The present area of European wetlands is only a fraction of their area before the start of large-scale human colonization of Europe. Many European wetlands have been exploited and/or managed for various purposes. Large wetland areas have been drained and reclaimed mainly for agriculture and establishment of human settlements. These threats to European wetlands persist. The main responses of European wetland to ongoing climate changes will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to lowered annual evapotranspiration and lowered organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most from water shortage, which may stregthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other. The main responses of European wetland to ongoing climate changes will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to lowered annual evapotranspiration and lowered organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most Manuscript Click here to download Manuscript: European_wetlands_20110124. doc 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 from water shortage, which may stregthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other.

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To propose a concept of their mutual diversity, twenty-nine permanent shallow floodplain pools and oxbows in the river Lužnice floodplain were analysed for area, depth, shape, flooding, and shading by terrestrial vegetation, and sampled in all seasons for their water chemistry, phytoplankton composition and biomass, and zooplankton composition. The sites are regularly flooded, eutrophic, and often shaded by surrounding vegetation. Cryptophyceae, Chrysophyceae and Euglenophyceae dominated the phytoplankton, while Cyanophytes were rare. Within the rich zooplankton assemblage (63 species), cladocerans and rotifers dominated. Correlation matrices and multivariate analyses indicated that shaded and relatively deeper sites had lower oxygen saturation and higher concentrations of PO 4 -P and NH 4 -N. Shade and relative depth correlated negatively with phytoplankton biomass and number of phytoplankton taxa, and positively with Cryptophytes and large cladocerans-thus indicating poor mixing, poor light availability and low fish pressure on herbivores. Decomposition of leaf litter increased oxygen consumption, while shade from terrestrial vegetation restricted photosynthesis and decreased oxygen production. Larger sites were more species-rich in phytoplankton and supported Euglenophyceae, green algae and rotifers.

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The diurnal vertical +gration (DVM) of the phytoplankton community was studied in a small (270 mZ), shallow (1.8 m), and frozen floodplain pool. Steep vertical gradients were detected in 02, NH;-N, NQ--N and P@-P profiles. The phytoplankton of the pool is characterized by year round dominance of Cryptophyceae: Cryptomonas curvata and Cryptomonas marssonii created more than 90% of total phytoplankton biomass during the time of study. DVM was studied by analysing vertical profiles six times duringa 24 hour cycle; samples were taken at 20cm intervals along the profiles. Koliella planktonica, the 'only nonmotile alga, showed a stable uniform distribution. Dinobryon divergens and Chrysococcus rufescens created a stable distinct concentration maximum at 40 cm. Unlike these three species, both Crypromonas spp. actively changed their position during the 24 hour cycle with distinctive evening downward and morning upward migration. The absence of filtering zooplankton excluded its influence on the patterns of phytoplankton DVM. The results showed the key role of PhAR (Photosynthetic active irradiance) in daypositioning of Crypromonas. Night-time uptake of phosphate andor ammonium at the bottom is probable, although direct evidence is lacking.

The stratification of two shallow and small pools, situated in a floodplain ecosystem, was investigated.A new methodological approach was applied. The parameter called summarized chemical and biological stratification (SCB), was derived from basic limnological parameters in order to evaluate the global intensity of chemical and biological stratification and to compare it with a thermal one.Three situations were described when the seasonal courses of thermal and SCB stratification were compared: 1. Both SCB and thermal stratification are present. 2. The water column is homogeneousthere is no stratification in the pool. 3. SCB stratification is present, but the water is homoiothermic. The thermal stratification is very unstable because of the small volume of the pools and frequent floods. The SCB stratification is of higher stability and it may persist in a homoiothermic water column. In comparison with temperate deep lakes, the thermal stratification does not play such an important role in initiating the chemical and biological stratification. The surfacekolume ratio and the depth in the pools are lower, which cause the "bottom-initiated" quick renovation of stratification even in homoiothermic water.The differences in oxygen regime, volume and localization of both investigated pools cause the differences in stratification patterns. Frequent oxygen depletions in one of the pools increase the intensity of stratification and influence its character. The anaerobic conditions lead to steeper gradients of basic nutrients, pH, alkalinity and water color.The occurrence of a unique phytoplankton community (Cryptophyceae) is probably closely related to the described stratification patterns.