Nitrogen, Phosphorus and granulometric characterization in nearshore sediments of Guanabara Bay: tentative application of a solid phase diagenetic model

Os teores de nitrogênio, fósforo total e carbono orgânico e a textura granulométrica foram analisados em diferentes níveis de profundidade de sedimentos costeiros na Baía de Guanabara (Brasil). Este trabalho teve por objetivo estimar os estoques destes elementos e avaliar a influência da dinâmica sedimentar sobre estes, em cinco diferentes ambientes deposicionais. Os parâmetros texturais exibiram variações verticais em três estações. Esta é uma evidência da ocorrência de modificações nos processos deposicionais, originando perfis anômalos de nutrientes nestes testemunhos. No entanto, este comportamento não se correlacionou com a granulometria, sendo, ao contrário, errático. A concentração de NT e PT no sedimento superficial variou de 0,56 a 6,00 m g . g'1 e 0,15 a 1,62 m g. g’1, respectivamente. Através da aplicação de um modelo diagenético de fase sólida foram estimados fluxos de cerca de 1,1 - 24,7 g P . m 2 . ano’1 e 2,2 - 67,2 g N . m’ . ano’1. Estes valores correspondem a 4 - 82% da demanda média anual de fósforo pelo fitoplâncton, e 2 - 45% da de nitrogênio.Total nitrogen, phosphorus and organic carbon were measured in sediment profiles, and correlated to granulometric distribution in different depth levels of nearshore sediments in Guanabara Bay (Brazil). This paper assesses the pool of these elements and the influence of sedimentary dynamics on it, in five different depositional environments. Textural parameters exhibit vertical changes in three stations. This is an evidence of changes in depositional processes, reflected by anomalous nutrient profiles. However, there was no correlation with granulometry, showing rather an erratic behaviour. Superficial sediment TN and TP ranged from 0.56 to 6.00 m g. g'1 and 0.15 to 1.62 m g. g'1, respectively. Tentative application of solid phase diagenetic model estimates fluxes of about 1.1- 24.7 g P . m’2 . y’1 and 2.2 - 67.2 g N . m’2 . y’l. These values correspond to 4 - 82% of phosphorus and 2 - 45% of nitrogen annual average phytoplanktonic demand

Nitrogen, Phosphorus and granulometric characterization in nearshore sediments of Guanabara Bay: tentative application of a solid phase diagenetic model

Total nitrogen, phosphorus and organic carbon were measured in sediment profiles, and correlated to granulometric distribution in different depth levels o f nearshore sediments in Guanabara Bay (Brazil). This paper assesses the pool o f these elements and the influence of sedimentary dynamics on it, in five different depositional environments. Textural parameters exhibit vertical changes in three stations. This is an evidence of changes in depositional processes, reflected by anomalous nutrient profiles. However, there was no correlation with granulometry, showing rather an erratic behaviour. Surficial sediment TN and TP ranged from 0.56 to 6.00 mg. g’1 and0.15to 1.62mg.g-1, respectively. Tentative application of solid phase diagenetic model estimates fluxes of about 1.1 - 24.7 g P . m*2 . y'1 and 2.2 - 67.2 g N . m‘2 . y'1. These values correspond to 4 - 82% o f phosphorus and 2 - 45% of nitrogen annual average phytoplanktonic demand.Os teores de nitrogênio, fósforo total e carbono orgânico e a textura granulométrica foram analisados em diferentes níveis de profundidade de sedimentos costeiros na Baía de Guanabara (Brasil). Este trabalho teve por objetivo estimar os estoques destes elementos e avaliar a influência da dinâmica sedimentar sobre estes, em cinco diferentes ambientes deposicionais. Os parâmetros texturais exibiram variações verticais em três estações. Esta é uma evidência da ocorrência de modificações nos processos deposicionais, originando perfis anômalos de nutrientes nestes testemunhos. No entanto, este comportamento não se correlacionou com a granulometria, sendo, ao contrário, errático. A concentração de NT e PT no sedimento superficial variou de 0,56 a 6,00 m g . g*1 e 0,15 a 1,62 m g. g’1, respectivamente. Através da aplicação de um modelo diagenético de fase sólida foram estimados fluxos de cerca de 1,1 - 24,7 g P . m'2 . ano*1 e 2,2 - 67,2 g N . m . ano'1. Estes valores correspondem a 4 - 82% da demanda média anual de fósforo pelo fitoplâncton, e 2 - 45% da de nitrogênio

In situ measurements of benthic primary production, respiration and nutrient fluxes in a hypersaline coastal lagoon of SE Brazil

Bentbic oxygen and nutrient ftuxes were measured in a section of the hypersaline carbonate-rich coastal lagoon of Araruama, SE-Brazil. In situ incubations of the sediment surface (Zm - 1.5) were performed at one station with light/dark chambers during september 1993 (early spring period) and april 1995 (earlyautumn period). The carbonate..rich aediments were covered by 1-3 mm thick microalgal mats, dominated by the cyanobaeteria Phormidium sp, Oscillatoria sp, and Lyngbya sp. Benthic net primary production rates were 15.4 ± 0.7 mmolC/m²/d in early spring and 33.8 ± 8.8 mmolC/m²/d in early autumn, total community respiration rates attained 35.3 ± 7.2 and 65.7 ± 16.9 mmolC/m²/d, and pelagic primary production rates 1.7 ± 0.7 and 4.0 ± 1.4 mmolC/m²/d, respectively. Total community metabolism was thus heterauophic and mainly driven by benthic metabolism. The benthic release rates af ammonia were 0.65 ± 0.32 mmolC/m²/day in early spring and 0.58± 0.42mmoVm ldaym early autumn, butwere near to negligible for orthophosphate. Pelagic primaryproduction was limited byphosphorous, in part, by the preferential release of étmmonia over orthophosphate from the sediment-water interface. The benthic primary production and nutrient release rates were within the range of other eury-to hypersaline carbonate-rich environments characterized by non- consolidated algat rats.Fluxos bênticos de oxigênio e nutrientes foram medidos numa seção da lagoa hipersalina e carbonática de Araruama, SE-Brasil Incubações in situ da superfície do sedimento (Zm = 1,5) foram realizadas em uma estação com câmaras claras/escuras nos meses de setembro de 1993 (início da primavera) e abril de 1995 (início do outono). Os sedimentos ricos em carbonatos eram recobertos por um tapete microalgal de 1-3 mm, dominados pelas cianobactérias Phormidium sp,Oscillatoria spLyngbya sp. As taxas de produção primária yquida foram 15,4 ± 0,7 mmolC/m²/d Id no iníCIO da primavera e 33,8 ± 8,8 mmolC/m Id no início do outono, as taxas de respiração total da comunidade alcançaram 35,3 ± 7,2 e 65,7 ± 16,9 mmolC/m²/d Id, e as taxas de produção primária pelágica 1,7 ± 0,7 e 4,0 ± 1,4 mmolC/m²/d, respectivamente. Desta forma, o metabolismo total da comunidade mostrou-se heterotrófico e guiado principalmente pela contornação bêntica. As taxas de liberação bêntica de amônia foram 0,65 ± 0,32 mmoVm ldia no início da primavera e 0,58 ± 0,42 mmolC/m²/dia no início do outono e insignificantes para fósforo. O fósforo representou o elemento limitante da produçao primária pelágica, em parte, pela liberação preferencial de amônia sobre ortofOsfato a partir da interface água-sedimento. A produção primária bêntica e as taxas de liberação de nutrientes se enquadraram dentro da faixa estabelecida para outros sistemas eury­e hipersalinos carbonáticos, caracterizados por tapetes algais não-consolidados

Land use effects on nutrient concentrations in a small watershed in northeast Brazil

Increases of N and P discharges from inland waters to coastal environments are the by-products of human activities such as agricultural practices. Therefore, the aim of this work is to evaluate the influence of land use change in nutrient concentrations in a small watershed in southern Bahia, Brazil. The study sites were characterized by secondary forest (P1), sand mining (P2), cocoa cultivation (P3), pasture (P4) and mangrove (P5). Dissolved forms of both nitrogen and phosphorus were higher than particulate forms in all sites. The DON concentration was higher than the DIN and the concentration of DON made up 60-73% of the total TDN. Seasonally, high variations between dry and rainy season were not observed in nutrient concentrations in Cururupe River Basin, with the exception of DON, which was higher in the rainy season. DIN, DON and PON export varies over the hydrological year indicating that fluxes were correlated with runoff. Even though the primary vegetation of The Cururupe River Basin was converted to different croplands, mainly cocoa production, the water quality presented low alterations in N and P export from upstream to downstream

Rheumatic heart disease in the modern era: recent developments and current challenges

Abstract Rheumatic heart disease (RHD) remains a major cause of preventable death and disability in children and young adults. Despite significant advances in medical technology and increased understanding of disease mechanisms, RHD continues to be a serious public health problem throughout the world, especially in low- and middle-income countries. Echocardiographic screening has played a key role in improving the accuracy of diagnosing RHD and has highlighted the disease burden. Most affected patients present with severe valve disease and limited access to life-saving cardiac surgery or percutaneous valve intervention, contributing to increased mortality and other complications. Although understanding of disease pathogenesis has advanced in recent years, key questions remain to be addressed. Preventing or providing early treatment for streptococcal infections is the most important step in reducing the burden of this disease

Efeito de incêndios florestais na estrutura e composição florística de uma área de cerrado sensu stricto na fazenda Água Limpa-DF<a name=tx></a> Effect of fire on the structure and floristic composition of a cerrado sensu stricto area in fazenda Água Limpa-DF

O objetivo desta pesquisa foi avaliar o efeito do fogo na estrutura e composição florística de uma área de 10 ha de cerrado sensu stricto, localizada na fazenda Água Limpa da Universidade de Brasília. Foram realizados dois inventários, sendo o primeiro em 1999, logo após a área ter sido totalmente queimada, devido a um incêndio criminoso, e o segundo em novembro de 2002. Quatro parcelas de 0,1 ha (20 x 50 m) foram tomadas, aleatoriamente, na área queimada. Todos os indivíduos lenhosos arbóreos vivos, com Db (diâmetro tomado a 0,30 m do solo) igual ou superior a 3 cm, foram identificados botanicamente, e seus diâmetros e alturas foram registrados. Valores de densidade, dominância, freqüência e índice de valor de cobertura foram obtidos para os dois levantamentos. A avaliação da similaridade florística entre os dois inventários foi realizada para dados qualitativos (presença e ausência de espécies), a partir do índice de Sfrensen. Os resultados mostraram que houve pouca mudança na composição florística da comunidade durante o período estudado. Entre os dois inventários houve um aumento de aproximadamente 125% na densidade por hectare. A similaridade entre os dois levantamentos foi alta (índice de Sfrensen igual a 0,68). A densidade florística, obtida a partir do índice de Shannon, foi baixa (cerca de 2,5) nas duas épocas monitoradas, quando comparada com pesquisas a longo prazo no cerrado sensu stricto da FAL (cerca de 3,5). Contudo, este valor é comum em áreas de cerrado que sofreram distúrbios. No segundo inventário, realizado três anos após o fogo, surgiram 13 espécies novas na área, o que comprova a sua recuperação e recolonização.<br>This research aimed to evaluate the effect of fire on the structure and floristic composition of a 10 ha cerrado sensu stricto area located at the Ecological and Experimental Reserve of the University of Brasilia, Fazenda Água Limpa-FAL. Two assessments were conducted in the area: the first, after the area had suffered a criminal fire in 1999, and the second in 2002. A sample of four 20 x 50 m permanent plots was assessed. All individuals with stems 5 cm diameter at 0,30 m (Db) from the ground level were registered, and had their Db and total height measured. Density, basal area, frequency and value of covering index were calculated for the two assessments. The floristic similarity between the two surveys was evaluated for qualitative data (presence and absence of species) based on the Sfrensen Index. Few changes were observed in the floristic composition of the community during the studied period. There was an increase of 125% in density by hectare from 1999 to 2002. A high similarity (Sfrensen Index equal to 0.68)was found between the two assessments while diversity (Shannon Index) was small (about 2.5). This value is smaller than those found in natural areas of the Cerrado sensu stricto at Fazenda Água Limpa, although it is common in areas with disturbances. Three years after fire 13 new species were verified in the area

Amazon River carbon dioxide outgassing fuelled by wetlands

River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle(1). A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial ecosystems(2). It is generally assumed that inland waters emit carbon that has been previously fixed upstream by land plant photosynthesis, then transferred to soils, and subsequently transported downstream in run-off. But at the scale of entire drainage basins, the lateral carbon fluxes carried by small rivers upstream do not account for all of the CO2 emitted from inundated areas downstream(3,4). Three-quarters of the world's flooded land consists of temporary wetlands(5), but the contribution of these productive ecosystems(6) to the inland water carbon budget has been largely overlooked. Here we show that wetlands pump large amounts of atmospheric CO2 into river waters in the floodplains of the central Amazon. Flooded forests and floating vegetation export large amounts of carbon to river waters and the dissolved CO2 can be transported dozens to hundreds of kilometres downstream before being emitted. We estimate that Amazonian wetlands export half of their gross primary production to river waters as dissolved CO2 and organic carbon, compared with only a few per cent of gross primary production exported in upland (not flooded) ecosystems(1,7). Moreover, we suggest that wetland carbon export is potentially large enough to account for at least the 0.21 petagrams of carbon emitted per year as CO2 from the central Amazon River and its floodplains(8). Global carbon budgets should explicitly address temporary or vegetated flooded areas, because these ecosystems combine high aerial primary production with large, fast carbon export, potentially supporting a substantial fraction of CO2 evasion from inland waters