State and role of invasive zebra mussel (\kur{Dreissena polymorpha}) in the Želivka Reservoir

The work is focused on the status and role of zebra mussels (Dreissena polymorpha) in the water reservoir Želivka. Literature review summarizes the basic characteristics of living zebra mussels and its impact on the aquatic ecosystem. Current knowledge about this invasive bivalves show that its presence in the water reservoir has certain advantages, but also disadvantages. The main advantage is that zebra as filtrator, increases the transparency of the water and provides food for the animals living in the aquatic environment, or in its vicinity. Disadvantages are then mainly from the economic point of view, the zebra clogs pipes and thus prevents water flow and attached to marker buoys, fishing nets and attaches to the hulls of ships that can be attacked from the inside. In field part population of zebra mussels was sampled in different parts of the reservoir and identified following parameters (temperature and oxygen stratification, coverage to substrate coverage depending on the depth and the substrate, the length of shells according to the horizontal and vertical gradient filtering capacity and the volume rate). The results showed that the incidence and size of shells affects both horizontal and vertical gradient. Zebra mussels occur most depth 1-9 m on rocky, or stony substrate. The greatest incidence was found at Budeč and at Hráz, where the water is less eutrophic than the Zahrádka. Based on these parameters, and literature data was calculated hypothetical filter capacity and discussed its possible impact on the ecosystem components of the reservoir