National Repository of Grey Literature 109 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Carbon metabolism and nutrient balance in a hypertrophic production fishpond
Hejzlar, Josef ; Potužák, J. ; Drozd, B. ; Rutegwa, M.
Semi-intensive production of fish in pond culture is based on natural food in the form of zooplankton or zoobenthos and supplemental feeding and manuring applied with balanced nutrient budget. Measurement of the metabolism (i.e., primary production and respiration by the method of continuous measurement of dissolved oxygen in the water column) and the input / output balance for C, N and P in the semi-intensive Dehtář fishpond in the 2015 growth season have shown that additions of fish feeding and manure were from the point of view of utilisable fish feeding in a 3 – 4 fold excess, the efficiency of nutrient transfer through fish food chains was low and that most of the primary production remained unused for fish production, resulting in eutrophication problems with accumulation of biomass in water, high respiration of phytoplankton and microbial chains, hypoxia conditions, and intense N and P cycling.
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.
Water in landscape and revitalisations
Petřík, Petr ; Salzmann, K. ; Hejzlar, Josef ; Pithart, D. ; Fanta, J.
How to return water to the landscape and keep it there? One of the strategic objectives and priorities of water protection should be the revitalization of the river and valley network, accompanied by a change of the approach to river network management.
Phosphorus concentration in the Orlík and Slapy reservoirs: a result of socio-economic trends in the catchment and climate change
Hejzlar, Josef ; Jarošík, Jiří ; Kopáček, Jiří ; Vystavna, Yuliya
Based on existing phosphorus data series in the Slapy and Orlík reservoirs and their main tributaries, we reconstructed P inputs to the reservoirs from the catchment during 1961–2016 and compiled\nempirical models of P retention. P concentrations in both reservoirs increased from the 1960s to 1991 and then declined, with the Slapy Reservoir having a significantly increased year-on-year\nvariability. Trends in the increase and decrease of P reflected the socio-economic development in the Vltava river basin, in particular sewerage, wastewater discharges, fertilizer application, livestock,\nand fishpond fisheries. In the Slapy reservoir after 1991, the P concentrations increased during wet summers and created conditions for growth of phytoplankton, whereas in dry summers they\ndecreased to mesotrophy. Climatic and hydrological processes have now apparently begun to compete with a generally decreasing P pollution and support eutrophication despite the drop in P loads from the catchment.
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.
Trends in the balance and material flows of phosphorus in the Czech Republic.
Hejzlar, Josef
In developed countries, many voices call for increasing the recycling of phosphorus (P) that is a strategic raw material for agriculture and other production sector; phosphorus is also causing environmental problems, for example. eutrophication. Using the methodology of material flow analysis, van Dijk et al. (Sci. Total Environ. 2016, 552: 1078-1093) quantified the main flows and stocks of P in 27 states of the European Union. The contribution presents and discusses data from that publication for the material flows P in the Czech Republic (CR) and compared with the EU. The P balance of CR shows the dependence on imported P through mineral fertilizers (1 kg/ca/yr), food and feed (1.5 kg/ca/yr) and also draws attention to significant environment losses and unused recycling potential. For example, municipal sludge (0.4 kg/ca/yr) and bone meal (0.25 kg/ca/yr) could replace 70% of the P amount in applied mineral fertilizers. P recycling rate in CR in comparison with EU-27 is below average (68% in livestock production, 21% in food production, 10% for human consumption). Agricultural production in CR still uses P reserves in the soil of mineral fertilizers in the past.
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.
Erosion of agricultural land and its importance for siltation and eutrophication of reservoirs in the Czech Republic
Krása, J. ; Jáchymová, B. ; Bauer, M. ; Dostál, T. ; Rosendorf, P. ; Hejzlar, Josef ; Borovec, Jakub ; Bečička, M.
In 58 large catchments of the Czech Republic (covering ca 35000 km2) the sediment transport processes were assessed. Amount of sediment flux into the streams and reservoirs from agricultural land was estimated. Sediment retention in all reservoirs was considered based on reservoirs‘ outflow. For thousands of small ponds the volumes and outflow had to be estimated based on reservoir areas and specific flow rates in catchments. The distributed approach allowed considering importance of particular agricultural fields for stream silting. The maps of annual sediment flow in all streams were derived. The sediment fluxes cause serious problems not only concerning eutrophication. For example Vltava river watershed up to Slapy dam (12 965 km2) exports 2.34 million tons of sediment by water erosion annually. 626 thousand ton is exported into the streams, and 615 500 t is then deposited in the reservoirs.

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1 Hejzlar, J.
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