Total and opportunistic algal cover in relation to environmental variables     

Krause-Jensen D  Carstensen J  Dahl K 《Marine pollution bulletin》2007,55(1-6):114-125

Based on a large data set from the national Danish monitoring program, spatial and temporal variability in total algal cover and in the fraction of opportunistic macroalgae was analysed in relation to environmental variables. Variations in water clarity and salinity combined with information on geographical location of sampling areas were found to explain almost 80% of the large-scale variation in algal cover between areas. As water clarity was largely regulated by concentrations of total-nitrogen (TN), and TN-concentrations by TN-input from land, total algal cover at given water depths was partly related to TN-input from land. The fraction of opportunistic algae responded predominantly to differences in salinity, the highest fractions being found in the most brackish areas. Temporal variability in algal cover and fraction of opportunists over the 14-year investigation period was much smaller than the variability between areas and could not be predicted from variations in environmental variables. In order for macroalgal cover to become a more sensitive indicator of water quality it would be necessary to either increase the sensitivity of the method or identify and include supplementary regulating factors in the model.  相似文献   

Development of crystallographic preferred orientations by nucleation and growth of new grains in experimentally deformed quartz single crystals   总被引：1，自引：1，他引：0  

Martine G.C. Vernooij  Bas den Brok  Karsten Kunze 《Tectonophysics》2006,427(1-4):35

Deformation experiments have been carried out to investigate the effect of dynamic recrystallisation on crystallographic preferred orientation (CPO) development. Cylindrical samples of natural single crystals of quartz were axially deformed together with 1 vol.% of added water and 20 mg of Mn₂O₃ powder in a Griggs solid medium deformation apparatus in different crystallographic orientations with compression direction: (i) parallel to <c>, (ii) at 45° to <c> and 45° to <a> and (iii) parallel to <a>. The experiments were performed at a temperature of 800 °C, a confining pressure of 1.2 GPa, a strain rate of  10^− 6 s^− 1, to bulk finite strains of  14–36%. The deformed samples were analysed in detail using optical microscopy, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Two different microstructural domains were distinguished in the deformed samples: (i) domains with undulatory extinction and deformation lamellae, and (ii) domains with new recrystallised grains. Within the domains of undulatory extinction, crystal-plastic deformation caused gradual rotations of the crystal lattice up to  30° away from the host orientation. New recrystallised grains show a strong CPO with c-axis maxima at  45° to the compression direction. This is the case in all experiments, irrespective of the initial crystallographic orientation. The results show that c-axes are not continuously rotated towards the new maxima. The new grains thus developed through a mechanism different from subgrain rotation recrystallisation. New grains have a subeuhedral shape and numerous microcavities, voids, fluid channels and fluid inclusions at their grain boundaries. No host control is recorded in misorientation axes across their large angle grain boundaries. New grains might have been created by nucleation from solution in the μm-scale voids and microfractures. The CPO most likely developed due to preferred growth of the freshly precipitated grains with orientations suitable for intracrystalline deformation at the imposed experimental conditions.  相似文献   

Characterisation of contemporary local climate change in the mountains of southwest Bulgaria     

Karsten Grunewald  Jörg Scheithauer  Jean-Marie Monget  Derek Brown 《Climatic change》2009,95(3-4):535-549

The Pirin Mountains in southwest Bulgaria spatially mark a transition between the Mediterranean and temperate climate zones. Therefore they are also particularly relevant for research on high mountain climate and the effect of landscape transformation. Historical climate records gathered in the area have been researched, checked and statistically examined. The mountainous climate has been characterised and trends in the evolution of temperature and precipitation since 1931 have been outlined. There are objective evidences for an increasing annual mean temperature, longer vegetative periods and local droughts in spring and autumn. Significant changes also appear in climatic threshold values such as the number of frost change days. This last parameter is very important for the sustainability of mountainous ecosystems.  相似文献   

Salinity dependence of parasite infestation in the European eel Anguilla anguilla in northern Germany     

Jakob  Eva; Hanel  Reinhold; Klimpel  Sven; Zumholz  Karsten 《ICES Journal of Marine Science》2009,66(2):358-366

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Local effects of blue mussels around turbine foundations in an ecosystem model of Nysted off-shore wind farm, Denmark     

Marie Maar  Karsten Bolding  Jens Kjerulf Petersen  Jrgen L.S. Hansen  Karen Timmermann 《Journal of Sea Research》2009,62(2-3):159

The development of off-shore wind farms along the coastline of north-west Europe is rapidly increasing; it is therefore important to study how this will affect the marine environment. The present study modelled the growth and feed-backs of blue mussels in natural beds and on turbine foundations in an off-shore wind farm (OWF) located in a shallow coastal ecosystem by coupling a dynamic energy budget (DEB) model to a small-scale 3D hydrodynamic–biogeochemical model. The model results showed that blue mussels located higher up in the water column on turbine pillars achieved a 7–18 times higher biomass than those located on the scour protection because the former experience an enhanced advective food supply. Secondly, the high biomasses of blue mussels on foundations created local ‘hot spots’ of biological activity and changed ecosystem dynamics due to their feed-backs e.g. ingestion of microplankton and copepods, excretion of ammonium and egestion of faecal pellets. The model results were supported by field measurements around foundations of Chl a concentrations and biomasses of the fauna community. Our study emphasised that OWFs seem to be particularly favourable for blue mussels in the western Baltic Sea and that the functioning of the OWFs as artificial reef ecosystems depends upon how the blue mussels interact with their local pelagic and benthic environment.  相似文献   

Discussion of “How to improve attribution of changes in drought and flood impacts”*     

Karsten Arnbjerg-Nielsen 《水文科学杂志》2020,65(3):487-488

ABSTRACT

The opinion paper by Kreibich et al. provides interesting insights into the interplay between floods and droughts, which are often ignored. The structure of the paper is original and the findings of high interest. It may however be difficult to obtain the required data to pursue the research agenda in actual catchments. This discussion paper suggests various ways in which the linkages between floods and droughts can be explored even if recorded data of sufficient detail is not available.  相似文献   

Modeling Advective Contaminant Transport During Soil Vapor Extraction   总被引：3，自引：0，他引：3  

Ronald W. Falta  Karsten Pruess  Dwayne A. Chesnut 《Ground water》1993,31(6):1011-1020

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Safeguarding the future marine environment of Europe     

Brigitte Langenhagen Mep  Karsten Seidel 《Marine pollution bulletin》1994,29(6-12):644-646

The priorities for the protection of the seas have been discussed extensively. Many consider that the problem of marine pollution can only be solved on the basis of joint international actions. This is particularly true for the various countries bordering on the North Sea. To implement such ‘Joint Actions’, a new understanding of safety, namely ‘global maritime safety’ should be discussed with all those involved.  相似文献   

Die geodynamische Entwicklung der Thiersee- und der Karwendelmulde (Nördliche Kalkalpen)     

Nagel  Karl -Heinz  Schütz  Karsten -Ingo  Schütz  Sylvia  Wilmers  Wilhelm  Zeil  Werner 《International Journal of Earth Sciences》1976,65(1):536-557

Zusammenfassung Die Thiersee- und die Karwendelmulde in den Nördlichen Kalkalpen sind als zwei getrennte, E-W-verlaufende Synklinen entwickelt. Ihre Länge zwischen Kufstein und Mittenwald beträgt über 70 km.Systematische geologische Aufnahmen — Kartierung, Stratigraphie, Sedimentologie und Gefügekunde — ergaben, daß die Thierseemuide im Raum von Achenkirch nicht — wie früher vermutet wurde — in die Karwendelmulde umbiegt. Die Auswertung von mehr als 45 000 Gefügemessungen mit Hilfe eines EDV-Programms bewies vielmehr, daß Thierseemuide und Karwendelmulde zwei parallele, unabhängige Strukturen sind, die durch die komplizierte tektonische Zone von Achenkirch getrennt werden.Die paläogeographische Entwicklung und der Ablauf der Bewegungen werden im Überblick skizziert.

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Systematic geological survey showed that the Thiersee and Karwendel synclines in the Northern Calcareous Alps are two parallel structures, separated by a slightly folded intersection. The synclines do not turn into each other, as was presumed by earlier workers.The tectonic situation in the area of Achenkirch was cleared by evaluation of more than 45,000 field texture data by a computer program. Mapping as well as stratigraphical and sedimentological analysis supports the tectonic model. The paleogeographic development and tectonic history are briefly described.

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Résumé Les dépressions du «Thiersee» et du «Karwendel», dans les Alpes calcaires du Nord, sont deux synclinaux indépendants de direction Est-Ouest. Elles font 70 km de long entre Kufstein et Mittenwald.Des relevés géologiques systématiques — levés géologiques, stratigraphie, sédimentologie et structurologie — démontrèrent que, dans la région d'Achenkirch, la dépression du «Thiersee» ne contourne pas la dépression du «Karwendel» (comme on l'a longtemps supposé!). L'exploitation par ordinateur de plus de 45.000 mesures structurales révéla au contraire, que ces dépressions sont deux structures parallèles et indépendantes, séparées par la zone tectonique complexe d'Achenkirch.Le développement paléogéographique et le déroulement des mouvements font l'objet d'une vue d'ensemble.

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Direct Sensor Orientation for Large Scale Mapping—Potential, Problems, Solutions     

Nac  Yastikli  Karsten  Jacobsen 《The Photogrammetric Record》2005,20(111):274-284

Georeferencing is one of the most important tasks in photogrammetry. Traditionally it has been achieved indirectly using the well-known method of aerial triangulation. With the availability of integrated GPS and inertial measurement units (IMU), this situation changed. Direct determination of exterior orientation is now possible. Today, direct and integrated sensor orientation is used for a wide range of sensors including lidar and SAR, as well as for digital line scanner systems and aerial cameras. This paper investigates the performance of direct and integrated sensor orientation for large scale mapping using the data-set of the 'Integrated Sensor Orientation' test of the European Organisation for Experimental Photogrammetric Research (OEEPE—now known as EuroSDR). The concept, potential, problems and solutions of direct and integrated sensor orientation are discussed.  相似文献