Late summer phytoplankton associations were studied qualitatively and quantitatively in 80 Hungarian lakes altogether (mostly shallow salt lakes, reservoirs, oxbows, gravel pit lakes). Equilibrium phases sensu Sommer et al. (1993) were found only in 17 lakes. Most of them were under some kind (high salt content or very low level of nutrients) of stress factor. It is concluded that environmental stress forces phytoplankton communities towards equilibrium. No relationship between occurrence of equilibria and trophic state was found. Species number of nonequilibrated lakes was almost three times as high as those in equilibrium. Of the 31 recently described (Reynolds et al., 2002) phytoplankton assemblages most of those were recognized that are likely to occur in shallow lakes. Separation of a functional group W S from W2 for Synura dominated lakes is suggested. It seemed also necessary to raise a group (Y Ph ) for lakes dominated by Phacotus. Sorting of Dinophyta species into different already described functional groups is desirable.
Late summer phytoplankton associations were studied qualitatively and quantitatively in 80 Hungarian lakes altogether (mostly shallow salt lakes, reservoirs, oxbows, gravel pit lakes). Equilibrium phases sensu Sommer et al. (1993) were found only in 17 lakes. Most of them were under some kind (high salt content or very low level of nutrients) of stress factor. It is concluded that environmental stress forces phytoplankton communities towards equilibrium. No relationship between occurrence of equilibria and trophic state was found. Species number of nonequilibrated lakes was almost three times as high as those in equilibrium. Of the 31 recently described (Reynolds et al., 2002) phytoplankton assemblages most of those were recognized that are likely to occur in shallow lakes. Separation of a functional group W S from W2 for Synura dominated lakes is suggested. It seemed also necessary to raise a group (Y Ph ) for lakes dominated by Phacotus. Sorting of Dinophyta species into different already described functional groups is desirable.
The Danube is a large eutrophic river and may be one of the best studied rivers in the world. This paper presents a short characterization of the biological water quality based on data from the 1986-1992 period, collected in the Southern Hungarian section at 1480.2 river km. Variations in the hydrological features (including discharge and turbulence) are the most important factors determining the total phytoplankton biomass in the River Danube. A good correlation has been found between chlorophyll a content and discharge, from early spring to autumn, whereas the suspended matter appeared weakly related to discharge. In addition, some taxonomic notes refer to the most common members of the phytoplankton, as well as to several rare taxa.
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