Comet assay in phytoplankton as biomarker of genotoxic effects of environmental pollution

Effects of cadmium exposure on haemocyte immune function of clam Ruditapes philippinarum at different temperatures

Haemocytes are crucial for the immune defence of mollusks. It is important to explore the immune performance of haemocytes of mollusks under the stress of heavy metals with global warming. In order to study the effects of cadmium (Cd) exposure and temperature stress on the haemocyte immune function of clam Ruditapes philippinarum, clams were exposed to different Cd concentrations (0.05, 0.10 and 0.25 mg/L) at 20 °C, 25 °C and 30 °C respectively. Haemocyte mortality, reactive oxygen species (ROS) and superoxide dismutase (SOD) activity were measured at day 1, day 3, day 5 and day 7. The results showed that the changes of the three indexes were not obvious when exposed to 0.05 mg/L of Cd at 20 °C, while significant differences were observed with the increase of temperature, Cd concentration and exposure time. Under a condition of relative high temperature coupling with high concentration of Cd, the clams were significantly influenced, showing an obvious synergistic effect. Selected indexes reflect the clam's response to the combined stress of temperature and Cd. Moreover, R. philippinarum might be an ideal biological index species to the Cd pollution.

Toxicity and genotoxicity of domestic sewage sludge in the freshwater snail Biomphalaria glabrata (Say, 1818)

Waste produced in homes is one of the main sources of pollutants in freshwater ecosystems. Therefore, it is imperative to implement methodologies that aid in environmental monitoring procedures. The use of organisms as biomonitors has grown increasingly prevalent as they are models that provide data that can be adequately evaluated. In this work, we investigated the genotoxic and cytotoxic effects caused by domestic sewage sludge through an analysis of biomarkers in the mollusk Biomphalaria glabrata. For the tests, increasing concentrations of 50, 100, 150, and 500 mg L^-1 of domestic sewage sludge were standardized, in addition to control groups. Assays were performed after the mollusks were exposed to the domestic sewage sludge in acute (48 h) and chronic (15 d) manner. Toxicity tests were performed with embryonic and adult snails. The cytoplasmic and nuclear changes were analyzed in the hemocyte cells. Lastly, genotoxic damage was analyzed using the comet assay. Adult snails and embryos of B. glabrata showed no significant morphological changes. Domestic sludge caused deleterious effects on mollusks as confirmed after cell genotoxicity tests. Therefore, based on the results obtained from the analysis of B. glabrata hemocytes, we can affirm that domestic sewage sludge causes genotoxic and cytotoxic effects on mollusk cells. Therefore, it is possible to conclude that the mollusk Biomphalaria glabrata can be used as a good low-cost alternative to assist in the biomonitoring of freshwater environments. Graphical Abstract.

Polyethylene, Polystyrene, and Polypropylene leachate impact upon marine microalgae Dunaliella tertiolecta

In the aquatic environment, plastics may release several hazardous substances of severe ecotoxicological concern not covalently bound to the polymers. The aim of this study was to examine the adverse effects of leachates of different virgin polymers, polypropylene (PP), polyethylene (PE), and polystyrene (PS) on marine microalgae Dunaliella tertiolecta. The tests carried out on D. tertiolecta included: growth inhibition, oxidative stress (DCFH-DA), and DNA damage (COMET assay). Polypropylene and PS leachates produced growth inhibition at the lowest concentration (3.1% of leachate). In contrast, a hormesis phenomenon was observed with PE leachates. An algae inhibition growth ranking (PP>PS>PE) was noted, based upon EC₅₀ values. Reactive oxygen species (ROS) generated were increased with leachates concentrations with PS exhibiting the highest ROS levels, while a marked genotoxic effect (30%) was found only with PP. All leachates were free from detectable quantities of organic compounds (GC/MS) but showed the presence of transition, post-transition and alkaline earth metals, metalloids, and nonmetals (<limit of quantification (LOQ) to 83.5 µg/L). Therefore, the observed toxic action might reasonably be attributable to the presence of metals and in conjunction with polymeric actions. This investigation underlines the need to better characterize the potential impact of virgin polymers.

A review of karenia mikimotoi: Bloom events, physiology, toxicity and toxic mechanism

Karenia mikimotoi is a worldwide bloom-forming dinoflagellate in the genus Karenia. Blooms of this alga have been observed since the 1930s and have caused mass mortalities of fish, shellfish, and other invertebrates in the coastal waters of many countries, including Japan, Norway, Ireland, and New Zealand. This species has frequently bloomed in China, causing great financial losses (more than 2 billion yuan, Fujian Province, 2012). K. mikimotoi can adapt to various light, temperature, salinity, and nutrient conditions, which together with its complex life history, strong motility, and density-dependent allelopathy, allows it to form blooms that are lethal to almost all marine organisms. However, its toxicity differs between subspecies and some target-species-specific toxicity has also been recorded. Significant gill disorder is observed in affected fish, to which the massive fish kills are attributed, rather than to the hypoxia that occurs in the fading stage of a bloom. However, although this species is haemolytic and cytotoxic, and generates reactive oxygen species, none of the isolated toxins or lipophilic extracts have toxic effects as extreme as those of the intact algal cells. The toxic effects of K. mikimotoi are strongly related to contact with intact cells. Several reasonable hypotheses of how and why this species blooms and causes mass mortalities have been proposed, but further research is required.

Potential chromosome damage, cell-cycle kinetics/and apoptosis induced by epoxiconazole in bovine peripheral lymphocytes in vitro

The epoxiconazole was tested in vitro for its potential on induction of chromosome damage and/or cell cycle kinetics in cultured bovine peripheral lymphocytes. Cytogenetic endpoints such as: Chromosome Aberrations (CA); Sister Chromatid Exchanges (SCE); Micronuclei (MN); Mitotic Index (MI); Proliferation Index (PI); and Cytokinesis Block Proliferation Index (CBPI) were investigated for 24 h and 48 h of incubation. The cultured lymphocytes were exposed to the epoxiconazole at concentrations of 2.5, 5, 10, 25, 50 and 100 μg mL^-1. From our results is evident that treatment of bovine peripheral lymphocytes with the epoxiconazole was not related to DNA damage; no genotoxic effect and/or clastogenic/aneugenic effects were recorded. However, epoxiconazole has ability to significantly affect cell cycle kinetics/and induce apoptosis. A decrease of proliferation in the MI, CBPI and identically in the PI were observed; hence, cytostatic/cytotoxic effects of epoxiconazole have been recorded. The prolonged time of exposure at the highest concentration caused an inhibition of the replication. Electrophoretic analysis confirmed the epoxiconazole potential to induce ladder-like patterns of DNA fragments that are a hallmark of apoptosis.

Evaluation of cytotoxic and genotoxic activity of fungicide formulation Tango® Super in bovine lymphocytes

Tango^® Super is a two-compound fungicide formulation widely employed in grain protection. However, details of Tango^® Super effects on cell cultures have not been fully investigated. In this study, bovine lymphocytes were exposed to a concentration range 0.5; 1.5; 3; 6; and 15 μg mL^-1 for 4 h to assess the cytotoxicity and genotoxicity of the fungicide. Our experiments revealed that this fungicide treatment reduced cell viability, decreased cell proliferation and provoked apoptotic cell death. Cell cycle analysis showed predominant accumulation of cells in the G₀/G₁ phase of the cell cycle. The fungicide was able to induce mitochondrial superoxide production accompanied by elevated levels of carbonylated proteins and changes in the lipid membrane composition. The fungicide did not induce micronuclei production, but stimulated both DNA double-strand breaks and the formation of p53 binding protein, which is accumulated during the DNA repair process at the site of double-strand breaks. Based on the obtained data we suppose that the fungicide-induced DNA damage is the result of oxidative stress, which may contribute to higher occurrence of apoptotic cell death. Because ergosterol biosynthesis-inhibiting fungicides are widely used in agriculture to ensure higher crop yields and may cause health impairment of animals and humans, there is a need for further testing to elucidate their potential genotoxic effects using in vivo and/or in vitro systems.

Evaluation of potential genotoxic/cytotoxic effects induced by epoxiconazole and fenpropimorph-based fungicide in bovine lymphocytes in vitro

Potential genotoxic/cytotoxic effects of the epoxiconazole/fenpropimorph-based fungicide were investigated using single cell gel electrophoresis and cytogenetic assays: chromosomal aberrations, sister chromatid exchanges, micronuclei and fluorescence in situ hybridization in cultured bovine lymphocytes. No statistically significant elevations of DNA damage and increases in cytogenetic endpoints were seen. However, evident cytotoxic effect presented as a decrease in mitotic and proliferation indices were recorded after exposure of bovine lymphocytes to the fungicide for 24 and 48 h at concentrations ranging from 3 to 15 µg mL(-1) (P < 0.05, P < 0.01, P < 0.001). Similarly, for 24 h an inhibition in the cytokinesis block proliferation index (CBPI) was obtained after exposure to the fungicide at concentrations ranging from 1.5 to 15 µg mL(-1) (P < 0.01, P < 0.001) in each donor.

Genotoxic and cytotoxic effects of ZnO nanoparticles for Dunaliella tertiolecta and comparison with SiO2 and TiO2 effects at population growth inhibition levels

The increasing use of oxide nanoparticles (NPs) in commercial products has intensified the potential release into the aquatic environment where algae represent the basis of the trophic chain. NP effects upon algae population growth were indeed already reported in literature, but the concurrent effects at cellular and genomic levels are still largely unexplored. Our work investigates the genotoxic (by COMET assay) and cytotoxic effects (by qualitative ROS production and cell viability) of ZnO nanoparticles toward marine microalgae Dunaliella tertiolecta. A comparison at defined population growth inhibition levels (i.e. 50% Effect Concentration, EC50, and No Observed Effect Concentration, NOEC) with SiO2 and TiO2 genotoxic effects and previously investigated cytotoxic effects (Manzo et al., 2015) was performed in order to elucidate the possible diverse mechanisms leading to algae growth inhibition. After 72h exposure, ZnO particles act firstly at the level of cell division inhibition (EC50: 2mg Zn/L) while the genotoxic action is evident only starting from 5mg Zn/L. This outcome could be ascribable mainly to the release of toxic ions from the aggregate of ZnO particle in the proximity of cell membrane. In the main, at EC50 and NOEC values for ZnO NPs showed the lowest cytotoxic and genotoxic effect with respect to TiO2 and SiO2. Based on Mutagenic Index (MI) the rank of toxicity is actually: TiO2>SiO2>ZnO with TiO2 and SiO2 that showed similar MI values at both NOEC and EC50 concentrations. The results presented herein suggest that up to TiO2 NOEC (7.5mg/L), the algae DNA repair mechanism is efficient and the DNA damage does not result in an evident algae population growth inhibition. A similar trend for SiO2, although at lower effect level with respect to TiO2, is observable. The comparison among all the tested nanomaterial toxicity patterns highlighted that the algae population growth inhibition occurred through pathways specific for each NP also related to their different physicochemical behaviors in seawater.

In vitro study of the effect of metabolism enzymes on benzo(a)pyrene-induced DNA damage in the scallop Chlamys farreri

Acute toxicity effect of benzo(a)pyrene (BaP) on isolated scallop (Chlamys farreri) digestive gland cells was studied and a dose-dependent increase in toxicity was observed. The 8 μg/L of BaP had a significant toxic effect on isolated cells (p<0.05). In order to study the mechanism of CYP450, GST, SOD and MXR transporters involved in the production of DNA strand breakage such as DNA adduct formation and oxidative DNA damage by BaP were investigated in isolated digestive gland cells. Isolated cells were exposed in vitro to 0.8 μg/L of BaP for 24h in the dark at 25 °C in the absence or presence of cytochrome P450 inhibitor, GST inhibitor, Pgp inhibitor and antioxidant enzyme inhibitor. DNA adduct and 8-OHdG content were measured using the Enzyme-linked Immunosorbent Assay. The result indicated that DNA strand breakage was increased to 2 times compared with the control in the 0.8 μg/L of BaP treatment groups. The BaP-induced DNA adduct and 8-OHdG content increased significantly by inhibiting GST, while only 8-OHdG increased significantly when SOD was inhibited. The content of DNA adduct and 8-OHdG had no significant change when CYP450 was inhibited, while it decreased significantly when MXR transporters were inhibited. The result proved that GST play a key role in eliminating the BaP-induced DNA adduct and 8-OHdG, and SOD also had an important function in reducing the production of BaP-induced 8-OHdG.

Acute effects of a prooxidant herbicide on the microalga Chlamydomonas reinhardtii: Screening cytotoxicity and genotoxicity endpoints

Since recent evidence has demonstrated that many types of chemicals exhibit oxidative and/or genotoxic potential on living organisms, reactive oxygen species (ROS) formation and DNA damage are currently the best accepted paradigms to assess the potential hazardous biological effects of a wide range of contaminants. The goal of this study was to evaluate the sensitivity of different cytotoxicity and genotoxicity responses on the model microalga Chlamydomonas reinhardtii exposed to the prooxidant herbicide paraquat. In addition to the growth endpoint, cell viability, mitochondrial membrane potential and presence of reactive oxygen species (ROS) were assayed as potential markers of cytotoxicity using flow cytometry (FCM). To study the effects of paraquat on C. reinhardtii DNA, several genotoxicity approaches were implemented for the first time in an ecotoxicological study on microalgae. Oxidative DNA base damage was analysed by measuring the oxidative DNA lesion 8-OHdG by FCM. DNA fragmentation was analysed by different methods: comet assay, and cell cycle analysis by FCM, with a particular focus on the presence of subG1-nuclei. Finally, effects on morphology of nuclei were monitored through DAPI staining. The evaluation of these endpoints showed that several physiological and biochemical parameters reacted to oxidative stress disturbances with greater sensitivity than integrative parameters such as growth rates or cell viability. The experiments revealed concentration-dependent cytotoxicity (ROS formation, depolarization of mitochondrial membrane), genotoxicity (oxidative DNA damage, DNA strand breakage, alterations in nuclear morphology), and cell cycle disturbances (subG1-nuclei, decrease of 4N population) in paraquat-treated cells. Overall, the genotoxicity results indicate that the production of ROS caused by exposure to paraquat induces oxidative DNA damage followed by DNA single- and double-strand breaks and cell cycle alterations, possibly leading to apoptosis in C. reinhardtii cells. This is supported by the observation of typical hallmarks of apoptosis, such as mitochondrial membrane depolarization, alterations in nuclear morphology and subG1 nuclei in cells exposed to the highest assayed concentrations. To our knowledge, this is the first study that provides a comprehensive analysis of oxidative DNA base damage in unicellular algal cells exposed to a prooxidant pollutant, as well as of its possible relation with other physiological effects. These results reinforce the need for additional studies on the genotoxicity of environmental pollutants on ecologically relevant organisms such as microalgae that can provide a promising basis for the characterization of potential pollutant hazards in the aquatic environment.

Suitability of cytotoxicity endpoints and test microalgal species to disclose the toxic effect of common aquatic pollutants

Pulse discharges of chemicals to aquatic environments may lead to high concentrations of them in surface waters for short periods of time, but enough to induce toxic effects on aquatic organisms; however, no many methods allow an early warning of toxicity of these agents. Acute effects of one representative chemical from each of three of the main groups of aquatic pollutants (pesticides, metals and pharmaceuticals) are studied on two green microalgal species (Chlamydomonas moewusii and Chlorella vulgaris). Flow cytometry protocols were used to detect the potential application of chlorophyll a fluorescent emission, cell viability, metabolic activity and membrane potential as cytotoxicity endpoints, besides an epifluorescence microscopy protocol for comet assay to detect genotoxicity level of cells. Obtained results confirm the suitability of them for the prospective assessment of the potential cytotoxicity of these aquatic pollutants. The two microalgal species analysed could be used as indicators in toxicity bioassays, being C. moewusii more sensitive than C. vulgaris. Among cell parameters assayed, the metabolic activity and the primary DNA damage stood out as sensitive cytotoxicity endpoints.

Genotoxic effects of commercial formulations of Chlorpyrifos and Tebuconazole on green algae

The alkaline single-cell gel electrophoresis assay (comet assay) was used for the study of the genotoxic effects of insecticide Chlorpyrifos and fungicide Tebuconazole (commercial formulations) on two freshwater green algae species, Pseudokirchneriella subcapitata and Nannocloris oculata, after 24 h of exposure. The percentage of DNA in tail of migrating nucleoids was taken as an endpoint of DNA impairment. Cell viability was measured by fluorometric detection of chlorophyll "a" in vivo and the determination of cell auto-fluorescence. Only the higher concentration of Chlorpyrifos tested resulted to affect significantly the cell viability of P. subcapitata, whereas cells of N. oculata were not affected. Tebuconazole assayed concentrations (3 and 6 mg/l) did not affect cell viability of both species. The results of comet assay on P. subcapitata showed that Chlorpyrifos concentration evaluated (0.8 mg/l) exerted a genotoxic effects; while for the other specie a concentration of 10 mg/l was needed. Tebuconazole was genotoxic at 3 and 6 mg/l for both species. The comet assay evidenced damage at the level of DNA simple strains molecule at pesticide concentrations were cytotoxicity was not evident, demonstrating that algae are models to take into account in ecological risk assessments for aquatic environments.

Earthworm tolerance to residual agricultural pesticide contamination: field and experimental assessment of detoxification capabilities

This study investigates if acclimatization to residual pesticide contamination in agricultural soils is reflected in detoxification, antioxidant enzyme activities and energy budget of earthworms. Five fields within a joint agricultural area exhibited different chemical and farming histories from conventional cultivation to organic pasture. Soil multiresidual pesticide analysis revealed up to 9 molecules including atrazine up to 2.4 ng g(-1) dry soil. Exposure history of endogeic Aporrectodea caliginosa and Allolobophora chlorotica modified their responses to pesticides. In the field, activities of soluble glutathione-S-transferases (sGST) and catalase increased with soil pesticide contamination in A. caliginosa. Pesticide stress was reflected in depletion of energy reserves in A. chlorotica. Acute exposure of pre-adapted and naïve A. caliginosa to pesticides (fungicide Opus(®), 0.1 μg active ingredient epoxiconazole g(-1) dry soil, RoundUp Flash(®), 2.5 μg active ingredient glyphosate g(-1) dry soil, and their mixture), revealed that environmental pre-exposure accelerated activation of the detoxification enzyme sGST towards epoxiconazole.

Microalga Euglena as a bioindicator for testing genotoxic potentials of organic pollutants in Taihu Lake, China

The microalga Euglena was selected as a bioindicator for determining genotoxicity potencies of organic pollutants in Meiliang Bay of Taihu Lake, Jiangsu, China among seasons in 2008. Several methods, including the comet assay to determine breaks in DNA and quantification of antioxidant enzymes were applied to characterize genotoxic effects of organic extracts of water from Taihu Lake on the flagellated, microalga Euglena gracilis. Contents of photosynthetic pigments, including Chl a, Chl b and carotenoid pigments were inversely proportion to concentrations of organic extracts to which E. gracilis was exposed. Organic extracts of Taihu Lake water also affected activities of superoxide dismutase (SOD) and peroxidase (POD) of E. gracilis. There were no statistically significant differences in SOD activities among seasons except in June but significant differences in POD activities were observed among all seasons. The metrics of DNA fragmentation in the alkaline unwinding assay (Comet assay), olive tail moment (OTM) and tail moment (TM), used as measurement endpoints during the genotoxicity assay were both greater when E. gracilis was exposed to organic of water collected from Taihu Lake among four seasons. It is indicated that the comet assay was useful for determining effects of constituents of organic extracts of water on E. gracilis and this assay was effective as an early warning to organic pollutants.

Potential health impact and genotoxicity analysis of drinking source water from Liuxihe Reservoir (P.R. China)

Water from the Liuxihe Reservoir (a source of drinking water for Guangzhou City, P. R. China) was analyzed for semi-volatile organic compounds (SVOCs) and the results were used for a potential health impact assessment and genotoxicity test with the microalgae Euglena gracilis. The SVOCs were tested using USEPA Method 525.2, and the health risk assessment was conducted at a screening level using the hazard quotient (HQ) approach. Alkaline single-cell gel electrophoresis (comet assay) was used to evaluate DNA damage and determine the genotoxicity of the source water. The concentrations of the SVOCs in Liuxihe Reservoir were very low and phthalic acid esters were the main SVOCs present. The mean HQ values of pollutants were all less than one, indicating no risk. However, the lifetime carcinogenic risks (LCRs) were found to be close to the threshold of 1.00E-5. The results show that the water in the Liuxihe Reservoir might pose a potential carcinogenic risk to local residents. The highly concentrated extracts of the water samples could induce DNA damage in the microalgal cells and a dose-effect relationship was identified. These results showed that Liuxihe Reservoir water, as a source of drinking water, could pose a potential LCR to local consumers.

Genotoxic response and oxidative stress induced by diclofenac, ibuprofen and naproxen in Daphnia magna

CONTEXT

Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used pharmaceuticals in Mexico, but there is not proper regulation on the sale, use and disposal. These drugs can enter water bodies by diverse pathways, attaining significant concentrations and inducing damage on hydrobionts.

OBJECTIVE

To evaluate the oxidative stress and consequent damage to genetic material induced by DCF, IBP and NPX on Daphnia magna.

METHODS

The acute toxicity assays were performed to 48-h by nonsteroidal anti-inflammatory drugs evaluated. A sublethal assay were done after 48 h of exposure to DCF, IBP and NPX added to water with the concentration equivalent to the lowest observed adverse effect level (LOAEL), 9.7 mg/L for DCF, 2.9 mg/L for IBP and 0.017 mg/L for NPX. The DNA damage (comet assay) was evaluated at 12, 48 and 96 h. The oxidative biomarkers were evaluated: lipid peroxidation; protein carbonyl content; activity of the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase.

RESULTS

D. magna exposed to DCF, IBP and NPX showed a significant increase (p < 0.05) with respect to controls in LPX. PCC was increased in IBP exposure. SOD and CAT activity were increased by exposure to IBP and NPX. GPX shows a significant increase with respect to control in IBP and DCF exposure and significant decrease by NPX exposure. DNA damage was observed in 48 and 96 h.

DISCUSSION AND CONCLUSION

DCF, IBP and NPX were responsible of alterations in biochemical biomarkers evaluated and DNA damage.

Prenatal epoxiconazole exposure effects on rat postnatal development

Although some studies have pointed out to embryo/fetal toxicity, knowledge about the potential toxicity of the fungicide epoxiconazole is still limited. Once the results of these previous studies have raised some concern, this study studied the effects of epoxiconazole maternal exposure on the physical endpoints in the development of rat pups. To accomplish that, the effects of epoxiconazole (50.0, 100.0, and 150.0  mg/kg) were examined when rats were exposed at two different developmental stages: during the first 6 days of pregnancy or in the organogenesis period (6-15 days). After parturition, pups were tested for growth and maturational milestones. Maternal exposure to the fungicide, independently of phase, resulted in significantly early mean time to vaginal opening and delayed time to testes descent in pups. Weight gain rate in pups and their mothers was not affected for the tested exposure period. The findings of this study emphasize that epoxiconazole maternal exposure may lead to alterations in developmental patterns in nursing pups, consistent with the known influence of epoxiconazole on steroid hormone synthesis.

Genotoxic effects of chlorpyrifos, cypermethrin, endosulfan and 2,4-D on human peripheral lymphocytes cultured from smokers and nonsmokers

Pesticides often cause environmental pollution and adverse effects on human health. We have chosen four structurally different pesticides (endosulfan, an organochlorine pesticide; chlorpyrifos, an organophosphate insecticide; cypermethrin, type II pyrethroid insecticide, and 2,4-dichlorophenoxyacetic acid, a chlorinated aromatic hydrocarbon acid pesticide) to examine and compare their effects on DNA damage in acutely cultured human lymphocytes by the comet assay. In addition, possible differences in response between smoking and nonsmoking subjects were also investigated. Venous blood samples were obtained from healthy male nonsmoker (n = 7) and smoker (n = 8) donors. Primary cultures of lymphocytes were prepared and test groups were treated with three different concentrations (1, 5, and 10 μM) of endosulfan, chlorpyrifos, cypermehrin, and 2,4-D. DNA damage was assessed by alkaline comet assay. We determined an increase in the ratio of DNA migration in human lymphocyte cell cultures as a result of treatment with cypermethrin, 2,4-D and chlorpyrifos at high concentration. Endosulfan had no significant genotoxic effect even at 10 μM concentration. We suggest that chlorpyrifos and cypermethrin are more potentially genotoxic than endosulfan and 2,4-D. Our findings also indicate that the only significant DNA damage between smokers and nonsmokers was observed in the 2,4-D-treated group.

Organic pollutants and ambient severity for the drinking water source of western Taihu Lake

Measurement of the organic compounds found in western Taihu Lake and evaluation of the ambient severity (AS) of the water using multimedia environmental goals (MEG) was conducted. The comet assay and the antioxidant enzyme approach were used to test the potential toxicity of water samples on the microalgae Euglena gracilis. Total concentrations of 25 organic pollutants in samples from two sites were 6.700 and 14.655 μg/l, respectively, with a calculated total ambient severity (TAS) of less than 1 and therefore minimal risk to human and ecological health. Organic extracts from the samples at these two sites was found to induce dose-dependent DNA damage on microalgae cells. DNA damage together with changes in superoxide dismutase (SOD) and peroxidase (POD) activities indicated that the potential pollutant toxicity was far higher at one of the two sites than at the other site. The comet assay combined with the activities of antioxidant enzymes may be of value as a biomarker for presence of organic pollutants in drinking water sources.

Genotoxicity of organic pollutants in source of drinking water on microalga Euglena gracilis

The potential toxicities of organic pollutants in the drinking water source at Meiliang Bay of Lake Taihu were investigated by comet assay and antioxidant enzyme approach on microalgae Euglena gracilis. The organic extracts of the water samples could induce DNA damage on microalgae cells. Statistically significant differences (P < 0.05) were observed at groups of 0.3x, 3x and 10x concentrations compared with the control and a solvent control (DMSO). The organic extracts also affected antioxidant enzyme activity and induced lipid peroxidation in the microalga. In the high dose group, there was an obvious increase in SOD content (P < 0.05). The results suggest that the concentrated organics from water sample extracts have adversary effects on E. gracilis and could possibly damage the ecosystem.

Comparative study of three analysis methods (TTGE, flow cytometry and HPLC) for xenobiotic impact assessment on phytoplankton communities

The impacts of the fungicide Opus (epoxiconazole) on marine phytoplankton communities were assessed in a 12-day field experiment using in situ microcosms maintained underwater at 6 m depth. Three community analysis methods were compared for their sensitivity threshold in fungicide impact detection. When phytoplankton communities were exposed to 1 microg l(-1) of epoxiconazole, no effects could be demonstrated using TTGE (Temporal Temperature Gradient gel Electrophoresis), flow cytometry or HPLC. When exposed to 10 microg l(-1), TTGE fingerprints from PCR amplified 18S rDNA of communities exhibited significant differences compared with controls (ANOSIM, P = 0.028). Neither flow cytometry counts, nor HPLC pigment profiles allowed to show significant differences in microcosms exposed to 10 microg l(-1) of epoxiconazole. When exposed to 100 microg l(-1), all three methods allowed to detect significant differences in treated microcosms, as compared to controls. The TTGE analysis appears in this study as the most sensitive method for fungicide impact assessment on eukaryote microbial communities.