945 resultados para subtropical estuaries


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Pós-graduação em Agronomia (Horticultura) - FCA

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Pós-graduação em Aquicultura - FCAV

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O fitoplancton é de grande importância para os estudos das interações solo-água, como indicadores de modificações químicas e biológicas nos ecossistemas naturais. O objetivo desse estudo foi determinar a composição química total do fitoplâncton nos estuários do rio Pará e Mocajuba (Pará, Brasil). As análises químicas foram realizadas na água superficial, sedimento de fundo (amostra total e fração biodisponível) e no fitoplancton, por espectrometria óptica e de massa com plasma indutivamente acoplado. A composição química elementar do fitoplancton é composta por elevadas concentrações de Ca, P, Mn, Fe, Zn, Al, Ba e Pb. O fitoplancton do estuário do rio Mocajuba é rico em Fe (2.967 a 84.750 µg g-1) e do rio Pará rico em Al (1.216 a 15.389 µg g-1), provavelmente com contribuição antropogênica. O material fitoplanctonico apresentou elevado fator de bioconcentração proveniente tanto da água quanto da fração biodisponível, e reflete a eficiência desses organismos em concentrar metais.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Brazilian Campos grasslands are ecosystems under high frequency of disturbance by grazing and fires. Absence of such disturbances may lead to shrub encroachment and loss of plant diversity. Vegetation regeneration after disturbance in these grasslands occurs mostly by resprouting from belowground structures. We analyzed the importance of bud bank and belowground bud bearing organs in Campos grasslands. We hypothesize that the longer the intervals between disturbances are, the smaller the size of the bud bank is. Additionally, diversity and frequency of belowground organs should also decrease in areas without disturbance for many years. We sampled 20 soil cores from areas under different types of disturbance: grazed, exclusion from disturbance for two, six, 15 and 30 years. Belowground biomass was sorted for different growth forms and types of bud bearing organs. We found a decrease in bud bank size with longer disturbance intervals. Forbs showed the most drastic decrease in bud bank size in the absence of disturbance, which indicates that they are very sensitive to changes in disturbance regimes. Xylopodia (woody gemmiferous belowground organs with hypocotyl-root origin) were typical for areas under influence of recurrent fires. The diversity of belowground bud bearing structures decreased in the absence of disturbance. Longer intervals between disturbance events, resulting in decrease of bud bank size and heterogeneity of belowground organs may lead to the decline and even disappearance of species that relay on resprouting from the bud bank upon disturbance. (C) 2014 Elsevier GmbH. All rights reserved.

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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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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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This study aimed to evaluate the sediment quality in the estuarine protected area known as Canan,ia-Iguape-Peruibe (CIP-PA), located on the southeastern coast of Brazil. The study was designed considering possible negative effects induced by the city of Canan,ia on the sediment quality of surrounding areas. This evaluation was performed using chemical and ecotoxicological analyses. Sediments were predominantly sandy, with low CaCO3 contents. Amounts of organic matter varied, but higher contents occurred closer to the city, as well as did Fe and Total Recoverable Oils and Greases (TROGs) concentrations. Contamination by Cd and Cu was revealed in some samples, while concentrations of Zn were considered low. Chronic toxicity was detected in all tested sediments and acute toxicity occurred only in sediments collected near the city. The principal component analysis (PCA) revealed an association among Cd, Cu, Fe, TROG, fines, organic matter, CaCO3, and chronic toxicity, whereas acute toxicity was found to be associated with Zn and mud. However, because Zn levels were low, acute toxicity was likely due to a contaminant that was not measured. Results show that there is a broad area within the CIP-PA that is under the influence of mining activities (chronic toxicity, moderate contamination by metals), whereas poorer conditions occur closer to Canan,ia (acute toxicity); thus, the urban area seems to constitute a relevant source of contaminants for the estuarine complex. These results show that contamination is already capable of producing risks for the local aquatic biota, which suggests that the CIP-PA effectiveness in protecting estuarine biota may be threatened.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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QuestionsWe aimed to analyse the effect of fire on flowering in subtropical grasslands, by addressing the following questions: will fire history affect flowering? If yes, do fire feedbacks influence flowering or is it just the removal of above-ground biomass? Are there differences in burned and mowed plots?LocationSubtropical grasslands in Southern Brazil (30 degrees 03S, 51 degrees 07W).MethodsWe established plots in areas with different fire histories: 30d (30 plots: five replicates), 1yr (14 replicates), 3yr (30 plots: five replicates) since the last fire, in experimentally burned and mowed plots (14 replicates each). We counted the number of flowering species, as well as the number of flowering stalks.ResultsGraminoid species flowered in highest numbers 1yr after fire, whilst forbs had more species flowering just after fire, indicating different reproductive strategies in post-fire environments. Mowing was not as efficient as fire in stimulating flowering. Finally, the different functional groups showed different flowering responses to time since last fire and to the different types of management.ConclusionsOur results show fire stimulated flowering. Although mowing can be a good alternative for maintaining plant diversity, our study showed that this practice is not as efficient as fire in stimulating flowering. However, fire season should be noted as a limiting factor to the recovery of C-3 grasses in these subtropical grasslands, and annual burns may be harmful to C-4 grasses, since they delay their flowering to the next post-fire growing season.