Aquaculture practices and potential human health risks: current knowledge and future priorities

Removal of antibiotics (sulfamethazine, tetracycline and chloramphenicol) from aqueous solution by raw and nitrogen plasma modified steel shavings

The removal of sulfamethazine (SMT), tetracycline (TC) and chloramphenicol (CP) from synthetic wastewater by raw (M₃) and nitrogen plasma modified steel shavings (M₃-plN₂) was investigated using batch experiments. The adsorption kinetics could be expressed by both pseudo-first-order kinetic (PFO) and pseudo-second-order kinetic (PSO) models, where correlation coefficient r² values were high. The values of PFO rate constant k_1p and PSO rate constant k_2p decreased as SMT-M₃>SMT-M₃-plN₂>TC-M₃-plN₂>TC-M₃>CP-M₃>CP-M₃-plN₂ and SMT-M₃>SMT-M₃-plN₂>TC-M₃>TC-M₃-plN₂>CP-M₃>CP-M₃-plN₂, respectively. Solution pH, adsorbent dose and temperature exerted great influences on the adsorption process. The plasma modification with nitrogen gas cleaned and enhanced 1.7-fold the surface area and 1.4-fold the pore volume of steel shavings. Consequently, the removal capacity of SMT, TC, CP on the adsorbent rose from 2519.98 to 2702.55, 1720.20 to 2158.36, and 2772.81 to 2920.11μg/g, respectively. Typical chemical states of iron (XPS in Fe2p3 region) in the adsorbents which are mainly responsible for removing antibiotics through hydrogen bonding, electrostatic and non- electrostatic interactions and redox reaction were as follows: Fe₃O₄/Fe²⁺, Fe₃O₄/Fe³⁺, FeO/Fe²⁺ and Fe₂O₃/Fe³⁺.

Occurrence, distribution, ecological and resistance risks of antibiotics in surface water of finfish and shellfish aquaculture in Bangladesh

The present study for the first time reports the occurrence, distribution, ecological and resistance risks of antibiotics in the surface water of freshwater finfish and brackish water shellfish aquaculture in Bangladesh. Among the nine targets, seven antibiotics were detected in finfish aquaculture, whereas four in shellfish aquaculture. The concentrations (ranges) and overall detection frequency of sulfamethoxazole (SMX) (nd-20.02 ng L^-1 and 73%), trimethoprim (TMP) (nd-41.67 ng L^-1 and 60%), tylosin (TYL) (nd-39.34 ng L^-1 and 60%), sulfadiazine (SDZ) (nd-17.97 ng L^-1 and 53%), sulfamethazine (SMT) (nd-11.71 ng L^-1 and 33%), sulfamethizole (SMZ) (nd-10.81 ng L^-1 and 40%) and penicillin G (PC_G) (nd-7.83 ng L^-1, 7%) were found in finfish aquaculture. In case of shellfish aquaculture, the concentrations (ranges) and overall detection frequency were for SMX (nd-16.77 ng L^-1 and 67%), TMP (nd-11.39 ng L^-1 and 20%), TYL (nd-0.16 ng L^-1 and 20%) and erythromycin-H₂O (ERY-H₂O) (nd-3.91 ng L^-1 and 20%). The present findings revealed that finfish aquaculture is more contaminated with the higher numbers and concentrations of antibiotics. The preliminary ecological and resistance risks assessment showed that the calculated risk quotients (RQs) were lower than one (RQs<1) for all the detected antibiotics in both aquaculture. Preliminary ecological and resistance risks assessment revealed that there were no adverse ecological and resistance risks, however, our study suggests that it is imperative to pay due attention to monitor the antibiotics contamination in rapid growing aquaculture sector of Bangladesh for the reduction of potential risks of antibiotics on aquatic organisms as well as human health.

Veterinary antibiotics in food, drinking water, and the urine of preschool children in Hong Kong

Due to the harmful effects of veterinary antibiotics (VAs) residues in food on children's health, urine samples from 31 preschool and primary school children were analyzed for 13 common VAs. Samples of raw and cooked pork, chicken, fish, milk and drinking water from the children's living areas were also analyzed for residual VAs. Urinalysis revealed one to four target antibiotics in 77.4% of the sample group, with concentrations as high as 0.36ng/mL. Norfloxacin and penicillin had the highest detection rates (48.4% and 35.5%, respectively), with median concentrations of 0.037 and 0.13ng/mL, respectively. The VA burden of children in HK was lower than that in Shanghai. Enrofloxacin, penicillin, and erythromycin were the most detected VAs in raw and cooked food. Only oxytetracycline was detected in terminal tap water, and none were detected in milk. Tetracycline and doxycycline hyclate were detected in organic eggs (up to 7.1ng/g) and regular eggs (up to 6.6ng/g), which were common in children's diets. Traditional Chinese cooking processes did not completely eliminate VAs, and the concentrations of some VAs increased, especially after frying and roasting. The estimated daily intake (EDI) results show that the contribution of dietary intake and that based on the urine concentrations of VAs were far below the acceptable daily intake (ADI). The EDIs from urine were significantly lower than those based on cooked foods. The highest level of achievement percentage (LAP) based on dietary consumption and urine concentrations were 39.7% and 1.79%, respectively, and thus current levels of exposure to VAs would not seem to pose a risk to children's health. However, harmful effects of residual VAs during developmental periods may occur with exposure to much lower doses than those considered harmful to adults, and further investigation of these emerging pollutants is urgently encouraged.

The effects of aquaculture on mercury distribution, changing speciation, and bioaccumulation in a reservoir ecosystem

A survey was conducted in a freshwater reservoir located in Guizhou province, south China, to investigate the influence of fish aquaculture activities on mercury (Hg) distribution, speciation change, and bioaccumulation. Water, sediment, and aquaculture fish samples were collected from aquaculture sites (AS) and the corresponding reference sites (RS). The results showed that total mercury (THg) concentration in overlying water in Wujiangdu reservoir reached 6.87 ± 14.9 ng L^-1. THg concentration in a different layer follows the sequence: surface layer > bottom layer > three intermediate layers with significant difference. In addition, the total methylmercury (TMeHg) concentration in overlying water was 0.113 ± 0.211 ng L^-1. The highest TMeHg was observed in the bottom layer. Both dissolved Hg (DHg) and dissolved methylmercury (DMeHg) accounted for more than 50% of THg and TMeHg in the top four layers of overlying water, respectively. In contrast, particulate Hg (PHg) and particulate methylmercury were the major portion of THg and TMeHg in bottom layer and reached to 67 and 58.7% of THg and TMeHg, respectively. Aquaculture activities were estimated to contribute an annual loading of approximately 69.8 ng g^-1of THg yearly in the top 1 cm of sediment underneath the rafts due to unconsumed fish feed. The extra loading of THg in sediment may have potential to stimulate the release of Hg to the overlying water. Both DMeHg and DHg in sediment pore water and organic matter (OM) contents in the top 4 cm of AS were noticeably higher than RS, which indicated that the accumulation of OM due to aquaculture activities promoted MeHg production in the top surface of sediment pore water. No significant difference was noted between THg in RS (296 ± 104 ng g^-1) and AS (274 ± 132 ng g^-1) in the solid phase. In addition, the sediments were net sources of both MeHg and inorganic Hg. For Hg in fish tissues, THg and inorganic Hg (IHg) in the liver were significantly higher (THg: p < 0.001, F = 9.98; IHg: p < 0.001, F = 13.1) than those in the other organs. In contrast, MeHg concentration in the muscle was significantly higher than (p < 0.01, F = 4.83) that in the other organs.

Removal of Antibiotic Florfenicol by Sulfide-Modified Nanoscale Zero-Valent Iron

Florfenicol (FF, C₁₂H₁₄Cl₂FNO₄S), an emerging halogenated organic contaminant of concern was effectively degraded in water by sulfidized nanoscale zerovalent iron (S-nZVI). Sulfidized nZVI (62.5 m² g^-1) that was prepared using a one-step method resulted in small Fe⁰/Fe-sulfide particles that were more stable against aggregation than unsulfidized nZVI (10.2 m² g^-1). No obvious removal of FF was observed by unsulfidized nZVI. S-nZVI degraded FF, having a surface area normalized reaction rate constant of 3.1 × 10^-4 L m^-2 min^-1. The effects of the S/Fe molar ratio, initial FF concentration, initial pH, temperature, and water composition on the removal of FF by S-nZVI, and on the formation of reaction products, were systematically investigated. Both dechlorination and defluorination were observed, resulting in four degradation products (C₁₂H₁₅ClFNO₄S, C₁₂H₁₆FNO₄S, C₁₂H₁₇NO₄S, and C₁₂H₁₇NO₅S). High removal efficiencies of FF by S-nZVI were achieved in groundwater, river water, seawater, and wastewater. The reactivity of S-nZVI was relatively unaffected by the presence of both dissolved ions and organic matter in the waters tested.

Sources and fate of antimicrobials in integrated fish-pig and non-integrated tilapia farms

Antimicrobial contamination in aquaculture products constitutes a food safety hazard, but little is known about the introduction and accumulation of antimicrobials in integrated fish-pig aquaculture. This study, conducted in 2013, aimed to determine the residues of 11 types of antimicrobials by UPLC-MS/MS analysis in fish feed (n=37), pig feed (n=9), pig manure (n=9), pond sediment (n=20), fish skin (n=20) and muscle tissue (n=20) sampled from integrated tilapia-pig farms, non-integrated tilapia farms and fish feed supply shops. There was a higher occurrence of antimicrobial residues in fish skin from both integrated and non-integrated farms, and in pig manure. Enrofloxacin (3.9-129.3μg/kg) and sulfadiazine (0.7-7.8μg/kg) were commonly detected in fish skin and muscle, pig manure and pond sediment from integrated farms, with different types of antimicrobials found in pig manure and tilapia samples. In non-integrated farms, sulfadiazine (2.5-89.9μg/kg) was the predominant antimicrobial detected in fish skin and muscle, fish feed and pond sediment. In general, antimicrobials seemed not to be commonly transmitted from pig to fish in tilapia-pig integrated farms, and fish feed, pig feed and pond sediment did not seem as important sources of the antimicrobials found in fish from both systems. The frequent findings of antimicrobial residues in fish skin compared with fish muscle was probably due to different pharmacokinetics in different tissue types, which have practical food safety implications since antimicrobial residues monitoring is usually performed analyzing mixed skin and fish muscle samples.

National Antimicrobial Resistance Monitoring System: Two Decades of Advancing Public Health Through Integrated Surveillance of Antimicrobial Resistance

Drug-resistant bacterial infections pose a serious and growing public health threat globally. In this review, we describe the role of the National Antimicrobial Resistance Monitoring System (NARMS) in providing data that help address the resistance problem and show how such a program can have broad positive impacts on public health. NARMS was formed two decades ago to help assess the consequences to human health arising from the use of antimicrobial drugs in food animal production in the United States. A collaboration among the Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, the United States Department of Agriculture, and state and local health departments, NARMS uses an integrated "One Health" approach to monitor antimicrobial resistance in enteric bacteria from humans, retail meat, and food animals. NARMS has adapted to changing needs and threats by expanding surveillance catchment areas, examining new isolate sources, adding bacteria, adjusting sampling schemes, and modifying antimicrobial agents tested. NARMS data are not only essential for ensuring that antimicrobial drugs approved for food animals are used in ways that are safe for human health but they also help address broader food safety priorities. NARMS surveillance, applied research studies, and outbreak isolate testing provide data on the emergence of drug-resistant enteric bacteria; genetic mechanisms underlying resistance; movement of bacterial populations among humans, food, and food animals; and sources and outcomes of resistant and susceptible infections. These data can be used to guide and evaluate the impact of science-based policies, regulatory actions, antimicrobial stewardship initiatives, and other public health efforts aimed at preserving drug effectiveness, improving patient outcomes, and preventing infections. Many improvements have been made to NARMS over time and the program will continue to adapt to address emerging resistance threats, changes in clinical diagnostic practices, and new technologies, such as whole genome sequencing.

Degradation of chloramphenicol by UV/chlorine treatment: Kinetics, mechanism and enhanced formation of halonitromethanes

Ultraviolet (UV)/chlorine process is considered as an emerging advanced oxidation process for the degradation of micropollutants. This study investigated the degradation of chloramphenicol (CAP) and formation of disinfection by-products (DBPs) during the UV/chlorine treatment. It was found that CAP degradation was enhanced by combined UV/chlorine treatment compared to that of UV and chlorination treatment alone. The pseudo-first-order rate constant of the UV/chlorine process at pH 7.0 reached 0.016 s^-1, which was 10.0 and 2.0 folds that observed from UV and chlorination alone, respectively. The enhancement can be attributed to the formation of diverse radicals (HO and reactive chlorine species (RCSs)), and the contribution of RCSs maintained more stable than that of HO at pH 5.5-8.5. Meanwhile, enhanced DBPs formation during the UV/chlorine treatment was observed. Both the simultaneous formation and 24-h halonitromethanes formation potential (HNMsFP) were positively correlated with the UV/chlorine treatment time. Although the simultaneous trichloronitromethane (TCNM) formation decreased with the prolonged UV irradiation, TCNM dominated the formation of HNMs after 24 h (>97.0%). According to structural analysis of transformation by-products, both the accelerated CAP degradation and enhanced HNMs formation steps were proposed. Overall, the formation of diverse radicals during the UV/chlorine treatment accelerated the degradation of CAP, while also enhanced the formation of DBPs simultaneously, indicating the need for DBPs evaluation before the application of combined UV/chlorine process.

Long-term spatiotemporal trends and health risk assessment of oyster arsenic levels in coastal waters of northern South China Sea

Long-term spatiotemporal trends and health risk assessment of oyster arsenic levels in the coastal waters of northern South China Sea were investigated in order to help improve the quality and safety control and sustainable aquaculture for mollusks in China. Cultured oysters (Crassostrea rivularis) collected from the waters of 23 bays, harbors, and estuaries along the coast of northern South China Sea from 1989 to 2012 were examined for spatial patterns and long-term temporal trends of oyster arsenic levels. Single-factor index and health risk assessment were used to quantify arsenic exposure to human health through oyster consumption. Overall, arsenic was detected in 97.4% of the oyster samples, and oyster arsenic levels were non-detectable-2.51 mg/kg with an average of 0.63 ± 0.54 mg/kg. Oyster arsenic levels in the coastal waters of northern South China Sea showed an overall decline from 1989 to 2012, remained relatively low since 2005, and slightly increased after 2007. Oyster arsenic levels in Guangdong coastal waters were much higher with more variation than in Guangxi and Hainan coastal waters, and the long-term trends of oyster arsenic levels in Guangdong coastal waters dominated the overall trends of oyster arsenic levels in the coastal waters of northern South China Sea. Within Guangdong Province, oyster arsenic levels were highest in east Guangdong coastal waters, followed by the Pearl River estuary and west Guangdong coastal waters. Single-factor index ranged between 0.27 and 0.97, and average health risk coefficient was 3.85 × 10^-5, both suggesting that oyster arsenic levels in northern South China Sea are within the safe range for human consumption. However, long-term attention should be given to seafood market monitoring in China and the risk of arsenic exposure to human health through oyster consumption.

Removal of antibiotics in sponge membrane bioreactors treating hospital wastewater: Comparison between hollow fiber and flat sheet membrane systems

Hollow fiber (HF) and flat sheet (FS) Sponge MBRs were operated at 10-20 LMH flux treating hospital wastewater. Simultaneous nitrification denitrification (SND) occurred considerably with TN removal rate of 0.011-0.020mg TN mgVSS^-1d^-1. Furthermore, there was a remarkable removal of antibiotics in both Sponge MBRs, namely Norfloxacin (93-99% (FS); 62-86% (HF)), Ofloxacin (73-93% (FS); 68-93% (HF)), Ciprofloxacin (76-93% (FS); 54-70% (HF)), Tetracycline (approximately 100% for both FS and HF) and Trimethoprim (60-97% (FS); 47-93% (HF). Whereas there was a quite high removal efficiency of Erythromycin in Sponge MBRs, with 67-78% (FS) and 22-48% (HF). Moreover, a slightly higher removal of antibiotics in FS than in HF achieved, with the removal rate being of 0.67-32.40 and 0.44-30.42µgmgVSS^-1d^-1, respectively. In addition, a significant reduction of membrane fouling of 2-50 times was achieved in HF-Sponge MBR for the flux range.

In vitro assessment of the antimicrobial activity of silver and zinc oxide nanoparticles against fish pathogens

BACKGROUND

Antibiotic resistance is a global issue that threatens public health. The excessive use of antibiotics contributes to this problem as the genes of antibiotic resistance can be transferred between the bacteria in humans, animals and aquatic organisms. Metallic nanoparticles could serve as future substitutes for some conventional antibiotics because of their antimicrobial activity. The aim of this study was to evaluate the antimicrobial effects of silver and zinc oxide nanoparticles against major fish pathogens and assess their safety in vitro. Silver nanoparticles were synthesized by chemical reduction and characterized with UV-Vis spectroscopy, transmission electron microscopy and zeta sizer. The concentrations of silver and zinc oxide nanoparticles were measured using inductively coupled plasma-mass spectrometry. Subsequently, silver and zinc oxide nanoparticles were tested for their antimicrobial activity against Aeromonas hydrophila, Aeromonas salmonicida subsp. salmonicida, Edwardsiella ictaluri, Edwardsiella tarda, Francisella noatunensis subsp. orientalis, Yersinia ruckeri and Aphanomyces invadans and the minimum inhibitory concentrations were determined. MTT assay was performed on eel kidney cell line (EK-1) to determine the cell viability after incubation with nanoparticles. The interaction between silver nanoparticles and A. salmonicida was investigated by transmission electron microscopy.

RESULTS

The tested nanoparticles exhibited marked antimicrobial activity. Silver nanoparticles inhibited the growth of both A. salmonicida and A. invadans at a concentration of 17 µg/mL. Zinc oxide nanoparticles inhibited the growth of A. salmonicida, Y. ruckeri and A. invadans at concentrations of 15.75, 31.5 and 3.15 µg/mL respectively. Silver nanoparticles showed higher cell viability when compared to zinc oxide nanoparticles in the MTT assay. Transmission electron microscopy showed the attachment of silver nanoparticles to the bacterial membrane and disruption of its integrity.

CONCLUSIONS

This is the first study on inhibitory effects of silver and zinc oxide nanoparticles towards A. salmonicida and A. invadans. Moreover, zinc oxide nanoparticles inhibited the growth of Y. ruckeri. In low concentrations, silver nanoparticles were less cytotoxic than zinc oxide nanoparticles and represent an alternative antimicrobial compound against A. hydrophila, A. salmonicida and A. invadans.

From ice-binding proteins to bio-inspired antifreeze materials

Ice-binding proteins (IBP) facilitate survival under extreme conditions in diverse life forms. IBPs in polar fishes block further growth of internalized environmental ice and inhibit ice recrystallization of accumulated internal crystals. Algae use IBPs to structure ice, while ice adhesion is critical for the Antarctic bacterium Marinomonas primoryensis. Successful translation of this natural cryoprotective ability into man-made materials holds great promise but is still in its infancy. This review covers recent advances in the field of ice-binding proteins and their synthetic analogues, highlighting fundamental insights into IBP functioning as a foundation for the knowledge-based development of cheap, bio-inspired mimics through scalable production routes. Recent advances in the utilisation of IBPs and their analogues to e.g. improve cryopreservation, ice-templating strategies, gas hydrate inhibition and other technologies are presented.

Distribution and sources of organic carbon, nitrogen and their isotopes in surface sediments from the largest mariculture zone of the eastern Guangdong coast, South China

China is the world's largest mariculture producer. However, there is limited detailed information on organic matter distribution generated by mariculture in China. This study assessed the total organic carbon (TOC), total nitrogen (TN), and isotopic composition (δ¹³C and δ¹⁵N) in surface sediments from Zhelin Bay in South China. TOC, TN, δ¹³C and δ¹⁵N ranged from 0.46-1.23%, 0.08-0.20%, -22.07 to -21.13‰ and 5.28-7.14‰, respectively, and followed similar spatial patterns. The C/N ratio coupled with isotopic composition (δ¹³C and δ¹⁵N), indicates that the TOC originated from both terrestrial and marine sources. In general, surface sediments of Zhelin Bay were dominated by marine derived organic carbon; this form of carbon was separately calculated based on δ¹³C-based two end-member mixing and C/N ratio models.

Microbial Diseases of Bivalve Mollusks: Infections, Immunology and Antimicrobial Defense

A variety of bivalve mollusks (phylum Mollusca, class Bivalvia) constitute a prominent commodity in fisheries and aquacultures, but are also crucial in order to preserve our ecosystem’s complexity and function. Bivalve mollusks, such as clams, mussels, oysters and scallops, are relevant bred species, and their global farming maintains a high incremental annual growth rate, representing a considerable proportion of the overall fishery activities. Bivalve mollusks are filter feeders; therefore by filtering a great quantity of water, they may bioaccumulate in their tissues a high number of microorganisms that can be considered infectious for humans and higher vertebrates. Moreover, since some pathogens are also able to infect bivalve mollusks, they are a threat for the entire mollusk farming industry. In consideration of the leading role in aquaculture and the growing financial importance of bivalve farming, much interest has been recently devoted to investigate the pathogenesis of infectious diseases of these mollusks in order to be prepared for public health emergencies and to avoid dreadful income losses. Several bacterial and viral pathogens will be described herein. Despite the minor complexity of the organization of the immune system of bivalves, compared to mammalian immune systems, a precise description of the different mechanisms that induce its activation and functioning is still missing. In the present review, a substantial consideration will be devoted in outlining the immune responses of bivalves and their repertoire of immune cells. Finally, we will focus on the description of antimicrobial peptides that have been identified and characterized in bivalve mollusks. Their structural and antimicrobial features are also of great interest for the biotechnology sector as antimicrobial templates to combat the increasing antibiotic-resistance of different pathogenic bacteria that plague the human population all over the world.

Electrocatalytic reduction of low-concentration thiamphenicol and florfenicol in wastewater with multi-walled carbon nanotubes modified electrode

The electrocatalytic reduction of thiamphenicol (TAP) and florfenicol (FF) was investigated with multi-walled carbon nanotubes (MWCNTs) modified electrode. MWCNTs was dispersed in pure water with the assistance of dihexadecyl phosphate (DHP), and then modified on glassy carbon electrode (GCE). The electrocatalytic reduction conditions, such as bias voltage, supporting electrolyte and its initial pH, and the initial concentrations of TAP and FF, were also optimized. The experimental results indicated that the removal efficiencies of 2mgL^-1 TAP and FF in 0.1M NH₃·H₂O-NH₄Cl solution (pH 7.0) reached 87% and 89% at a bias voltage of -1.2V after 24h electrocatalytic reduction, respectively. The removal process could be described by pseudo first-order kinetic model, and the removal rate constants of TAP and FF were obtained as 0.0837 and 0.0915h^-1, respectively. The electrocatalytic reduction products of TAP and FF were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the possible reduction mechanisms were preliminarily analyzed. Electrocatalytic reduction is promising to remove low-concentration TAP and FF in wastewater with the MWCNTs modified electrode, and may cut down their toxicity through dehalogenation and carbonyl reduction.

Industrial release of fluoroquinolones (FQs) in the waste water bodies with their associated ecological risk in Pakistan

The unchecked production and use of fluoroquinolones (FQs) for the treatment of infections in human and livestock has increased in Pakistan, which resulted in large amount of antibiotics in water bodies. In the current study, the prevalence and associated ecological risk of three FQs were investigated in waste-water bodies and sludge samples of Kahuta and Hattar industrial zones. The average concentrations of ciprofloxacin (CIP), enrofloxacin (ENR) and levofloxacin (LEV) in the waste-water samples were slightly higher in Kahuta (i.e. 58, 32.9, and 36.7μgL^-1 respectively), than those in Hattar sites (i.e. 42.1, 41.2, and 48.9μgL^-1 respectively). However, the concentrations of CIP, ENR and LEV in the sludge samples were significantly higher (i.e. 159; 153 and 164μgkg^-1 respectively) in Hattar sites, compared to those in Kahuta sites (i.e. 129, 58 and 91μgkg^-1 respectively). The uses of FQs in the health sector resulted in water pollution and poses the ecological risk to aquatic organisms. The individual risk associated with CIP was highest in Kahuta industrial sites for green algae ranging (2900-9100) followed by M. aeruginosa (5800-18200), cyanobacteria (580-18204) and invertebrates (24.2-75.8). These values suggested that the prevalence of antibiotics in the waste-disposal sites could be potential risk for the aquatic ecosystem, and harmful to biodiversity.

Effect of florfenicol and thiamphenicol exposure on the photosynthesis and antioxidant system of Microcystis flos-aquae

Florfenicol (FF) and thiamphenicol (TAP) are two typical pharmaceuticals used widely as therapeutica antibiotic agents in aquaculture. However, little is known about the potential adverse effects of these two antibiotics on non-target organisms in the aquatic ecosystem. In this study we investigated the effects of FF and TAP on photosynthesis and the antioxidant system of the cyanobacteria Microcystis flos-aquae. Over a concentration range of 0.001-1μg/L, the results showed that both FF and TAP significantly increased the chlorophyll a content of M. flos-aquae, while the superoxide dismutase (SOD) activity, catalase (CAT) activity and the levels of malondialdehyde (MDA) changed slightly. In contrast, the chlorophyll a content of M. flos-aqua was significantly inhibited (p<0.01) at high concentrations (>1μg/L) of FF and TAP, reaching a 46% inhibition level at 50μg/L FF and 56% inhibition at 100μg/L TAP. At the same time, the activities of SOD and CAT along with MDA content also increased significantly (p<0.01), indicating that the high concentrations of both FF and TAP led to oxidative stress in the algae. In addition, the M. flos-aquae fluorescence parameters (Fv/Fm, Fv/Fo, alpha, ETRmax and Ik) increased with increasing concentration of both FF and TAP, which may be the result of the increasing photoprotection capacity.

Establishment and characterization of a cell line from the head kidney of golden pompano Trachinotus ovatus and its application in toxicology and virus susceptibility

A cell line derived from the head kidney of golden pompano Trachinotus ovatus (TOHK) was established and characterized in this study. The TOHK cells grew most rapidly at 28° C and the optimum foetal bovine serum concentration in L-15 medium was 10%. The TOHK cells have a diploid chromosome number of 2N = 54. The transfection efficiency of TOHK cells was 7·5% at the 15th passage and 72% at the 40th passage. The transfection efficiency in TOHK cells was high, so these cells are suitable for foreign gene expression. The cytotoxic effects of heavy metals and extracellular products from Vibrio anguillarum and Vibrio alginolyticus were demonstrated in TOHK cells, so this TOHK cell line could also be applied in environmental monitoring of heavy metals and pathogenic bacteria. TOHK cell line showed high virus susceptibility, such as grouper nervous necrosis virus (GNNV) and Singapore grouper iridovirus (SGIV). Then, TOHK cell line could be used for the study of viral pathogenesis and the development of antiviral strategies.

Usage, residue, and human health risk of antibiotics in Chinese aquaculture: A review

Aquaculture is a booming industry in the world and China is the largest producer and exporter of aquatic products. To prevent and treat diseases occurred in aquaculture, antibiotics are widely applied. However, the information of antibiotics used in Chinese aquaculture is still limited. Based on peer-reviewed papers, documents, reports, and even farmer surveys, this review summarized antibiotics used in Chinese aquaculture. In 2014, more than 47.4 million tonnes of farmed aquatic products were produced in mainland China. The outputs in the east and south parts of China can reach as much as 600 times higher than those in the northwest areas, which is clearly separated by the "Hu Line" - a line that marks a striking difference in the distribution of population. A total of 20 antibiotics belonging to eight categories have been reported for use, mainly via oral administration. However, only 13 antibiotics have been authorized for application in Chinese aquaculture and 12 antibiotics used are not authorized. Totally, 234 cases on antibiotic residues in Chinese aquatic products were recorded, including 24 fish species, eight crustacean species, and four mollusk species. Thirty-two antibiotics have been detected in aquatic products; quinolones and sulfonamides were the dominated residual chemicals. For specific compound, ciprofloxacin, norfloxacin, and sulfisoxazole have the highest concentrations. Except for a few cases, all residual concentrations were lower than the maximum residue limits. Through the consumption of aquatic products tainted by antibiotics, humans may acquire adverse drug reactions or antibiotic-resistant bacteria. However, the risk of antimicrobial resistance in human body, when exposed to antibiotics at sub-inhibitory concentrations, has not been exhaustively considered in the risk assessment. In addition, a national comprehensive investigation on the amount of antibiotics used in Chinese aquaculture is still needed in future studies.

Concentration and Human Health Implications of Trace Metals in Fish of Economic Importance in Lagos Lagoon, Nigeria

BACKGROUND

The most significant sources of food-borne diseases are microbiological and chemical hazards. The health risk due to consumption of food from aquatic ecosystems contaminated with hazardous chemicals including metals has increased globally, especially in developing countries like Nigeria.

OBJECTIVES

The concentration and human health implications of trace metals in fish of economic importance in Lagos lagoon were investigated by determining the degree of contamination with heavy metals of selected fish from Lagos lagoon and assessing the possible health risks associated with fish consumption.

METHODS

Fish of economic importance including Caranx hippos, Chrysichthys nigrodigitatus, Elops lacerta, Galeoides decadactylus, Ilisha africana, Liza falcipinnis, Lutjanus goreensis, Mugil cephalus, Pseudotolithus senegalensis, Sarotherodon spp, Sphyraena spp, and Tilapia spp were bought from fishermen fishing in Lagos lagoon. The fish tissue samples were digested and analyzed in five replicates for heavy metals (lead, cadmium, iron, manganese and zinc) using a Varian AA600 atomic absorption spectrometer.

RESULTS

There were considerable variations in the concentrations of heavy metals among different species. The twelve fish species collected from Lagos lagoon were found to contain various concentrations of heavy metals and the levels of accumulation of these heavy metals varied across different species. Lead, cadmium, and manganese were present in all the studied fish species at higher concentrations than the maximum allowable concentrations in fish recommended by the Food and Agricultural Organization (FAO) and World Health Organization (WHO). The target hazard quotient (THQ) estimated for individual heavy metals through consumption of different fish species was less than 1 for all individual heavy metal in all the fish species.

CONCLUSIONS

Controls on the dumping of wastes in the lagoon are needed, along with regular monitoring. Currently, no potential non-carcinogenic health risks from ingestion of a single heavy metal through consumption of these fish species was found.

Effect of forestry-waste biochars on adsorption of Pb(II) and antibiotic florfenicol in red soil

Biochars derived from Pinus massoniana and Cunninghamia lanceolata trunks (abbreviated as PB and CB, respectively) were used to investigate their potential capabilities to improve lead (Pb(II)) and antibiotic florfenicol (FLO) immobilization in soil. Results shows that, after incubation for 60 days, the maximum adsorption capacities (Q _m ) of biochar-treated soils (soil-PB and soil-CB) for Pb(II) was increased by 27 and 14 %, respectively, compared with pristine soil sample. In the case of FLO, however, the Q _m of biochar-treated soils were enhanced by 266 and 206 % for soil-PB and soil-CB, respectively. The increased Pb(II) adsorption was mainly due to the enhanced interactions between Pb(II) and oxygen-containing functional groups and aromatic structures in biochars. Whereas, the improvement of FLO adsorption was achieved through electrostatic interaction, hydrogen bonding, and van der Waals forces interactions between FLO molecule and biochars. Regardless of the similarities in chemical compositions between two biochars, significantly higher surface area and total pore volume of PB than CB biochar may be the key factors accounting for the differences in adsorption efficiencies for Pb(II) and FLO between Soil-PB and Soil-CB.

Characterization of CTX-M enzymes, quinolone resistance determinants, and antimicrobial residues from hospital sewage, wastewater treatment plant, and river water

Multidrug-resistant (MDR) bacteria are widespread in hospitals and have been increasingly isolated from aquatic environments. The aim of the present study was to characterize extended-spectrum β-lactamase (ESBL) and quinolone-resistant Enterobacteriaceae from a hospital effluent, sanitary effluent, inflow sewage, aeration tank, and outflow sewage within a wastewater treatment plant (WWTP), as well as river water upstream and downstream (URW and DRW, respectively), of the point where the WWTP treated effluent was discharged. β-lactamase (bla) genes, plasmid-mediated quinolone resistance (PMQR), and quinolone resistance-determining regions (QRDRs) were assessed by amplification and sequencing in 55 ESBL-positive and/or quinolone-resistant isolates. Ciprofloxacin residue was evaluated by high performance liquid chromatography. ESBL-producing isolates were identified in both raw (n=29) and treated (n=26) water; they included Escherichia coli (32), Klebsiella pneumoniae (22) and Klebsiella oxytoca (1). Resistance to both cephalosporins and quinolone was observed in 34.4% of E. coli and 27.3% of K. pneumoniae. Resistance to carbapenems was found in 5.4% of K. pneumoniae and in K. oxytoca. Results indicate the presence of bla_CTX-M (51/55, 92.7%) and bla_SHV (8/55, 14.5%) ESBLs, and bla_GES (2/55, 3.6%) carbapenemase-encoding resistance determinants. Genes conferring quinolone resistance were detected at all sites, except in the inflow sewage and aeration tanks. Quinolone resistance was primarily attributed to amino acid substitutions in the QRDR of GyrA (47%) or to the presence of PMQR (aac-(6')-Ib-cr, oqxAB, qnrS, and/or qnrB; 52.9%) determinants. Ciprofloxacin residue was absent only from URW. Our results have shown strains carrying ESBL genes, PMQR determinants, and mutations in the gyrA QRDR genes mainly in hospital effluent, URW, and DRW samples. Antimicrobial use, and the inefficient removal of MDR bacteria and antibiotic residue during sewage treatment, may contribute to the emergence and spreading of resistance in the environment, making this a natural reservoir.

Leaching behavior of veterinary antibiotics in animal manure-applied soils

Agricultural fields worldwide are being contaminated by the escalating application of veterinary antibiotics (VAs) via animal manure and biosolids applied as fertilizers or of wastewater for irrigation, resulting in soil degradation and damage to the health of terrestrial environments. This paper describes a series of column studies investigating the leaching behavior of five VAs, tetracycline (TC), sulfamethazine (SMZ), norfloxacin (NOR), erythromycin (ERY) and chloramphenicol (CAP), under different simulated rainfall conditions that could occur in agricultural environments. Our aim was to explore the effects of acid rain and torrential rain on the leaching of different VAs and to determine their leaching behaviors along the soil profile. The results showed that acid rain accelerated the accumulation of VAs from animal manure in surface soil while long rainfall durations promoted the downward migration of VAs in soil. Under acid rain conditions, a higher concentration of VAs remained in the animal manure. More VAs were eluted to deeper soil layers and the leachate under extreme rainfall conditions. The leachability of VAs was higher in sandy soil than in clay or loamy soil. SMZ and ERY posed a higher risk to deeper soil layers and groundwater, while NOR and TC tended to persist in surface soil, which can be explained by their different physicochemical properties in soil. Moreover, the general trends from two model assessments and soil column measurements appeared to be in agreement. SMZ had a high leachability, while NOR tended to accumulate in soils. This study provided vital insight into the persistence mechanisms of VAs in terrestrial environments and their potential risks to soils and groundwater.

Heavy metals in fish tissues/stomach contents in four marine wild commercially valuable fish species from the western continental shelf of South China Sea

The concentrations of heavy metals (Cd, Pb, Cr, Ni, Cu and Zn) were determined in four commercially valuable fish species (Thunnus obesus, Decapterus lajang, Cubiceps squamiceps and Priacanthus macracanthus), collected in the western continental shelf of the South China Sea. Concentrations of Cd, Pb, Cr, Ni, Cu, and Zn in fish muscles were 0.006-0.050, 0.13-0.68, 0.18-0.85, 0.11-0.25, 0.12-0.77, and 2.41-4.73μg/g, wet weight, respectively. Concentrations of heavy metals in all species were below their acceptable daily upper limit, suggesting human consumption of these wild fish species may be safe, with health risk assessment based on the target hazard quotients (THQ) and total THQ, indicating no significant adverse health effects with consumption. The average concentrations of Zn were higher in gills than in stomach contents, backbones or muscle, while conversely, the other heavy metals had higher concentrations in stomach contents than in other tissues.

Nutrients, heavy metals and microbial communities co-driven distribution of antibiotic resistance genes in adjacent environment of mariculture

With the rapid development of aquaculture, the large amounts of pollutants were discharged into the aquatic environment, where the detected antibiotic resistance genes (ARGs) have drawn increasing attention due to their potential threats to ecological environment and human health. Thus, the impact of mariculture on ARGs was assessed and the underlying mechanism of their propagation was explained. Sediments from eight sampling sites were collected along a mariculture drainage ditch, and the sediment in Yellow River Delta National Park was used as a non-mariculture control. Microbial ARGs qPCR array and illumina sequencing of 16S rRNA gene were applied to examine the changing patterns of ARGs and bacterial communities. Results showed that 18 ARGs (3 fluoroquinolone, 1 aminoglycoside, 3 macrolide-lincosamide-streptogramin B, 2 tetracycline, and 9 beta-lactam resistance genes) were influenced by mariculture, and ARGs abundance and diversity were significantly increased in mariculture sediments (p < 0.05). A remarkable shift in bacterial community structure and composition was also observed. The abundance of most of ARGs were significantly decreased in the estuary samples, implying that seawater had a significant dilution effect on the ARGs emission from the mariculture sites. Partial redundancy analysis showed that nutrients, heavy metals, and bacteria communities might directly and indirectly contribute to ARGs propagation, suggesting that the profile and dissemination of ARGs were driven by the combined effects of multiple factors in mariculture-impacted sites.

EMA and EFSA Joint Scientific Opinion on measures to reduce the need to use antimicrobial agents in animal husbandry in the European Union, and the resulting impacts on food safety (RONAFA)

EFSA and EMA have jointly reviewed measures taken in the EU to reduce the need for and use of antimicrobials in food-producing animals, and the resultant impacts on antimicrobial resistance (AMR). Reduction strategies have been implemented successfully in some Member States. Such strategies include national reduction targets, benchmarking of antimicrobial use, controls on prescribing and restrictions on use of specific critically important antimicrobials, together with improvements to animal husbandry and disease prevention and control measures. Due to the multiplicity of factors contributing to AMR, the impact of any single measure is difficult to quantify, although there is evidence of an association between reduction in antimicrobial use and reduced AMR. To minimise antimicrobial use, a multifaceted integrated approach should be implemented, adapted to local circumstances. Recommended options (non-prioritised) include: development of national strategies; harmonised systems for monitoring antimicrobial use and AMR development; establishing national targets for antimicrobial use reduction; use of on-farm health plans; increasing the responsibility of veterinarians for antimicrobial prescribing; training, education and raising public awareness; increasing the availability of rapid and reliable diagnostics; improving husbandry and management procedures for disease prevention and control; rethinking livestock production systems to reduce inherent disease risk. A limited number of studies provide robust evidence of alternatives to antimicrobials that positively influence health parameters. Possible alternatives include probiotics and prebiotics, competitive exclusion, bacteriophages, immunomodulators, organic acids and teat sealants. Development of a legislative framework that permits the use of specific products as alternatives should be considered. Further research to evaluate the potential of alternative farming systems on reducing AMR is also recommended. Animals suffering from bacterial infections should only be treated with antimicrobials based on veterinary diagnosis and prescription. Options should be reviewed to phase out most preventive use of antimicrobials and to reduce and refine metaphylaxis by applying recognised alternative measures.

Effect of dietary poly-β-hydroxybutyrate (PHB) on growth performance, intestinal health status and body composition of Pacific white shrimp Litopenaeus vannamei (Boone, 1931)

In the present study, the effect of dietary supplementation of poly-β-hydroxybutyrate (PHB) on the growth performance, intestinal digestive and immune function, intestinal short-chain fatty acids (SCFA) content and body composition of Pacific white shrimp Litopenaeus vannamei (Boone, 1931) was evaluated. The shrimp was fed for 35 days with four different diets: 0%, 1%, 3% and 5% PHB supplemented feed. The results indicated that supplementation of PHB significantly increased the growth performance of the shrimp, and the feed conversion rate (FCR) in 3%PHB treatment group was significantly lower than the control (P < 0.05). The intestinal amylase, lipase and trypsin activity in the three PHB treatment groups were all significantly higher than that of the control (P < 0.05), but the pepsin activity were only significantly affected by 3%PHB treatment (P > 0.05). The activities of intestinal immune enzymes such as total antioxidant capacity (T-AOC) and inducible nitric oxide synthase (iNOS) was significantly induced by 3%PHB treatment (P < 0.05), while lysozyme (LSZ) activity was significantly affected by 5%PHB treatment and nitric oxide (NO) content was significantly induced in three PHB treatments. Meanwhile, PHB induced significantly the expression level of intestinal heat shock protein 70 (HSP70), Toll and immune deficiency (Imd) gene. HE staining showed that PHB induced the intestinal health status of L. vannamei. Intestinal SCFA content analysis revealed that the content of propionic and butyric acid of 3%PHB treatment were significantly higher than that of the control (P < 0.05). Body composition analysis showed that the crude protein in 3% and 5%PHB treatments, and the crude lipid in 1% and 5%PHB treatments were all significantly higher than the control (P < 0.05). These results revealed that PHB could improve the growth performance, modulated intestinal digestive and immune function, increased intestinal SCFA content and body composition in L. vannamei, and the optimum dietary PHB requirement by L. vannamei was estimated at 3% (w/w) diet.

Establishment and characterization of a mid-kidney cell line derived from golden pompano Trachinotus ovatus, a new cell model for virus pathogenesis and toxicology studies

Golden pompano Trachinotus ovatus, a popularly cultured and commercially important marine fish worldwide, has been recognized as a promising candidate for mariculture. However, outbreaks of infectious bacterial or viral diseases and environmental deterioration have led to great economic losses in T. ovatus aquaculture recently. In our research, we established a new mid-kidney cell line, designated as TOK, from golden pompano, T. ovatus. The optimized growth temperature and working concentration of fetal bovine serum (FBS) were 28°C and 10-20%, respectively. Foreign genes could express well in TOK cells. The modal number of TOK cells was 54. The TOK cells were susceptive to Singapore grouper iridovirus (SGIV) and red-spotted grouper nervous necrosis virus (RGNNV), and the virus could propagate in cells. Propagation was verified by qRT-PCR, and virions were observed under electron microscopy. Cytotoxicity analysis revealed that TOK cells were sensitive to different concentrations of extracellular products (ECPs) from Vibrio alginolyticus and V. anguillarum. Moreover, heavy metals (Cd, Cu, and Hg) also showed dose-dependent cytotoxicity to the TOK cell line. We established a mid-kidney cell line from T. ovatus which could be applied to cytotoxicity assays of heavy metals. The newly established TOK cell line possesses great application potential in genetic manipulation, virus-host interaction studies, and toxicity assays of bacterial extracellular products and heavy metals.

Competitive sorption of heavy metals by water hyacinth roots

Heavy metal pollution is a global issue severely constraining aquaculture practices, not only deteriorating the aquatic environment but also threatening the aquaculture production. One promising solution is adopting aquaponics systems where a synergy can be established between aquaculture and aquatic plants for metal sorption, but the interactions of multiple metals in such aquatic plants are poorly understood. In this study, we investigated the absorption behaviors of Cu(II) and Cd(II) in water by water hyacinth roots in both single- and binary-metal systems. Cu(II) and Cd(II) were individually removed by water hyacinth roots at high efficiency, accompanied with release of protons and cations such as Ca²⁺ and Mg²⁺. However, in a binary-metal arrangement, the Cd(II) sorption was significantly inhibited by Cu(II), and the higher sorption affinity of Cu(II) accounted for its competitive sorption advantage. Ionic exchange was identified as a predominant mechanism of the metal sorption by water hyacinth roots, and the amine and oxygen-containing groups are the main binding sites accounting for metal sorption via chelation or coordination. This study highlights the interactive impacts of different metals during their sorption by water hyacinth roots and elucidates the underlying mechanism of metal competitive sorption, which may provide useful implications for optimization of phytoremediation system and development of more sustainable aquaculture industry.

Co-occurrence of mobile genetic elements and antibiotic resistance genes in municipal solid waste landfill leachates: A preliminary insight into the role of landfill age

Since municipal solid waste (MSW) landfill harbours miscellaneous wastes, pollutants and microorganisms, it gradually becomes a huge potential reservoir for breeding antibiotic resistance genes (ARGs). The objective of this study was to determine the prevalence and diversity of ARGs associated with various mobile genetic elements (MGEs) in MSW landfill leachates. The relationship of ARGs with leachate characteristics was also studied to explore the influence of landfill age. Seven sulfonamides (sulfapyridine, sulfadiazine, sulfathiazole, sulfamethoxazole, sulfamerazine, sulfamethazine and sulfaquinoxaline), three encoded ARGs (sul-I, sul-II and sul-III) and four types of MGEs (plasmids, transposons, integrons and insertion sequences) were quantified in leachates with landfill ages ranging from 3 months-6 years. ARGs increased to an absolute concentration of 10⁶ copies/μL and were positively correlated (p < 0.05) to MGEs. Significant correlations (p < 0.05) were also discovered among ARGs and the increasing humic acids, heavy metals (Zn, Cu and Co) and antibiotics (except for sulfathiazole and sulfaquinoxaline), implying landfilling might contribute to the enrichment of ARGs in the long-term. Non-target full scans revealed the role of persistent unknown compounds in stimulating the ARGs dissemination. Overall, this study demonstrates the exacerbation of ARGs pollution in landfill environment and a detailed delineation of the complex inter-relationships between ARGs and the substances harbouring in landfills is badly required.

Detection of environmental impacts of shrimp farming through multiple lines of evidence

In order to evaluate the impact of semi-intensive shrimp farming, comparisons between Control and Impact areas were made based on multiple lines of evidence using an asymmetrical design. Water and sediment samples were collected in four shrimp farms located in Todos os Santos Bay, Bahia, Brazil. Nutrients, trace elements and macrobenthic assemblages were evaluated using uni- and multivariate analyzes. Significant differences were observed between Impact and Control areas for the water column dataset (i.e., ancillary variables, SPM, dissolved nutrients and major and trace elements in SPM), whereas no significant differences were observed for the chemistry of sediments. Macrobenthic assemblages were negatively affected by shrimp farm activities. Impacted sites presented the lowest abundance, richness and different structure of macrofaunal benthic assemblages. Farms clearly produced negative impacts in the Todos os Santos Bay. This conclusion was only possible to be reached through the use of multiple lines of evidence. Chemistry and benthic assemblages data combined produced a better description of the quality and impacts of the evaluated environments. Different conclusions would have been reached if chemistry and ecology results were studied separately vs. together.

Tracking aquaculture-derived fluoroquinolones in a mangrove wetland, South China

Aquaculture in mangrove wetlands has been developed rapidly, causing various environmental problems (e.g., antibiotic residue). In the present study, the levels and distributions of a well-known class of antibiotics (fluoroquinolones; FQs), including norfloxacin (NOR), ciprofloxacin (CIP), and enrofloxacin (ENR), were examined in sediment and mangrove plant (Aegiceras corniculatum) from a mangrove wetland in the Zhanjiang Mangrove National Nature Reserve, South China. NOR and CIP were detected in all sediment samples, with concentrations ranging from 4.3 to 64.2 ng/g and from 7.62 to 68.5 ng/g on a basis of dry weight (dw), respectively, whereas ENR was found with relatively lower frequency (<78%) and lower concentrations (<19.3 ng/g). Sediments in mangrove rhizosphere area contained considerably higher concentrations of all FQs (except for ENR). FQs were largely varied in mangrove plant tissues; NOR and ENR were not detected in leaf and root samples, respectively. CIP featured an increasing tendency from the root to the upper parts of plants, whereas a decreasing trend was found for NOR. Three bioconcentration factors (BCF_s) of FQs, including BCFs for roots (BCF_r), branches (BCF_b), and leaves (BCF_l) were calculated, and most of them exceeded 1. Especially for NOR, its BCF_r can reach up to 9.9, indicating that Aegiceras corniculatum has a strong ability to accumulate FQs from sediment and/or surrounding environment. For NOR and CIP, strong positive relationships were observed between BCF_r and concentrations in root, but no significant correlations were observed between BCF_r and root lipid of mangrove plant. More studies are needed to investigate the uptake mechanism of antibiotics in mangrove plants.

Comparison of the effects of dietary single and multi-probiotics on growth, non-specific immune responses and disease resistance in starry flounder, Platichthys stellatus

An 8-week feeding trial was conducted to evaluate the effects of dietary probiotics on growth performance and non-specific immune responses in starry flounder, Platichthys stellatus. Fish averaging 46.5 ± 0.65 g (mean ± SD) were fed one of the six experimental diets; one control (Cont), and five other diets were prepared by supplementing single-probiotics 1 (Bacillus subtilis; SP₁, 2 × 10⁹ CFU kg^-1 diet), single-probiotics 2 (Bacillus licheniformis; SP₂, 2 × 10⁹ CFU kg^-1 diet), multi-probiotics 1 (Bacillus subtilis + Bacillus licheniformis; MP₁, 2 × 10⁹ CFU kg^-1 diet), multi-probiotics 2 (commercial probiotics; Bacillus subtills + Bacillus licheniformis + Paenibacillus polymyxa + Aspergillus oryzae + Saccharomyces cerevisiae; MP₂, 2 × 10⁹ CFU kg^-1 diet) and oxytetracycline (OTC) at 5 g OTC kg^-1 diet. At the end of 8 weeks feeding trial, weight gain (WG) and specific growth rate (SGR) of fish fed SP₁, MP₁ and MP₂ diets were significantly higher than those of fish fed control diet (P < 0.05). Superoxide dismutase (SOD) activity of fish fed MP₂ diet was significantly higher than those of fish fed OTC diet (P < 0.05). Nitro blue tetrazolium (NBT) activity and lysozyme activity of fish fed SP₁, MP₁ and MP₂ diets were significantly higher than those of fish fed OTC diet (P < 0.05). However, there was no significant difference among fish fed SP₁, SP₂, MP₁ and MP₂ diets. During the Edwardsiella tarda challenge test, the first mortality occurred on day 2. After the 14 days challenge test, cumulative survival rate of fish fed MP₁ and MP₂ diets were significantly higher than those of fish fed control diet (P < 0.05). However, there was no significant difference among fish fed SP₁, SP₂, MP₁, MP₂ and OTC diets in survival rate at the termination of the challenge test. Although there was little advantage in immunological parameters with fish fed MP diets, single and multi-probiotics were equally effective statistically. These results demonstrated that single or multi-probiotics had equal beneficial effect as an antibiotic replacer in terms of growth performance, non-specific immune responses and disease resistance in starry flounder.

Zero valent iron produces dichloroacetamide from chloramphenicol antibiotics in the absence of chlorine and chloramines

Dichloroacetamide (DCAcAm) is an important type of nitrogenous disinfection byproduct. This study is the first to report that DCAcAm can be formed in the absence of chlorinated disinfectants (chlorine and chloramines). This can occur through reduction of three chloramphenicol (CAP) antibiotics by zero valent iron (ZVI). The effects of key experimental parameters, including reaction time, ZVI dose, pH, temperature, water type, and the presence of humic acid (HA) on the formation of DCAcAm were ascertained. The DCAcAm yields from three CAPs all presented the trend of increasing first and then decreasing with time and also increased with increasing ZVI dosage. DCAcAm yields from the ZVI reduction route were higher than those resulting from the chlorination of some previously identified DCAcAm precursors. Acidic conditions favored the formation of DCAcAm by the ZVI route. In addition, lower temperatures increased DCAcAm yields at extended contact times (>12 h). DCAcAm formed from the three CAPs in the presence of HA was lower than in the absence of HA. The formation potential of DCAcAm from the reduction of authentic waters spiked with CAPs by ZVI showed good linear correlations with initial concentrations of the three CAPs. This allows the formation of DCAcAm from the reduction of CAPs by ZVI to be predicted. Given that many wastewater and drinking water distribution networks contain unlined cast iron pipes, reactions between CAPs and ZVI may contribute to the formation of DCAcAm in such systems.

Influence of waterborne arsenic on nutritive and potentially harmful elements in gilthead seabream (Sparus aurata)

Fish are an important source of nutrients in human nutrition. Although arsenic (As) is considered potentially carcinogenic for human being, very little is known about its toxicity in fish biology. To increase our knowledge of the effect of exposure to waterborne As on fish, gilthead seabream (Sparus aurata) were exposed to 5 μM As₂O₃ and the bioaccumulation of macronutrients (Ca, K, Mg, Na, P), micronutrients (Fe, Mn, Zn) and Potentially Harmful Elements (As, Cd) was determined using spectrometric techniques. All elements were determined in the muscle and liver of non-exposed fish and those exposed to As for 2, 10 or 30 days. The concentrations of K, Na, Mg, Mn and Zn (in muscle) and Fe and Mn (in liver) of control (non-exposed) fish were higher than those determined in exposed fish. Furthermore, neither As nor Cd accumulated in the edible part (muscle) of seabream and were only evident in liver after 30 days of continuous exposure to As, but both concentrations remained below legally established limits.

Human health risks from heavy metals in fish of Buriganga river, Bangladesh

Heavy metals are known to cause deleterious effects on human health through food chain. Human health risks were evaluated from consumption of heavy metal contaminated fish from Buriganga River in Bangladesh. Whole body of five fish species (Puntius ticto, Puntius sophore, Puntius chola, Labeo rohita and Glossogobius giuris) were analyzed which contained various concentrations of Cd, As, Pb, Cr, Ni, Zn, Se, Cu, Mo, Mn, Sb, Ba, V and Ag. Concentrations of Mn, Zn, Se and Pb in all fish species were above the Food Safety Guideline (FSG) by WHO/FAO. Assessment of noncarcinogenic health hazard by target hazard quotient (THQ) indicated no concern from consumption of these fish except for Mn. However, all metals together may affect human health as revealed by hazard index (HI). The target cancer risk (TR) values suggested carcinogenic risk from Ni and As. Taken together it can be concluded that there is potential human health risk in consuming fish from river Buriganga.

Effects of Eryngii mushroom (Pleurotus eryngii) and Lactobacillus plantarum on growth performance, immunity and disease resistance of Pangasius catfish (Pangasius bocourti, Sauvage 1880)

This study was conducted to evaluate the effects of Eryngii mushroom, Pleurotus eryngii (PE), and Lactobacillus plantarum single or combined on growth, innate immune response and disease resistance of the Pangasius catfish, Pangasius bocourti. Two hundred forty fish were divided into four treatments, i.e., 0 g kg(-1) PE (Control, Diet 1), 3 g kg(-1) PE (Diet 2), 10(8) cfu g(-1) L. plantarum (Diet 3) and 3 g kg(-1) PE + 10(8) cfu g(-1) L. plantarum (Diet 4). Fish were culture in glass tanks with water volume approximately of 150 l, and each treatment had four replications with 15 fish per replication. Following 30, 60 and 90 days of the feeding trial, specific growth rate (SGR), feed conversion ratio (FCR), serum lysozyme, phagocytosis and respiratory burst activities were measured. SGR and FCR were significantly improved in fish fed supplemented diets after 90 days of the feeding trial. Serum lysozyme, phagocytosis and respiratory burst activity of fish were significantly stimulated by both PE and L. plantarum diets; however, the highest innate immune response was observed in fish fed synbiotic diet. At the end of the experiment, five fish were randomly selected for a challenge test against Aeromonas hydrophila. The post-challenge survival rate of the fish fed supplemented diets was significantly greater than the control treatment, and the highest post-challenge survival rate was observed in synbiotic diet. The results revealed that dietary supplementation of PE and L. plantarum stimulated growth, immunity and disease resistance of the P. bocourti.

Essential oils to control ichthyophthiriasis in pacu, Piaractus mesopotamicus (Holmberg): special emphasis on treatment with Melaleuca alternifolia

In vitro effect of the Melaleuca alternifolia, Lavandula angustifolia and Mentha piperita essential oils (EOs) against Ichthyophthirius multifiliis and in vivo effect of M. alternifolia for treating ichthyophthiriasis in one of the most important South American fish, Piaractus mesopotamicus (Holmberg), were evaluated. The in vitro test consisted of three EOs, each at concentrations of 57 μL L(-1) , 114 μL L (-1) , 227 μL L(-1) and 455 μL L (-1) , which were assessed once an hour for 4 h in microtitre plates (96 wells). The in vitro results demonstrated that all tested EOs showed a cytotoxic effect against I. multifiliis compared to control groups (P < 0.05). The in vivo treatment for white spot disease was performed in a bath for 2 h day(-1) for 5 days using the M. alternifolia EO (50 μL L (-1) ). In this study, 53.33% of the fish severely infected by I. multifiliis survived after the treatment with M. alternifolia (50 μL L (-1) ) and the parasitological analysis has shown an efficacy of nearly 100% in the skin and gills, while all the fish in the control group died. Furthermore, the potential positive effect of M. alternifolia EO against two emergent opportunistic bacteria in South America Edwardsiella tarda and Citrobacter freundii was discussed.

Effects of halide ions on photodegradation of sulfonamide antibiotics: Formation of halogenated intermediates

The occurrence of sulfonamide antibiotics (SAs) in estuarine waters urges insights into their environmental fate for ecological risk assessment. Although many studies focused on the photochemical behavior of SAs, yet the effects of halide ions relevant to estuarine and marine environments on their photodegradation have been poorly understood. Here, we investigated the effects of halide ions on the photodegradation of SAs with sulfapyridine, sulfamethazine, and sulfamethoxazole as representative compounds. Results showed that halide ions did not significantly impact the photodegradation of sulfapyridine and sulfamethoxazole, while they significantly promoted the photodegradation of sulfamethazine. Further experiments found that ionic strength applied with NaClO4 significantly enhanced the photodegradation of the SAs, which was attributed to the decreased quenching rate constant of the triplet-excited SAs ((3)SA(∗)). Compared with ionic strength, specific Cl(-) effects retarded the photodegradation of the SAs. Our study found that triplet-excited sulfamethazine can oxidize halide ions to produce halogen radicals, subsequently leading to the halogenation of sulfamethazine, which was confirmed by the identification of both chlorinated and brominated intermediates. These results indicate that halide ions play an important role in the photochemical behavior of some SAs in estuarine waters and seawater. The occurrence of halogenation for certain organic pollutants can be predicted by comparing the oxidation potentials of triplet-excited contaminants with those of halogen radicals. Our findings are helpful in understanding the photochemical behavior and assessing the ecological risks of SAs and other organic pollutants in estuarine and marine environment.

Spatial-temporal trend and health implications of polycyclic aromatic hydrocarbons (PAHs) in resident oysters, South China Sea: A case study of Eastern Guangdong coast

Spatial and temporal distributions of polycyclic aromatic hydrocarbons (PAHs) were investigated in Eastern Guangdong coast, China. Total PAH concentrations in oysters ranged from 231 to 1178ng/g with a mean concentration of 622ng/g dry weight. Compared with other bays and estuaries, PAH levels in oysters were moderate. Spatial distribution of PAHs was site specific, with relatively high PAH concentrations observed in Zhelin Bay and Kaozhouyang Bay. Based on the Spearman test analysis, only PAH concentration in oysters from Jiazi Harbor showed a significant increasing trend (P<0.05). Three-ring PAHs were the most abundant, accounting for 54.2%-88.4% of total PAHs. Diagnostic ratios suggested that PAHs were derived mainly from petroleum origin. BaP and ∑4PAH concentrations were well within the European Union limits (5ng/g and 30ng/g wet weight, respectively). The incremental lifetime cancer risks (ILCR) for PAHs were <10(-5), indicating that the adverse health risks associated with oyster consumption in this area were minimal.

Antimicrobial Compounds from Eukaryotic Microalgae against Human Pathogens and Diseases in Aquaculture

The search for novel compounds of marine origin has increased in the last decades for their application in various areas such as pharmaceutical, human or animal nutrition, cosmetics or bioenergy. In this context of blue technology development, microalgae are of particular interest due to their immense biodiversity and their relatively simple growth needs. In this review, we discuss about the promising use of microalgae and microalgal compounds as sources of natural antibiotics against human pathogens but also about their potential to limit microbial infections in aquaculture. An alternative to conventional antibiotics is needed as the microbial resistance to these drugs is increasing in humans and animals. Furthermore, using natural antibiotics for livestock could meet the consumer demand to avoid chemicals in food, would support a sustainable aquaculture and present the advantage of being environmentally friendly. Using natural and renewable microalgal compounds is still in its early days, but considering the important research development and rapid improvement in culture, extraction and purification processes, the valorization of microalgae will surely extend in the future.

Heavy metals in aquatic organisms of different trophic levels and their potential human health risk in Bohai Bay, China

Fourteen aquatic organism samples were collected from Bohai Bay, and concentrations of five heavy metals were measured to evaluate the pollution levels in aquatic organisms and the potential risk to human health. The concentrations of Zn and Cu were much higher than those of Cd, Cr, and Pb in all the organisms. In general, the heavy metal concentration levels were in the order phytoplankton < zooplankton < fish < shrimp < shellfish. Heavy metal concentrations in higher trophic-level aquatic organisms in Bohai Bay were compared to those in the organisms from other worldwide coastal waters. The concentration levels of most heavy metals were higher than the 75th percentile, except that Pb concentration was between the 25th and 50th percentiles. The calculated bioconcentration factors (BCF) of Cr, Cu, and Pb for phytoplankton were less than 100, indicating no accumulation in primary producers. The bioaccumulation factor (BAF) of Pb for zooplankton was the highest, indicating significant Pb accumulation in zooplankton. For higher trophic-level aquatic organisms, the order of BAF values was fish < shrimp < shellfish for most metals except for Pb. The human health risk assessment suggests that strict abatement measures of heavy metals must be taken to decrease the health risk caused by consuming aquatic products.

Adsorption of Antibiotics on Graphene and Biochar in Aqueous Solutions Induced by π-π Interactions

The use of carbon based materials on the removal of antibiotics with high concentrations has been well studied, however the effect of this removal method is not clear on the actual concentration of environments, such as the hospital wastewater, sewage treatment plants and aquaculture wastewater. In this study, experimental studies on the adsorption of 7 antibiotics in environmental concentration of aqueous solutions by carbon based materials have been observed. Three kinds of carbon materials have shown very fast adsorption to antibiotics by liquid chromatography-tandem mass spectrometry (LC-MS-MS) detection, and the highest removal efficiency of antibiotics could reach to 100% within the range of detection limit. Surprisedly, the adsorption rate of graphene with small specific surface area was stronger than other two biochar, and adsorption rate of the two biochar which have approximate specific surface and different carbonization degree, was significantly different. The key point to the present observation were the π-π interactions between aromatic rings on adsorbed substance and carbon based materials by confocal laser scanning microscope observation. Moreover, adsorption energy markedly increased with increasing number of the π rings by using the density functional theory (DFT), showing the particular importance of π-π interactions in the adsorption process.

Ecotoxicological potential of antibiotic pollution-industrial wastewater: bioavailability, biomarkers, and occurrence in Mytilus galloprovincialis

Environmental pollution by pharmaceutical residues has become a major problem in many countries worldwide. However, little is known about the concentrations of pharmaceuticals in water sources in Tunisia. Residues in the natural environment have been of increasing concern due to their impact on bacteria resistance development and toxicity to natural communities and ultimately to public health. In this work, we collected the wastewater sample from a pharmaceutical industry, which specializes in the antibiotics manufacture, during the years 2014-2015. Generally, this effluent is discharged into the marine environment and causes environmental problems. The Mediterranean mussel Mytilus galloprovincialis was commonly used as a model organism for its peculiar morphofunctional properties which also make it an excellent marine environmental biomonitoring species. The histological sections of mussel, which are exposed at different dilutions of pharmaceutical wastewater (PW), indicate a large pathological power revealed on the gills. On the other hand, genotoxicity of the studied effluent was evaluated using comet assay for quantification of DNA fragmentation in gill cells. Results show that PW exhibited a statistically significant (p < 0.001) genotoxic effect in a dose-dependent manner. However, the toxic effects of PW decreased significantly after its treatment with Bacillus atrophaeus. Toxicities can be imputed to the presence of antibiotics. In fact, chemical analysis of the gills of mussel M. galloprovincialis using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) showed the presence of some antibiotic residues. These concentrations decrease to half in mussels treated with PW biodegraded by B. atrophaeus.