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The species composition, longitudinal distribution and seasonal dynamics of zooplankton were studied in the Zagyva River, Hungary. A total of 108 taxa was recorded from which 61 were new for the river. Rotatoria was the most abundant group, microcrustaceans were less important, only nauplii and copepodites were represented in similar individual numbers. Frequent species included Anuraeopsis fissa, Pompholyx spp., Keratella cochlearis, Brachionus angularis, Bdelloida sp., Bosmina longirostris. Dominance of cosmopolitan species was observed both in the river and its reservoir, and species characteristic of eutrophic waters were of major importance in the latter. There was a downstream decrease in zooplankton densities, which was explained by modified conditions. The relatively large number of individuals in autumn months, and the characteristic large number of individuals in the upper section contrasted general findings of potamoplankton dynamics. On the basis of the species abundance matrix, three river sections can be distinguished (upper, middle, lower section). Due to waste water discharges - received from the Tarjan Stream - we found extremely high number of individuals and the lowest diversity at the sampling site Nagybatony (148 rkm).

The Rackeve-Soroksar Danube has a great importance as it is the second largest side arm in the Hungarian section of the river Danube and many demands of exploitation are expected. The aim of this study is to analyse the spatial and temporal changes of the zooplankton (Copepoda, Cladocera) community in this river arm, moreover the similarity patterns of zooplankton communities in different Hungarian water bodies are presented in special consideration of the Rackeve-Soroksar Danube. Basically this study is based on data from literature, however our data are also used for compiling the database for the spatio-temporal changes of the Rackeve-Soroksar Danube. We put emphasis on the three typical sections of the side arm, as these are stressed due to hydromorphological aspects, but creating artificial borders are objectionable as well. The results show that both spatial and temporal changes are evident, what is more, the stagnant water character of the side arm should be underlined.

Climate change is one of the most crucial ecological problems of our age with great influence. Seasonal dynamics of aquatic communities are — among others — regulated by the climate, especially by temperature. In this case study we attempted the simulation modelling of the seasonal dynamics of a copepod species, Cyclops vicinus , which ranks among the zooplankton community, based on a quantitative database containing ten years of data from the Danube's God area. We set up a simulation model predicting the abundance of Cyclops vicinus by considering only temperature as it affects the abundance of population. The model was adapted to eight years of daily temperature data observed between 1981 and 1994 and was tested successfully with the additional data of two further years. The model was run with the data series of climate change scenarios specified for the period around 2070- 2100. On the other hand we looked for the geographically analogous areas with the God region which are mostly similar to the future climate of the God area. By means of the above-mentioned points we can get a view how the climate of the region will change by the end of the 21 st century, and the way the seasonal dynamics of a chosen planktonic crustacean species may follow this change. According to our results the area of God will be similar to the northern region of Greece. The maximum abundance of the examined species occurs a month to one and a half months earlier, moreover larger variances are expected between years in respect of the abundance. The deviations are expected in the direction of smaller or significantly larger abundance not observed earlier.

In the years 2004 and 2005, we collected samples of phytoplankton, zooplankton, and macroinvertebrates in an artificial small pond in Budapest (Hungary). We set up a simulation model predicting the abundances of the cyclopoids, Eudiaptomus zachariasi, and Ischnura pumilio by considering only temperature and the abundance of population of the previous day. Phytoplankton abundance was simulated by considering not only temperature but the abundances of the three mentioned groups. When we ran the model with the data series of internationally accepted climate change scenarios, the different outcomes were discussed. Comparative assessment of the alternative climate change scenarios was also carried out with statistical methods.

Present paper is a review on the Rackeve-Soroksar Danube in ecological standpoint. The goal of this study is to collect and evaluate all of available publications in that conception, concerning this Danube arm. Phytoplankton, zooplankton, macroinvertebrates, vertebrates, macrophytes and also water chemistry, water management, geographical description are presented. The review comprises the main studies beginning with the earliest faunistic publications up to the recent ecological, multidisciplinary investigations. Spatial and temporal patterns likewise water quality are considered as important. Additionally checklist of aquatic invertebrate and vertebrate fauna are given based on data from literature.

In the years 2004 and 2005 we collected samples of phytoplankton, zooplankton and macroinvertebrates in an artificial small pond in Budapest. We set up a simulation model predicting the abundance of the cyclopoids, Eudiaptomus zachariasi and Ischnura pumilio by considering only temperature as it affects the abundance of population of the previous day. Phytoplankton abundance was simulated by considering not only temperature, but the abundance of the three mentioned groups. This discrete-deterministic model could generate similar patterns like the observed one and testing it on historical data was successful. However, because the model was overpredicting the abundances of Ischnura pumilio and Cyclopoida at the end of the year, these results were not considered. Running the model with the data series of climate change scenarios, we had an opportunity to predict the individual numbers for the period around 2050. If the model is run with the data series of the two scenarios UKHI and UKLO, which predict drastic global warming, then we can observe a decrease in abundance and shift in the date of the maximum abundance occurring (excluding Ischnura pumilio, where the maximum abundance increases and it occurs later), whereas under unchanged climatic conditions (BASE scenario) the change in abundance is negligible. According to the scenarios GFDL 2535, GFDL 5564 and UKTR, a transition could be noticed.