100 resultados para LOTIC ENVIRONMENTS
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The freshwater phytoplankton, responsible for a significant part of primary production in rivers and lakes, is of great importance for matter and energy available to other trophic levels of structuring aquatic food chains. In recent decades, the construction of dams, especially for the generation of electricity, produced changes not only in physical and chemical characteristics of rivers, but also in biocoenosis of these ecosystems. Thus, research is needed to expand the basic knowledge about these environments and subsidize actions appropriate conservation and management. Considering that lotic environments are relatively little studied, and the river-reservoir interaction, the work aims to analyze the limnological conditions and assemblies phytoplankton along the gradient established by the Itaipu reservoir and downstream stretch of the Paraná River. During two periods of the year, winter and summer, we analyzed nine sampling stations: one in lentic environment (the dam), six on the Parana River (each 5 km), at the mouth of a river Monday and another at the mouth of the Iguazu river. The phytoplankton community was composed of 315 taxa, with the class Bacillariophyceae most specious. At every point the richness was higher in summer and with a longitudinal trend in the increasing points after falling after the dam and the contribution of the tributaries. The number of taxa common to the three rivers was low in both study periods. The higher taxa can be explained by the variety of environments sampled, different residence times of water and nutrient concentrations, whereas the rivers Iguazu and Monday suffer high human influence. The greater abundance of organisms in the dam, in both periods, it should be the class Cryptophyceae contributing over 75% of total phytoplankton in point. In cluster analysis (composition and abundance)...(Complete abstract click electronic access below)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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To contribute to the knowledge of lotic zooplankton from dammed and free stretches, we tested the hypothesis that the ecological attributes are different between these environments, which are subjected to several effects caused by different hydrological conditions. The study was carried out in the low Iguacu river, a large hydrographic basin in the south of Brasil. Two samplings were performed, one in the dry period (April/04) and the other in the atypical rainy period (July/04), in five stations downstream a large reservoir, and other 12 stations in four tributaries representing the upper, intermediate and low regions of each river. The observations suggest a clear spatial distribution of zooplankton in lotic stretches subjected or not to damming, mainly due to the effects of physical, chemical and biological variables. Furthermore, the atypical rainfall promoted alterations in community structure when compared to the dry period.
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Por meio de observações sub e supra-aquáticas foram registradas associações alimentares do tipo nuclear-seguidor entre três espécies de peixes characiformes - Chalceus epakros, Hemiodus semitaeniatus e Hemiodus unimaculatus - e uma espécie de raia de água doce - Potamotrygon orbignyi - nas bacias dos rios Teles Pires e Xingu, no Centro-Oeste do Brasil. Os peixes teleósteos foram observados seguindo as raias quando estas revolviam o substrato à procura de invertebrados, formando discretas nuvens de sedimento. Essas situações atraíram os peixes que se aproximaram das raias para se alimentar de pequenas presas e outros tipos de alimentos expostos desta forma. Esse é um típico exemplo de relação comensal onde um participante é beneficiado enquanto o outro não é prejudicado e representa o segundo registro na literatura de associação alimentar do tipo nuclear-seguidor entre raias potamotrigonídeas e peixes teleósteos, demonstrando o potencial de estudos naturalísticos para a descoberta de novas interações envolvendo espécies de peixes de água doce.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Uma ampla variedade de patógenos oportunistas tem sido detectadas nos tubos de alimentação de água dos equipos odontológicos, particularmente no biofilme formado na superfície do tubo. Entre os patógenos oportunistas encontrados nos tubos de água, Pseudomonas aeruginosa é reconhecida como uma das principais causadoras de infecções nosocomiais. Foram coletadas 160 amostras de água e 200 amostras de fomites em quarenta clinicas odontológicas na cidade de Barretos, São Paulo, Brasil, durante o período de Janeiro a Julho de 2005. Setenta e seis cepas de P. aeruginosa, isoladas a partir dos fomites (5 cepas) e das amostras de água (71 cepas), foram analisadas quanto à susceptibilidade à seis drogas antimicrobianas freqüentemente utilizadas para o tratamento de infecções provocadas por P. aeruginosa. As principais suscetibilidades observadas foram para a ciprofloxacina, seguida pelo meropenem. A necessidade de um mecanismo efetivo para reduzir a contaminação bacteriana dentro dos tubos de alimentação de água dos equipos odontológicos foi enfatizada, e o risco da exposição ocupacional e infecção cruzada na prática odontológica, em especial quando causada por patógenos oportunistas como a P. aeruginosa foi realçado.
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Membrane integrity, as measured by electrical conductivity (EC), is suggested as an indicator of seed vigor in soybean [Glycine max (L.) Merrill] seeds. This study evaluated the effect of storage time and temperature on EC of six soybean seed lots (two lots each of high, medium and low vigor). All seed lots were adjusted to 120 g kg(-1) seed moisture, sealed in aluminum foil packets and placed in storage at 10 and 20 degreesC or stored unsealed in multi-wall paper bags in warehouse (WH) conditions at Lexington, KY, USA for 486 days. Four of the six seed lots were also stored unsealed at 10 degreesC. All seed lots were sampled at 3-month intervals and evaluated for seed moisture (SMC), standard germination (SG) and vigor [accelerated aging (AA) and EC]. After 91 and 204 days in storage, samples initially stored at 20 degreesC and WH were moved to 10 degreesC and sampled at the same intervals. Seed moisture content for unsealed samples equilibrated at 107 g kg(-1) (+/-9 g kg(-1)) in both the WH and 10 degreesC environments. No change in SG occurred for seeds stored sealed (120 g kg(-1)) at 10 degreesC, except for the low vigor seed lots which declined significantly at the last sample date. The AA germination declined significantly for all, seed lots stored sealed at 10 degreesC, however the EC did not change during the same storage period. Seeds stored sealed at 20 degreesC and unsealed in the WH showed rapid declines in AA and SG and significant increases in EC. When these seeds were moved to 10 degreesC, however, the AA continued to decline while the EC remained at the same level (no significant change) for the remainder of the seed storage period. Thus whilst the AA declined in all environments, the EC only increased at higher temperatures (20 degreesC, WH) but showed little change during storage at 10 degreesC. Thus, precautions must be taken if using EC to measure soybean seed vigor following storage at 10 degreesC.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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The presence of various pathogenic fungi in rather unsuspected hosts and environments has always attracted the attention of the scientific community. Reports on the putative role of animals in fungal infections of humans bear important consequences on public health as well as on the understanding of fungal ecology. Fungi are ubiquitous in nature and their great capacity for adaptation allows them to survive and indeed, to thrive, in plants, trees and other natural substrata. Nonetheless, we are just beginning to learn the significance that these diverse fungal habitats have on the increasing number of immunosuppressed individuals. The accidental or permanent presence of fungi in animals, plants, soils and watercourses should not be taken too lightly because they constitute the source where potential pathogens will be contracted. If those fungal habitats that carry the largest risks of exposure could be defined, if seasonal variations in the production of infectious propagules could be determined, and if their mode of transmission were to be assessed, it would be possible to develop protective measures in order to avoid human infection. Additionally, unsuspected avenues for the exploration of fungal survival strategies would be opened, thus enhancing our capacity to react properly to their advancing limits. This paper explores several ecological connections between human pathogenic fungi and certain animals, trees, waterways and degraded organic materials. The occurrence of such connections in highly endemic areas will hopefully furnish more precise clues to fungal habitats and allow the design of control programs aimed at avoiding human infection.
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Many studies show environmental enrichment is correlated with benefits to captive animals; however, one should not always assume this positive relationship given that enrichment increases the amount of resources that a territorial animal must defend and possibly affects its aggressive dynamics. In this study, we tested if environmental enrichment affects aggressive interactions in the aggressive fish Nile tilapia (Oreochromis niloticus). We compared fights staged between pairs of male tilapia of similar size (= matched in resource holding potential) in a novel arena that was either barren or enriched, to examine whether enrichment enhances territory value in line with theoretical predictions, with the potential for compromised welfare. We evaluated time elapsed until the first attack (latency), frequency of aggressive interactions and fight duration. We detected fight dynamic differences at the pair level. Higher resource value generated increased aggression but had no effect on fight duration or latency. This conclusion is in line with game theory predictions concerning resource value and contradicts the theory that enrichment of the environment will serve welfare purposes. (C) 2010 Elsevier GmbH. All rights reserved.