Harmful algal blooms (HABs), dissolved organic matter (DOM), and planktonic microbial community dynamics at a near-shore and a harbour station influenced by upwelling (SW Iberian Peninsula)     

Sofia Loureiro  Albert Reñé  Esther Garcés  Jordi Camp  Dolors Vaqué 《Journal of Sea Research》2011,65(4):401-413

The surface microalgal community, including harmful species, dissolved organic matter (DOM), and bacterial and viral populations were studied during an annual cycle (November 2007–October 2008) in a Near-shore (NS) and a Harbour (H) station located in an upwelling area (Sagres, SW Iberian Peninsula). The higher water residence time, water stability and shallowness of harbours in comparison with open waters likely contributed to the differences found between stations regarding chemical variables, statistical correlations and harmful algal proliferations. Also, several differences were noticed from a previous assessment (Loureiro et al., 2005) including higher SST, lower nitrate and chlorophyll a concentrations, along with a shift in the microplankton community structure from diatom to nanoflagellate predominance. These variations feasibly reflect the response of this dynamic system to regional environmental modifications contributing to the understanding of common patterns in environmental change trends. The division of the sampling period into (1) non-upwelling (Non-Uw), (2) “spin-up” of upwelling (SU-Uw), and (3) “spin-down” and relaxation-downwelling (SD-Rel) stages allowed the identification of natural groupings of microplankton samples by Multi Dimensional Scaling (MDS) analysis. Dissolved organic nitrogen (DON) and viruses were the most significant abiotic and biotic variables, respectively, contributing to the dissimilarities between these stages (SIMPER analysis) and, therefore, potentially affecting the microplankton community structure. Harmful algal species and a stable viral community appeared to be favoured by SD-Rel conditions. Data seem to indicate that both Gymnodinium catenatum and Heterosigma akashiwo, the most abundant potentially harmful species, have been imported into the sampling area. Also, the H location, together with potential retention sites developing around the Cabo de São Vicente upwelling centre, may contribute to the local accumulation of harmful species. The associations found between harmful algal species and bacterioplankton and virioplankton call for detailed studies in order to evaluate species-specific interactions.  相似文献   

Three-dimensional convection simulations of the outer layers of the Sun using realistic physics     

F. J. Robinson  P. Demarque  L. H. Li  S. Sofia  Y.-C. Kim  K. L. Chan  D. B. Guenther 《Monthly notices of the Royal Astronomical Society》2003,340(3):923-936

  相似文献   

What determines the institutional performance of environmental regimes?: A case study of the Mediterranean Action Plan     

Sofia Frantzi   《Marine Policy》2008,32(4):618-629

Although there is fierce debate about how best to evaluate the effectiveness of international regimes, most writers regard institutional effectiveness as the best measure. This article examines the institutional effectiveness of one regime—the Barcelona Convention (or the Mediterranean Action Plan)—where there are sharply contrasting views of its institutional effectiveness. The study finds that the regime was indeed successful when created, but its contemporary institutional performance is inadequate. The article demonstrates that there is no simple answer as to whether a regime is effective; instead, in most cases it depends on the specific criteria each approach employs.  相似文献   

Tree-ring growth variability in the Austrian Alps: the influence of site, altitude, tree species and climate     

Sofia Leal  Thomas M. Melvin  Michael Grabner  Rupert Wimmer  Keith R. Briffa 《Boreas: An International Journal of Quaternary Research》2007,36(4):426-440

We present an extensive new network of ring-width chronologies, comprising data from 100 sites within the Austrian Eastern Alps, made up of multiple tree species. Principal components analysis and cluster analysis were used to identify five separate high-frequency tree-growth signals from these data. Tree-growth variability at these sites is explained by site altitude and species differences that moderate the effects of the annually varying climatic forcing on tree growth. Recently developed, two-century long gridded climate data sets for the Greater Alpine Region were used to assess the relationship between climate and tree growth. Tree growth at low altitudes is controlled mainly by spring-summer moisture availability. At high altitudes precipitation is no longer a limiting factor and growth is mostly determined by summer temperature. In the intermediate altitudinal range, we did not find any direct relationships with specific climatic variables. High-altitude chronologies suitable for reconstructing past temperatures and low-altitude chronologies suitable for reconstructing past precipitation were identified.  相似文献   

Flow of Canadian basin deep water in the Western Eurasian Basin of the Arctic Ocean     

Göran Björk  Leif G. Anderson  Martin Jakobsson  Dennis Antony  Björn Eriksson  Patrick B. Eriksson  Benjamin Hell  Sofia Hjalmarsson  Timothy Janzen  Sara Jutterström  Johanna Linders  Ludvig Löwemark  Christian Marcussen  K. Anders Olsson  Bert Rudels  Emma Sellén  Morten Sølvsten 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(4):577-586

The LOMROG 2007 expedition targeted the previously unexplored southern part of the Lomonosov Ridge north of Greenland together with a section from the Morris Jesup Rise to Gakkel Ridge. The oceanographic data show that Canadian Basin Deep Water (CBDW) passes the Lomonosov Ridge in the area of the Intra Basin close to the North Pole and then continues along the ridge towards Greenland and further along its northernmost continental slope. The CBDW is clearly evident as a salinity maximum and oxygen minimum at a depth of about 2000 m. The cross-slope sections at the Amundsen Basin side of the Lomonosov Ridge and further south at the Morris Jesup Rise show a sharp frontal structure higher up in the water column between Makarov Basin water and Amundsen Basin water. The frontal structure continues upward into the Atlantic Water up to a depth of about 300 m. The observed water mass division at levels well above the ridge crest indicates a strong topographic steering of the flow and that different water masses tend to pass the ridge guided by ridge-crossing isobaths at local topographic heights and depressions. A rough scaling analysis shows that the extremely steep and sharply turning bathymetry of the Morris Jesup Rise may force the boundary current to separate and generate deep eddies.  相似文献   

Reconstruction of food conditions for Northeast Atlantic bivalve species based on Dynamic Energy Budgets     

Vnia Freitas  Joana F.M.F. Cardoso  Sílvia Santos  Joana Campos  Jan Drent  Sofia Saraiva  Johannes IJ. Witte  Sebastiaan A.L.M. Kooijman  Henk W. Van der Veer 《Journal of Sea Research》2009,62(2-3):75

Required assimilated energy to support observed growth was reconstructed for four common bivalve species (Mya arenaria, Cerastoderma edule, Mytilus edulis and Macoma balthica) from various Northeast Atlantic coastal areas, along the species distributional range. The approach applied was based on the Dynamic Energy Budget (DEB) theory whereby observed growth patterns in the field, in combination with prevailing temperatures, were used to reconstruct the average food intake experienced in the field scaled to the maximum possible. For all species, results suggest food limitation over the range of locations. In general, reconstructed food intake indicated better conditions for C. edule compared to the other species, while M. edulis presented the lowest food conditions in all the areas. Despite the indications for a latitudinal trend in primary production, no clear pattern or relationship between reconstructed food conditions and latitude was observed suggesting that any trend may be overruled by local conditions.  相似文献   

Valuing the recovery of overexploited fish stocks in the context of existence and option values     

Elena Ojea  Maria L. Loureiro 《Marine Policy》2010

The current reduction in commercial fish stocks is a problem of global concern. In response to this situation, administrations around the world are attempting to recover critical stocks by implementing new regulations based on catching restrictions and recovery plans. These restrictions have negative effects on local economies, but species recovery also brings important benefits to society in the long term. Given that the recovery of endangered species also results in considerable non-use economic value, this paper employs contingent valuation techniques to measure individual preferences for different recovery levels. We distinguish primarily between existence and option values linked to various levels of the desired stocks and discuss how these values influence willingness to pay (WTP) estimates. Our results show that recovered stocks for hake and Norwegian lobster increase local welfare, and show that the median household WTP is about 17.73€ for a recovery programme regulated by the European Union.  相似文献   

Late Holocene climate change in central Sweden inferred from lacustrine stable isotope data     

Sofia Andersson  Gunhild Rosqvist  Melanie j. leng  Stefan Wastegård  Maarten Blaauw 《第四纪科学杂志》2010,25(8):1305-1316

  相似文献   

Exploring the 7:4 mean motion resonance—II: Scattering evolutionary paths and resonance sticking     

Patryk Sofia Lykawka  Tadashi Mukai 《Planetary and Space Science》2006,54(1):87-100

In our preliminary study, we have investigated basic properties and dynamical evolution of classical TNOs around the 7:4 mean motion resonance with Neptune (a∼43.7 AU), motivated by observational evidences that apparently present irregular features near this resonance (see [Lykawka and Mukai, 2005a. Exploring the 7:4 mean motion resonance—I. Dynamical evolution of classical trans-Neptunian objects (TNOs). Space Planet. Sci. 53, 1175-1187]; hereafter “Paper I”). In this paper, we aim to explore the dynamical long-term evolution in the scattered disk (but not its early formation) based on the computer simulations performed in Paper I together with extra computations. Specifically, we integrated the orbital motion of test particles (totalizing a bit more than 10,000) placed around the 7:4 mean motion resonance under the effect of the four giant planets for the age of the Solar System. In order to investigate chaotic diffusion, we also conducted a special simulation with on-line computation of proper elements following tracks in phase space over 4-5 Gyr. We found that: (1) A few percent (1-2%) of the test particles survived in the scattered disk with direct influence of other Neptunian mean motion resonances, indicating that resonance sticking is an extremely common phenomenon and that it helps to enhance scattered objects longevity. (2) In the same region, the so-called extended scattered TNOs are able to form via very long resonance trapping under certain conditions. Namely, if the body spends more than about 80% of its dynamical lifetime trapped in mean motion resonance(s) and there is the action of a k+1 or (k+2)/2 mean motion resonance (e.g., external mean motion resonances with Neptune described as (j+k)/j with j=1 and 2, respectively). According to this hypothetical mechanism, 5-15% of current scattered TNOs would possess thus probably constituting a significant part of the extended scattered disk. (3) Moreover, considering hot orbital initial conditions, it is likely that the trans-Neptunian belt (or Edgeworth-Kuiper belt) has been providing members to the scattered disk, so that scattered TNOs observed today would consist of primordial scattered bodies mixed with TNOs that came from unstable regions of the trans-Neptunian belt in the past.Considering the three points together, our results demonstrated that the scattered disk has been evolving continuously since early times until present.  相似文献   

Water-Tank Studies of Separating Flow Over Rough Hills   总被引：1，自引：1，他引：0  

J. B. R. Loureiro  A. S. Monteiro  F. T. Pinho  A. P. Silva Freire 《Boundary-Layer Meteorology》2008,129(2):289-308

The present work investigates the lower boundary condition for flows over a steep, rough hill. Simple asymptotic arguments together with the mixing-length hypothesis are used to derive a local analytical solution that is tested against three different flow conditions. In all, 36 velocity profiles are compared with the proposed expression. The experiments were carried out in a water channel and velocity measurements were made through laser Doppler anemometry. The extent of separated flow was made to vary as a function of the roughness and the Reynolds number. The analysis includes regions of attached as well as separated flow. In particular, the solution of Stratford is studied at the points of separation and re-attachment and found to apply equally well in rough walls.  相似文献