Repositório Institucional da Universidade de Aveiro
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Acute toxicity of atrazine, endosulfan sulphate and chlorpyrifos to Vibrio fischeri, Thamnocephalus platyurus and Daphnia magna, relative to their concentrations in surface waters from the Alentejo region of Portugal
No full textEcotoxicological effects of the herbicide atrazine and the insecticides endosulfan sulphate and chlorpyrifos were evaluated using a test battery comprising aquatic organisms from different trophic levels. According to the categories established in the EU legislation, atrazine can be considered non-harmful for the species tested, while the insecticides can be considered very toxic for the crustaceans. The results of acute toxicity tests showed that the sensitivity of organisms were as follows: Thamnocephalus platyurus > Daphnia magna > Vibrio fischeri. Chlorpyrifos may act as a toxic compound in the aquatic environment of Guadiana River, as it may be detected in water at levels that promote toxic effects.POCI - project GG/GGP/ME621-0167/05FEDE
Transport and acclimation conditions for the use of an estuarine fish (Pomatoschistus microps) in ecotoxicity bioassays: Effects on enzymatic biomarkers
No full textAcclimation of organisms for ecotoxicity testing is in general processed according to Organisation for Economic Co-operation and Development (OECD) and/or Environmental Protection Agency (EPA) guidelines, under controlled conditions. However, when organisms are collected in the field, their capture, transport and adaptation to laboratory conditions are factors of stress. Ill their natural habitat, estuarine fish are exposed to considerable fluctuations of environmental variables, while in laboratory they are acclimated to constant conditions and this can be per se a factor of stress that may influence biomarker responses. Therefore, it is important to investigate the effects of these procedures on estuarine fish performance before using them as test organisms in ecotoxicity bioassays. The goal of the present study was to investigate the effects of transporting the common goby, Pomatoschistus microps from the field (natural populations) to the laboratory and of its acclimation to laboratory conditions on the enzymes acetylcholinesterase (AChE), lactate dehydrogenase (LDH) and glutathione S-transferases (GSTs). Fish were collected in a reference site of the Minho River estuary (NW of Portugal) and the activities of the biomarkers were monitored before and after the transport of organisms to the laboratory and during the acclimation period (at 5, 10 and 15 days). The activities of all the enzymes indicated that capture and transport conditions had no effects on enzymatic activities. Furthermore, AChE, LDH and GST presented higher activities at the end of the acclimation period than at beginning, suggesting a physiological adaptation to laboratory conditions. This adaptation should be taken into consideration ill the experimental design to avoid bias in the interpretation of effects of xenobiotics on biomarkers. (c) 2008 Elsevier Ltd. All rights reserved.RISKA project - FCT/ POCTI/BSE/46225/2002EU/FEDER progra
Nickel response in function of temperature differences: effects at different levels of biological organization in Daphnia magna
No full textIn this study, gene transcription profiling in combination with the assessment of systemic parameters at individual and population levels were applied to study the (toxic) effects induced through temperature stress in the presence or the absence of an additional chemical stressor (nickel) in Daphnia magna. It was illustrated that lower temperatures were mainly characterized by a reduction of growth and lipid content, while higher temperatures caused an increase of both endpoints. Many of the differentially regulated transcripts could be correlated with processes affected at higher hierarchical levels of biological organization. Gene clusters with probable roles in producing offspring (peak expression at 22 degrees C), enhancing the metabolic rate (temperature related expression) and translational processes (increased expression at 14 degrees C) were identified. However, it was not possible to pinpoint a specific subset of genes, exclusively responding to temperature or nickel and allowing a retrospective identification of the particular stressor. Overall, extreme temperatures caused a higher level of stress in the organisms in comparison to nickel exposure. Moreover, organisms subjected to the natural stressor appeared to be less capable of dealing with the additional chemical stressor and as a result activate or repress more gene pathways. (C) 2011 Elsevier Inc. All rights reserved
The use of Daphnia magna immobilization tests and soil microcosms to evaluate the toxicity of dredged sediments
No full textThis paper evaluates the feasibility of using the buffering capacity of natural soil for the remediation of dredged material before being disposed in soil landfills. To achieve that, an Integrated Soil Microcosms (ISM) system was designed to produce elutriates and leachates from the sediment/soil percentage mixtures. Furthermore, to investigate the biological effects of the contaminated sediments, the toxicity behavior of leachates and elutriates was assessed and compared by performing acute (48 h) toxicity assays with the cladoceran Daphnia magna as test organism. Sediment samples contaminated with industrial residues were collected in November-December 2007 in a river area under the influence of the effluents from a chlor-alkali industry (Ebro River basin in Flix Reservoir, NE Spain). Uncontaminated natural soil was collected from a pesticide-free field. Particle size, pH, conductivity, total organic carbon, organic matter content, and soil and sediment moisture were determined. Eighty ISM were set up in the laboratory. To each ISM, 3 kg of fresh soil was added to form a 20-cm deep layer. Sediment and soil were mixed in the following proportions: 0:100, 10:90, 20:80, 35:65, and 50:50 (percent sediment/soil). Five hundred grams of the mixtures were placed at the top of each microcosm to form a 10-cm deep layer. The Integrated Soil Microcosm experiment ran for 60 days. Elutriates were obtained at days 1, 7, 14, 30, and 60 while leachates were collected at days 7, 14, and 30. At each sampling time, the toxicity of the extracted elutriate and collected leachate was evaluated by performing D. magna immobilization tests. From the results, it was apparent that the toxicity of contaminated sediments decreased with the increasing percentage of fresh soil that was added as a buffer. The results also exhibited that the obtained elutriates caused significant mortalities in D. magna at day 1 and day 7, though a slight reduction in the mortality of D. magna was observed by day 30. Conversely, a different pattern of toxicity was observed in the case of the produced leachates, where no mortality of D. magna was observed at day 7, but the toxicity increased with time resulting in some mortality of D. magna by day 30. Through the leaching process, toxic contaminants present in the soil/sediment mixtures seemed to be washed out through a 30-cm soil column leading to an increased toxicity of the leachates over time and to a decreased toxicity of the soil/sediment mixtures used to obtain the elutriates. Soil microcosms using natural soil as a buffer can be used to evaluate the toxicity of contaminated sediments and also to assess the environmental impacts on soil organisms and ground waters as a result of run-off and infiltration processes. The high mortality of D. magna exposed to elutriates observed at the beginning of the experiment (day 1) indicated the presence of hazardous toxicants in the sediments collected from the Ebro River
Suitability of five cladoceran species from Mexico for in situ experimentation
No full textAlthough they are highly suited for site-specific risk assessment, little attention has been given to in situ ecotoxicological experimentation in tropical regions. This study intended to assess the suitability of five freshwater cladocerans from Mexico for in situ experiments. Juveniles of Ceriodaphnia cornuta, Macrothrix triserialis group, Simocephalus vetulus, Diaphanosoma birgei, and Pseudosida cf. ramosa, from two populations, were used to perform seven day laboratory and in situ experiments. Pseudosida cf. ramosa was very sensitive to handling and was discarded from further evaluations. Ceriodaphnia cornuta reproduced significantly more neonates, with smaller coefficients of variation, than M. triserialis and S. vetulus. Also due to its worldwide distribution in the tropics, C corn uta is suggested to be highly suitable for in situ experiments. (C) 2010 Elsevier Inc. All rights reserved
Protein differential expression induced by endocrine disrupting compounds in a terrestrial isopod
No full textEndocrine disrupting compounds (EDCs) have been studied due to their impact on human health and increasing awareness of their impact on wildlife species. Studies concerning the organ-specific molecular effects of EDC in invertebrates are important to understand the mechanisms of action of this class of toxicants but are scarce in the literature. We have used a dose/response approach to unravel the protein expression in different organs of isopods exposed to bisphenol A (BPA) and vinclozolin (Vz) and assess their potential use as surrogate species. Male isopods were exposed to a range of Vz or of BPA concentrations. After animal dissection, proteins were extracted from gut, hepatopancreas and testes. Protein profiles were analysed by electrophoresis and differentially expressed proteins were identified by MALDI mass spectrometry. EDCs affected proteins involved in the energy metabolism (arginine kinase), proteins of the heat shock protein family (Hsp70 and GRP78) and most likely microtubule dynamics (tubulin). Different proteins expressed at different concentrations in different organs are indicative of the organ-specific effects of BPA and Vz. Additionally, several proteins were up-regulated at lower but not higher BPA or Vz concentrations, bringing new data to the non-monotonic response curve controversy. Furthermore, our findings suggest that some common responses to EDCs in both vertebrates and invertebrates may exist. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved
Defect studies on fast and thermal neutron irradiated GaN
No full textSingle crystalline epitaxial GaN films were irradiated with fast (E > 1 MeV) or with fast and thermal neutrons. These irradiation conditions allow the separation of the effect of transmutational doping with Ge due to nuclear reactions with thermal neutrons on the damage production. High resolution X-ray diffraction showed an expansion of the c-lattice parameter after irradiation which is reversed after annealing at 1000 °C. The effect of neutron irradiation on the optical properties of GaN samples was investigated using photoluminescence and Raman spectroscopies. With above band gap excitation the PL spectra of the as-irradiated sample with fast and thermal neutrons is dominated by broad emission bands in the UV and yellow spectral range whereas no PL is observed for the fast neutron as-irradiated sample. Annealing the as-irradiated samples promotes the damage recovery and noticed changes are observed in the PL spectra. Raman scattering spectra indicate an increase of the intensity of the disorder activated phonons revealing higher lattice damage for the irradiation with fast and thermal neutrons.FCT-BPD/18958/200
Spatial distribution of Mn-related emission in GaP studied by cathodoluminescence and photoluminescence
No full textCathodoluminescence (CL) from untreated as well as heat-treated GaP:Te:Mn samples has been investigated. Spectra of untreated samples present two emission bands that peak at 585 and 730 nm. The CL image shows bright spots associated with dislocations, as well as doping striations. The red band (730 nm) is higher at these bright spots. Heat treatments enhance the red-band emission, while the bright spot contrast remains. Timeresolved photoluminescence indicates that the red band is due to excitons bound to complexe
Luminescence at 1.96 eV in n-type GaP
No full textIn n-type GaP a luminescence band with maximum at 1.96 eV is found that does not behave like the SiGa-SiP donor-acceptor pair recombination. It is shown that the temperature dependence of intensity and peak energy is consistent with the luminescence of an exciton bound to a complex
Non-radiative processes in deep centres of diamond
No full textThe N3 centre in diamond is shown to have delayed luminescence above 170 K, following excitation into the N3 absorption band and at all temperatures for excitation into the N4 absorption band. At low temperatures a new slow luminescing band of vibronic origin is observed. The results give independent evidence of the metastable states found in the N3 centre by other methods