Authors:D. Figueiredo, B. Castro, M. Pereira and A. Correia
In 2005, a severe drought occurred in Portugal, with several reservoirs becoming dry in the southern region. A set of 20 Portuguese water bodies were analysed through denaturing gradient gel electrophoresis (16SrDNA-DGGE) and DNA sequencing to assess its bacterioplankton diversity under these particular conditions. Environmental parameters were determined to assess the trophic conditions of each water body. Most water bodies fell into the meso-to eutrophic and hypereutrophic state. In general, the levels for conductivity, pH and total suspended solids were higher than the average data from previous years. Dominant phylotypes belonged to Cyanobacteria, Actinobacteria Alphaproteobacteria, Betaproteobacteria and Bacteroidetes groups. Despite the geographic distance, common phylotypes could be recorded among water bodies. Bacteroidetes dominated at Sousa River and were related to high nutrient levels. Cyanobacteria dominated at Alentejo reservoirs and correlated with higher conductivity values. However, Actinobacteria showed ubiquitous phylotypes throughout several samples, suggesting its persistence over geographically distant water bodies. This study showed a clear deterioration of water quality, from a physico-chemical point of view; furthermore, dominance of Cyanobacteria and Actinobacteria in reservoirs used for drinking water supply were also detected, which may become a concerning issue. However, the most severe bacterial community composition variations between summer 2005 and others were mainly related to higher water residence times. Thus, along with the expected intensification of drought episodes, with severe effects particularly in Southern Europe, it is clearly predictable an intensification in risks for water quality maintenance and even Public Health.
Authors:C. Mothé, D. Correia, F. de França and A. Riga
Enhanced oil recovery
process is based on the injection of chemical products (e.g. polymers, surfactants,
gases) or thermal energy (originating from the injection of e.g. steam, hot
water, in situ combustion) to recover crude oil. One of these processes use
polymer solution to mobilize the oil in the reservoir. In this work the thermal
decomposition kinetic of xanthan gum, guar gum and a blend (50/50 mass/mass%)
was studied according to Ozawa–Flynn–Wall method. According to
the kinetic analysis, the studied systems were copmpatible. The rheological
behavior of the samples was studied in distilled water and seawater at different
temperatures. Only the blend was studied in distilled water presented synergism
(enhancement in material properties like stability and viscosity) which was
confirmed through rheology.
Authors:R. A. Correia, A. M. A. Franco and J. M. Palmeirim
The Mediterranean Sea has separated the sclerophyllous forests of southern Europe and northern Africa for millions of years, but its role structuring forest bird assemblages remains unclear. To address this issue we sampled bird assemblages in cork oak woodlands located north and south of the Strait of Gibraltar and compared abundance, diversity, and species and guild assemblage structure between regions. Abundance and diversity patterns were remarkably similar, but dissimilarity analyses of species and guild composition revealed differences in bird assemblage structure between regions. Differences are partly attributable to the effect of the Mediterranean as barrier to the dispersal of forest birds; a few species were unable to colonize North Africa, and many that colonized it remained in sufficient isolation to evolve into distinct taxa. In addition to this divergence of biogeographic genesis, assemblages also differ because in North African cork oak woodlands forest and insectivorous specialist species are less abundant. This dissimilarity could be due to the effect of different exploitation levels present in each region. Managed cork oak woodlands are widespread in the Western Mediterranean, and are valuable because they conciliate economic exploitation with high biodiversity. In North Africa these woodlands are of greater conservation concern because they harbour endemic bird species that give its assemblage a distinct character, cover a smaller area, and are currently under greater pressure from overexploitation. These results highlight the importance to implement management practices that increase resilience and maintain biodiversity value throughout the range of cork oak woodlands.