National Repository of Grey Literature 23 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
You cannot step into the same fishpond twice - an evolution of fishpond ecosystems to hypertrophy
Vrba, Jaroslav ; Benedová, Z. ; Jezberová, Jitka ; Matoušů, Anna ; Musil, M. ; Nedoma, Jiří ; Pechar, L. ; Potužák, J. ; Řeháková, Klára ; Šimek, Karel ; Šorf, M. ; Zemanová, J.
Shallow manmade fishponds in south Bohemia were used for fish production for centuries, however, their ecosystems have changed dramatically due to excessive nutrient loading and fish stocking. Preliminary results of ten sampled fishponds suggested their hypertrophic status at present, while their plankton structure and dynamics reflected the actual size/age class of fish stock consisting predominantly of common carp. Planktivorous fish (both young carp and whitefish) remarkably reduced abundance, size, and species diversity of crustacean zooplankton, in particular large daphnids, whereas larger carp itself did not cause such a strong top-down effect. All other plankton components, i.e. phytoplankton, bacteria, protists, and rotifers showed rather high abundance and diversity, and suggested a reasonable impact of various microbial processes and interactions in the recent hypertrophic ecosystems.
Lakes of the Czech Republic physico-geographical a physico limnological characteristics
Šobr, Miroslav ; Janský, Bohumír (advisor) ; Kříž, Vladislav (referee) ; Vrba, Jaroslav (referee)
J e ze r a C e s kér ep ub l i lE fyz i c ko ge o g r af c kéa fyz i ká lně J i ntno l o gi cké p o mě ry Lakes of the Czeclt Republic physico-geographical and physicoJimnological clnracteristics (Etiglish veÍsion) IntroducÍiotl In comparison with other European regions, there are orrly a few oflakes oťnatural origin in the Czech Republic. In our country, there are neither high mountains with network of glacial lakes nor vast lowlands of northem type with tlre lďie plateau' There are neither vast, fully developed karsts regions, nor active volcanic areas nor sea shores. The fluvial lakes originated in tlre floodplains oťseveral waterways are one tlre most numerolls types of lakes ir-r the courrtry. In the river floodplains there had been massive rnining of gravel-sand alluvium sedirnents which is connected to tlre origination oť the lakes o| arrthropogenic origin. These ale also rather frequent irr the areas of coal mining, especially of lignite coal and other mineral resources. And the last numerous type of lakes includes the water bodies in the peat bog and moor land areas which are scattered alorrg the wlrole mountain border range in the Czeclr Republic (JANSKÝ, ŠosnBr AL. 2003). In comparison to the world's lakes, the lakes in the Czecir Republic are of far smaller size and volume dimensions. They are...
Seasonal dynamics and vertical distribution of Crustacea in the deep stratified reservoir Josefův Důl (the Jizera Mountains, Czech Republic)
Adámek, Radek ; Hořická, Zuzana (advisor) ; Vrba, Jaroslav (referee)
The zooplankton of Josefův Důl, a large and deep drinking water reservoir recovering from acidification, develop in relation to the improving water chemistry but also predation by salmonid fish re-stocked at the end of the 1990s. Crustacea are represented by small numbers of several species only, and nothing is known about their distribution in the water column. Recently, picocyanobacteria Merismopedia sp. became dominant in the phytoplankton, which hampers substantially the treatability of the raw water. The aim of the thesis is to describe the seasonal dynamics and vertical distribution of Crustacea in the Josefův Důl reservoir, together with parameters of the environment, and to study their possible diurnal vertical migrations in the summer period.
Long-term trends in water quality of pond Světin relation to fish management
Altmann, Martin ; Duras, Jindřich (advisor) ; Vrba, Jaroslav (referee)
Fishpond ecosystems provide many other services besides fish production. One of them is the retention of nutrients and thus ability to change the quality of the through flowing water, thereby ability to influence the overall quality of surface waters. In the case of the fishpond Svět in Třeboň it is also recreation, as the pond is an integral part of the tourism of the town. Water quality in the fishpond and its retention capacity of phosphorus is connected with the fish management and the inflow of nutrients from the catchment basis, especially within a cascade of ponds and densely populated or agricultural regions. This thesis evaluates seasonal (2013, 2015) and long term (2007-2015) trend of water quality of pond Svět in Třeboň in relation to fish management. Furthermore, mass balance was calculated for 2015 and estimated for 2013. The years 2015 and 2013 (the first years of production cycle) varied considerably in amount of annual rainfall. The year 2015 was extremely dry and 2013 very aqueous. Different hydrological conditions caused different seasonal courses in hydrochemistry parameters and its concentrations. The water quality of fishpond Svět is in the most of parameters better in comparison with other production fishponds in the Třeboň region and also the intensity of fish management is...
Water Footprint. Calculation of water footprint of wheat, maize, sugarbeet and tomatoes in the Czech Republic
Landová, Lucie ; Hák, Tomáš (advisor) ; Vrba, Jaroslav (referee)
Fresh water is a renewable resource but it is also finite. Around the world, there are now numerous signs that human water use exceeds sustainable levels. Groundwater depletion, low or nonexisting river flows, and worsening pollution levels are among the more obvious indicators of water stress. Satisfying the increased demands for food, water, and material goods of a growing population while at the same time protecting the ecological services provided by natural water ecosystems requires new approaches to using and managing fresh water. There has been little attention to the fact that the organization and characteristics of a production and supply chain does actually strongly influence the volumes of water consumption and pollution that can be associated with a final consumer product. Uncovering hidden link between consumption and water use can form the basis for the formulation of new strategies of water governance. That is why in this diploma thesis we focus on introducing the indicator of freshwater use that looks not only at direct water use of a consumer or producer, but also at the indirect water use - water footprint. At a global scale, most of the water use occurs in agricultural production. That is the reason why we have chosen water-intensive goods like crops to show how water footprint...
Reintroduction of a copepod species Cyclops abyssorum (Crustacea) and its impact on zooplankton in Plešné Lake
Křenová, Radka ; Vrba, Jaroslav (referee) ; Sacherová, Veronika (advisor)
Abstract Plešné Lake is a small glacial lake in the Bohemian Forest. In the 1980th, it was heavily influenced by an acification event caused by severe atmospheric pollution. Due to some extreme parameters in the water chemistry (mainly low pH and high concentration of toxic aluminum compounds) several zooplankton species got extinct. Among these, two species important in lakes food web: Daphnia spp. and Cyclops abyssorum. They, however, survived the acidification period in one of the Bohemian Forest Lake: Prášilské. Although recovery of lakes from acidification is usually followed by return of some species or colonization by others, recolonization of Plešné Lake is assumed to be very slow or impossible from external sources thanks to the remote position of the lake. Therefore in the fall of 2004 two zooplankton species (Daphnia longispina and Cyclops abyssorum) were artificially reintroduced into Plešné Lake. In the course of 4 years that followed only Cyclops abyssorum appeared in the lake, Daphnia longispina was not recorded. My thesis focuses on several aims. First, I evaluate the development of C. abyssorum population. Second, I studied the competition between C. abyssorum and another copepod species - Heterocope saliens, acidotolerant species which never disappeared from the lake. Third, I...
Biogeochemické cykly ekologicky významných prvků v měnících se přírodních podmínkách lesních ekosystémů NP Šumava
Správa národního parku Bayerische Wald ; Česká zemědělská univerzita, Fakulta lesnická a environmentální ; Ústav pro hydrodynamiku AV ČR, Praha ; Hydrobiologický ústav AV ČR, České Budějovice ; Česká geologická služba, Praha ; Beudert, Burkhart ; Máca, Petr ; Šír, Miloslav ; Tesař, Miroslav ; Metelka, Václav ; Vrba, Jaroslav ; Kopáček, Jiří ; Oulehle, Filip ; Hofmeister, Jeňýk ; Hruška, Jakub
Zpráva shrnuje poznatky získané v období listopad 2004 - prosinec 2005, které jsou doplněny o předchozí pozorování členů autorského kolektivu. Zaměření je na biogeochemické a hydrologické charakteristiky území na obou stranách Šumavy. Zpráva je rozdělena do částí: Zhodnocení látkových toků v NP Šumava na třech povodích s různým typem managementu; Chemismus půd a jehličí ve studovaných povodích; Modelování dlouhodobého vývoje chemismu vod a půd; Změny chemismu a oživení Rachelsee na Šumavě v důsledku kůrovcové kalamity a zotavování ekosystému z acidifikace; Vyhodnocení vodního režimu půd na lokalitách lišících se vegetačním krytem v Národním parku Šumava; Vliv usazených srážek na vodní a látkovou bilanci malého horského povodí.
Possibilities and specifications of usage of social networks in logistics
Vrba, Jaroslav ; Molnár, Zdeněk (advisor) ; Měsíček, Libor (referee)
The main purpose of this thesis is to examine current most important social networks usable in Czech Republic and evaluate usefulness for logistic companies. The aims of thesis are basics of internet marketing, separation of social networks and evaluation their commercial potential. Author attaches his research in form of questionnaire aimed on current usage social networks in logistic companies and compiles recommendations how use social network for commercial purpose.
The fluorescence assay of aminopeptidase activity as an alterantive indicator of water quality?
Vrba, Jaroslav ; Svoboda, J. ; Fuksa, J. K.
Recent water quality/pollution control uses standard chemical, biological or microbiological indicators that provide information on water status with a delay of several days. Though they characterise direct impact of released compounds on water quality in a recipient, they do not well reflect consequent reaction of the ecosystem on increased pollution. Following the Water Framework Directive 2000/60/EC we focused on such alternative microbial indicators that would allow for instant evaluation of ecological status of running waters and ongoing in-stream processes. Recently, activities of different extracellular enzymes have been suggested as indicators of both trophic status of lakes and organic or faecal pollution of streams. This contribution evaluates an indication potential of the extracellular aminopeptidase assay.
Development of microbial activity in the Vltava River - a longitudinal profile to Podolí and downstream
Svoboda, J. ; Vrba, Jaroslav ; Simanov, L. ; Fuksa, J. K.
Extracellular ß-glucosidase activity, bacterial number (direct counts and MPA colony forming units), chlorophyll .i.a./i. concentration, BOD.sub.5./sub., and COD were measured along the Vltava River and its reservoir cascade in 2000 (April-September;n = 5-8). The study demonstrated an important role of reservoirs in water quality management and, in particular, the dominant role of the microbes in matter transfers, decomposition, and nutrient dynamics in the transient zones of reservoirs.

National Repository of Grey Literature : 23 records found   1 - 10nextend  jump to record:
See also: similar author names
2 Vrba, J.
4 Vrba, Jakub
15 Vrba, Jan
1 Vrba, Jindřich
4 Vrba, Jiří
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