Enrofloxacin hydrochloride toxicological effects on crucian carp reflected by serological changes and neurotoxicity.

Due to its water solubility and wide applicability, enrofloxacin hydrochloride (EH) may enter aquatic ecosystems and cause negative effects on aquatic organisms. This study aimed to explore toxicological effects via serological changes and neurotoxicity, which were induced by EH exposure in crucian carp (Carassius auratus var. Pengze). The drug residues in brain tissue and protein content in serum were determined to analyze serological changes. Alterations in brain tissue structure and function, cerebral microvessels permeability, and the expressions of gene and protein regarding blood-brain barrier (BBB) were studied to reflect the neurotoxicity. Employing a validated high-performance liquid chromatography (HPLC) method, EH residues could be detected at various time-points throughout the experiment. Enzyme-linked immunosorbent assay (ELISA) showed that EH increased the levels of S100B, NSE and GFAP proteins in serum. Additionally, there was a significant positive correlation between serum S100B, NSE protein contents and EH residues (P < 0.05). Hematoxylin and eosin (H&E) staining revealed brain damage from EH exposure by the formation of vacuoles in brain glial cells, pyknosis of the nucleus, and a decrease in cell population density. Transmission electron microscope (TEM) revealed morphological changes in microvessels and condensation of astrocyte nucleus. Evans blue (EB) permeability test visualized an obvious increase in cerebral microvessels leakage. The real-time quantitative PCR (qPCR) results indicated that EH up-regulated the mRNA expression levels of S100B, NSE and GFAP, down-regulated the mRNA expression levels of P-gp, ZO-1, Occludin and Claudin-5. The Western blot (WB) results demonstrated increased NSE and GFAP protein expressions, decreased P-gp and Occludin protein expressions following EH exposure in brain, in consistent with the gene expressions, respectively. In conclusion, these findings indicated that EH brought about marked rise in serum biomarker levels and disrupted the central nervous system (CNS) of crucian carp. These data would help elucidate the mechanism underlying EH-induced neurotoxicological effects.

Removal characteristics of microplastics in sewage flowing through a long-term operation surface flow wetland.

Microplastics (MPs) in sewage pose significant threats to aquatic system. Surface flow wetland (SFW) is a common natural wetland type, and is also used as a cheap and easy-to-build sewage treatment system for small and scattered settlements. However, seasonal variation patterns of MPs in sewage removed by SFW are still limited. Therefore, a field investigation was conducted in an SFW that has been operated for 17 years. The concentration of microplastics in the influent of the SFW (CMPs, in) ranged from 56 ± 6 to 250 ± 14 items L-1. The dominant plastic types were fibers and polyethylene terephthalate (PET). CMPs, in were high in summer and winter, significantly related to the seasonal dressing habits. The removal efficiencies of MPs in SFW were 48.03-92.32 % in different seasons, and the mechanisms of MP removal were different with traditional pollutants. Before flowing out occasionally or by heavy precipitation, MPs were primarily trapped in the SFW and underwent certain oxidation. Simulation experiments demonstrated that 47.5-92.9 % of MPs would be trapped in the SFW, and plants would significantly enhance the trapping capacities. This study sheds light on the seasonal variation characteristics and patterns of MPs in actual sewage, and clarifies the fate of MPs in a long-term operation SFW.

Structural characteristics and thermal performances of lauric-myristic-palmitic acid introduced into modified water hyacinth porous biochar for thermal energy storage.

Water hyacinth (WH) was used to prepare biochar for phase change energy storage field to realize encapsulation and enhance thermal conductivity of phase change materials (PCMs) in this work. The maximum specific surface area of modified water hyacinth biochar (MWB) obtained by lyophilization and carbonization at 900 °C was 479.966 m2/g. Lauric-myristic-palmitic acid (LMPA) was used as phase change energy storage material, LWB900 and VWB900 were used as porous carriers respectively. Modified water hyacinth biochar matrix composite phase change energy storage materials (MWB@CPCMs) were prepared by vacuum adsorption method, with loading rates of 80 % and 70 % respectively. The enthalpy of LMPA/LWB900 was 105.16 J/g, which was 25.79 % higher than that of LMPA/VWB900, and the energy storage efficiency was 99.1 %. Moreover, the introduction of LWB900 increased the thermal conductivity (k) of LMPA from 0.2528 W/(m·K) to 0.3574 W/(m·K). MWB@CPCMs have good temperature control capability, and the heating time of LMPA/LWB900 was 15.03 % higher than that of LMPA/VWB900. In addition, after 500 thermal cycles, the maximum change rate of enthalpy of LMPA/LWB900 was 6.56 %, and it maintains a phase change peak, showing better durability than LMPA/VWB900. This study shows that the preparation process of LWB900 is the best, and the adsorption of LMPA has high enthalpy value and stable thermal performance, realizing the sustainable development of biochar.

Pivotal role of water molecules in the photodegradation of pymetrozine: New insights for developing green pesticides.

Photodegradation of the insecticide pymetrozine (PYM) was studied on surface of wax films, and in aqueous and nonaqueous phase. The half-life of PYM on the wax surface was approximately 250 times longer than in water. Scavenging experiments, laser flash photolysis, and spectra analysis indicated the first singlet excited state of PYM (S1 *PYM) to be the most important photoinduced species initiating the photodegradation. Quantum chemistry calculations identified significant molecular torsion and changes in the structure C-CN-N of S1 *PYM, and the absolute charges of the CN atoms increased and the bond strength weakened. Free energy surface analysis, and O18 labeling experiments further confirmed that the mechanism was two-step photoinduced hydrolysis. The first step is the hydrolysis of S1 *PYM at CN upon reaction with 2-3 water molecules (one H2O molecule as the catalyst). The second step is an intramolecular hydrogen transfer coupled with the cleavage of C-N bond and formation of two cyclic products. During the interactions, water molecules experience catalytic activation by transferring protons, while there is a negligible solvent effect. Clarifying the detailed photodegradation mechanisms of PYM is beneficial for the development of green pesticides that are photostable and effective on leaf surfaces, and photolabile and detoxified in the aquatic environment.

Characteristic and Properties of Ternary Shape-Stabilized Composite Phase Change Materials Based on Expanded Graphite.

Myristic acid-palmitic acid-tetradecanol/expanded graphite (MA-PA-TD/EG) and myristic acid-stearic acid-lauric acid/ expanded graphite (MA-SA-LA/EG) were obtained. MA-PA-TD/EG and MA-SA-LA/EG for the optimum mass ratio of 8:1 were investigated by DSC, FT-IR, TG, and SEM, and it was shown that MA-PA-TD and MA-SA-LA phase change materials were evenly distributed in expanded graphite through capillary force. Phase transition temperatures of MA-PA-TD/EG and MA-SA-LA/EG before and after cooling and heating cycles were 34.14, 34.39 °C and 30.21, 30.33 °C, respectively, and MA-PA-TD/EG and MA-SA-LA/EG had good stability. On the other hand, MA-PA-TD/EG was 67% faster than that of MA-PA-TD during solid-liquid phase change, and MA-SA-LA/EG was 63% faster than that of MA-SA-LA. Meanwhile, MA-PA-TD/EG and MA-SA-LA/EG had good thermal stability and heat storage according to thermogravimetric experiments. Therefore, MA-PA-TD/EG and MA-SA-LA/EG are suitable for practical application in buildings.

Effects of MC-LR on histological structure and cell apoptosis in the kidney of grass carp (Ctenopharyngodon idella).

Microcystin-LR (MC-LR) is a well-known hepatotoxin; however, increasing evidence suggests that it might induce kidney injury. Grass carp (Ctenopharyngodon idella) is one of the most important farmed species and may be affected by MC-LR releasing into waterbody during cyanobacterial bloom. Here, this present study aimed to explore the nephrotoxicity of grass carp by MC-LR. The grass carp received a single intraperitoneal injection of different doses of MC-LR (0, 25, 75, and 100 µg/kg body weight (BW)), and the kidneys were isolated at 24 and 96 h post-injection (hpi). Histopathological examination revealed kidney lesions, with severe hemorrhage, necrosis of the interstitium, and dilation of Bowman's capsule in the 75 and 100 µg MC-LR/kg BW groups. Under transmission electron microscopy, a larger number of swelling and vacuolated degeneration of mitochondria were observed; moreover, apoptotic features, such as condensed chromatin and shrinkage of cells, were observed in the 75 and 100 µg MC-LR/kg BW groups at 96 hpi. MC-LR significantly upregulated the number of apoptotic cells in the 75 and 100 µg/kg BW groups at 96 hpi as indicated by terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) assay (P < 0. 05). The results of quantitative assays showed that the mRNA expression of Bax, caspase-9, and caspase-3 in grass carp kidney were significantly increased at 96 hpi in the 75 and 100 µg MC-LR/kg BW groups compared with that in the control group, but Bcl-2 mRNA expression was significantly decreased in all the treatment groups at 24 and 96 hpi. Taken together, these results indicated that MC-LR damaged the kidney structure and resulted in renal apoptosis which may occur via the mitochondrial pathway.

Spatial and seasonal variations of antibiotic resistance genes and antibiotics in the surface waters of Poyang Lake in China.

Antibiotic resistance genes (ARGs) and antibiotics in the aquatic environment raise health concerns particularly on the dispersal and persistence of antibiotic resistance. Large lakes, which serve as catch basins of anthropogenic inputs provide an ideal environment for understanding the occurrence and accumulation of ARGs and antibiotics in freshwater environments. Here, the largest freshwater lake in China, Poyang Lake, located in the developing district of Yangtze valley was used to study the characterization of the spatial and seasonal variation of both ARGs and antibiotics. Results showed that twelve tested ARGs (sul1, sul2, sul3, tetA, tetB, tetC, tetH, tetW, tetO, tetM, qnrS, and qnrB) were detected in the surface waters of Poyang Lake, with a detection frequency ranging from 19.2% to 100%, and sul2 and tetA genes were identified as potential indicators of ARG pollution in this region. Among the 11 analyzed antibiotics, sulfonamides were the predominant antibiotics with a contribution of more than 50% to the total concentrations of tested antibiotics. The total concentrations of both ARGs and antibiotics were higher in the dry season than those in the wet season. Furthermore, ARGs and antibiotics in the surface waters also varied with sampling locations, being consistently at riverine tributaries. Positive correlations were also observed between the concentrations of ARGs and antibiotics, as well as the integron gene (intI1), indicating that antibiotics and intI1 may be playing important roles in the occurrence and dispersal of ARGs in the surface waters. Lastly, our results suggest that intensive anthropogenic activities related to antibiotic usage have substantially contributed to the occurrence and persistence of ARGs and antibiotics in Poyang Lake.

Effects of norfloxacin nicotinate on the early life stage of zebrafish (Danio rerio): Developmental toxicity, oxidative stress and immunotoxicity.

Norfloxacin nicotinate (NOR-N), an adduct of norfloxacin (NOR) and nicotinic acid, has been widely used for replacing NOR in animal husbandry and fishery industry. Nowadays, increasing evidences showed that NOR could pose toxic effects on fish and other aquatic organisms, but as its adduct, whether NOR-N could cause adverse effects on aquatic organisms is still unclear. To evaluate the toxic effects of NOR-N on the early life stage of zebrafish, we determined the changes in embryonic development (hatching rate, body length, malformation rate and mortality), antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (Gpx)) activities, malondialdehyde (MDA) content and gene expression levels related to antioxidant enzymes (Cu/Zn-sod, Mn-sod, CAT and Gpx) and innate immune system (tumor necrosis factor α (TNFα), interferon (IFN), Interleukin-1 beta (IL-1ß), IL-8, CXCL-clc, CC-chemokine, lysozyme (Lzy) and complement factors (C3)) after embryonic exposure to NOR-N till 96 hpf. The results showed that NOR-N exposure could decreased the hatching rate and body length, and increased abnormality and mortality as concentration-dependent during embryonic development process. NOR-N induced oxidative stress in zebrafish larvae through increasing the contents of MDA and the activities of SOD, CAT and Gpx, as well as the mRNA levels of genes related to these antioxidant enzymes. Moreover, the expression of TNFα, IFN, IL-1ß, IL-8, CXCL-clc, CC-chemokine, Lzy and C3 genes were significantly up-regulated after exposure to high concentration (5 and/or 25 mg/L) of NOR-N till 96 hpf, indicating that the innate immune system in zebrafish larvae was disturbed by NOR-N. Overall, our results suggested that NOR-N caused development toxicity, oxidative stress and immunotoxicity on the early life stage of zebrafish. Thus, widespread application of NOR-N might pose potential ecotoxicological risk on aquatic ecosystems.

Levels and human health risk assessments of heavy metals in fish tissue obtained from the agricultural heritage rice-fish-farming system in China.

China began to practice Rice-fish-farming system (RFFS) 1700 years ago. Nowadays, the widely spread of metals could be potential threats to the quality of RFFS fish. In this study, Pb, Cd, Hg, As and Cr as the top five most toxic heavy metals were determined in six species of RFFS fish meat obtained from 7 provinces in south China. The mean concentrations of metals in RFFS fish followed Pb (36.89 µg/kg) > As (33.36 µg/kg) > Cr (18.54 µg/kg) > Hg (16.35 µg/kg) > Cd (2.01 µg/kg), which were mostly lower in comparison with fish from traditional aquaculture systems raised by fish feeds. Grass carp obtained lower metal concentrations compared with other fishes, possibly indicating the importance of feeding habits of RFFS fish. Concentrations of metals in fish and RFFS sediment were in good correlations, and benthic fish obtained high pollution levels, suggesting the accumulation of metals through the direct contact with sediment. Risks assessments coupled with Monte Carlo simulation indicated the potential non-carcinogenic risks and carcinogenic risks decreased following As > Hg > Cr ≈ Pb > Cd, and As > Cr > Cd > Pb, respectively. These results suggested RFFS is still a successful mode of green agriculture.

The thermal performance of biological tissue under moxibustion therapy.

An understanding of the thermal performance of biological tissue under moxibustion with ash cleaning and distance adjustment (ACDA) is helpful for the optimization and standardization of moxibustion clinical treatment. This study compared surface temperature distribution of burning moxa stick with and without ash cleaning. The experimental of moxibustion treatment on in-vitro tissue and human abdomen were conducted and corresponding numerical models were developed. The effect of ACDA on thermal performance of biological tissue under moxibustion therapy were analyzed. The results show that the surface temperature of burning moxa stick with ash cleaning maintained at a higher range compared to that without ash cleaning. During moxibustion with ACDA process in in-vitro tissue experiment, the temperature increase (ΔT) at skin surface almost fluctuated in the same temperature range, and the ΔT in subcutaneous tissue (>11 mm) kept increasing. Relatively, these ΔT under moxibustion treatment without ACDA showed different trends and these values were all much smaller than those with ACDA. In addition, the position of maximum temperature of tissue under moxibustion with and without ACDA was fixed on treatment acupoint and moved away from treatment acupoint, respectively. Besides, the surface temperature of human abdomen tissue under moxibustion treatment with ACDA can be maintained at 46 °C-50 °C for a longer time compared to that under moxbustion without ACDA. In conclusion, moxibustion with ACDA can create a larger and more durable thermal effect on biological tissue. The results also suggest that ACDA may be helpful to improve moxibustion therapy efficacy in clinic treatments.

Relationship between nutrients and plankton biomass in the turbidity maximum zone of the Pearl River Estuary.

Nutrients, dissolved and particulate organic carbon and plankton (bacterio-, phyto- and zoo-) were compared in the turbidity maximum zone (TMZ) and adjacent areas (non-TMZ) in the Pearl River estuary. Our results showed that high levels of suspended substances had marked effect on dynamics of nutrients and plankton in the TMZ. Based on the cluster analysis of total suspended solids (TSS) concentrations, all stations were divided into two groups, TMZ with average TSS of 171mg/L and non-TMZ of 45mg/L. Suspended substances adsorbed PO43- and dissolved organic carbon, resulting in higher particulate phosphorus and organic carbon (POC) and lower PO43- and DOC in the TMZ, compared to the non-TMZ. However, suspended substances had limited effect on nitrogenous nutrients. Phytoplankton growth was light-limited due to high concentrations of suspended substances in the TMZ and a peak of phytoplankton abundance appeared in the non-TMZ. In contrast, the highest bacterial abundance occurred in the TMZ, which was likely partly responsible for low DOC levels. Two peaks of zooplankton abundance observed in the TMZ and non-TMZ in the Pearl River estuary were primarily supported by bacteria and phytoplankton, respectively. Our finding implied that high levels of suspended solids in the TMZ affect the trophic balance.

Occurrence and elimination of antibiotic resistance genes in a long-term operation integrated surface flow constructed wetland.

Wetland construction is a recommended domestic sewage treatment technique, owing to its simplicity and cost efficiency. Concentrations of 14 antibiotic resistance genes (ARGs) in an integrated surface flow constructed wetland (ICW) steadily operated over 10 years were investigated in the winter and summer. Domestic sewage was observed to be the primary source of ARGs in the ICW, and 77.8% and 59.5% removal rates of total targeted ARGs in the ICW were achieved in the winter and summer, respectively. Concentrations of five ARGs (sul1, tetA, tetC, tetE, and qnrS) in the winter and of six ARGs (sul1, sul3, tetA, tetC, tetE, and qnrS) in the summer were increased throughout the treatment process. Strong correlations were found between ARGs in water and those found in sediments, especially in the summer, indicating that ARGs may be exchanged between water and sediment. Strong positive correlations were also observed between concentrations of intI1 and several ARGs, implying that mobile genetic elements may play a key role in the dissemination of ARGs in an ICW. Our study results suggest aqueous ARGs could be effectively removed via an ICW and that ICWs can also act as reservoirs of specific ARGs.

Occurrences and distribution of sulfonamide and tetracycline resistance genes in the Yangtze River Estuary and nearby coastal area.

The role of highly impacted estuaries needs to be examined with respect to the spread of antibiotic resistance genes in the environment. In the present study, sulfonamide resistance (sul), tetracycline resistance (tet) and class I integron (int1) genes were ubiquitous in the sediments of the Yangtze Estuary (YE) and nearby coastal area, and exhibited a declining trend from the inner estuary to the coast. Good relationships were only observed between int1 and sul1 genes, implying that int1 gene is essential to the proliferation of sul1 gene. A non-significant correlation between int1 and 16S rRNA genes indicated that the int1 gene came from pollution sources of ARGs instead of being intrinsic in environmental bacterial populations. Sulfonamides were rarely detected in the sediments of this region, so could not result in the production of sul genes in the local environment.

Effects of norfloxacin on hepatic genes expression of P450 isoforms (CYP1A and CYP3A), GST and P-glycoprotein (P-gp) in Swordtail fish (Xiphophorus Helleri).

The presence of antibiotics including norfloxacin in the aquatic environment may cause adverse effects in non-target organisms. But the toxic mechanisms of fluoroquinolone to fish species are still not completely elucidated. Thus, it is essential to investigate the response of fish to the exposure of fluoroquinolone at molecular or cellular level for better and earlier prediction of these environmental pollutants toxicity. The sub-chronic toxic effects of norfloxacin (NOR) on swordtail fish (Xiphophoru s helleri) were investigated by measuring mRNA expression of cytochrome P450 1A (CYP1A), cytochrome P450 3A (CYP3A), glutathione S-transferase (GST) and P-glycoprotein (P-gp) and their corresponding enzyme activities (including ethoxyresorufin O-deethylase, erythromycin N-demethylase and GST. Results showed that NOR significantly affected the expression of CYP1A, CYP3A, GST and P-gp genes in swordtails. The gene expressions were more responsive to NOR exposure than their corresponding enzyme activities. Moreover, sexual differences were found in gene expression and enzyme activities of swordtails exposed to NOR. Females displayed more dramatic changes than males. The study further demonstrated that the combined biochemical and molecular parameters were considered as useful biomarkers to improve our understanding of potential ecotoxicological risks of NOR exposure to aquatic organisms.

The role of class I integrons in the dissemination of sulfonamide resistance genes in the Pearl River and Pearl River Estuary, South China.

Antibiotic resistance genes (ARGs), as a newly emerging contaminant, are unique because they are disseminated through horizontal gene transfer in the environment. In the present study, a class 1 integron gene (int1) and various ARGs (sul1, sul2, sul3, qnrS, and ermB) were measured in water and sediment samples from the Pearl River (PR) to the Pearl River Estuary (PRE), where there is a distinct gradient in anthropogenic impact. The int1, sul1, and sul2 genes were detected in all samples, and their concentrations exhibited a clear trend of decline consistent with anthropogenic impact. Both the int1 and sul genes had dynamically migrated between water and sediments. The relative abundance of the int1 gene normalized to the 16S rRNA gene correlated significantly with the total concentrations of antibiotics in water and sediments. Good correlations were also observed between the abundance of int1 and each type of sul gene in the samples. However, the sul1 gene showed a much stronger relationship with int1 in different seasons, probably due to the presence of sul1 in the conserved region of class 1 integron. Our results strongly support that integrons play an important role in the dissemination of ARGs in human-impacted aquatic environments.

[Preliminary studies on the occurrence of antibiotic resistance genes in typical aquaculture area of the Pearl River Estuary].

Traditional and quantitative PCR techniques were used to determine the occurrence and quantities of ARGs, including three types of genes resistant to sulfonamide, seven for tetracycline resistance and one for quinolone resistance, as well as one integron gene in typical aquaculture of the Pearl River Estuary. The results showed that all genes except for tetW were detectable in the aquaculture environment, and sull, sul2 and int1 were the most frequently detected genes (detectable percentage, 100% ). Relative abundances of ARGs increased with the prolongation of rearing time under the same aquaculture pattern, suggesting a cumulative effect. Moreover, the occurrences of ARGs in the ponds were different with different aquaculture patterns, indicating that the aquaculture pattern might play an important role in the abundances and distributions of ARGs. Relative abundances of intl, as a horizontal mobile genetic element, were significantly correlated to the levels of sull and the total ARGs (P < 0. 05). The total concentration of antibiotics exhibited a good positive correlation with the total concentration of ARGs in sediments (P <0. 05). All results elucidated that extensive residues of antibiotics in the aquaculture substantially increased the abundances of ARGs probably owning to the induction of horizontal gene transfer of ARGs among bacteria.

Metagenomic profiles of antibiotic resistance genes (ARGs) between human impacted estuary and deep ocean sediments.

Knowledge of the origins and dissemination of antibiotic resistance genes (ARGs) is essential for understanding modern resistomes in the environment. The mechanisms of the dissemination of ARGs can be revealed through comparative studies on the metagenomic profiling of ARGs between relatively pristine and human-impacted environments. The deep ocean bed of the South China Sea (SCS) is considered to be largely devoid of anthropogenic impacts, while the Pearl River Estuary (PRE) in south China has been highly impacted by intensive human activities. Commonly used antibiotics (sulfamethazine, norfloxacin, ofloxacin, tetracycline, and erythromycin) have been detected through chemical analysis in the PRE sediments, but not in the SCS sediments. In the relatively pristine SCS sediments, the most prevalent and abundant ARGs are those related to resistance to macrolides and polypeptides, with efflux pumps as the predominant mechanism. In the contaminated PRE sediments, the typical ARG profiles suggest a prevailing resistance to antibiotics commonly used in human health and animal farming (including sulfonamides, fluoroquinolones, and aminoglycosides), and higher diversity in both genotype and resistance mechanism than those in the SCS. In particular, antibiotic inactivation significantly contributed to the resistance to aminoglycosides, ß-lactams, and macrolides observed in the PRE sediments. There was a significant correlation in the levels of abundance of ARGs and those of mobile genetic elements (including integrons and plasmids), which serve as carriers in the dissemination of ARGs in the aquatic environment. The metagenomic results from the current study support the view that ARGs naturally originate in pristine environments, while human activities accelerate the dissemination of ARGs so that microbes would be able to tolerate selective environmental stress in response to anthropogenic impacts.

The distribution and partitioning of common antibiotics in water and sediment of the Pearl River Estuary, South China.

Antibiotics released into the aquatic environment play an important role in the spread of antibiotic resistance. In the Pearl River Estuary (PRE) and the coastal zone, the concentrations of antibiotics decreased from the Pearl River to the estuary, suggesting that antibiotics primarily originated from river tributaries and terrigenous sources. Within the PRE area, the concentrations of antibiotics in water were higher in the west coast than the east side, reflecting the high density of anthropogenic activities and hydraulic conditions along the west riverbank. Seasonal variations were also observed for most of detected antibiotics in water. The pseudo-partitioning coefficient of norfloxacin had a good correlation with the TOC content of sediments, as did erythromycin-H2O with the pH of water. The results suggest that environmental conditions can significantly affect the distribution of antibiotics between water and sediment.

Differentiating anthropogenic impacts on ARGs in the Pearl River Estuary by using suitable gene indicators.

Antibiotic resistance genes (ARGs) are increasingly a focus of concern because they pose a potential health risk. The Pearl River (PR) and Pearl River Estuary (PRE) show a distinct gradient in anthropogenic impacts, in particular associated with the use of antibiotics, from the river, to the estuary, and on to the coast. In this study, two surveys were conducted in the PR and PRE areas during the winter and summer of 2011, respectively. Seven tet genes consisting of efflux pump (tetA, tetC, and tetH) and ribosomal protection proteins (tetB, tetM, tetO, and tetW) were analyzed using the polymerase chain reaction (PCR) technique. The tet genes, with the exception of tetA and tetH, were widely detected in the PR and PRE environments. The tet genes exhibited a trend of an increase in total concentration and diversity with the degree of anthropogenic impacts from the river to the coast, indicating that riverine input was the main source of ARGs in the region. Significant correlations were observed between tet genes and antibiotic concentrations, as well as among different environmental compartments (water and sediments). The distribution patterns of tet genes were similar between the potential sources of pollution and the highly-impacted sites, but were significantly different between less-impacted sites and highly-impacted ones or pollution sources. The results suggest that ARGs and antibiotics may be released from identical sources, and transported in a similar manner in estuary/coastal environments close to sources of pollution.

Assessment of toxic effects of triclosan on the swordtail fish (Xiphophorus helleri) by a multi-biomarker approach.

The toxic effects of triclosan (TCS) on the swordtail fish (Xiphophorus helleri) were assessed based on various biomarkers including enzymatic activities of ethoxyresorufin O-deethylase (EROD), erythromycin N-demethylase (ERND) and glutathione-s-transferase (GST) and mRNA expression levels of CYP1A, CYP3A, glutathione S-transferase (GST) and P-glycoprotein (P-gp). The acute toxicity test showed the LC(50) value of 1.47 mg L(-1) for TCS. The mRNA expressions of CYP1A, CYP3A, GST and P-gp showed dose-effect relationships in female swordtail fish when exposed to TCS, These mRNA expression levels were found more sensitive to TCS exposure than the enzymatic activities of EROD, ERND and GST do. In addition, the male fish displayed higher gene expression levels and more dramatic changes in enzyme activities than the females did. Our data further demonstrated that TCS was a typical inducer to Phase I and Phase II metabolism enzymes and genes, suggesting it is a potential ecotoxicological risk to aquatic ecosystems.