Nickel oxide nanoparticles (NiO-NPs) are abundantly utilized on a large scale in different applications due to positive attributes and cause environmental pollution that may affect not only aquatic organisms but also the human beings. The co-precipitation method was used to synthesize NiO-NPs and particles were characterized through Fourier-transform infrared (FTIR) analysis, Scanning electron microscope (SEM) and X-ray diffraction (XRD). FTIR and SEM confirmed the attached functional group and crystal structure of synthesized nanoparticles, respectively. From XRD pattern, average particle size, X-ray density, lattice parameters (a, b and c) and volume of unit cell of nickel oxide nanoparticles were found to be 53.44 nm, 6.65 g/cm3, (a =b=c=4.56 Å) and 94.81 Å3, respectively. During this study, the acute toxicity of NiO-NPs was determined by using fish, Labeo rohita. The mean 96-h LC50 and lethal concentration were measured as 418.26 and 634.94 mg/L, respectively. The activity of catalase and superoxide dismutase was determined in fish gills and liver after chronic exposure to sub-lethal concentration of NiO-NPs for 90 days and sampling was done in 15, 30, 45, 60, 75 and 90 days. Significant time dependent variations in the activity of catalase and superoxide dismutase were determined in tissues of the gills and liver than control group during studied time interval. The overall results indicated that induced toxicity of NiO-NPs in aquatic organisms may be due to release of Ni ions from NiO-NPs and NPs induce toxicity in cells through oxidative stress under long term exposure.

With the fast development of industries relevant to nanotechnology, the inappropriate disposal of nanoproducts may initiate a new source of pollution in aquatic ecosystems, thus posing a possible danger to aquatic life. This study evaluated the eco-toxicological effects of waterborne copper oxide nanoparticles (CuO-NPs) having a 32.84nm size and rod shape on a freshwater fish, Labeo rohita. 96-h LC50 of CuO-NPs was 353.98mg/L. Two sub-lethal concentrations equivalent to 1/3rd and 1/5th LC50/96h (70.79 and 117.99 mg/L) of CuO-NPs were selected for 15, 30, and 45-day exposure tests. Bioaccumulation for the 1/3rd 96h LC50 was significantly higher compared to 1/5th of 96-h LC50 of CuO-NPs. There was a sharp decrease in the CAT activity and this decline ultimately increased the TBARS contents. The highest percentage of damaged nuclei and genetic damage index in fish erythrocytes was recorded at the highest concentration and after 45 days of treatment. The adverse effects of CuO-NPs were examined to be dose and duration dependent with increasing extent during all studied time intervals. Summarizing, exposure to sublethal concentrations of CuO-NPs is sufficient to cause alterations in ecotoxicological endpoints such as metal overload, oxidative stress and genotoxicity after chronic exposure.

Concerns regarding zinc oxide nanoparticles (ZnO-NPs) have gained much attention due to their unique properties and widespread applications in cosmetics, electronics and medicinal industry that may induce an adverse impact not only on specific ecosystem but also on human health. ZnO-NPs were synthesized by co-precipitation method and characterization was done by Scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) analysis. SEM showed the hexagonal wurtzite crystal structure of particles. From XRD pattern, average particle size, lattice parameters (a and c), X-ray density and volume of unit cell of zinc oxide nanoparticles were 52.22 nm, (a =3.25 Å and c=5.21 Å), 5.0 g/cm3 and 54.82 Å3, respectively. FT-IR confirmed the attached compound of synthesized nanoparticles. The acute toxicity of ZnO-NPs was determined by using fish, Labeo rohita as a genetic model during this study. The mean 96-h LC50 and lethal concentration were measured as 31.15 and 57.84 mg/L, respectively. Oxidative stress in terms of catalase, lipid peroxidation and superoxide dismutase was also determined in fish gills, muscle, liver and heart after chronic exposure of ZnO-NPs for 80 days and sampling were done on 20, 40, 60 and 80 days. Significantly decreased catalase and superoxide dismutase activity was determined in selected fish organs. However, level of lipid peroxidation was significantly increased in the fish organs as compared to control group. The overall results indicated that induced toxicity mechanism of ZnO-NPs in aquatic ecosystem was oxidative stress

During present study, the copper (Cu) mediated oxidative stress was measured that induced DNA damage by concentrating in the tissues of fish, Catla catla (14.45±1.24g; 84.68±1.45mm) (Hamilton,1822). Fish fingerlings were retained in 5 groups for 14, 28, 42, 56, 70 and 84 days of the exposure period. They were treated with 2/3, 1/3, 1/4 and 1/5 (T1-T4) of 96h lethal concentration of copper. Controls were run along with all the treatments for the same durations. A significant (p < 0.05) dose and time dependent concentration of Cu was observed in the gills, liver, kidney, muscles, and brain of C. catla. Among organs, the liver showed a significantly higher concentration of Cu followed by gills, kidney, brain, and muscles. Copper accumulation in these organs caused a significant variation in the activities of enzymes viz. superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). The SOD activity varied significantly in response to the exposure time of Cu as 56 > 70 > 42 > 84 > 28 > 14 days while CAT activity exhibited an inverse relationship with the increase in Cu concentration. POD activity showed a significant rise with an increase in Cu exposure duration. Comet assay exhibited significant DNA damage in the peripheral erythrocytes of Cu exposed C. catla. Among four exposure concentrations, 2/3rd of LC50 (T1) caused significantly higher damage to the nuclei compared to control. Increased POD and SOD activity, as well as a decrease in CAT activity in response to Cu, demonstrates the involvement of a protective mechanism against reactive oxygen species (ROS), whereas increased ROS resulted in higher DNA damage. These above-mentioned molecular markers can be efficiently used for the biomonitoring of aquatic environments and conservation of edible fish fauna.

No abstract