Características biogeoquímicas da interação atmosfera - criosfera na Antártica ocidental / Biogeochemical characteristics of the interaction atmosphere - cryosphere in the occidental Antarctic

Atualmente a comunidade científica discute as diferenças de padrões climáticos entre o leste e o oeste antártico. Enquanto de forma geral observa-se instabilidade no setor oeste, o clima da antártica oriental demonstra relativa estabilidade climática. Abordando este contexto, neste estudo analisamos dois testemunhos de gelo recente de duas regiões com características climáticas diferentes do continente Antártico. No Platô Detroit situado na Península Antártica (64o10'S/060o0'O), analisamos a variabilidde de Black Carbon (BC) ao longo de 20 metros de neve. O BC encontrado na Península Antártica apresentou baixas concentrações comparáveis as encontradas no gelo do Artico período pré-industrial. Nossos resultados sugerem que sua variabilidade corresponde à sazonalidade dos períodos de queimada nos continentes do Hemisfério Sul. No interior do continente Antártico, analisamos o particulado em geral por um processo de microanálise ao longo de um testemunho de 40 metros extraído em Mont Johns (79o55'S/094o23'O). Encontramos uma tendência negativa na deposição de poeira mineral (AISi) entre 1967 e 2007. Nossos resultados sugerem que esta tendência seja resultado de um crescente isolamento dos ventos ao redor da Antártica. Este aumento na intensidade dos ventos reflete por sua vez o resfriamento da alta atmosfera no centro antártico causado pela depleção da camada de ozônio na região. Adicionalmente, amostras de diferentes microambientes de Patriot Hills (80o18'S/081o21'O) foram coletadas de maneira asséptica para análise microbiológica. As amostras foram cultivadas em meio R2 e paralelamente o DNA total extraído foi sequenciado pela técnica de pirosequenciamento. Os resultados preliminares desta análise mostram grande riqueza de espécies dos mais variados grupos. Os resultados deste trabalho caracterizam três diferentes parâmetros relacionados a deposição atmosférica em duas áreas do continente antártico pouco exploradas e de grande interesse científico...

The antarctic ice cap stores paleoclimatological information within layers of snow and ice. Antarctic ice has revealed the higher resolution paleoclimactic database for the last 800 kyr. Atmospheric transport plays a fundamental role on the composition and sources of particulate matter found in the Antarctic ice. It has been related to several climatic processes that changes the quantity and quality of exogenous aerosols reaching Antarctica. Therefore, studies of the particulate matter deposits along the snow/ice layers may suggest changes on atmospheric transport patterns. This work, analyze two recent ice cores from two climatic distinct regions of the Antarctic continent. One retrieved from Detroit Plateau/Antarctic Peninsula (64o10'S/060o0'W), in which we have analyze Black Carbon (BC) deposition and variability along 20 meters of snow. BC found in the Antarctic Peninsula showed low concentrations (varing between 0,014 and 3,733ppb), comparable to the concentrations found on Arctic ice dated from before the industrial revolution period. Our results suggest that peaks of BC detected correspond, mostly, to biomass burning seasons in the South Hemosphere, not speficically from South America. The second one, of 40 m, was retrieved from Central-West Antarctica, Mont Johns (79o55'S/094o23'W), in which we analyzed the mineral dust abundance thought M.E.V. - E.D.X. technique. In this study we found negative trends in mineral dust (inferred from Fe, Ti and AISi) deposition between 1967 and 2007, in contrast to similar works in Sub-antarctic regions. We demonstrate that this trend is a consequence of the persistent "atmospheric isolation" that encloses the Central and East Antarctic regions due to the increasing winds around Antarctica within this period. It has been documented that westerlies intensification reflect the upper atmosphere cooling above Central Antarctica caused by the stratospherical ozone layer depletion. As part of the polar site...

Ecological aspects of the antimicrobial resistance in bacteria of importance to human infections

In view of the intimate relationship of humans with coastal lagoons (used for recreation, tourism, water supply, etc.), the discharge of domestic effluents may lead to the establishment of routes of dissemination of pathogenic microorganisms, including microorganisms carrying genes for resistance to antimicrobials, through the surrounding human communities. The objective of the present investigation was to relate the presence of antimicrobial-resistant bacteria to the environmental characteristics of three coastal lagoons, comparing the results with those from hospital sewage. Of the lagoons evaluated, two (Geriba and Imboassica) receive domestic sewage discharge, and the other (Cabiunas) is still in a natural state. We isolated in a culture medium containing 32 1/4ìg/ml of Cephalothin, fecal coliforms (E. coli), non-fecal coliforms (Klebsiella, Enterobacter, Serratia, and Citrobacter), non-glucose-fermenting Gram-negative bacilli, and Aeromonas sp. In cultures from the hospital drain we found strains showing numerous markers for resistance to most of the 11 antimicrobials tested. On the other hand, in cultures from Cabiunas and Imboassica lagoons, we found strains showing resistance only to antibiotics frequently observed in non-selective situations (considered as "common" markers). The capacity for dilution in the ecosystem, and salinity appeared related with the occurrence of multi-resistant bacterial strains. The intensity of recent fecal contamination was not shown to be associated with the numbers and types of markers found.