by using Eichhornia crassipes

This study aimed to determine the optimal conditions for organic matter removal from wastewater by Eichhornia crassipes (E.C). As a matter of fact, a complete factorial design was used to determine the effect of residence time (X₁), plant density (X₂) and initial chemical oxygen demand (COD) concentration (X₃) on the phytoremediation process. The process's performance was measured on COD (Y₁), NH₄⁺ (Y₂) and PO₄^3- (Y₃), with the results indicating a reduction of 8.59-81.71% of COD (Y₁); 22.53-95.81% of NH₄⁺ (Y₂) and 0.54-99.35% of PO₄^3- (Y₃). Then, the first-order models obtained for COD, NH₄⁺ and PO₄^3- removal were validated using different statistical approaches such as statistical and experimental validation. Moreover, multi-response optimization was carried out through different scenarios. On the whole, the results obtained indicated that two serial ponds are required for an optimum organic matter removal by Eichhornia crassipes. Indeed, for the first pond, a residence time of 15 days is needed with a plant density of 60 ft/m² and an initial concentration of about 944 mg/L. The second was the same residence time as the first with similar plant density of 60 ft/m² and an initial load 192 mg/L (> 200 mg/L). Optimal organic matter removal from wastewater using Eichhornia crassipes requires two ponds arranged in chain.

Occurrence and distribution of antibiotics in surface water impacted by crab culturing: a case study of Lake Guchenghu, China

The objective of this study was to evaluate the occurrence, distribution, potential sources, and ecological risk of antibiotics in aqueous phase of Lake Guchenghu, China. Target antibiotics in surface water of Lake Guchenghu, adjacent streams, and crab ponds were detected seasonally. The results showed that erythromycin-H₂O (1.60-2450 ng/L), sulfadiazine (ND-654 ng/L), and florfenicol (ND-919 ng/L) were the predominant antibiotics in Lake Guchenghu. The concentrations of antibiotics in Lake Guchenghu Basin showed obvious seasonal variation, with the highest concentration in summer. In general, the concentrations of antibiotics in crab ponds and streams were higher than those in the lake and spatial distributions of antibiotics were affected by pollution sources. The types and origins of antibiotics indicated that wastewater from ponds was the main source of antibiotics in the lake. Risk assessment suggested that as individual compound, erythromycin-H₂O and clarithromycin posed a high risk to algae while other compounds might pose low or no risk. The mixture of antibiotics may pose a high risk to aquatic organisms in Lake Guchenghu. Overall, our study revealed the occurrence and spatiotemporal variation of antibiotics in Lake Guchenghu, which was related with crab culturing.

Rapid Analysis of Illegal Cationic Dyes in Foods and Surface Waters Using High Temperature Direct Analysis in Real Time High-Resolution Mass Spectrometry

A high temperature desorption (HTD) direct analysis in real time-high-resolution mass spectrometric (DART-HRMS) method was developed for the rapid analysis of four banned cationic dyes. Rhodamine B is used to dye foods, while malachite green, crystal violet, and methylene blue are added to fishponds as antimicrobials. A simple induced phase separation extraction was used to pretreat samples. The DART-HRMS method employed two temperature steps, i.e., 200 °C for drying, purification, and enrichment of sample solution and 500 °C for thermal desorption and ionization of analytes. The calibration curves of dyes in the range of 50-2000 ng/mL were linear using deuterated malachite green as an internal standard. The LODs vary for all analytes between 0.1 and 30 ppb depending on the matrix and experimental conditions. Through analyses of real samples, two chili powders and one chili oil were found to be contaminated by rhodamine B. The concentrations were comparable with those found by an HPLC-MS/MS method.

A Novel Adaptation Mechanism Underpinning Algal Colonization of a Nuclear Fuel Storage Pond

Geochemical analyses alongside molecular techniques were used to characterize the microbial ecology and biogeochemistry of an outdoor spent nuclear fuel storage pond at Sellafield, United Kingdom, that is susceptible to seasonal algal blooms that cause plant downtime. 18S rRNA gene profiling of the filtered biomass samples showed the increasing dominance of a species closely related to the alga Haematococcus pluvialis, alongside 16S rRNA genes affiliated with a diversity of freshwater bacteria, including Proteobacteria and Cyanobacteria High retention of 137Cs and 90Sr on pond water filters coincided with high levels of microbial biomass in the pond, suggesting that microbial colonization may have an important control on radionuclide fate in the pond. To interpret the unexpected dominance of Haematococcus species during bloom events in this extreme environment, the physiological response of H. pluvialis to environmentally relevant ionizing radiation doses was assessed. Irradiated laboratory cultures produced significant quantities of the antioxidant astaxanthin, consistent with pigmentation observed in pond samples. Fourier transform infrared (FT-IR) spectroscopy suggested that radiation did not have a widespread impact on the metabolic fingerprint of H. pluvialis in laboratory experiments, despite the 80-Gy dose. This study suggests that the production of astaxanthin-rich encysted cells may be related to the preservation of the Haematococcus phenotype, potentially allowing it to survive oxidative stress arising from radiation doses associated with the spent nuclear fuel. The oligotrophic and radiologically extreme conditions in this environment do not prevent extensive colonization by microbial communities, which play a defining role in controlling the biogeochemical fate of major radioactive species present.IMPORTANCE Spent nuclear fuel is stored underwater in large ponds prior to processing and disposal. Such environments are intensively radioactive but can be colonized by microorganisms. Colonization of such inhospitable radioactive ponds is surprising, and the survival mechanisms that microbes use is of fundamental interest. It is also important to study these unusual ecosystems, as microbes growing in the pond waters may accumulate radionuclides present in the waters (for bioremediation applications), while high cell loads can hamper management of the ponds due to poor visibility. In this study, an outdoor pond at the U.K. Sellafield facility was colonized by a seasonal bloom of microorganisms, able to accumulate high levels of 137Cs and 90Sr and dominated by the alga Haematococcus This organism is not normally associated with deep water bodies, but it can adapt to radioactive environments via the production of the pigment astaxanthin, which protects the cells from radiation damage.

Metagenomic analysis revealed the prevalence of antibiotic resistance genes in the gut and living environment of freshwater shrimp

Antibiotic resistance disseminating from animals and their environments is a public issue that poses significant threats to human health. In the present study, the diversity and abundance of antibiotic resistance genes (ARGs) in 15 samples from the guts and related aquaculture environments (water and sediment) of shrimp were investigated. In total, 60 ARGs, 102 ARGs and 67 ARGs primarily belonging to 13, 15 and 15 different types were detected in the shrimp gut, pond water and sediment samples, respectively. Efflux pump and target modification were the predominant resistance mechanisms in all samples. It was found that Aeromonas, Yersinia and Clostridium XlVb were significantly correlated with the distribution of the ARGs. Besides, the relative abundance of ARGs was positively correlated with the levels of mobile genetic elements (MGEs). Moreover, variation partitioning analysis showed that MGEs, contributing to 74.46% of the resistome variation, played an important role in the affecting of the antibiotic resistome than the bacterial communities and their joint effects. Collectively, this study provides comprehensive information to better understand the ARG dissemination in aquaculture environments and to improve the ecological management of aquatic ecosystems.

Seasonal variation of heavy metals in water, sediment, and highly consumed cultured fish (Labeo rohita and Labeo bata) and potential health risk assessment in aquaculture pond of the coal city, Dhanbad (India)

The extent of heavy metal pollution and their impact on the various component of urban aquaculture pond (India) were investigated on the basis of seasonal variation. The water, sediment, and fish samples (Labeo rohita and Labeo bata) were collected and analyzed to assess the metal toxicity. In the sediment, geoaccumulation index (I_geo), contamination factor (CF), pollution load index (PLI), and ecological risk index (ERI) were calculated. The estimated daily dietary intake (EDI) for As, Cd, Cr, Mn, Pb, and Zn was estimated in adult and children on the basis an average amount of fish consumed by the Indian people and its associated health hazard with was also assessed in terms of target hazard quotients (THQs). The concentration of metals in all the analyzed samples was found higher during pre-monsoon season. While, in case of fish, L. bata species has higher metal accumulation rate during both the seasons than the L. rohita because of their bottom dweller feeding habit. The order of metals in L. bata muscles is Zn > Mn > Pb > Cr > As > Cd. The I_geo value for Zn (2.66 to 3.68) was found to be highest and followed by Cd (1.65 to 3.52) and Pb (1.52 to 2.55) indicating moderate to highly polluted sediment quality. The values of ERI were significantly high during pre-monsoon period and varied from 319 to 557, representing very high metal contamination. From the human health perspective, present study highlighted that the local inhabitants who rely on this valuable pond for fish consumption are exposed chronically to As and Pb pollution due to higher THQ values, especially from the intake of L. bata.

Consumption of water from ex-mining ponds in Klang Valley and Melaka, Malaysia: A health risk study

Evaluation of health risks due to heavy metals exposure via drinking water from ex-mining ponds in Klang Valley and Melaka has been conducted. Measurements of As, Cd, Pb, Mn, Fe, Na, Mg, Ca, and dissolved oxygen, pH, electrical conductivity, total dissolved solid, ammoniacal nitrogen, total suspended solid, biological oxygen demand were collected from 12 ex-mining ponds and 9 non-ex-mining lakes. Exploratory analysis identified As, Cd, and Pb as the most representative water quality parameters in the studied areas. The metal exposures were simulated using Monte Carlo methods and the associated health risks were estimated at 95th and 99th percentile. The results revealed that As was the major risk factor which might have originated from the previous mining activity. For Klang Valley, adults that ingested water from those ponds are at both non-carcinogenic and carcinogenic risks, while children are vulnerable to non-carcinogenic risk; for Melaka, only children are vulnerable to As complications. However, dermal exposure showed no potential health consequences on both adult and children groups.

Tissue distribution, bioaccumulation characteristics and health risk of antibiotics in cultured fish from a typical aquaculture area

The negative impacts of residual antibiotics in the environment on ecosystem and human health are big concerns. However, little information is available on the antibiotic bioaccumulation in aquaculture farms. In this study, the bioaccumulative potentials of 21 antibiotics in the plasma, bile, liver and muscle of cultured fish from a typical aquaculture area were systematically investigated.

RESULTS

indicated that antibiotic distribution in the cultured fish was mainly influenced by species and specific substances. The mean values of log bioaccumulation factors (Log BAFs) for the detected antibiotics were in the range of 0.43-3.70, 0.36-4.75, -0.31-4.48, and 0.23-4.33 in the fish plasma, bile, liver and muscle tissues, respectively. For grass carp, both ciprofloxacin and enrofloxacin showed high transportability from the plasma to the muscle and liver. The correlations of various antibiotic concentrations between the plasma and the other three tissues indicated that the concentrations of ciprofloxacin and enrofloxacin in the fish tissues could be predicted by their concentrations in the plasma. Based on the calculated hazard quotients, human health risk evaluation of antibiotic exposure by fish consumption indicated that the consumption of these cultured fish posed low risks to human health.

Seasonal variation in environmental DNA detection in sediment and water samples

The use of aquatic environmental DNA (eDNA) to detect the presence of species depends on the seasonal activity of the species in the sampled habitat. eDNA may persist in sediments for longer than it does in water, and analysing sediment could potentially extend the seasonal window for species assessment. Using the great crested newt as a model, we compare how detection probability changes across the seasons in eDNA samples collected from both pond water and pond sediments. Detection of both aquatic and sedimentary eDNA varied through the year, peaking in the summer (July), with its lowest point in the winter (January): in all seasons, detection probability of eDNA from water exceeded that from sediment. Detection probability of eDNA also varied between study areas, and according to great crested newt habitat suitability and sediment type. As aquatic and sedimentary eDNA show the same seasonal fluctuations, the patterns observed in both sample types likely reflect current or recent presence of the target species. However, given the low detection probabilities found in the autumn and winter we would not recommend using either aquatic or sedimentary eDNA for year-round sampling without further refinement and testing of the methods.

Effects of iron and calcium carbonate on contaminant removal efficiencies and microbial communities in integrated wastewater treatment systems

In the paper, we explored the influences of different dosages of iron and calcium carbonate on contaminant removal efficiencies and microbial communities in algal ponds combined with constructed wetlands. After 1-year operation of treatment systems, based on the high-throughput pyrosequencing analysis of microbial communities, the optimal operating conditions were obtained as follows: the ACW10 system with Fe³⁺ (5.6 mg L^-1), iron powder (2.8 mg L^-1), and CaCO₃ powder (0.2 mg L^-1) in influent as the adjusting agents, initial phosphorus source (PO₄^3-) in influent, the ratio of nitrogen to phosphorus (N/P) of 30 in influent, and hydraulic retention time (HRT) of 1 day. Total nitrogen (TN) removal efficiency and total phosphorus (TP) removal efficiency were improved significantly. The hydrolysis of CaCO₃ promoted the physicochemical precipitation in contaminant removal. Meanwhile, Fe³⁺ and iron powder produced Fe²⁺, which improved contaminant removal. Iron ion improved the diversity, distribution, and metabolic functions of microbial communities in integrated treatment systems. In the treatment ACW10, the dominant phylum in the microbial community was PLANCTOMYCETES, which positively promoted nitrogen removal. After 5 consecutive treatments in ACW10, contaminant removal efficiencies for TN and TP respectively reached 80.6% and 57.3% and total iron concentration in effluent was 0.042 mg L^-1.

Homogeneous and selective detection of cadmium ions by forming fluorescent cadmium-protein nanoclusters

We synthesized fluorescent Cd nanoclusters (CdNCs) through a protein-directed method, and the synthesis method was utilized for a homogeneous, ultrasensitive, and selective detection of cadmium ion (Cd²⁺). CdNCs were synthesized using a modified protein-directed method for developing a rapid Cd²⁺ detection system. For rapid Cd²⁺ detection, the reaction time was reduced by optimizing the reaction conditions such as temperature, reducing agent concentration, and protein concentration. The synthesized CdNCs had ca. 2 nm diameter and showed strong fluorescence at 485 nm under 365 nm UV light. The fluorescence of the CdNCs increased with increasing Cd²⁺ concentrations, and the limit of detection in deionized water was 15.68 fM. This method enables the detection of Cd²⁺ through the Cd concentration-dependent formation of fluorescent CdNCs in tap, fountain, and pond water samples with detection limits of 0.75, 7.65, and 48.2 fM, respectively. The sensitivity and specificity of our method are comparable to those of several existing methods for Cd²⁺ detection. Furthermore, the system enables the homogeneous detection of Cd²⁺ without separation and washing, thereby broadening its application in analytical chemistry.

Insight into the risk of replenishing urban landscape ponds with reclaimed wastewater

Increasing use of reclaimed wastewater (RW) for replenishing urban landscape ponds has aroused public concern about the water quality. Three ponds replenished with RW in three cities in China were chosen to investigate 22 indexes of water quality in five categories. This was achieved by comparing three pairs of ponds in the three different cities, where one pond in each pair was replenished with RW and the other with surface water (SW). The nutrients condition, heavy metal concentration and ecotoxicity did not differ significantly between RW- and SW-replenished ponds. By contrast, significant differences were observed in algal growth and pathogen risk. RW ponds presented a Cyanophyta-Chlorophyta-Bacillariophyta type with high algal diversity while SW ponds presented a Cyanophyta type with low diversity. Regrowth of bacterial pathogens and especially survival of viral pathogens in RW, was the main driver behind the higher risk for RW ponds compared with SW ones. The duration of RW replenishment was proved to have a marked impact on the algal growth and pathogen risk. With continued RW replenishment, non-dominant algal species subjected to decrease while dominant species were enhanced resulting in the biomass increasing but diversity declining, and the risk posed by viral pathogens might become greater.

Effects of portable solar water quality control machines on aquaculture ponds

The effects of a portable solar water quality control machine (PSWM) on water quality and sediment of aquaculture ponds were studied in bream aquaculture ponds in Shanghai, China. PSWM operation reduced the temperature and dissolved oxygen (DO) differences between upper and lower water levels. Concentrations of NH₄⁺-N, NO₂^--N, TN, TP, COD and TSS increased rapidly and reached maximums at 12 h. The density and biomass of phytoplankton and levels of chlorophyll a reached maximums after 40 h of PSWM operation. In a 165-day study, the mean concentrations of NH₄⁺-N, NO₂^--N and the available phosphorous (AP) in the PSWM ponds were significantly lower than in the control ponds, but the TP was significantly greater than the control ponds. Compared with the test began, the thickness of the sediment in PSWM ponds declined by 12.4 ± 4.3 cm, the control ponds increased by 5.0 ± 2.3 cm and the TN and AP levels in sediment significantly declined. PSWM treatment increased the production of bream and silver carp by 30 and 25%, respectively, and the feed coefficient was reduced by 24.2%. Use of PSWM in bream aquaculture ponds improved water quality, reduced sediment, reduced aquaculture pollution emissions and increased production.

Use of macroinvertebrate assemblages for assessing performance of stabilization ponds treating effluents from sugarcane and molasses processing

Wastewater discharge from sugarcane processing is a significant pollutant of tropical aquatic ecosystems. For most developing countries, monitoring of the level of pollutants is done mostly through chemical analysis, but this does not reflect potential impacts on aquatic assemblages. In addition, laboratory facilities for accurate concentration measurements are often not available for regular monitoring programs. In this study, we investigated the use of benthic macroinvertebrates for biological monitoring in western Kenya. Benthic macroinvertebrates were sampled in stabilization ponds treating wastewater from sugarcane- and molasses-based processing plants to assess their composition and abundance in relation to different concentrations of chemical variables. Optimum concentrations and tolerance values were identified for various taxa, and a biotic index was developed that combined tolerance values (ranked between 0 and 10) for the various macroinvertebrate taxa. A succession in composition and distribution of macroinvertebrate taxa was observed from the inlet to the outlet of the pond systems. Diptera dominated in the first ponds that had high concentrations of chemical oxygen demand (COD), biological oxygen demand (BOD₅), and nutrients, while intolerant Ephemeroptera, Plecoptera, and Trichoptera (EPT) appeared as the concentrations dropped in subsequent ponds. The effluent quality was classified as "good," "fair," and "poor," corresponding with biotic index value ranges 0-3.50, 3.51-6.50, and 6.51-10, respectively. During validation, the index grouped sites with respect to levels of measured environmental variables. The study revealed that the developed biotic index would help in monitoring the quality of sugarcane processing and molasses effluents before release into recipient aquatic ecosystems, replacing the need for costly chemical analyses.

Antibiotic resistance genes (ARGs) in duck and fish production ponds with integrated or non-integrated mode

Antibiotic resistance genes (ARGs) are emerging micropollutants with environmental persistence. Aquaculture environments are considered as potential reservoirs for ARGs pollution and horizontal gene transfer (HGT). This study analyzed water and sediment from eight culture ponds (integrated culture: duck-fish pond; monoculture: duck pond and fish pond) and a control pond (without any aquaculture activity) in Zhongshan, South China. Seventeen types of ARGs were detected in all ponds, which conferring resistance to four classes of antibiotics including tetracycline (tetA, tetB, tetC, tetE, tetG, tetL, tetA-P, tetM, tetO, tetS, tetW and tetX), AmpC beta-lactamase products (EBC and FOX), sulfonamide (sul1 and sul2) and erythromycin (ermA), with class 1 integron (intI1) as motility gene. The total concentrations of detected ARGs in culture pond water were much higher than control (about 1.6-4.0 times). Integrated culture showed lowest absolute abundance of ∑ARGs in water (3.686 × 10⁷ copies mL^-1) and the highest in sediment (4.574 × 10⁸ copies g^-1). Monoculture ponds showed higher relative abundance of ∑ARGs both in water (fish pond: 0.5149) and sediment (duck pond: 0.4919). As the main contributor to the ARGs abundance and significant correlations with ∑tet, ∑ARGs and intI1 (P < 0.01), tetA was suggested to be a potential indicator for the abundance of tetracycline resistance genes in these classes of aquaculture modes in the Pearl River Delta. This study provides a case for the ARGs abundance in aquaculture and as a reference for the upcoming health risk assessment in aquatic environment.

Embryonic exposure to model naphthenic acids delays growth and hatching in the pond snail Lymnaea stagnalis

Naphthenic acids (NAs), a class of structurally diverse carboxylic acids with often complex ring structures and large aliphatic tail groups, are important by-products of many petrochemical processes including the oil sands mining activity of Northern Alberta. While it is evident that NAs have both acute and chronic harmful effects on many organisms, many aspects of their toxicity remain to be clarified. Particularly, while substantive data sets have been collected on NA toxicity in aquatic prokaryote and vertebrate model systems, to date, nothing is known about the toxic effects of these compounds on the embryonic development of aquatic invertebrate taxa, including freshwater mollusks. This study examines under laboratory conditions the toxicity of NAs extracted from oil sands process water (OSPW) and the low-molecular weight model NAs cyclohexylsuccinic acid (CHSA), cyclohexanebutyric acid (CHBA), and 4-tert-butylcyclohexane carboxylic acid (4-TBCA) on embryonic development of the snail Lymnaea stagnalis, a common freshwater gastropod with a broad Palearctic distribution. Evidence is provided for concentration-dependent teratogenic effects of both OSPW-derived and model NAs with remarkably similar nominal threshold concentrations between 15 and 20 mg/L and 28d EC₅₀ of 31 mg/L. In addition, the data provide evidence for substantial toxicokinetic differences between CHSA, CHBA and 4-TBCA. Together, our study introduces Lymnaea stagnalis embryonic development as an effective model to assay NA-toxicity and identifies molecular architecture as a potentially important toxicokinetic parameter in the toxicity of low-molecular weight NA in embryonic development of aquatic gastropods.

Comparison of gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry with electron ionization for determination of N-nitrosamines in environmental water

N-nitrosamines are trace organic contaminants of environmental concern when present in groundwater and river water due to their potent carcinogenicity. Therefore, N-nitrosamine analysis is increasingly in demand. Gas chromatography-mass spectrometry (GC-MS) and GC-tandem mass spectrometry (GC-MS/MS), both with electron ionization (EI), were compared for analysis of nine N-nitrosamines extracted from environmental water matrices. A total of 20 fishpond water, river water, and groundwater samples from Sihui and Shunde, China were collected for a survey of N-nitrosamine concentrations in real water samples. Various solid-phase extraction (SPE) conditions and GC conditions were first examined for the pre-concentration and separation steps. The analysis of N-nitrosamines in environmental waters demonstrated that their quantification with GC-MS poses a challenge due to the occurrence of co-eluting interferences. Conversely, the use of GC-MS/MS increased selectivity because of the fragmentation generated from precursor ions in the 'multiple reaction monitoring' (MRM) mode, which is expected to extract target analytes from the environmental water matrix. Thus, the high performance of GC-MS/MS with EI was used to quantify nine N-nitrosamines in environmental waters with detection limits of 1.1-3.1 ng L^-1. N-nitrosodimethylamine (NDMA) concentrations were in the range of N.D. to 258 ng L^-1. Furthermore, other N-nitrosamines, except N-nitrosomethylethylamine (NMEA), N-nitroso-di-n-propylamine (NDPA) and N-nitrosopiperidine (NPIP), were also detected. Our findings suggest that GC-MS/MS with EI would be widely applicable in identifying N-nitrosamines in environmental waters and can be used for routine monitoring of these chemicals.

Assessing spatial and temporal variability of acid-extractable organics in oil sands process-affected waters

The acid-extractable organic compounds (AEOs), including naphthenic acids (NAs), present within oil sands process-affected water (OSPW) receive great attention due to their known toxicity. While recent progress in advanced separation and analytical methodologies for AEOs has improved our understanding of the composition of these mixtures, little is known regarding any variability (i.e., spatial, temporal) inherent within, or between, tailings ponds. In this study, 5 samples were collected from the same location of one tailings pond over a 2-week period. In addition, 5 samples were collected simultaneously from different locations within a tailings pond from a different mine site, as well as its associated recycling pond. In both cases, the AEOs were analyzed using SFS, ESI-MS, HRMS, GC×GC-ToF/MS, and GC- & LC-QToF/MS (GC analyses following conversion to methyl esters). Principal component analysis of HRMS data was able to distinguish the ponds from each other, while data from GC×GC-ToF/MS, and LC- and GC-QToF/MS were used to differentiate samples from within the temporal and spatial sample sets, with the greater variability associated with the latter. Spatial differences could be attributed to pond dynamics, including differences in inputs of tailings and surface run-off. Application of novel chemometric data analyses of unknown compounds detected by LC- and GC-QToF/MS allowed further differentiation of samples both within and between data sets, providing an innovative approach for future fingerprinting studies.

Invertebrates in stormwater wet detention ponds - Sediment accumulation and bioaccumulation of heavy metals have no effect on biodiversity and community structure

The invertebrate diversity in nine stormwater wet detention ponds (SWDP) was compared with the diversity in eleven small shallow lakes in the western part of Denmark. The SWDPs and lakes were chosen to reflect as large a gradient of pollutant loads and urbanization as possible. The invertebrates as well as the bottom sediments of the ponds and shallow lakes were analyzed for copper, iron, zinc, cadmium, chromium, lead, aluminum, nickel, arsenic and the potentially limiting nutrient, phosphorus. The Principal Component Analysis showed that invertebrates in SWDPs and lakes differed with respect to bioaccumulation of these elements, as did the sediments, albeit to a lesser degree. However, the Detrended Correspondence Analysis and the TWINSPAN showed that the invertebrate populations of the ponds and lakes could not be distinguished, with the possible exception of highway ponds presenting a distinct sub-group of wet detention ponds. The SWDPs and shallow lakes studied seemed to constitute aquatic ecosystems of similar taxon richness and composition as did the 11 small and shallow lakes. This indicates that SWDPs, originally constructed for treatment and flood protection purposes, become aquatic environments which play a local role for biodiversity similar to that of natural small and shallow lakes.

PAH related effects on fish in sedimentation ponds for road runoff and potential transfer of PAHs from sediment to biota

Road runoff is an important source of pollution to the aquatic environment, and sedimentation ponds have been installed to mitigate effects on the aquatic environment. The purpose of this study was to investigate if a) fish from sedimentation ponds were affected by road pollution and; b) the transfer of PAHs from road runoff material to aquatic organisms was substantial. Minnow from a sedimentation pond (Skullerud) near Oslo (Norway) had higher levels of CYP1A enzyme and DNA stand breaks than minnow from the nearby river, but high concentrations of PAH-metabolites in bile revealed that both populations were highly exposed. Principal component analysis revealed that CYP1A and age of fish were correlated, while levels of PAH-metabolites were not correlated to CYP1A or DNA damage. Minnow from a lake un-affected by traffic had much lower levels of PAH-metabolites than the exposed fish, and also an improved condition. The latter results indicate that fish health was affected by road runoff. A closer investigation of PAH levels of the ecosystems of two sedimentation ponds (Skullerud and Vassum) and nearby environments were conducted. The concentration of the 16 EPA PAHs in sediments of the sedimentation ponds were high (1900-4200ngg(-1)), and even higher levels were observed in plants. Principal component analysis of selected ion chromatograms of PAHs showed a clear separation of plants vs. sediments. The plants preferentially accumulated the high molecular PAHs, both from sedimentation ponds with a petrogenic PAH isomer ratio in sediments; and from a lake with pyrogenic PAH isomer ratio in sediments.

Laboratory and field validation of a simple method for detecting four species of non-native freshwater fish using eDNA

This paper presents the first phase in the development and validation of a simple and reliable environmental (e)DNA method using conventional PCR to detect four species of non-native freshwater fish: pumpkinseed Lepomis gibbosus, sunbleak Leucaspius delineatus, fathead minnow Pimephales promelas and topmouth gudgeon Pseudorasbora parva. The efficacy of the approach was demonstrated in indoor tank (44 l) trials in which all four species were detected within 24 h. Validation was through two field trials, in which L. gibbosus was detected 6-12 h after its introduction into outdoor experimental ponds and P. parva was successfully detected in disused fish rearing ponds where the species was known to exist. Thus, the filtration of small (30 ml) volumes of pond water was sufficient to capture fish eDNA and the approach emphasised the importance of taking multiple water samples of sufficient spatial coverage for detecting species of random or patchy distribution.

Biospectroscopy reveals the effect of varying water quality on tadpole tissues of the common frog (Rana temporaria)

Amphibians are undergoing large population declines in many regions around the world. As environmental pollution from both agricultural and urban sources has been implicated in such declines, there is a need for a biomonitoring approach to study potential impacts on this vulnerable class of organism. This study assessed the use of infrared (IR) spectroscopy as a tool to detect changes in several tissues (liver, muscle, kidney, heart and skin) of late-stage common frog (Rana temporaria) tadpoles collected from ponds with differing water quality. Small differences in spectral signatures were revealed between a rural agricultural pond and an urban pond receiving wastewater and landfill run-off; these were limited to the liver and heart, although large differences in body size were apparent, surprisingly with tadpoles from the urban site larger than those from the rural site. Large differences in liver spectra were found between tadpoles from the pesticide and nutrient impacted pond compared to the rural agricultural pond, particularly in regions associated with lipids. Liver mass and hepatosomatic indices were found to be significantly increased in tadpoles from the site impacted by pesticides and trace organic chemicals, suggestive of exposure to environmental contamination. Significant alterations were also found in muscle tissue between tadpoles from these two ponds in regions associated with glycogen, potentially indicative of a stress response. This study highlights the use of IR spectroscopy, a low-cost, rapid and reagent-free technique in the biomonitoring of a class of organisms susceptible to environmental degradation.

Agricultural runoff pollution control by a grassed swales coupled with wetland detention ponds system: a case study in Taihu Basin, China

The performance of a field grassed swales (GSs) coupled with wetland detention ponds (WDPs) system was monitored under four typical rainfall events to assess its effectiveness on agricultural runoff pollution control in Taihu Basin, China. The results indicated that suspended solids (SS) derived from the flush process has significant influence on pollution loads in agricultural runoff. Determination of first flush effect (FFE) indicated that total suspended solids (TSS) and total phosphorus (TP) exhibited moderate FFE, while chemical oxygen demand (COD) and total nitrogen (TN) showed weak FFE. Average removal efficiencies of 83.5 ± 4.5, 65.3 ± 6.8, 91.6 ± 3.8, and 81.3 ± 5.8 % for TSS, COD, TN, and TP were achieved, respectively. The GSs played an important role in removing TSS and TP and acted as a pre-treatment process to prevent clogging of the subsequent WDPs. Particle size distributions (PSDs) analysis indicated that coarse particles larger than 75 μm accounted for 80 % by weight of the total particles in the runoff. GSs can effectively reduce coarse particles (≥75 μm) in runoff, while its removal efficiency for fine particles (<75 μm) was low, even minus results being recorded, especially for particles smaller than 25 μm. The length of GSs is a key factor in its performance. The WDPs can remove particles of all sizes by sedimentation. In addition, WDPs can improve water quality due to their buffering and dilution capacity during rainfall as well as their water purification ability during dry periods. Overall, the ecological system of GSs coupled with WDPs is an effective system for agricultural runoff pollution control.

Biodegradability and Molecular Composition of Dissolved Organic Nitrogen in Urban Stormwater Runoff and Outflow Water from a Stormwater Retention Pond

Dissolved organic nitrogen (DON) can be a significant part of the reactive N in aquatic ecosystems and can accelerate eutrophication and harmful algal blooms. A bioassay method was coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to determine the biodegradability and molecular composition of DON in the urban stormwater runoff and outflow water from an urban stormwater retention pond. The biodegradability of DON increased from 10% in the stormwater runoff to 40% in the pond outflow water and DON was less aromatic and had lower overall molecular weight in the pond outflow water than in the stormwater runoff. More than 1227 N-bearing organic formulas were identified with FT-ICR-MS in the stormwater runoff and pond outflow water, which were only 13% different in runoff and outflow water. These molecular formulas represented a wide range of biomolecules such as lipids, proteins, amino sugars, lignins, and tannins in DON from runoff and pond outflow water. This work implies that the urban infrastructure (i.e., stormwater retention ponds) has the potential to influence biogeochemical processes in downstream water bodies because retention ponds are often a junction between the natural and the built environment.

Food wastes as fish feeds for polyculture of low-trophic-level fish: bioaccumulation and health risk assessments of heavy metals in the cultured fish

The major purpose of this study was to use different types of food wastes which serve as the major sources of protein to replace the fish meal used in fish feeds to produce quality fish. Two types of food waste-based feed pellets FW A (with cereals) and FW B (with cereals and meat products) and the commercial feed Jinfeng® were used to culture fingerlings of three low-trophic-level fish species: bighead carp, grass carp, and mud carp (in the ratio of 1:3:1) for 1 year period in the Sha Tau Kok Organic Farm in Hong Kong. Heavy metal concentrations in all of the fish species fed with food waste pellets and commercial pellets in Sha Tau Kok fish ponds were all below the local and international maximum permissible levels in food. Health risk assessments indicated that human consumption of the fish fed with food waste feed pellets was safe for the Hong Kong residents. The present results revealed that recycling of food waste for cultivating low-trophic-level fish (mainly herbivores and detritus feeders) is feasible, and at the same time will ease the disposal pressure of food waste, a common problem of densely populated cities like Hong Kong.

Drinking water contributes to high salt consumption in young adults in coastal Bangladesh

Increasing salinity of freshwater from environmental and anthropogenic influences is threatening the health of 35 million inhabitants in coastal Bangladesh. Yet little is known about the characteristics of their exposure to salt (sodium), a major risk factor for hypertension and related chronic diseases. This research examined sodium consumption levels and associated factors in young adults. We assessed spot urine samples for 282 participants (19-25 years) during May-June 2014 in a rural sub-district in southwestern coastal Bangladesh and measured sodium levels of their potable water sources. The significant factors associated with high sodium consumption were determined from logistic regression analyses. Mean sodium content in tube-well water (885 mg/L) was significantly higher than pond water (738 mg/L) (P = 0.01). Fifty three percent of subjects were consuming sodium at levels above the WHO recommended level (≥2 g/day). The users of tube-well water were more likely to consume sodium above this recommended level than pond water users. Salinity problems are projected to increase with climate change, and with large populations potentially at risk, appropriate public health and behavior-change interventions are an urgent priority for this vulnerable coastal region along with targeted research to better understand sodium exposure pathways and health benefits of alternative water supplies.