Aquaculture Water Samples Research Articles

Combined Electrochemical Deposition and Photo-Reduction to Fabricate SERS-Active Silver Substrates: Characterization and Application for Malachite Green Detection in Aquaculture Water.

This research introduces a novel approach using silver (Ag) nanostructures generated through electrochemical deposition and photo-reduction of Ag on fluorine-doped tin oxide glass substrates (denoted as X-Ag-AgyFTO, where 'X' and 'y' represent the type of light source and number of deposited cycles, respectively) for surface-enhanced Raman spectroscopy (SERS). This study used malachite green (MG) as a Raman probe to evaluate the enhancement factors (EFs) in SERS-active substrates under varied fabrication conditions. For the substrates produced via electrochemical deposition, we determined a Raman EF of 6.15 × 104 for the Ag2FTO substrate. In photo-reduction, the impact of reductant concentration, light source, and light exposure duration were examined on X-Ag nanoparticle formation to achieve superior Raman EFs. Under optimal conditions (9.0 mM sodium citrate, 460 nm blue-LED at 10 W for 90 min), the combination of blue-LED-reduced Ag (B-Ag) and an Ag2FTO substrate (denoted as B-Ag-Ag2FTO) exhibited the best Raman EF of 2.79 × 105. This substrate enabled MG detection within a linear range of 0.1 to 1.0 µM (R2 = 0.98) and a detection limit of 0.02 µM. Additionally, the spiked recoveries in aquaculture water samples were between 90.0% and 110.0%, with relative standard deviations between 3.9% and 6.3%, indicating the substrate's potential for fungicide detection in aquaculture.

Metabolites and metabolic pathway analysis of sulfadimidine in carp (Cyprinus carpio) based on UHPLC-Q-orbitrap HRMS

Sulfadimidine (SM2) is an N-substituted derivative of p-aminobenzenesulfonyl structure. This study aimed to analyze the metabolism of SM2 in carp (Cyprinus carpio). The carps were fed with SM2 at a dose of 200 mg/(kg · bw) and then killed. The blood, muscle, liver, kidney, gill, other guts, and carp aquaculture water samples were collected. The UHPLC-Q-Exactive Plus Orbitrap-MS was adopted for determining the metabolites of SM2 in the aforementioned samples. Twelve metabolites, which were divided into metabolites in vivo and metabolites in vitro, were identified using Compound Discoverer software. The metabolic pathways in vivo of SM2 in carp included acetylation, hydroxylation, glucoside conjugation, glycine conjugation, carboxylation, glucuronide conjugation, reduction, and methylation. The metabolic pathways in vitro included oxidation and acetylation. This study clarified the metabolites and metabolic pathways of SM2 in carp and provided a reference for further pharmacodynamic evaluation and use in aquaculture.

Electrochemical sensor based on hollow Au/Pd/Ag dendrites prepared by galvanic replacement from a choline chloride-ethylene glycol deep eutectic solvent

This study presents a simple approach to fabricating a hollow dendritic Au/Pd/Ag electrode through a galvanic replacement reaction (GRR) in a choline chloride-ethylene glycol deep eutectic solvent. The resulting electrode's morphological, structural, and compositional features were characterized using SEM, TEM, XRD, and XPS techniques, with the XPS depth profile providing insights into metal content ratio variations along the electrode's depth. The results emphasize the significant impact of immersion time on both morphological evolution and composition. Cyclic voltammetry investigations revealed significantly enhanced current density in furaltadone (FTD) detection compared to bimetallic and single metallic electrodes. The proposed electrochemical sensor exhibited a dynamic linear range for FTD spanning 1.67–625 μM, accompanied by a low detection limit of 91.7 nM, as confirmed by differential pulse voltammetry (DPV) quantitative experiments. The selectivity, reproducibility, stability, and recovery of the as-prepared sensors were evaluated, particularly in aquaculture water samples, underscoring the practical applicability of the electrodes for furaltadone sensing. This innovative trimetallic electrode design opens avenues for advanced electrochemical sensors with enhanced performance characteristics.

Prevalence and transmission risk of colistin and multidrug resistance in long-distance coastal aquaculture

Due to the wide use of antibiotics, intensive aquaculture farms have been recognized as a significant reservoir of antibiotic resistomes. Although the prevalence of colistin resistance genes and multidrug-resistant bacteria (MDRB) has been documented, empirical evidence for the transmission of colistin and multidrug resistance between bacterial communities in aquaculture farms through horizontal gene transfer (HGT) is lacking. Here, we report the prevalence and transmission risk of colistin and multidrug resistance in 27 aquaculture water samples from 9 aquaculture zones from over 5000 km of subtropical coastlines in southern China. The colistin resistance gene mcr−1, mobile genetic element (MGE) intl1 and 13 typical antibiotic resistance genes (ARGs) were prevalent in all the aquaculture water samples. Most types of antibiotic (especially colistin) resistance are transmissible in bacterial communities based on evidence from laboratory conjugation and transformation experiments. Diverse MDRB were detected in most of the aquaculture water samples, and a strain with high-level colistin resistance, named Ralstonia pickettii MCR, was isolated. The risk of horizontal transfer of the colistin resistance of R. pickettii MCR through conjugation and transformation was low, but the colistin resistance could be steadily transmitted to offspring through vertical transfer. The findings have important implications for the future regulation of antibiotic use in aquaculture farms globally to address the growing threat posed by antibiotic resistance to human health.

Multifunctional 3D magnetic carbon aerogel for adsorption separation and highly sensitive SERS detection of malachite green

This work presents a novel strategy for the synthesis of a recyclable aerogel and its multifunctional application as effective adsorption material for organic pollutants and as a high-quality SERS substrate for on-site detection measurement. Silver nanoparticles (Ag NPs) were uniformly dispersed and adsorbed on the surface of an Fe3C-loaded carbon aerogel, resulting in the formation of a three-dimensional Ag–Fe3C–MCA (magnetic carbon aerogel) composite. The substrate preparation led to Ag–Fe3C–MCA with a mesoporous structure for high adsorption capacity, together with magnetic properties for easy separation capability. The Ag–Fe3C–MCA composite demonstrated an efficient removal ability for malachite green (MG), with an adsorption capacity of 296.7 mg g−1. Moreover, Ag–Fe3C–MCA composite provided ultrasensitive surface-enhanced Raman scattering detection for MG molecules, obtaining a limit of detection (LOD) of 3 × 10−10 M. Aquaculture water samples with spiked MG concentrations were used to simulate practical scenarios. The Ag–Fe3C–MCA presented has a significant potential for the removal of hazardous residues in wastewater, together with an efficient and sensitive method of quantification, all on the same substrate.

In-situ SERS detection of quinolone antibiotic residues in aquaculture water by multifunctional Fe3O4@mTiO2@Ag nanoparticles

Antibiotic residues in aquaculture environments disrupt the ecosystem balance and pose a potential hazard to human health when entering the food chain. Therefore, ultra-sensitive detection of antibiotics is necessary. In this study, a multifunctional Fe3O4@mTiO2@Ag core–shell nanoparticle (NP), synthesized using a layer-by-layer method, was demonstrated to be useful as an enhanced substrate for in-situ surface-enhanced Raman spectroscopy (SERS) detection of various quinolone antibiotics in aqueous environments. The results showed that the minimum detectable concentrations of the six investigated antibiotics were 1 × 10−9 mol/L (ciprofloxacin, danofloxacin, enoxacin, enrofloxacin, and norfloxacin) and 1 × 10−8 mol/L (difloxacin hydrochloride) under the enrichment and enhancement of Fe3O4@mTiO2@Ag NPs. Additionally, there was a good quantitative relationship between the antibiotics concentrations and SERS peak intensities within a certain detection range. The results of the spiked assay of actual aquaculture water samples showed that the recoveries of the six antibiotics ranged from 82.9% to 113.5%, with relative standard deviations ranging from 1.71% to 7.24%. In addition, Fe3O4@mTiO2@Ag NPs achieved satisfactory results in assisting the photocatalytic degradation of antibiotics in aqueous environments. This provides a multifunctional solution for low concentration detection and efficient degradation of antibiotics in aquaculture water.

Natural Luffa cylindrica sponge sorbent for the solid phase extraction of estrone, 17-β-estradiol, and testosterone in aquaculture water

The bare natural fibrous skeleton of Luffa cylindrica (LC) sponge gourd was simply prepared and used as a sorbent in the vortex-assisted solid phase extraction (VA-SPE) of three steroid hormones, estrone (E1), 17-β-estradiol (E2), and testosterone (T) from aquaculture water samples. The extracted compounds were analysed by high performance liquid chromatography with a diode array detector (HPLC-DAD). Extraction with the prepared sorbent was highly efficient, completing within 10 min. The developed method showed good linearity in a concentration range of 15–1000 μg L−1 for E1, E2, and T. The limits of detection (LODs) were 9.6 ± 0.1 μg L−1 for E1, 9.8 ± 0.1 μg L−1 for E2, and 9.7 ± 0.1 μgL−1 for T. The respective limits of quantitation (LOQs) were 32.1 ± 0.3 μg L−1, 32.7 ± 0.4 μg L−1, and 32.2 ± 0.5 μg L−1. Good reproducibility (RSD < 3.5%, n = 6), good precision (RSD < 6.8%, n = 6), and excellent reusability (n = 22, RSD < 8%) were achieved. Recoveries from real spiked samples ranged from 70.2 ± 0.1% to 98.9 ± 4.7% with RSDs lower than 6.0%. The proposed method is simple, fast, inexpensive, and eco-friendly, with potential applications in the trace analysis of steroid hormones. Novelty statementOnly a few studies have focused on sample preparation for the simultaneous determination of steroid hormones in aquaculture water. The authors believe that the use of unmodified naturally available Luffa cylindrica as a solid phase extraction (SPE) sorbent has not yet been reported. This work successfully developed, for the first time from the bare fibrous skeleton of Luffa cylindrica, a very simple and low-cost SPE sorbent to extract E1, E2, and T for simultaneous determination by HPLC.

Incorporating Cerium Vanadate into Multi-Walled Carbon Nanotubes for Fabrication of Sensitive Electrochemical Sensors toward Sulfamethazine Determination in Water Samples

We developed a simple hydrothermal technique for the fabrication of a flexible integrated composite containing cerium vanadate (CeVO4) and multi-walled carbon nanotubes (MWCNTs). The CeVO4/MWCNTs composite possessed good conductivity and interesting electrochemical catalytic performance when immobilized on a glassy carbon electrode (GCE). This CeVO4/MWCNTs-GCE sensor provided excellent analytical performance for the detection of the sulfonamide antibacterial drug sulfamethazine (SMZ). Benefiting from the significantly enlarged surface area of the modified electrode and the catalytic effect of CeVO4-MWCNTs, the sensor offered high sensitivity, good stability, fine selectivity, and a remarkable limit of detection (LOD) of 0.02 μM. Furthermore, the sensor also exhibited ideal performance with good recovery and precision when applied to SMZ residue detection in real aquaculture water samples.

Visual LAMP method for the detection of Vibrio vulnificus in aquatic products and environmental water

BackgroundA visual, rapid, simple method was developed based on a loop-mediated isothermal amplification (LAMP) assay to detect Vibrio vulnificus in aquatic products and aquaculture waters.ResultsGenomic DNA was extracted from Vibrio vulnificus using the boiling method, and optimized primers were used to detect the gyrB gene using a visual LAMP method. The sensitivity of the assay was 10 fg/μL, and the obtained results were stable and reliable. Out of 655 aquatic product samples and 558 aquaculture water samples, the positive rates of Vibrio vulnificus detection were 9.01% and 8.60%, respectively, which are markedly higher than those of the traditional culture identification methods.ConclusionThe relatively simple technical requirements, low equipment cost, and rapid detection make the visual LAMP method for the detection of Vibrio vulnificus a convenient choice for field detection in the aquaculture industry.

Establishment and clinical application of a detection method for the infectious hypodermal and hematopoietic necrosis virus in water

To better understand the distribution of viruses in water, we established a method of concentrating the infectious hypodermal and hematopoietic necrosis virus (IHHNV) in aquaculture. In our study, tangential flow ultrafiltration was established to concentrate the virus from water samples. The results showed that the best filtration columns for the concentration of IHHNV were microfiltration columns (CFP-2-E-4MA) and ultrafiltration columns (UFP-50-C-4MA). The results showed that the average concentration recovery of IHHNV was 67.11%. The method was then used to detect viruses in aquaculture water samples, water samples carried with imported parent shrimp and the dissolved water of imported frozen shrimp. The results showed that the sensitivity of virus detection in water is 46copies / μL, and our methods can be an important tool for aquatic biological security in shrimp ponds and the risk assessment of water carried with imported live animals.

A Fluorescence Method Based on N, S-Doped Carbon Dots for Detection of Ammonia in Aquaculture Water and Freshness of Fish

Excessive ammonia can cause the death of fish and the eutrophication of the water environment, so ammonia detection is essential for environmental monitoring. In this study, a highly selective sensing strategy for ammonia detection based on N, S co-doped carbon dots (N, S-CDs) was developed. The as-prepared N, S-CDs exhibited excellent photoluminescence properties and fluorescent stability. N, S-CDs demonstrated fluorescence quenched in the presence of ammonia in the wide linear range of 2–80 mmol/L, and were highly selective towards ammonia over metal ions. Furthermore, a possible fluorescence quenching mechanism is proposed. N, S-CDs were further applied to detection of ammonia in aquaculture water samples and river water samples, showing good practicability with recoveries from 0.93 to 1.27 and relative standard deviations (RSDs) of 0.54% to 17.3%. N, S-CDs were also successfully used to determine the freshness of bighead carps.

Fully integrated 3D-printed electrochemical cell with a modified inkjet-printed Ag electrode for voltammetric nitrate analysis

To address the need for low-cost analytical tools for on-site aquaculture water quality monitoring, miniaturized electrochemical sensor systems can be readily fabricated using additive manufacturing technologies such as 3D printing and inkjet printing. In this work, we report the design and fabrication of an additively manufactured electrochemical platform featuring a reusable 3D-printed electrochemical cell with integrated reference and counter electrodes, and a replaceable inkjet-printed Ag (IJP-Ag) working electrode. The electrochemical cell was 3D-printed with acrylonitrile butadiene styrene (ABS) filament and features a 3D-printed ABS-carbon counter electrode and a Ag|AgCl|gel-KCl reference electrode with a 3D-printed porous junction directly integrated along the sides of the sample compartment. The application of the integrated cell is demonstrated with the analysis of nitrate ions on the IJP-Ag electrode, which was modified with electrodeposited nanostructured Ag to enhance sensitivity to nitrate reduction. Linear sweep voltammetry (LSV) was successfully applied to detect nitrate with a LOD of 1.40 ppm and a sensitivity of 0.2086 μA ppm−1 in a background of artificial brackish aquaculture water (pH 8.0). The sensor response showed intra- and inter-electrode reproducibility and no significant interferences to most of the commonly encountered cations and anions in brackish water. The electrochemical sensor system was also applied to nitrate determination in real aquaculture water samples and demonstrated no significant differences with the results obtained using the standard spectrophotometric method at a 95% confidence level. Our results show how additive manufacturing is a promising approach to readily fabricate fit-for-purpose, low-cost miniaturized electrochemical sensor systems for point-of-use applications.

An "on-off" fluorescent probe based on cucurbit[7]uril for highly sensitive determination of ammonia nitrogen in aquaculture water.

A novel "on-off" fluorescent probe was synthesized for highly sensitive and ultra-trace determination of ammonia nitrogen in aquaculture water. Ammonium can react with formaldehyde and sodium hydroxide to form a ring substance (urotropine), which shows no fluorescence signal. Palmatine hydrochloride (PAL) can enter the hydrophobic cavity of cucurbit[7]uril (CB[7]), eventually forming a 1 : 1 host guest complex called PAL@CB[7] under neutral or acidic conditions, which has strong green fluorescence with the maximum excitation (λex) wavelength at 343 nm, and the maximum emission (λem) wavelength at 500 nm, while urotropine has a fluorescence quenching effect on the fluorescence enhancement system of PAL@CB[7]. Therefore, a fluorescent chemosensor based on PAL@CB[7] and the reaction of ammonia nitrogen with formaldehyde was developed. The results indicate that the linearity range and the limit of detection of the proposed method are 1-300 μg L-1 with a good correlation coefficient (r2 = 0.9966) and 1.8 × 10-2 μg L-1, respectively. Under the optimal conditions, the method was employed for the detection of ammonia nitrogen in real aquaculture water samples, revealing high selectivity and sensitivity. In the future, the combination of the "on-off" fluorescence method, a portable hardware system and intelligent algorithms will provide technology support for the design of on-line sensors for measuring ammonia nitrogen in aquaculture water.

Large-volume electric field-assisted multiphase extraction of malachite green from water samples: A multisample device and method validation

In this work, a new large-volume multiphase, multi-sample electroextraction device was developed and applied to selectively extract malachite green (MG) from water samples. This device was easily constructed with ordinary materials and capable of extracting ten samples simultaneously, obtaining MG preconcentrated on a solid support, to fit into a pipette tip. A multi-well plate was applied to extract MG from aquaculture water samples, and the extracts containing the desorbed MG were analysed by LC-DAD and LC-MS/MS. The signals from both detectors were used in two independent validation procedures. Linearity, matrix effect, selectivity, precision, trueness, and limits of detection and quantification were all evaluated. For both detectors, linearity was demonstrated in the range of 0.5–5 μg L−1 (R2 > 0.98). Matrix effect was insignificant for LC-DAD only, and the average preconcentration factor was about 60 times. Recoveries ranged from 94 to 113% for LC-DAD and 95–115% for LC-MS/MS analysis. ANOVA was applied to estimate the standard deviation under repeatability (6.96–8.61% for LC-DAD and 5.98–7.41% for LC-MS/MS) and within-reproducibility (6.96–8.61% for LC-DAD and 6.56–7.41% for LC-MS/MS) conditions. The limits of detection and quantification for LC-MS/MS analysis were 4.29 and 28.74 ng L−1, respectively, while, for LC-DAD, these limits were 14.29 and 95.81 ng L−1, respectively. The results demonstrated that the developed method was suitable for determining MG in water samples, and the large-volume multiphase, multi-sample electroextraction device proved to be a powerful sample preparation technique to obtain high clean-up and large preconcentration levels, which are of paramount importance for environmental applications.

A Sensitive and Selective Electrochemical Sensor for Sulfadimethoxine Based on Electropolymerized Molecularly Imprinted Poly (o-aminophenol) Film

Background: As a broad-spectrum antibiotic of the sulfonamide family, Sulfadimethoxine (SDM) has been widely utilized for therapeutic and growth-promoting purposes in animals. However, the use of SDM can cause residual problems. Even a low concentration of SDM in the aquatic system can exert toxic effects on target organisms and green algae. Therefore, the quantitation of SDM residues has become an important task. Methods: The present work describes the development of a sensitive and selective electrochemical sensor for sulfadimethoxine based on molecularly imprinted poly(o-aminophenol) film. The molecular imprinted polymer film was fabricated by electropolymerizing o-aminophenol in the presence of SDM after depositing carboxylfunctionalized multi-walled carbon nanotubes onto a glassy carbon electrode surface. SDM can be quickly removed by electrochemical methods. The imprinted polymer film was characterized by cyclic voltammetry, differential pulse voltammetry and scanning electron microscopy. Results: Under the selected optimal conditions, the molecularly imprinted sensor shows a linear range from 1.0 × 10-7 to 2.0 × 10-5 mol L-1 for SDM, with a detection limit of 4.0 × 10-8 mol L-1. The sensor was applied to the determination of SDM in aquaculture water samples successfully, with the recoveries ranging from 95% to 106%. Conclusion: The proposed sensor exhibited a high degree of selectivity for SDM in comparison to other structurally similar molecules, along with long-term stability, good reproducibility and excellent regeneration capacity. The sensor may offer a feasible strategy for the analysis of SDM in aquaculture water samples.

Cultivating the Macroalgal Holobiont: Effects of Integrated Multi-Trophic Aquaculture on the Microbiome of Ulva rigida (Chlorophyta)

Ulva is a ubiquitous macroalgal genus of commercial interest. Integrated Multi Trophic Aquaculture (IMTA) systems promise large-scale production of macroalgae due to their high productivity and environmental sustainability. Complex host-microbiome interactions play a decisive role in macroalgal development, especially in Ulva spp. due to algal growth- and morphogenesis-promoting factors released by associated bacteria. However, our current understanding of the microbial community assembly and structure in cultivated macroalgae is scant. We aimed to determine (i) to what extent IMTA settings influence the microbiome associated with U. rigida and its rearing water, (ii) to explore the dynamics of beneficial microbes to algal growth and development under IMTA and (iii) to improve current knowledge of host-microbiome interactions. We examined the diversity and taxonomic composition of the prokaryotic communities associated with wild versus IMTA-grown Ulva rigida and surrounding seawater by 16S rRNA gene amplicons. With 3141 Amplicon Sequence Variants (ASVs), the prokaryotic richness was higher in water than in association with U. rigida. Bacterial ASVs were more abundant in aquaculture water samples than water collected from the lagoon. The beta diversity analysis revealed distinct prokaryotic communities associated with Ulva collected in both aquacultures and coastal waters. Aquaculture samples (water and algae) shared 22% of ASVs, whereas natural, coastal lagoon samples only 9%. While cultivated Ulva selected 239 (8%) host-specific ASVs, wild specimens possessed more than twice host-specific ASVs (17%). Cultivated U. rigida specimens enriched the phyla Cyanobacteria, Planctomycetes, Verrucomicrobia, and Proteobacteria. Within the Gammaproteobacteria, while Glaciecola mostly dominated the microbiome in cultivated algae, the genus Granulosicoccus characterized both Ulva microbiomes. In both wild and IMTA settings, the phylum Bacteroidetes was more abundant in the bacterioplankton than in association with U. rigida. However, we observed that the Saprospiraceae family within this phylum was barely present in lagoon water but very abundant in aquaculture water. Aquacultures promoted the presence of known morphogenesis-inducing bacteria in water samples. Our study suggests that IMTA significantly shaped the structure and composition of the microbial community of the rearing water and cultivated U. rigida. Detailed analysis revealed the presence of previously undetected taxa associated with Ulva, possessing potentially unknown functional traits.

Extended Spectrum Beta-Lactamase and Metallo Beta-Lactamase Producing Pseudomonas Species Isolated From Fish Pond Water in Ibadan, Nigeria

ABSTRACT Gram-negative bacteria that produce Extended-spectrum beta-lactamase (ESBL) and metallo beta-lactamase (MBL) show resistance to beta-lactam antibiotics. This study was to determine Beta-lactamases-producing Pseudomonas species in fish ponds. Pseudomonas species isolated from aquaculture water samples using Pseudomonas base agar were characterised biochemically. The detection of ESBL and MBL was made by double disc synergy and imipenem-EDTA combined disc methods, respectively. Antimicrobial susceptibility was by disc diffusion method. The 94 Pseudomonas species isolated comprised P. aeruginosa (62.8%), P. stutzeri (14.9%), P. putida (9.8%) and P. fluorescens (12.8%). P. aeruginosa 16 (16.3%) and P. stutzeri 4 (4.3%) produced ESBL, but 2 (10%) P. aeruginosa and 1 (5%) P. stutzeri produced MBL. Resistance of ESBL producers to trimethoprim was 55.5% and 7 (35.0%) were multidrug resistant. Detection of ESBL and MBL in Pseudomonas spp. from this study implies environmental health risk. Antibiotics misuse in aquaculture and discharge of untreated aquaculture wastewater into the environment should be discouraged.

Ionic Liquid-based Hollow Fiber Liquid-Liquid-Liquid Microextraction Combined with Capillary Electrophoresis for the Determination of Sulfonamides in Aquaculture Waters.

Ionic liquid-based hollow-fiber liquid-liquid-liquid microextraction (IL-HF-LLLME) coupled to capillary electrophoresis (CE) has been developed for the determination of six sulfonamides (SAs) in aquaculture waters. A series of extraction parameters was optimized to enhance the extraction efficiency, which included type and pore size of hollow fiber, type and composition of extraction solvent, pH value of donor phase, the concentration of acceptor phase and the mass ratio of donor phase to acceptor phase along with extraction temperature and time. Under optimal conditions, the IL-HF-LLLME-CE method provided a wide liner range for six SAs from 2 to 1,000μgL-1 (r2≥0.9995), the limits of the detection from 0.25 to 0.48 and the enrichment factors from 122 to 230, respectively. Relative standard deviations for intra- and interday precision were 1.4-5.3% and 1.8-7.5% (n=5), respectively. The proposed method was successfully applied for the determination of trace-level SAs in seven real-world aquaculture water samples with good recoveries (80.4-100.7%). Also, sulfamerazine and sulfamethoxazole were detected at the level of 0.52-1.60μgL-1 in two water samples. Due to its good sensitivity, simple operation, short analysis time and eco-friendliness, the developed method has a great application potential in analysis of trace SA residues in aquaculture waters.

Prevalance of vibrio SPP. Isolated from aquaculture and environment in Cai Be district, Tien Giang province

The prevalence of Vibrio spp. incommercial seafood and the aquaculture water collected in Cai Be district, Tien Giang province, Viet Nam was studied. More than five hundred samples including 311 aquaculture water samples and 190 seafood samples were collected and analyzed. The results showed that there were 161 water samples and 82 seafood samples containing 8 species of Vibrio spp. Among those V. parahaemolyticus, V. mimicus, and V. alginolyticus were the most abundant.

Highly sensitive and selective method for detection of trace amounts of nitrite in aquaculture water by SERRS coupled with diazo reaction

Based on modified diazo reaction, a novel surface-enhanced resonance Raman scattering (SERRS) method employed for ultrasensitive, highly selective, and ultra-trace determination of nitrite in aquaculture water was demonstrated. The azo dyes, which are formed by 4-aminothiophenol, nitrite, and N-(1-naphthyl) ethylenediamine dihydrochloride in acid conditions, can exhibit high SERS signal on Ag nanoparticles. Subsequently, the concentration of nitrite can be determined from the intensity of SERRS of derivative. Under optimal conditions, a linear relationship between Raman intensity and the nitrite concentration was found in the range of 0.1–15.0 μmol L−1 with a good correlation coefficient (R2 = 0.9921) at 1380 cm−1, and the limit of detection can reach as low as 16.4, 24.0, 9.0, and 24.6 nmol L−1 at 1138, 1332, 1380 and 1418 cm−1, respectively. Additionally, the results indicate that the present method can be applied to detect nitrite in real aquaculture water samples without influence of interfering ions. This study provides a feasible method for accurate, trace, and fast field detection of nitrite in aquaculture water with strong potential to be used for on-line and on-site optical sensors of nitrites.