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Gestoso I.,University of Vigo | Gestoso I.,Marine and Environmental science Center | Arenas F.,CIIMAR - Interdisciplinary Center of Marine and Environmental | Olabarria C.,University of Vigo
Journal of Experimental Marine Biology and Ecology

Predicted climate change scenarios for the end of this century suggest a substantial warming and ocean acidification of sea surface waters. Physiological performance of marine coastal organisms will be affected leading to changes in whole communities. In particular, ocean acidification poses an important threat for shelled molluscs. Nevertheless, climate change impacts are species-specific and responses may even differ among species that play a similar role in the ecosystems. Currently, two mussel species, the native Mytilus galloprovincialis Lamarck 1819 and the non-indigenous Xenostrobus securis Lamarck 1819, share the same habitat along shores in the inner part of the Galician Rias Baixas (NW Spain) forming mixed patchy clumps. Here, we used an experimental approach in mesocosms to evaluate the effects of increasing temperature and acidification on mussel clumps of different composition (monospecific and mixed clumps). Our model systems were artificially constructed clumps resembling those found on rocky shores. Responses to environmental stressors were measured on several functioning variables at the individual (i.e. survivorship, growth, condition index and composition of shell) and clump level (i.e. respiration, ammonia and phosphate excretion rates). The decrease of pH had a lethal effect and reduced growth on the native mussels. The invader was more resilient although individual responses were very often shaped by the composition of the clump. The reduced pH and, especially the high temperature conditions, tended to cause an increase in respiration rates of all types of clumps. Interactions between the two species seemed to modulate many effects at both individual and clump levels highlighting the complexity of responses when considering multiple stressors. © 2015 Elsevier B.V. Source

Lopes F.C.,University of Coimbra | Pereira A.J.,University of Coimbra | Mantas V.M.,Marine and Environmental science Center | Mpengo H.K.,Sonangol SP
Journal of African Earth Sciences

Recognition of the main morphostructural features of the western edge of the Huila Plateau (SW Angola) can be done by using remote sensing techniques associated with field work. A digital elevation model (DEM) of the area was built for this purpose. This model is based on altimeter data acquired from the Aster sensor, on which image processing techniques such as enhancement techniques, contrast change and filtering were applied. Other techniques, such as RGB colour composition, were also tested. The processed satellite images were interpreted by visual process and the results were then compared with available geological maps (scale 1: 1 000 000). To facilitate both analysis and interpretation, the edge of the plateau was divided into three sectors: northern (or Chongoroi Edge), central (or Humpata Edge) and southern (or Oncocua Edge). For each sector, the main morphological aspects and main lineament systems were identified and characterized. In the specific case of the central sector, these parameters were also confirmed by field work. This study shows that the morphology of the western edge of the plateau is dominated by N50°W-N60°W, N60°E and N-S trending main tectonic systems. These results have important implications in terms of geological mapping and regional tectonics as well as in land-use planning and other areas, such as hydrogeology or geotechnics. © 2016 Elsevier Ltd. Source

Crespo D.,University of Coimbra | Leston S.,University of Coimbra | Leston S.,Marine and Environmental science Center | Martinho F.,University of Coimbra | And 3 more authors.

The invasive bivalve Corbicula fluminea is described as a freshwater species but can colonize estuarine upper reaches. In a 46-day field experiment, the survival ability of the species along an estuarine gradient was tested. Our goal was to understand its tolerance limits in a transitional area and in which conditions a potential invasion in the estuary could thrive, in order to predict the potential threat of the species distribution and settlement along the freshwater–estuarine continuum. The Lethal Time (LT) method was adapted to this field test with success. The population held an adult stock in the most upstream areas of the estuary (salinity <0.5). Dispersal mechanisms allowed the species to be present in the downstream areas, however, with a different population structure as consequence of the interaction of the diverse physico-chemical gradients of the estuary, in particular different salinity and temperature combinations. During winter, the species was able to survive in all test sites, with practically no mortality, while in summer LT50 (median lethal time) changed considerably when comparing the upstream and the most downstream sites [82 days (predicted value) vs. 9 days, respectively]. Still, 100% mortality was never achieved, adding concern to the species invasion potential in this estuary. © 2016 Springer International Publishing Switzerland Source

Chen A.S.,University of Exeter | Leandro J.,Ruhr University Bochum | Leandro J.,Marine and Environmental science Center | Djordjevic S.,University of Exeter
Urban Water Journal

In urban areas, overloaded sewers may result in surcharge that causes surface flooding. The overflow from sewer systems mainly starts at the inlets until the pressure head in the manhole is high enough to lift up its cover, at which stage the surcharged flow may be discharged via the gap between the bottom of the manhole cover and the ground surface. In this paper, we propose a new approach to simulate such a dynamic between the sewer and the surface flow in coupled surface and sewer flow modelling. Two case studies are employed to demonstrate the differences between the new linking model and the traditional model that simplifies the process. The results show that the new approach is capable of describing the physical phenomena when manhole covers restrict the drainage flow from the surface to the sewer network and reduce the surcharge flow and vice versa. © 2015 Taylor & Francis Source

Domingues R.B.,University of Algarve | Domingues R.B.,Marine and Environmental science Center | Guerra C.C.,University of Algarve | Barbosa A.B.,University of Algarve | Galvao H.M.,University of Algarve
Aquatic Ecology

The Ria Formosa coastal lagoon is one of the most important and vulnerable ecosystems in Portugal, and it is subjected to strong anthropogenic pressures and natural nutrient inputs associated with coastal upwelling. The aim of this study was to evaluate the occurrence of nutrient and light limitation of phytoplankton growth during the productive period, and assess potential impacts of limitation on ecosystem eutrophication. Inorganic nutrients were added to natural microcosms filled with water collected at the landward and seaward boundaries, in summer 2012. Experimental treatments were incubated in situ under two different light intensities during 24 h. Phytoplankton composition, abundance and biomass, net growth rates and nutrient consumption were evaluated. At the landward location, potential nutrient limitation by nitrogen was observed. Nitrogen addition led to a significant increase in N consumption, resulting in higher phytoplankton growth, mainly diatoms, in all N-enriched treatments, under both light intensities. Significant consumption of silica and phosphorus was not reflected on growth, and it was probably due to luxury consumption. At the seaward station, phytoplankton, mainly cyanobacteria and eukaryotic picophytoplankton, were primarily limited by light, due to a deeper mixed layer. Nutrients were not limiting the phytoplankton growth due to import of nutrients from upwelled waters to the adjacent coastal zone. © 2015, Springer Science+Business Media Dordrecht. Source

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