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The cobalt oxide nanoparticles (Co3O4 NPs) were synthesized via the green method using Piper nigrum (P. nigrum) leaves extract and were calcined at different temperatures. The crystalline nature was studied through x-ray diffractometer (XRD). With increasing calcination, the amorphous phase transitioned to the crystalline phase. Diffuse reflectance spectroscopy (DRS) was used to observe UV-Visible light absorbance phenomenon, and Tauc’s plot was used to calculate the band gap energy, which was found to decrease with calcination. Scanning electron microscopy (SEM) was used to analyze the surface morphology, and Fourier transform infrared (FTIR) spectroscopy was used to classify the surface functional groups. The antibacterial efficacy of the Co3O4 NPs was examined against Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), whereas its antioxidant potential was explored against ABTS free radicals. Antibacterial and antioxidant potentials of Co3O4 NPs were found to decrease with increasing calcination.

The aim of this study was to explore the antibacterial and antioxidant efficacy of nickel oxide nanoparticles (NiO NPs). The Raphanus sativus (R. sativus) extract mediated NiO NPs were calcined at 100, 300, 600 and 900 ℃ in a muffle furnace for 3 h. The increased intensity of diffraction bands in the X-ray diffraction (XRD) spectrum suggest that the degree of crystallinity increases with increasing calcination temperature. The desired elements was depicted in the energy dispersive X-rays (EDX) spectrum confirm the purity of the NiO Sample. The variation in surface morphology and increase in the particles size from 12.78 to 51.42nm was determined from the transmission electron microscope (TEM) micrographs. The shift toward higher wavelength was observed in the diffuse reflectance spectroscopy (DRS) spectra with increasing calcination temperature, results into a clear decrease in band gap from 3.12 to 2.86 eV. The presence of hydroxyl group along with other organic moieties were confirm through Fourier transform infrared (FTIR) spectroscopy analysis. The biological potential of the calcined NiO NPs was examined during the antibacterial and antioxidant experiments. The antibacterial effect of NiO NPs was studied using the agar well diffusion process, and the ABTS free radical scavenging potential of NiO NPs was also assessed. The activity of NiO NPs calcined at 100 °C is greater than that of those calcined at higher temperatures.

Mussel aquaculture activities in coastal areas are growing rapidly throughout the world, inducing an increasing interest and concern for their potential impact on coastal marine environments. We have investigated the impact of organic loads due to the biodeposition of a mussel farm in a lagoonar ecosystem of the Mediterranean Sea (Bizerta lagoon, northern Tunisia) on the benthic environment. The most evident changes in the benthic habitat under the farm were a strong reduction of oxygen penetration into the bottom sediments and a large accumulation of chlorophyll a (concentrations up to 16 µg g −1 ), phaeopigments (concentrations up to 48 µg g −1 ) and total organic matter (concentrations up to 12%). Results from univariate analysis of the nematofaunal data show that the nematode abundance increased in all the stations located inside the mussel farm (I1, I2, I3) and the site I2, located in the centre of the mussel farm, was the most affected. At this site, Shannon-Wiener index H , species richness (d), evenness (J ) and number of species (S) decreased significantly. Results from multivariate analyses of the species abundance data demonstrated that responses of nematode species to the organic matter enrichment were varied: Mesacanthion diplechma was eliminated at the most affected station (I2), whereas the abundances of Paracomesoma dubium, Terschellingia longicaudata and T. communis were significantly enhanced. Responses of free-living nematodes to mussel farm biodeposition (elimination of some species and increase or decrease of some others) could lead to food limitation for their predators that, ultimately, could alter entire communities and ecosystems. Consequently, we suggest that site-specific hydrodynamic and biogeochemical conditions should be taken into account when planning new mussel farms, and meiobenthic communities should be monitored before and after farm development to prevent excessive modifications of benthic assemblage structure.

Microcosms were used to assess the impact of chromium on free-living marine nematodes. Nematodes were exposed to three chromium concentrations (500 ppm (dm, dry mass), 800 ppm (dm) and 1,300 ppm (dm)), and effects were examined after 4 weeks. Results showed significant differences between univariate measures of control nematodes and those from medium- and high-chromium microcosms. Most, decreased significantly with increasing level of chromium contamination. The medium-chromium treatment seems to be the minimal concentration that could has a negative effect on nematodes. Results from multivariate analyses demonstrated that responses of nematode species to chromium treatments were varied: Leptonemella aphanothecae was eliminated at all doses tested and seemed to be intolerant species to chromium; Daptonema normandicum and Sabatieria longisetosa which significantly increased at 500 ppm chromium (dm) appeared to be "opportunistic" species at this dose whereas the two Bathylaimus species (Bathylaimus capacosus and Bathylaimus tenuicaudatus) which increased at all the doses tested seemed to be "chromium resistant". As we think such "opportunistic" and "resistant" species could be used as sensitive indicators of unsafe marine food. The use of microcosms has allowed the effects of the chromium on nematodes to be assessed individually, which was not possible in the field.

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The objective of this study was to test the hypotheses that (1) free-living marine nematodes respond in a differential way to diesel fuel if it is combined with three trace metals (chromium, copper, and nickel) used as smoke suppressants and that (2) the magnitude of toxicity of diesel fuel differs according to the level of trace metal mixture added. Nematodes from Sidi Salem beach (Tunisia) were subjected separately for 30 days to three doses of diesel fuel and three others of a trace metals mixture. Simultaneously, low-dose diesel was combined with three amounts of a trace metal mixture. Results from univariate and multivariate methods of data evaluation generally support our initial hypothesis that nematode assemblages exhibit various characteristic changes when exposed to different types of disturbances; the low dose of diesel fuel, discernibly non-toxic alone, became toxic when trace metals were added. For all types of treatments, biological disturbance caused severe specific changes in assemblage structure. For diesel fuel-treated microcosms, Marylynnia bellula and Chromaspirinia pontica were the best positive indicative species; their remarkable presence in given ecosystem may predict unsafe seafood. The powerful toxicity of the combination between diesel fuel and trace metals was expressed with only negative bioindicators, namely Trichotheristus mirabilis, Pomponema multipapillatum, Ditlevsenella murmanica, Desmodora longiseta, and Bathylaimus capacosus. Assemblages with high abundances of these species should be an index of healthy seafood. When nematodes were exposed to only trace metals, their response looks special with a distinction of a different list of indicative species; the high presence of seven species (T. mirabilis, P. multipapillatum, Leptonemella aphanothecae, D. murmanica, Viscosia cobbi, Gammanema conicauda, and Viscosia glabra) could indicate a good quality of seafood and that of another species (Oncholaimellus mediterraneus) appeared an index of the opposite situation.

Free-living nematodes are the most abundant taxa among the meiobenthos and the predominant prey for bottom-feeding fishes. They are able to accumulate toxicants from sediments which explain their use in this study as possible tools in nutritional quality assessment of fishes. Nematodes from sediments of Ghar El Melh lagoon (Tunisia) were subjected to cobalt and/or zinc enrichment in a microcosm experiment for 30 days. Three levels (low, medium, and high) of each treatment were used. Nematode abundance and diversity significantly decreased, and the taxonomic structure was altered. Results from multivariate analyses of the species abundance data revealed that all treatments were significantly different from the control. Both univariate and multivariate analyses of the data showed that the differential response occurred in all treatments, but the assemblages from microcosms contaminated with zinc alone were much more negatively affected compared with those exposed to cobalt alone. The presence of cobalt simultaneously with zinc seems to reduce its impact on nematode species composition. Such a result is suggestive of antagonistic interactions between these two metals. The responses of nematode species to the cobalt and zinc treatments were varied. Oncholaimellus mediterraneus, Oncholaimus campylocercoides, and Neochromadora trichophora were significantly affected with cobalt contamination but, they were not eliminated. Exposed to zinc, Hypodontolaimus colesi was eliminated and seemed to be an intolerant species versus this metal. Some of these species, "cobalt-sensitive" or "zinc-sensitive", were also affected by the metal combination even at low dose: O. mediterraneus, N. trichophora, and H. colesi. Differential sensitivity to cobalt and/or zinc may result in a subsequent competitive release of more tolerant species. A list of this kind of species was established to be used as a possible preventive tool versus contaminated fish. This was most evidently the case in Marylynnia stekhoveni and O. campylocercoides which increased at all doses of cobalt and zinc, respectively. These two resistant species have also the opportunity to dominate the nematode assemblage when the studied metals were added together. The level of health risk is probably higher for humans assimilating additional amount of cobalt and zinc, especially heavy smokers and/or patients using some medications including salts of these metals.