National Repository of Grey Literature 23 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Hydrobiological monitoring of Medard Lake in 2017
Hejzlar, Josef ; Nedoma, Jiří ; Znachor, Petr ; Seďa, Jaromír ; Peterka, Jiří
The report summarizes the results of hydrobiological monitoring of Medard Lake 2017 and contains recommendations for further research activities. At the beginning of 2017, the lake was almost full, and at the end of March the last 30 cm water column was filled from the Ohře river. The ecosystem of the lake has reached its final nutrient load, which will be characterized by low levels of carrying capacity with low productivity planktonic and fish communities and specific seasonal changes in chemistry and biological parameters.
Hydrobiological monitoring of Medard Lake in 2016
Hejzlar, Josef ; Borovec, Jakub ; Nedoma, Jiří ; Znachor, Petr ; Seďa, Jaromír ; Peterka, Jiří
Presented report summarizes the results of hydrobiological monitoring of Medard Lake in 2016 and recommends further monitoring actions. Between November 2015 and June 2016 final flooding from river Ohře took place, resulting in enrichment of the lake ecosystem by large amount of nutrients at the beginning of vegetation season what affected seasonal development of chemical as well as biological parameters, from phytoplankton to fish.
Structure of zooplankton in reservoirs of the Jizera Mountains during the peaking anthropogenic acidification and recovery from acidification (1992-2011)
Bímová, Tereza ; Hořická, Zuzana (advisor) ; Seďa, Jaromír (referee)
Acidic atmospheric deposition and acidification of soil and water on the Earth's surface, due to emissions of sulfur and nitrogen into the atmosphere, have led to drastic changes in the composition of surface waters and their biota in many regions of the world over the last century. The number of species and biomass of phytoplankton, zooplankton and benthos were reduced, or some components (zooplankton, zoobenthos, fish) became extinct. In the Jizera Mountains (Northern Bohemia, Czech Republic), the man-made acidification has always been combined with a natural acidity (dystrophy) of waters, caused by a high amount of organic acids. Despite a strong recovery of water chemistry from acidification, that has started in the 1990s, biological recovery is delayed and much more complex. This master thesis is a study of the succession of zooplankton (crustaceans) in mountain reservoirs Souš, Bedřichov and Josefův Důl after decades of strong acidification. Biological recovery from acidification has been in progress differently in the drinking water reservoir Souš, which has long been limed, in the Bedřichov reservoir with naturally high content of organic material, and in the drinking water reservoir Josefův Důl, which is the largest and deepest one and which was most affected by acidification. Recovery of...
Environmental gradients in canyon-shaped reservoirs
Stodola, Jakub ; Petrusek, Adam (advisor) ; Seďa, Jaromír (referee)
The occurrence of environmental gradients in canyon-shaped reservoirs is influenced mainly by the size of reservoir and water retention time. The reservoir must be large and deep enough for environmental gradients to occur there. In such reservoirs vertical and horizontal gradients can be found. Presence of vertical gradients in lakes is relatively common, whereas horizontal gradients abound in deep canyon reservoirs. An example is the gradient of nutrients, the quantity of which decreases in the direction from the inflow towards the dam. Vertical abiotic gradients are the same for reservoirs and lakes. These are mainly gradients of light, heat, dissolved and oxygen. Some abiotic horizontal gradients may be present in both to reservoirs and lakes. The abiotic gradients also often affect the biotic ones. For example the gradient of nutrients affects the gradient of all organisms in the reservoir. Each species living in the reservoir prefers different type of environmental conditions, which may be given by a combination of these gradients. The areas preferred by particular cladoceran species can overlap quite extensively. In the Daphnia longispina species complex, co-occurrence of parental species may result in interspecific hybridization, and possibly formation of hybrid zones. The hybrids can often...
Vertical distribution of the freshwater jellyfish under natural and laboratory conditions
Hutňan, Martin ; Petrusek, Adam (advisor) ; Seďa, Jaromír (referee)
Vertical distribution of freshwater jellyfish Craspedacusta sowerbii was observed in an experimental set-up (two thermally stratified transparent perspex columns of 78 l volume) in two seasons. Light intensity and temperature gradients were established in order to uncover influence of these factors on vertical distribution of the medusae; unlike situation in the field, these were not accompanied with hypoxic conditions in the deeper layers. Medusae accumulated at depths that corresponded to the temperature of acclimation tank. Diel vertical migrations (DVM) of male medusae were observed in a thermally stratified water body. Crustaceoplankton (main food source of Craspedacusta) also showed differences in spatial distribution during day and night. Vertical distribution of medusae was limited by the bottom border of the epilimnion. The observations lead me to the following conclusions: 1) Behavior of Craspedacusta sowerbii under laboratory conditions supported the hypothesis that change in light intensity is the primary proximate cue controlling DVM. 2) A factor playing critical role in jellyfish vertical distribution is temperature. At both laboratory and field observations, medusae aligned with the bottom border of the epilimnion; this was consistent under different oxygen stratification patterns. 3) DVM...
Effects of dispersal and local processes on genetic structure of populations Daphnia curvirostris and Daphnia pulex: genetic variability within and among river flood-plains
Repovský, Marek ; Seďa, Jaromír (referee) ; Černý, Martin (advisor)
- 3 - Abstract Only a few studies have compared patterns of genetic variation among populations of different Daphnia species in the case of natural systems of river catchments. We assumed that as a result of dendritic nature of rivers and streams, the most genetic differentiation should be found between populations from different catchments and the least should be in the same sub-catchment. This is beacause it is much easier for animals restricted to passive dispersal via stream channel to disperse between adjacent streams in the same sub-catchment than between catchments. Using allozyme data based on six polymorphic enzyme loci, we present an analysis of genetic differentiation among 45 Daphnia curvirostris and 39 Daphnia pulex populations, separated by less than 100 m to more than 500 km from each other. The genetic population structure of the two species was strikingly similar, consistent with their similar metapopulation ecology. The mean FST value (differentiation within populations) was 0.32 and 0.30 and a hierarchical analysis showed that most genetic differentiation was between populations (68 and 70 %), less was present among populations within catchments (26 and 19 %) and the least was present among whole catchments (6 and 11 %). In spite of the large range of geographic distances, there was only...
The influence of nutrient loading, meteorological and hydrological conditions and operating manipulations on phytoplankton in the water suply reservoir Římov.
Hejzlar, Josef ; Jarošík, Jiří ; Nedoma, Jiří ; Seďa, Jaromír ; Znachor, Petr
Analysis of data collected during long-term and complex limnologic monitoring of the Římov reservoir in the period 1983 – 2015, which depict the development of physico-chemical conditions, hydrology and hydrodynamics of the reservoir with links to biological data on phytoplankton, zooplankton etc. showed that the concentration and species composition of phytoplankton depend on the supply and availability of nutrients, but are also influenced by climatic and hydrological conditions and water management operation of the reservoir.\n
Hydrobiological monitoring of Medard Lake in 2015.
Hejzlar, Josef ; Borovec, Jakub ; Nedoma, Jiří ; Znachor, Petr ; Seďa, Jaromír ; Peterka, Jiří
Presented report is summarizing the results of the hydrobiological monitoring of Medard Lake in 2015 and recommends further monitoring actions. In 2015 the lake was not flooding from river Ohře, therefore the water level increase was realized only by precipitation and inflow from lake’s own drainage area. Furthermore, it was the first year without stocking of maraena whitefish and brown trout.
Hydrobiological monitoring of Medard Lake in 2014
Hejzlar, Josef ; Borovec, Jakub ; Nedoma, Jiří ; Znachor, Petr ; Seďa, Jaromír ; Peterka, Jiří
Presented report is summarizing the results of the hydrobiological monitoring of Medard Lake in 2014 and recommends further monitoring actions. In 2014 the lake was not flooding from river Ohře, therefore the water level increase was realized only by precipitation and inflow from lake’s own drainage area. Forming of fish stock was realized according to stocking plans.

National Repository of Grey Literature : 23 records found   1 - 10nextend  jump to record:
See also: similar author names
5 Šeda, Jan
1 Šeda, Jaroslav
5 Šéda, Jan
Interested in being notified about new results for this query?
Subscribe to the RSS feed.