Repositório Institucional da Universidade de Aveiro
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On the solution sets to differential inclusions on an unbounded interval
No full textWe prove that for F: [0,∞) × n → K (n) a Lipschitzian multifunction with compact values, the set of derivatives of solutions of the Cauchy proble
The use of Chironomus riparius larvae to assess effects of pesticides from rice fields in adjacent freshwater ecosystems
No full textA bioassay with Chironomus riparius larvae, using larval development and growth as endpoints, was carried out inside a rice field and in the adjacent wetland channel in Portugal, during pesticide treatments (molinate, endosulfan and propanil) to determine impact caused by pesticide contamination in freshwater ecosystems. The bioassay was also performed under laboratory conditions, to assess whether in situ and laboratory bioassays demonstrated comparable results. Growth was inhibited by concentrations of endosulfan (2.3 and 1.9 mu g L-1 averages) in water from rice field in both the field and laboratory, and by concentrations of endosulfan (0.55 and 0.76 mu g L-1 averages) in water from the wetland channel in the laboratory bioassay, while development was not affected. C riparius larvae were not affected by, molinate and propanil concentrations. The results indicate that endosulfan treatments in rice fields may cause an ecological impairment in adjacent freshwater ecosystems. The results also indicate that laboratory testing can be used to assess in situ toxicity caused by pesticide contamination. (c) 2006 Elsevier Inc. All rights reserved.FCT - SFRH/BD/2935/200
Estuarine sediment toxicity tests on diatoms: sensitivity comparison for three species
No full textExperimental populations of three marine and estuarine diatoms were exposed to sediments with different levels of pollutants, collected from the Aveiro Lagoon (NW of Portugal). The species selected were Cylindrotheca closterium, Phaeodactylum tricornutum and Navicula sp. Previous experiments were designed to determine the influence of the sediment particle size distribution on growth of the species assayed. Percentage of silt-sized sediment affect to growth of the selected species in the experimental conditions: the higher percentage of silt-sized sediment, the lower growth. In any case, percentages of silt-sized sediment less than 10% did not affect growth. In general, C. closterium seems to be slightly more sensitive to the selected sediments than the other two species. Two groups of sediment samples were determined as a function of the general response of the exposed microalgal populations: three of the six samples used were more toxic than the other three. Chemical analysis of the samples was carried out in order to determine the specific cause of differences in toxicity. After a statistical analysis, concentrations of Sn, Zn, Hg, Cu and Cr (among all physico-chemical analyzed parameters), in order of importance, were the most important factors that divided the two groups of samples (more and less toxic samples). Benthic diatoms seem to be sensitive organisms in sediment toxicity tests. Toxicity data from bioassays involving microphytobentos should be taken into account when environmental risks are calculated. (c) 2006 Elsevier Ltd. All rights reserved.MECASEC - CTM2006-01473/MA
Environmental pollution and natural populations: A biomarkers case study from the Iberian Atlantic coast
No full textThe degradation of estuaries is a result of human activities which overloads the environment with substances of both industrial and/or natural origins. Bioindicators have been consistently used to interpret effects of contaminants in the environment. In this study, the use of biomarkers (particular measurable characteristics of a bioindicator organism) was used to evaluate the contamination by xenobiotics of Crangon crangon natural populations. The central aim was to evaluate the capability of a battery of biomarkers to discriminate sites with different types of contamination. The activity of the enzymes cholinesterases (ChE), lactate dehydrogenase (LDH) and glutathione Stransferases (GST) were used as biomarkers. In addition, the ChE form(s) present in the cephalotorax of C. crangon were characterised. Organisms were seasonally sampled from winter 2001/2002 to autumn of 2002, at "reference" sites and at sites that receive agricultural, industrial and/or urban effluents. Results obtained in the characterisation of ChE with different substrates and selective inhibitors demonstrate that the form of ChE present in the cephalotorax of C crangon shows proprieties of vertebrates' AChE and therefore it may be classified as true AChE-like ChE. The battery of biomarkers exhibited seasonal and local variations, apparently related to agricultural, industrial or urban effluent contamination. The tested biomarkers proved to be able to discriminate sources of environmental contamination, and confirms C crangon as a sensitive species suitable to be used as a bioindicator. (c) 2006 Published by Elsevier Ltd.CONTROL - PDCTM/C/MAR/15266/1999RISKA - FCT/ POCTI/BSE/46225/2002EU/FEDER progra
Foundation studies for cadmium accumulation studies in terrestrial isopods - diet selection and diet contamination
No full textFood palatability studies were carried out with the terrestrial isopods Porcellio dilatatus and Porcellinoides pruinosus. They were provided with leaves of lettuce (Lactuca sativa), pea (Pisum sativum), Elodea and alder (Alnus glutinosa) to determine their suitability as food substrates for metal accumulation tests with these isopods. Lettuce, pea and Elodea were also assessed for their ability to take up cadmium in hydroponic culture. In the feeding trials, growth, consumption and assimilation indices indicated that lettuce may be a suitable food, while the plant contamination trials indicated that lettuce and Elodea could take up large quantities of cadmium into the leaves. These studies form part of a project to develop a system for delivering metal contaminants to terrestrial isopods for metal accumulation studies that incorporate the principles of trophic transfer. (c) 2005 Elsevier SAS. All rights reserved.FC
Evidence for the Stepwise Stress Model: Gambusia holbrooki and Daphnia magna under acid mine drainage and acidified reference water stress
No full textThe Stepwise Stress Model (SSM) states that a cascade of regulative behavioral responses with different intrinsic sensitivities and threshold values offers increased behavioral plasticity and thus a wider range of tolerance for environmental changes or pollutant exposures. We tested the SSM with a widely introduced fish Gambusia holbrooki (Girard) (Pisces, Poeciliidae) and the standard laboratory test species Daphnia magna Straus (Crustacea, Daphniidae). The stress was simulated by short-term exposure to acid mine drainage (AMD) and to acidified reference water (ACID). Recording of behavioral responses with the multispecies freshwater biomonitor (MFB) generated continuous time-dependent dose-response data that were modeled in three-dimensional (313) surface plots. Both the pH-dependent mortalities and the strong linear correlations between pH and aqueous metals confirmed the toxicity of the AMD and ACID gradients, respectively, for fish and Daphnia, the latter being more sensitive. AMD stress at pH <= 5.5 amplified circadian rhythmicity in both species, while ACID stress did so only in G. holbrooki. A behavioral stepwise stress response was found in both species: D. magna decreased locomotion and ventilation (first step) (AMD, ACID), followed by increased ventilation (second step) (AMD). G. holbrooki decreased locomotion (first step) (AMD, ACID) and increased ventilation at intermediate pH levels (second step) (AMD). Both species, although from different taxonomic groups and feeding habits, followed the SSM, which might be expanded to a general concept for describing the behavioral responses of aquatic organims to pollution. Stepwise stress responses might be applied in online biomonitors to provide more sensitive and graduated alarm settings, hence optimizing the "early warning" detection of pollution waves.Cost Effective Tools for Ecological Risk AssessmentIAV/82/00PRAXIS/C/MGS/10200/1998FCT - SFRH/BPD/8345/2002FCT - SFRH/BPD/8891/ 200
In situ and laboratory microalgal assays in the tropics: A microcosm simulation of edge-of-field pesticide runoff
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Effects of Two Insecticides on Survival, Growth and Emergence of Chironomus riparius Meigen
No full textEffects of chlorpyrifos and cypermethrin on the survival, growth and emergence of Chironomus riparius were determined on a life-cycle study. Although neither cypermethrin nor chlorpyrifos affected larval survival or growth, a decrease in the number of emerged midges and in the number of females over males, as well as in female biomass, were found for both insecticides. The results from this study indicate that multiple biological endpoints and extended periods of exposure are needed in order to achieve a better screening of insecticide toxicity.FCT - SFRH/BM/8402/2002FCT - PTDC/BIABDE/72841/200
Toxic Element Concentrations in the Razorbill Alca torda (Charadriiformes, Alcidae) in Portugal
No full textThe present study provides the first data on inorganic element levels (As, Cd, Co, Cr, Cu, Hg, Mn, Pb, Se, and Zn) in juvenile, immature, and adult razorbills (Alca torda) collected along the central coast of Portugal. Element concentrations were assessed by ICP-MS in kidney, liver, muscle, and feathers of 28 razorbills, including 4 juveniles, 17 subadults, and 7 adults. The effect of age and tissue on element accumulation was also assessed. The detected levels in razorbills may indicate a possible contamination risk by Hg and Cr. With respect to bird tissues, higher accumulation of Se and Cd was detected in kidney, Zn and Pb in feathers, and As and Mn in liver. Age was found to affect the accumulation of Cd, Cr, Cu, Hg, and Mn, juveniles presenting higher levels of Cu and Mn than older individuals. In razorbill kidney, Zn-Hg constituted the most significant relationship among metal concentrations. Liver presented the highest number of significant relationships (mostly involving Zn and Co). With regard to feathers, the most significant relationships involved Se, Zn, Cr and Cu concentrations. Positive linear relationships were detected among kidney, liver, and muscle, with emphasis on relationships involving Se and Hg, which may be indicative of similar accumulation/regulation mechanisms in those organs. Element concentrations are discussed in view of possible detoxification mechanisms in seabirds.SEID/CRUP - project HP 2005-0011 (ACIN)FCT/MCTES - SFRH/BPD/27014/200
Genetic structure of the wild boar population in Portugal: Evidence of a recent bottleneck
Get PDFThe present study assesses the degree of genetic structure and the presence of recent genetic bottlenecks in the wild boar population in Portugal. One hundred and ten individuals were sampled after capture during organised legal drive hunts, conducted in 58 municipalities across the continental territory, during the game seasons of 2002/2003 and 2003/2004. Individuals were genetically typed Lit six microsatellite loci using multiplex PCR amplification. Significant deviations from Hardy-Weinberg equilibrium were found for the total population of wild boar in Portugal. Wild boar population genetic structure was assessed using Bayesian methods, Suggesting the existence of three subpopulations (North, Centre and South). Tests were conducted to detect the presence of potential migrants and hybrids between subpopulations. After exclusion of these individuals, three sets of wild boars representative of respective subpopulations were distinguished and tested for the effects of recent bottlenecks. Genetic distances between pairs of subpopulations were quantified using F(ST) and R(ST) estimators, revealing a variation of 0.138-0.178 and 0.107-0.198, respectively. On the basis of genetic and distribution data for Portuguese wild boar from the beginning of the 20th century, a model of strong demographic decline and contraction to isolated refuge areas Lit the national level, followed by a recovery and expansion towards former distribution limits is suggested. Some evidence points to present admixture among subpopulations in contact areas. (C) 2008 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GmbH. All rights reserved.USDA - US Pig Genome Coordination ProjectFCT - SFRH/BM/ 13034/200