986 resultados para Potamogeton crispus
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A continuous biostratigraphic sequence has been established, possibly from as low as the sedgwickii Biozone but certainly throughout the Telychian Stage (?sedgwickii, turriculatus, ?crispus, griestoniensis and crenulata biozones). Thirty-three taxa have been recorded, including the new genus Wandograptus wandovalensis sp. nov., the new species Pseudostreptograptus queenslandensis and the new subspecies Dictyonema paululum australis and Stimulograptus sedwickii loydelli. A number of species have been recorded from Australia for the first time: Dictyonema cf. geniculatum Bulman, Petalolithus kurcki (Rickards), Pristiograptus initialis (Kirste), Monoclimacis directa Zalasciewicz, Monograptus aff. distans (Portlock), Monograptus sartorius Törnquist, and Torquigraptus pragensis (Bouček). Nine forms have been left under open nomenclature. The type section for the Poley Cow Formation yields a griestoniensis biozone fauna close to the top, and this level can be correlated with a griestoniensis Biozone fauna in the Broken River crossing section, again just below the top of the formation. Further north, griestoniensis Biozone faunas have also been recognized, beyond Diggers Creek, and in the Quinton Formation at Top Hut, enabling a reliable time plane throughout the region. At Top Hut, the highest graptolitic strata yield a crenulata Biozone fauna; and stratigraphically lower sequences, referable to the ?sedgwickii, turriculatus and ?crispus biozones, have been established on the Broken River section. It is likely that a full Telychian (Upper Llandovery) sequence occurs in the Poley Cow and Quinton formations enabling accurate correlation with other parts of the world.
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Estudou-se em laboratório a atividade moluscicida de 68 extratos de 23 plantas brasileiras. As soluções em água desclorada dos extratos hexânicos e etanólico, nas concentrações de 1, 10 e 100 ppm, foram testadas sobre caramujos adultos e desovas de Biomphalaria glabrata, criados em laboratório. As plantas que demonstraram ação moluscicida na concentração de 100 ppm foram: Arthemisia verlotorum Lamotte, Caesalpinia peltophoroides Benth, Cassia rugosa G.Don., Eclipta alba Hassk, Euphorbia pulcherrima Willd, Euphorbia splendens Bojer, Joannesia princeps Vell, Leonorus sibiricus L.,Macrosiphonia guaranitica Muell,Nerium oleander L., Palicourea nicotianaefolia Cham, e Schlech., Panicum maximum M., Rumex crispus L., Ruta graveolens L., e Stryphnodendron barbatiman M.
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Gammarus aequicauda and Sphaeroma hookeri are the most abundant macroinvertebrates on Ruppia cirrhosa (1275 and 1290 individuals.m-2) and Potamogeton pectinatus (140 and 680 individuals. m-2) in Tancada lagoon, a Mediterranean coastal lagoon in the Ebro Delta (NE Spain). Consumption and assimilation efficiencies were calculated from bell jar experiments. Gammarus grazing effects are higher than Sphaeroma on both Ruppia cirrhosa and Potamogeton pectinatus. Green Ruppia leaves lost 0.3 mg per mg Gammarus per day, while Potamogeton leaves lost 0.2 mg per mg Gammarus per day. Decomposing Ruppia leaves lost 0.35-0.54 mg per mg Gammarus per day. Losses of weight by both Ruppia and Potamogeton due to Sphaeroma feeding were less than half those by Gammarus. Assimilation efficiencies are higher for Gammarus (44-78% feeding on Ruppia 2% feeding on Potamogeton) than for Sphaeroma (26-48%) feeding on Ruppia). These assimilation efficiencies were higher than those reported by other authors working at higher latitudes perhaps because of the higher temperature under which the experiments were carried out.
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Coastal lagoons where salinity varies within a wide range during the year are colonized by euryhaline macrophytes which can develop extensive beds. Seasonal changes in biomass of Ruppia cirrhosa and Potamogeton pectinatus were studied in Tancada Lagoon (Ebro Delta, NE Spain) in order to reveal the environmental factors controlling their population development. Ruppia cirrhosa occupy a larger area of the lagoon than Potarnogeton pectinatus. Their maximum above ground biomasses are also different (495 g m-2 and 351 g m-2 ash free dry weight, respectively). Below ground biomass of Ruppia cirrhosa is between 9 and 53 % of the above ground biomass, while it is 3-40 % for Potamogeton pectinatus. Chlorophyll a contents show fluctuations similar to biomass. Low salinity and high turbidity caused by freshwater inflows favour Potamogeton expansion, while Ruppia development is favoured by high salinity and transparent water.
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This work aims to characterise the current autotrophic compartment of the Albufera des Grau coastal lagoon (Menorca, Balearic Islands) and to assess the relationship between the submerged macrophytes and the limnological parameters of the lagoon. During the study period the submerged vegetation was dominated by the macrophyte Ruppia cirrhosa, which formed dense extensive meadows covering 79% of the surface. Another macrophyte species, Potamogeton pectinatus, was also observed but only forming small stands near the rushing streams. Macroalgae were only occasionally observed. Macrophyte biomass showed a clear seasonal trend, with maximum values in July. The biomass of R. cirrhosa achieved 1760 g DW m-2, the highest biomass ever reported for this species in the literature. The seasonal production-decomposition cycle of the macrophyte meadows appears to drive the nutrient dynamics and carbon fluxes in the lagoon. Despite the significant biomass accumulation and the absence of a washout of nutrients and organic matter to the sea, the lagoon did not experience a dystrophic collapse. These results indicate that internal metabolism is more important than exchange processes in the lagoon.
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Gammarus aequicauda and Sphaeroma hookeri are the most abundant macroinvertebrates on Ruppia cirrhosa (1275 and 1290 individuals.m-2) and Potamogeton pectinatus (140 and 680 individuals. m-2) in Tancada lagoon, a Mediterranean coastal lagoon in the Ebro Delta (NE Spain). Consumption and assimilation efficiencies were calculated from bell jar experiments. Gammarus grazing effects are higher than Sphaeroma on both Ruppia cirrhosa and Potamogeton pectinatus. Green Ruppia leaves lost 0.3 mg per mg Gammarus per day, while Potamogeton leaves lost 0.2 mg per mg Gammarus per day. Decomposing Ruppia leaves lost 0.35-0.54 mg per mg Gammarus per day. Losses of weight by both Ruppia and Potamogeton due to Sphaeroma feeding were less than half those by Gammarus. Assimilation efficiencies are higher for Gammarus (44-78% feeding on Ruppia 2% feeding on Potamogeton) than for Sphaeroma (26-48%) feeding on Ruppia). These assimilation efficiencies were higher than those reported by other authors working at higher latitudes perhaps because of the higher temperature under which the experiments were carried out.
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Durante abril de 2005 se realizó una campaña de muestreo de la vegetación acuática macroscópica en las cuencas de los ríos Foix, Besòs y Llobregat, sumando un total de 68 estaciones de muestreo. El objetivo principal fue evaluar el estado trófico de dichas cuencas mediante el índice trófico generado en España denominado IVAM (Índice de Vegetación Acuática Macroscópica). Se identificaron un total de 44 táxones, 8 géneros de Cyanophyta, 5 de Rodophyta, 2 de Xantophyceae, 3 de Bacillariophyceae, 15 de Clorophyta, 8 de Spermatophyta, 1 liquen y 2 briófitos (musgos y hepáticas). La cuenca del Llobregat fue la más diversa (37 t´axones), seguida del Besós (33) y el Foix (25). Los táxones más frecuentes fueron Cladophora, Vaucheria, Oedogonium, Apium, Rorippa y Oscillatoria, además de los musgos. Las fanerógamas fueron escasas, destacando los g´eneros Ranunculus, Zannichellia y Potamogeton. Los táxones que alcanzaron una mayor puntuación del IVAM (valor de tolerancia, vt = 8), aunque poco frecuentes, fueron Ranunculus, Cymbella, Rivularia, Nostoc, Tolypothrix, Chroococcus y Lemanea, todos indicadores de aguas oligotr´oficas. En aguas de buena calidad pero algo eutrofizadas (aguas mesotróficas, vt = 6), los táxones más frecuentes fueron Chara, Monostroma y Hildenbrandia, además de las hepáticas y un liquen. Según la calificación de los tramos en clases de estado trófico realizada por el IVAM, el 38.2% de los tramos presentaron una buena calidad (clases I y II) mientras que el 61.8% presentaron un estado trófico alterado (clases III, IV y V). La respuesta del IVAM a la concentración de nutrientes (fosfato, amonio, nitrito y nitrato) fue siempre significativa, destacando la alta correlación alcanzada con el ión fosfato (r = 0.71, p < 0.001), superior a la alcanzada por otros índices de diatomeas y macrófitos de resolución taxonómica específica. Este hecho confirma la ventaja de utilizar el IVAM en la evaluación del estado trófico de los ríos, ya que sin necesidad de alcanzar un nivel taxonómico de especie se obtiene una respuesta adecuada a dicha perturbación.
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Objective: To summarise and critically evaluate the evidence informing the provision of standard care practices and psychosocial interventions following stillbirth. Background: Stillbirth is increasingly recognised as a significant bereavement experience with the potential to cause substantial psychological distress for parents. Standard care practices and psychosocial interventions to support parents have undergone dramatic changes, with limited basis in evidence. Methods: A systematic narrative review was conducted of quantitative studies examining interventions designed to reduce psychological distress in parents following the loss of a stillborn baby. Results: Twenty-five studies met the inclusion criteria for the review. Substantial methodological weaknesses were identified among reviewed studies, including small and heterogeneous loss samples, weak study designs and lack of clarity in reported methods and outcomes. Inadequate replication of many findings substantially limits the generalisability of the evidence. Conclusion: Tentative evidence was found for the provision of mementoes of the baby and information regarding the cause of the loss, support group attendance, and cognitive behavioural interventions for parents identified with clinical levels of distress. Contradictory findings for the impact of contact with the baby prevent the formation of clear conclusions for this practice. Due to the methodological weaknesses prevalent in the research identified, the current evidence base is not considered sufficiently able to reliably inform care practices and intervention approaches. High-quality research evidence in this field is urgently required.
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Submersed vegetation is a common feature in about 70% Pyrene an high mountain (>1500 m a.s.l.) lakes. Isoetids and soft-water elodeids are common elements of this underw ater flora and can form distinct vegetation units (i.e. patches of vegetation dominated by different species) within complex mosaics of vegetation in shallow waters (<7 m). Since is oetids exert a strong influence on sediment biogeochemistry due to high radial oxygen loss, we examined the small scale characteristics of the lake environment (water and sediment) associated to vegetation patches in order to ascertain potential functional differences among them. To do so, we characterised the species composition and biomass of the main vegetation units from 11 lakes, defined plant communities based on biomass data, and then related each community with sediment properties (redox and dissolved nutrient concentration in the pore water) and water nutrient concentration within plant canopy. We also characterised lake water and sediment in areas without vegetation as a reference. A total of twenty-one vegetation units were identified, ranging from one to five per lake. A cluster analysis on biomass species composition suggested seven different macrophyte communities that were named after the most dominant species:Nitella sp.,Potamogeton praelongus, Myriophyllum alterniflorum, Sparganium angustifolium , Isoetes echinospora,Isoetes lacustris and Carex rostrata . Coupling between macrophyte communities and their immediate environment (overlying water and sediment) was manifested mainly as variation in sediment redox conditions and the dominant form of inorganic nitrogen in pore-water. These effects depended on the specific compositi on of the community, and on the allocation between above- and belowground biomass, and could be predicted with a model relating the average and standard deviation of sediment redox potential from 0 down to -20 cm, across macrophyte communities. Differences in pore-water total dissolved phosphorus were related to the trophic state of the lakes. There was no correlation between sediment and water column dissolved nutrients. However, nitrate concentrations tended to be lower in the water overlaying isoetid communities, in apparent contradiction to the patterns of dissolved nitrates in the pore-water. These tendencies were robust even when comparing the water over laying communities within the same lake, thus pointing towards a potential effect of isoetids in reducing dissolved nitrogen in the lakes.
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The biological variation in nature is called biodiversity. Anthropogenic pressures have led to a loss of biodiversity, alarming scientists as to what consequences declining diversity has for ecosystem functioning. The general consensus is that diversity (e.g. species richness or identity) affects functioning and provides services from which humans benefit. The aim of this thesis was to investigate how aquatic plant species richness and identity affect ecosystem functioning in terms of processes such as primary production, nutrient availability, epifaunal colonization and properties e.g. stability of Zostera marina subjected to shading. The main work was carried out in the field and ranged temporally from weeklong to 3.5 months-long experiments. The experimental plants used frequently co-occur in submerged meadows in the northern Baltic Sea and consist of eelgrass (Z. marina), perfoliate pondweed (Potamogeton perfoliatus), sago pondweed (P. pectinatus), slender-leaved pondweed (P. filiformis) and horned pondweed (Zannichellia palustris). The results showed that plant richness affected epifaunal community variables weakly, but had a strong positive effect on infaunal species number and functional diversity, while plant identity had strong effects on amphipods (Gammarus spp.), of which abundances were higher in plant assemblages consisting of P. perfoliatus. Depending on the starting standardizing unit, plant richness showed varying effects on primary production. In shoot density-standardized plots, plant richness increased the shoot densities of three out of four species and enhanced the plant biomass production. Both positive complementarity and selection effects were found to underpin the positive biodiversity effects. In shoot biomass-standardized plots, richness effects only affected biomass production of one species. Negative selection was prevalent, counteracting positive complementarity, which resulted in no significant biodiversity effect. The stability of Z. marina was affected by plant richness in such that Z. marina growing in polycultures lost proportionally less biomass than Z. marina in monocultures and thus had a higher resistance to shading. Monoculture plants in turn gained biomass faster, and thereby had a faster recovery than Z. marina growing in polycultures. These results indicate that positive interspecific interactions occurred during shading, while the faster recovery of monocultures suggests that the change from shading stress to recovery resulted in a shift from positive interactions to resource competition between species. The results derived from this thesis show that plant diversity affects ecosystem functioning and contribute to the growing knowledge of plant diversity being an important component of aquatic ecosystems. Diverse plant communities sustain higher primary productivity than comparable monocultures, affect faunal communities positively and enhance stability. Richness and identity effects vary, and identity has generally stronger effects on more variables than richness. However, species-rich communities are likely to contain several species with differing effects on functions, which renders species richness important for functioning. Mixed meadows add to coastal ecosystem functioning in the northern Baltic Sea and may provide with services essential for human well-being.
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Determinou-se o efeito do pH na ação de algumas subst âncias promotoras de germinação em sementes de Chenopodium album L., Avena fatua L. e Rumex crispus L. A azida de sódio (A), nitrato de potássio + etileno (NE), NE + A, NE + A + tiuréia + peróxido de hidrogênio foram testados em solo (em bandej as) e em papel (in vitro) com soluções tampão em ambiente controlado. O efeito do NE no estímulo à germinação de sementes não foi afetado pelo pH na faixa de 3 a 9. A azida de sódio foi a substância que mais afetou as sementes, sendo este efeito pH dependente. Este composto foi extremamente deletério em sementes de C. album e A. fatua em solo ácido (pH 4,0), enquanto em solo básico ele estimulou a germinação em sementes de A. fatua, através da superação da dormência A combinação de NE + A em pH 6,2 inibiu a germinação de C. album e A. fatua, mostrando um antagonismo entre estes compostos. A mistura dos cinco compostos reduziu a influência do pH na ação deletéria da azida de sódio. O efeito deletério da azida foi menos afetado pela temperatura do que sua ação como superador de dormência. A solução extraída do solo não afetou a resposta de tratamentos químicos in vitro em diferentes temperaturas comparado a soluções tampão em pH semelhante. Discute-se a influência das características do solo na eficácia de substâncias químicas como superadores de dormência ou tratamentos deletérios às sementes.
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Shallow coastal areas are dynamic habitats that are affected by a variety of abiotic and biotic factors. In addition to the natural environmental stress, estuarine and coastal seagrass ecosystems are exposed to effects of climate change and other anthropogenic impacts. In this thesis the effect of different abiotic (shading stress, salinity and temperature) and biotic stressors (presence of co-occurring species) and different levels and combinations of stressors on the performance and survival of eelgrass (Zostera marina) was assessed. To investigate the importance of scale for stress responses, varying levels of biological organization (genotype, life stage, population and plant community) were studied in field and aquarium experiments. Light limitation, decreased salinity and increased temperature affected eelgrass performance negatively in papers I, II and III, respectively. While co-occurring plant species had no notable effect on eelgrass in paper IV, the presence of eelgrass increased the biomass of Potamogeton perfoliatus. The findings in papers II and III confirmed that more extreme levels of salinity and temperature had stronger impacts on plant performance compared to intermediate levels, but intermediate levels also had more severe effects on plants when they were exposed to several stressors, as illustrated in paper II. Thus, multiple stressors had negative synergetic effects. The results in papers I, II and III indicate that future changes in light climate, salinity and temperature can have serious impacts on eelgrass performance and survival. Stress responses were found to vary among genotypes, life stages and populations in papers I, II and III, respectively, emphasizing the importance of study scale. The results demonstrate that while stress in general affects seagrass productivity negatively, the severity of effects can vary substantially depending on the studied scale or level of biological organization. Eelgrass genotypes can differ in their stress and recovery processes, as observed in paper I. In paper II, eelgrass seedlings were less prone to abiotic stress compared to adult plants, but stress also decreased their survival considerably. This indicates that recruitment and re-colonization through seeds might be threatened in the future. Variation among population responses observed in paper III indicates that long-term local adaptation under differing selection pressures has caused divergence in salinity tolerance between Baltic eelgrass populations. This variability in stress tolerance observed in papers I and III suggests that some eelgrass genotypes and populations have a better capacity to adapt to changes and survive in a changing environment. Multiple stressors and biological level-specific responses demonstrate the uncertainty in predicting eelgrass responses in a changing environment. As eelgrass populations may differ in their stress tolerance both within and across regions, conservation strategies at both local and regional scales are urgently needed in order to ensure the survival of these important ecosystems.
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La question de recherche à la base de cette étude soulève le point de la nature paradoxale du canon de représentation égyptien qui démontre, simultanément, une certaine rigidité dans l’application de règles stylistiques et iconographiques établies, particulièrement dans l’art non commandité par l’État, et des preuves de transformation et d’intégration de motifs nouveaux. Partant de cette problématique, l’étude vise à identifier les mécanismes par lesquels ce canon permet, à la fois, l’innovation et le maintien d’une certaine tradition. L’approche est de nature double et consiste tout d’abord à identifier de grandes tendances et discontinuités stylistiques et iconographiques sur les bols de faïence du Moyen au Nouvel Empire. De plus, elle tente de déterminer si les transformations d’ordre sociopolitique et idéologique, survenant à ces périodes, peuvent être lues dans les variations stylistiques et iconographiques trouvées sur les bols de faïence. Après une description du champ conceptuel de la « représentation » en contexte égyptien, l’auteur effectue l’analyse iconographique exhaustive de ce qui constitue l’apport majeur de son étude, un corpus de 500 bols et fragments de faïence provenant de divers sites égyptiens du Moyen au Nouvel Empire. Les données ont été traitées par le biais de la méthode d’analyse iconologique proposée par Panofsky, qui lui permet de dévoiler un grand nombre de continuités et de transformations d’ordre stylistique et iconographique pour les différentes périodes. Plusieurs facteurs semblent avoir été à l’origine de ces transformations, dont la fluctuation entre un contexte de centralisation et de décentralisation politique de l’État, ainsi que l’intégration de motifs étrangers (proche-orientaux et égéens) résultant d’un contact accru entre l’Égypte et les régions voisines. De plus, les transformations idéologiques apportées par le règne d’Akhénaton et par la « contre-réforme » idéologique à la période ramesside, semblent avoir également contribué à des innovations au sein du canon, même si ce dernier maintient une certaine continuité légitimée par le pouvoir étatique. Le canon de représentation, devient ainsi une forme de langage dont l’État se sert et qui, parfois malgré lui, se transforme et fluctue selon les réalités des différentes périodes.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)