Population dynamics of mayflies in a constant temperature spring stream in West Carpathians     

Kvetoslava Bottová  Tomáš Derka  Marek Svitok 《Limnologica》2013,43(6):469-474

We examined the life history and secondary production of four Ephemeroptera species (Baetis alpinus Pictet, 1843–1845, Baetis rhodani Pictet, 1843–1845, Rhithrogena carpatoalpina Klonowska, Olechowska, Sartoriet & Weichselbaumer, 1987 and Habroleptoides confusa Sartori & Jacob, 1986) in a temperature stable cold spring stream at Prosiek valley (Cho?ské vrchy Mts., West Carpathians, Slovakia). We have found asynchronous bivoltine life cycle for the most abundant species B. alpinus with growth rate positively correlated to photoperiod length. R. carpatoalpina have shown unusual asynchronous univoltine life cycle and B. rhodani have shown uncommonly low abundance in mayfly community. Total secondary production of mayfly community was very low, reaching 1654.8 mg DW m^?2 y^?1. We suggest that the observed asynchrony in growth could be related to the lack of temperature control.  相似文献   

Buried Late Weichselian thermokarst landscape discovered in the Czech Republic,central Europe     

Jan Ho&#x;ek  Jind&#x;ich Prach  Marek K&#x;íek  Petr &#x;ída  Piotr Moska  Petr Pokorný 《Boreas: An International Journal of Quaternary Research》2019,48(4):988-1005

Pronounced climatic warming associated with the Late Weichselian Pleniglacial‐to‐Lateglacial transition caused considerable environmental changes throughout the former periglacial zones (in Europe ~53°–46°N). During permafrost degradation and subsequent ground subsidence (i.e. thermokarst processes), the landscape changed rapidly. In this study we investigated a flat mid‐altitude area in south Bohemia, Czech Republic, lying close to the southern limit of the Weichselian permafrost. We discovered palaeo‐lake basins with sedimentary infillings up to 11 m in depth. According to radiocarbon and palynostratigraphical dating, these basins were formed at the onset of the Late Pleniglacial‐to‐Lateglacial transition, whereas the smaller depressions were formed later. We suggest that the basins resulted from thermal and fluvio‐thermal erosion of the former permafrost and represent remnants of discontinuous gullies and possibly collapsed frost mounds (pingo/lithalsa scars). The formation of this a fossil thermokarst landscape was climatically driven and multiple phased, with the major phase during the climatic warming and wetting at the onset of GI‐1e (Bølling) and the minor phase during GI‐1c (Allerød). This study enhances knowledge of the palaeogeography of the former European periglacial zone by showing that Late Pleistocene thermokarst activity could have had a significant impact on the evolution of the landscape of at least some regions of central Europe along the southern limit of the continuous permafrost zone. The research also points to a similar history for the physical transformation of the landscape of the former European periglacial zone and current thermokarst landscapes and could be a valuable source of information with respect to the future transformation of the Arctic under conditions of ongoing global warming.  相似文献   

The role of the Polochic Fault as part of the North American and Caribbean Plate boundary: Insights from the infill of the Lake Izabal Basin     

Jonathan Obrist-Farner  Andreas Eckert  Marek Locmelis  James L. Crowley  Byron Mota-Vidaure  Emanuele Lodolo  Joshua Rosenfeld  Edward Duarte 《Basin Research》2020,32(6):1347-1364

The Lake Izabal Basin in Guatemala is a major pull-apart basin along the sinistral Polochic Fault, which is part of the North American and Caribbean plate boundary. The basin infill contains information about the tectonic and sedimentological processes that have imparted a significant control on its sedimentary section. The inception of the basin has been linked to the relative importance of the Polochic Fault in the tectonic history of the plate boundary; yet, its sedimentological record and its inception age have been poorly documented. This study integrates diverse datasets, including industry reports, well logs and reports, well cuttings, vintage seismic data, outcrop observations and geochronological data to constrain the initial infill and age of inception of the basin. The integrated data show that during the Oligocene–Miocene, a marine carbonate platform was established in the region which was later uplifted and eroded in the early Miocene. The fluvial–lacustrine deposits above this carbonate platform are part of the initial infill of the basin and are constrained with zircon weighted-mean ²⁰⁶Pb/²³⁸U ages of 12.060 ± 0.008 from a volcanic tuff ~30 m above the unconformity. Sandstone, mudstone and coal dominate the interval from 12 to 4 Ma, with an increase in conglomerate correlating to the uplift of the Mico Mountains and San Gil Hill at 4 Ma. Fault switch activity between the Polochic and Motagua faults has been hypothesized to explain total offset along the Polochic Fault and the geologic and geodetic slip rates along the two faults. The 12 Ma age determined for the initial infill of the basin confirms this hypothesis. Consequently, our study confirms that at ~12 Ma the Polochic Fault served as the main fault of the plate boundary with inferred slip rates ranging from 13 to 21 mm/yr with a strong possibility that the Polochic Fault was, at some point between 15 Ma and 7 Ma, the only active fault of the plate boundary. The results of this study show that tectonic records preserved in sediments of strike-slip basins improve the understanding of the relative significance of individual faults and the implications with respect to strain partitioning throughout its tectonic history.  相似文献   

Book Review     

Marek Lewandowski 《Pure and Applied Geophysics》2010,167(11):1451-1452

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Fungal Selenium(VI) Accumulation and Biotransformation—Filamentous Fungi in Selenate Contaminated Aqueous Media Remediation          下载免费PDF全文

Martin Urík  Katarína Boriová  Marek Bujdoš  Peter Matúš 《洁净——土壤、空气、水》2016,44(6):610-614

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Elastic properties of seafloor sediments from the modelling of amplitudes of multiple water waves recorded on the seafloor off Bear Island,North Atlantic   总被引：1，自引：0，他引：1  

Marek Grad  Rolf Mjelde  Wojciech Czuba  Aleksander Guterch  the IPY Project Group 《Geophysical Prospecting》2012,60(5):855-869

Wide‐angle seismic data acquired by use of air‐guns and ocean bottom seismometers (OBS) contain strong direct water arrivals and multiples, generally considered as noise and thus not included in the modelling. However, a recent study showed that standard ray‐tracing modelling of the water multiples recorded off the Bear Island, North Atlantic, provided a reliable estimate of the velocity distribution in the water layer. Here, we demonstrate that including the amplitudes in the modelling provide valuable information about the V_P contrast at the seafloor, as well as the V_P/V_S ratio and attenuation (Q_P) of the uppermost sediments. The V_P contrast at the seafloor is estimated at about 250 m/s, within a precision of approximately ±30 m/s. The V_P/V_S ratio in the uppermost sedimentary layer is modelled in the range 2.25–2.50 and the Q_P factor is estimated at 1000 for the water, 30–50 for the uppermost layer and 40–50 for the second sedimentary layer. The values obtained for the sediments suggest a lithology dominated by silty clays, with porosity below average.  相似文献   

X-ray irradiation in XTE J1817−330 and the inner radius of the truncated disc in the hard state     

Marek Gierli&#;ski  Chris Done  Kim Page 《Monthly notices of the Royal Astronomical Society》2008,388(2):753-760

The key aspect of the very successful truncated disc model for the low/hard X-ray spectral state in black hole binaries is that the geometrically thin disc recedes from the last stable orbit at the transition to this state. This has recently been challenged by direct observations of the low/hard state disc from CCD data. We reanalyse the Swift and RXTE campaign covering the 2006 outburst of XTE J1817−330, and show that these data actually strongly support the truncated disc model as the transition spectra unambiguously show that the disc begins to recede as the source leaves the disc-dominated soft state. The disc radius inferred for the proper low/hard state is less clear-cut, but we show that the effect of irradiation from the energetically dominant hot plasma leads to an underestimate of the disc radius by a factor of 2–3 in this state. This may also produce the soft excess reported in some hard-state spectra. The inferred radius becomes still larger when the potential difference in stress at the inner boundary, increased colour temperature correction from incomplete thermalization of the irradiation, and loss of observable disc photons from Comptonization in the hot plasma is taken into account. We conclude that the inner disc radius in XTE J1817−330 in the low/hard spectral state is at least six to eight times that seen in the disc-dominated high/soft state, and that recession of the inner disc is the trigger for the soft-hard-state transition, as predicted by the truncated disc models.  相似文献   

Radio-loudness of active galaxies and the black hole evolution     

Marek Sikora  &#x;ukasz Stawarz  Jean-Pierre Lasota 《New Astronomy Reviews》2008,51(10-12):891

Active galactic nuclei (AGNs) form two distinct sequences on the radio-loudness–Eddington ratio plane. The ‘upper’ sequence contains radio selected AGNs, the ‘lower’ sequence is composed mainly of optically selected AGNs. The sequences mark the upper bounds for the radio-loudness of two distinct populations of AGNs, hosted, respectively, by elliptical and disk galaxies. Both sequences show the same dependence of the radio-loudness on the Eddington ratio (an increase with decreasing Eddington ratio), which suggests that another parameter in addition to the accretion rate must play a role in determining the efficiency of jet production in AGNs. We speculate that this additional parameter is the spin of the black hole, assuming that black holes in giant elliptical galaxies have (on average) much larger spins than black holes in disc galaxies. Possible evolutionary scenarios leading to such a spin dichotomy are discussed. The galaxy-morphology related radio dichotomy breaks down at high accretion rates where the dominant fraction of luminous quasars being hosted by giant ellipticals is radio-quiet. This indicates that the production of powerful jets at high accretion rates is in most cases suppressed and, in analogy to X-ray binary systems (XRB) during high and very high states, may be intermittent. Such intermittency can be caused by switches between two different accretion modes, assuming that only during one of them an outflow from the central engine is sufficiently collimated to form a relativistic jet.  相似文献   

Hoarfrost and rime chemistry in Poland—An introductory analysis from meteorological perspective     

Żaneta Polkowska  Mieczysław Sobik  Marek Błaś  Kamila Klimaszewska  Barbara Walna  Jacek Namieśnik 《Journal of Atmospheric Chemistry》2009,62(1):5-30

Hoarfrost and rime analysis was based on the collection of samples between 2003 and 2006 from 8 sites, which represent both lowland (northern) and mountainous (southern) parts of Poland. On the other hand 4 of these sites belong to “urban” and 4 to “rural” category. pH, conductivity, SO₄²⁻, NO₃⁻, Cl⁻, H⁺, NH₄⁺, Ca²⁺, Mg²⁺, Na⁺, K⁺ have been determined in order to study the chemistry of hoarfrost and rime. Higher total inorganic ionic content (TIC) in hoarfrost and rime (2.46 meq·l⁻¹ and 1.23 meq·l⁻¹ respectively) was observed when compared with precipitation (0.37 meq·l⁻¹). Large variability of TIC and chemical composition of individual samples were typical at each of the measurement sites depending on emission patterns, atmospheric conditions and local terrain topography. Higher concentrations of both hoarfrost and rime occurred in southern (mountainous) rather than in northern (lowland) part of Poland which can be explained by worse pollutant dispersion conditions in the south. The surprisingly low hoarfrost concentrations in urban coastal stations in the area of the Bay of Gdansk were attributed to the cleaning effect of nocturnal breeze-type circulation, best pronounced in cool part of the year. Due to relatively high pollutant concentration and long duration, hoarfrost and rime are at least significant factors in environmental processes in different ecosystems in Poland.  相似文献   

The Late Vistulian and Holocene evolution of Jezioro Lake: a record of environmental change in southern Poland found in deposits and landforms     

Maria Fajer  Jan Maciej Waga  Mariusz Rzetala  Artur Szymczyk  Ma?gorzata Nita  Robert Machowski  Martyna A. Rzetala  Marek Ruman 《Journal of Paleolimnology》2012,48(4):651-667

Jezioro Lake is the only natural lake in southern Poland outside mountainous areas to have existed continuously since the Pleistocene. The record of environmental change in the Late Vistulian (Weichselian) and Holocene is preserved in the deposits and landforms around the lake. This paper presents the results of paleogeographical and paleoecological research that emabled us to reconstruct the history of the Jezioro Lake. At the end of the Vistulian period, the outlet of the lake was blocked by a parabolic dune moving in from the west. Limnic sedimentation was evident in the sediment core at all levels from the Holocene, with remains of Cladocera, Chironomidae larvae, and aquatic plants. The lake did not disappear at that time, although its area decreased by a factor of 12 by the end of the period. Paleobotanical research permitted the reconstruction of sequences of plant communities and changes in nutrient status and water level. An initial oligotrophic lake, as indicated by the presence of Iso?tes lacustris L., changed to a eutrophic lake, as indicated by the presence of Potamogeton natans L. and Nuphar sp., then the lake progressed to the present-day dystrophic lake that is surrounded by a swamp. The profile of organic deposits contains a record of environmental change at least since the Younger Dryas in southern Poland.  相似文献