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A litter bag experiment was performed in a healthy and a die-back reed stand of Lake Ferto˝/ Neusiedler See. Mass loss, hemicellulose, cellulose, lignin, C, N, S and P concentrations of Phragmites australis leaves and culms were determined. Leaves decomposed faster than culms at both sites. After 33 months 82-90% of the leaf and 39-43% of the culm mass was lost, corresponding to a fibre loss of 82-90% and 32-35%, respectively. The N, C and S concentrations increased as decomposition proceeded, while the P concentrations decreased. The decaying coefficient model gave the best fit of the mathematical models tested (single exponential, decaying coefficient and composite exponential model). No significant differences in decomposition rates were detected between the two sites.

-The biomass and composition of the phytoplankton was studied at seven sampling stations located at different water bodies (open water, inner pond and canal) of a large, shallow turbid lake (Lake Fertő , Neusiedlersee). The open water was characterized by picocyanobacteria and meroplanktonic diatoms, the artificial canal by epiphytic diatoms, cryptophytes and chlorophytes. The inner ponds, based on the phytoplankton composition, were positioned between these water bodies. High picoplankton abundance (>10 6 cells.mL x1 ) and predominance (up to 80% contribution to the total phytoplankton biomass) were detected in the open water and the inner ponds, which was hypothesized to be the result of the turbid environment by the suppression of the top down control and by light-limitation. Information on the diversity of the picoplankton in the open water of the lake has been presented first time in this study. Based on molecular analysis (16S rRNA gene and cpcBA-IGS region) the dominant group of picocyanobacteria belonged to the Cyanobium gracile cluster (group A) of the picophytoplankton clade in April. Members of two other picocyanobacterial groups (group B and C) were also detected.

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We studied the structure and population dynamics of zooplankton assemblages in the water bodies (eu-, para-, plesiopotamal and conjunctive water bodies) of a temperate floodplain during flood events. Here we report differences in the species composition of these water bodies in the two stages of flood pulses: rising vs. receding. During the receding period the proportion of larger and tychoplanktonic species increased. Similarity among zooplankton assemblages of these floodplain water bodies increased during the rising and decreased during the receding period. Species richness, diversity and population density values of zooplankton assemblages increased during the receding period in all types of water bodies except the eupotamal. The guild ratio of rotifer assemblages showed characteristic, but somewhat ambiguous changes. We conclude that the hydrological regime affects the structure and dynamics of zooplankton assemblages on the floodplain. IntroductionSpatial and temporal variability induces high productivity and biodiversity in terrestrial and aquatic components of the river-floodplain systems (SHIEL et al., 1998;ARMITAGE et al., 2003). Understanding the ecological functions of natural river-floodplain systems is important to establish criteria to protect the biota of these sites (BERCZIK and BUZETZKY, 2006). Introduction of the Flood Pulse Concept (JUNK et al., 1989) stimulated renewed interest in the connection between large rivers and their floodplains; since then numerous studies have focused on the zooplankton of large rivers. These efforts have indicated that inshore retention and hydrological connectivity are a major determinant of zooplankton assembly (HEIN et al., 1999;BARANYI et al., 2002;RECKENDORFER et al., 1999;ZIMMERMANN-TIMM et al., 2007). In contrast, most hydro-ecological research projects on large rivers and their floodplains focus just on fish and/or benthic invertebrate assemblages, thus neglecting the importance of zooplankton communities in the food-web of river-floodplain systems. Concomitantly an assessment of their suitability as a biomonitoring tool is also neglected (BORJA et al., 2008;RESH, 2008

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