Differential herbivory of invasive algae by native fish in the Mediterranean Sea     

F. Tomas  E. Cebrian  E. Ballesteros 《Estuarine, Coastal and Shelf Science》2011

The potential role of generalist herbivores to serve as a source of biotic resistance against algal invasion in marine ecosystems has been poorly examined. The present study investigates the capacity of Mediterranean herbivorous fishes to consume three of the most invasive seaweeds of the Western Mediterranean (Caulerpa racemosa, Lophocladia lallemandii and Womersleyella setacea) and examines vertical and temporal variations of such consumption. Our results show that although fish feed throughout the depth gradient examined (5–35 m), they concentrate in shallow waters, and can consume high amounts of C. racemosa. Such high ingestion of C. racemosa does not appear to be random, since this alga is consistently chosen when offered in pairs with several native species. Conversely, L. lallemandii and W. setacea are barely eaten by fish even though they can be very abundant in the field throughout the year. Our results suggest that fish could be an important controlling agent that has been overlooked in temperate marine invasions, and they may be able to provide certain resistance to C. racemosa invasion. In contrast, they are unlikely to exert any important control effects on L. lallemandii or W. setacea.  相似文献   

An Efficient System for Creating Synthetic InSAR Images from Simulations     

Xiaoru Yuan  Yingchun Liu  David A. Yuen  Baoquan Chen  Tomas Pergler  Yaolin Shi 《Pure and Applied Geophysics》2008,165(3-4):671-691

In this work we visualize tsunami and earthquake simulation results with graphics hardware acceleration. The rapid improvement in the computational power of graphics hardware and its programmability has made general computation on Graphics Processing Units (GPUs) very compelling. We generate Synthetic InSAR images using GPUs. Interference phenomena have formed the underlying theory for Interferometric Synthetic Aperture Radar (InSAR) in unveiling dynamical Earth movements. In our approach light path differences are defined by the surface values to be visualized. These path differences then modulate the lighting intensity to generate the interference patterns. We can interactively visualize surface deformation patterns by leveraging the computational power of GPUs. Our visualization method is applied to simulations of rupture fault displacements during the tsunamogenic earthquake events, which are vital to understanding the subsequent wave propagation. We also integrate the visualization results into Google Earth virtual globe to provide the geological context of the visualized regions.  相似文献   

Orthogonal Variance Structures in Lake Water Quality Data and Their Use for Geo-chemical Classification of Dimictic, Glacial/Boreal Lakes     

Tomas K. E. Thierfelder 《Aquatic Geochemistry》2000,6(1):47-64

The accumulating volumes of data collected within environmental monitoring programs facilitate the use of exploratory statistical methods of data analysis as a supplement to traditional methods of characterizing lake water quality. When principal component analysis and multidimensional scaling are applied to a matrix containing approximately 24000 samples of lake water quality variables pH, alkalinity, conductivity, hardness, color, Secchi depth and total phosphorus concentration, it is found that the total matrix variance can be approximately reproduced in an orthogonal two-dimensional base with transformations of hardness and color as best principal component representatives. This base is suggested as an empirical lake classification standard where the variance structure of subset lake populations (such as single lakes) can be referenced to the water quality standard of the generic population. Since the principal axes of the base exclusively contain inorganic and organic related variables respectively, the combined inorganic/organic characteristics of the lake can be expressed with the hardness and color variables alone. With the data matrix being large enough to produce high significance levels, and with variable ranges wide enough to represent a majority of dimictic, glacial/boreal lakes, the analysis results should be valid in many lakes throughout the world.  相似文献   

Improved Parameter Resolution with Markov Chain Monte Carlo Simulation of Different Aquifer Tests     

Tomas Perina 《Ground water》2020,58(6):993-999

Hydraulic testing for aquifer characterization at contaminated sites often includes tests of short duration and of different types, such as slug tests and pumping tests, conducted at different phases of investigation. Tests conducted on a well cluster installed in a single aquifer can be combined in aggregate inverse analysis using an analytical model for groundwater flow near a test well. A genetic algorithm performs parallel search of the parameter space and provides starting parameter values for a Markov chain Monte Carlo simulation to estimate the parameter distribution. This sequence of inverse methods avoids guessing of the initial parameter vector and the often encountered difficult convergence of gradient-based methods and estimates the parameter covariance matrix from a distribution rather than from a single point in the parameter space. Combination of different tests improves the resolution of the estimated aquifer properties and allows an assessment of the uniformity of the aquifer. Estimated parameter correlations and standard deviations are used as relative metrics to distinguish well resolved and poorly resolved parameters. The methodology is demonstrated on example field tests in unconfined and leaky aquifers.  相似文献   

Stable Stratification Effects on Flow and Pollutant Dispersion in Boundary Layers Entering a Generic Urban Environment   总被引：1，自引：1，他引：0  

J. M. Tomas  M. J. B. M. Pourquie  H. J. J. Jonker 《Boundary-Layer Meteorology》2016,159(2):221-239

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Spatial and temporal distribution of phytoplankton in a highly stratified estuary (Zrmanja, Adriatic Sea)     

Zrinka Buri&#;  Ivona Cetini&#;  Damir Vili&#;i&#;  Katarina Caput Mihali&#;  Marina Cari&#;  & Goran Oluji&#; 《Marine Ecology》2007,28(S1):169-177

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Comment on “A cost-effective device and methodology to compute aquifer transmissivity and piezometry from free-flowing artesian wells”: technical note published in Hydrogeology Journal (2022) 30:1917–1931, by Alix Toulier,Patrick Lachassagne,Heru Hendrayana,Arif Fadillah,and Hervé Jourde     

Perina  Tomas 《Hydrogeology Journal》2023,31(3):843-844

Hydrogeology Journal -  相似文献   

Discharge experiments simulating chemical evolution on the surface of Titan     

Kristof Plankensteiner  Bernd M. Rode  Tomas Mikoviny  Armin Hansel  Georg Fischer  Helmut O. Rucker 《Icarus》2007,187(2):616-619

Saturn's moon Titan has been considered as one of the few places in our Solar System, where atmospheric and surface conditions could have produced organic compounds essential as precursors for an evolution of life. The Cassini-Huygens mission has provided new data on Titan's atmosphere and surface, which enabled us to simulate the chemical processes occurring under these conditions. Possible lightning events on Titan cannot only produce higher hydrocarbons, but also allow surface water ice to participate in the reaction scenario, resulting in CHO, CHN, and CHON compounds including several molecules relevant for the formation of amino acids and nucleic acids.  相似文献   

Public-space planning in four Nordic cities: Symbolic values in tension     

Merle Jacob  Tomas Hellström 《Geoforum》2010,41(4):657-665

This article takes its point of departure in the assumption that values shape planning practices and that alternatively one can reconstruct such values from the way planning interventions are argued and evaluated. We contend that planners’ discourses involve implicit value commitments that are observable in their representations of public space and implicated in the results of public-space planning. The paper builds an empirical case from representations of public space elaborated in planning documents developed by planners in four medium-sized Nordic cities. We show how these planning representations form four thematic value clusters concerning urban public space, namely leisure-play, identity-unity, power-organization and unruliness-change. Together these clusters constitute a value framework which reveals a number of central tensions relating to the way that planners seek to balance order and spontaneity in public space. The paper concludes by outlining and discussing these values and the tensions they represent.  相似文献   

Atmospheric forcing of Fram Strait sea ice export: a closer look   总被引：2，自引：0，他引：2  

Maria Tsukernik  Clara Deser  Michael Alexander  Robert Tomas 《Climate Dynamics》2010,35(7-8):1349-1360

Fram Strait is the primary region of sea ice export from the Arctic and therefore plays an important role in regulating the amount of sea ice and freshwater within the Arctic. We investigate the variability of Fram Strait sea ice motion and the role of atmospheric circulation forcing using daily data during the period 1979–2006. The most prominent atmospheric driver of anomalous sea ice motion across Fram Strait is an east–west dipole pattern of Sea Level Pressure (SLP) anomalies with centers of action located over the Barents Sea and Greenland. This pattern, also observed in synoptic studies, is associated with anomalous meridional winds across Fram Strait and is thus physically consistent with forcing changes in sea ice motion. The association between the SLP dipole pattern and Fram Strait ice motion is maximized at 0-lag, persists year-round, and is strongest on time scales of 10–60 days. The SLP dipole pattern is the second empirical orthogonal function (EOF) of daily SLP anomalies in both winter and summer. When the analysis is repeated with monthly data, only the Barents center of the SLP dipole remains significantly correlated with Fram Strait sea ice motion. However, after removing the leading EOF of monthly SLP variability (e.g., the North Atlantic Oscillation), the full east–west dipole pattern is recovered. No significant SLP forcing of Fram Strait ice motion is found in summer using monthly data, even when the leading EOF is removed. Our results highlight the importance of high frequency atmospheric variability in forcing Fram Strait sea ice motion.  相似文献