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Hydrobiological monitoring of Medard lake in 2019
Hejzlar, Josef ; Nedoma, Jiří ; Znachor, Petr ; Seďa, Jaromír ; Peterka, Jiří
Presented report summarizes the results of hydrobiological monitoring of Medard Lake in 2019 and recommends further monitoring actions. The year 2019 was the second year after the lake was filled, when no more water from the Ohře River was filled and only small tributaries from the small river basin flowed into the lake. Thus, the ecosystem of the lake has reached a final state in terms of hydrological regime and nutrient load, characterized by very low water exchange, low trophic levels with low productivity of planktonic communities, development of submerged macrovegetation in coastal zones and specific seasonal changes in chemistry and biological parameters.
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Prediction of phosphorus concentration and trophic conditions in reservoirs
Hejzlar, Josef ; Kopáček, Jiří ; Vystavna, Yuliya
The model prediction of phosphorus (P) concentration in reservoirs is important for controlling water quality and trophic conditions, e.g. to determine to what level external P load should be reduced in order to decrease trophic conditions and achieve good ecological potential. The mass balance of P for 26 reservoirs and lakes in the Czech Republic showed that the relationship between the inflow P concentration and the in-reservoir P concentration is not determined solely by hydrological parameters (water residence time or hydraulic load) or inflow P concentration but is fundamentally influenced by the internal P loading from sediments and in-reservoir P cycling. These are individual characteristics of each reservoir and may change, for example with sediment accumulation or changes in external P load. Therefore, the prediction models need to be assembled and calibrated for each reservoir individually and the model structure should be adapted to their specific conditions.
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Hydrobiological monitoring of Medard Lake in 2018
Hejzlar, Josef ; Nedoma, Jiří ; Znachor, Petr ; Seďa, Jaromír ; Peterka, Jiří
Presented report summarizes the results of hydrobiological monitoring of Medard Lake in 2018 and recommends further monitoring actions. The year 2018 was the first year after the lake was filled, when no more water from the Ohře River was filled and only small tributaries from the small river basin flowed into the lake. Thus, the ecosystem of the lake has reached a final state in terms of hydrological regime and nutrient load, characterized by very low water exchange, low trophic levels with low productivity of planktonic communities, development of submerged macrovegetation in coastal zones and specific seasonal changes in chemistry and biological parameters.
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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.
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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.
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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.
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