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The Danube is the second-longest river in Europe that is subjected to various man-made alterations, including those related to hydro-power plants. We surveyed and analyzed the presence and abundance of macrophytes in the main channel from 2582 river kilometers (rkm) to 171 rkm. We also assessed selected habitat parameters in the sampled river stretches. Sixty-eight different plant species were recorded along the entire course. Among neophytes, we found Elodea nuttallii, E. canadensis, Vallisneriaspiralis and Azolla filiculoides. Based on similarity analysis, we distinguished 15 plant communities, most of which were defined as associations, which were classified into 5 alliances and represented three vegetation classes, namely vegetation of rooted hydrophytes Potamogetonetea, the vegetation of pleustophytes Lemnetea and vegetation of marshes Phragmitetea. The number and abundance of plant species, as well as plant communities recorded in single stretches, varied along the course. Canonical correspondence analysis (CCA) revealed that environmental parameters explained 21% of plant species composition. CCA runs with neophytes explained 41% of the variance, and current velocity, water transparency, species number and bank structure were significant variables. The present study revealed that the free-running sections of the river are poor in number and abundance of plant species, whereas impounded reaches mainly show an opposite result.

Anthropogenic impacts on carp pond environments have increased over the last 100–150 years in Central Europe. Present semi-intensive carp pond management combines natural food resources, supplementary feeding and additional intensification measures such as manuring, liming, and winter and summer drainage. Despite increased eutrophication and fish stock pressure, many carp ponds still serve as habitats for threatened biota, including macrophytes. Both the ecologically essential role of aquatic macrophytes and the impacts that reared fish may have on them have been repeatedly reported in the literature; however, information is scattered and there exists no multidisciplinary synthesis of knowledge of fish farming and plant interactions for European carp ponds. In this review, we show that macrophytes from different ecological groups have specific demands regarding optimal ecological conditions (e.g. pH and trophy level); hence, they can act as indicators of a water body’s ecological status. Nevertheless, the overall ecological ranges of many species (i.e. the limits enabling their survival) remain rather broad. Moreover, interactions between the different elements within carp pond ecosystems are complex and change rapidly, facilitating the co-existence of macrophytes with contradictory ecological demands. As the literature suggests, carp ponds may play a role in biodiversity protection that is just as important (or even more so) than that of natural wetlands. Sustainable, environmentally friendly carp pond management is undoubtedly the best means of preserving the unique natural and cultural value of these aquatic ecosystems for the future.

This study was carried out in the Bucegi Natural Park, a protected area of the Romanian Carpathians. It aims at documenting the potential sensitivity of six widespread Natura 2000 habitat types and of all plants with conservative value (200 taxa) in the mountain area, to the changes in temperature and humidity, predicted for this century. Regional expert knowledge and environmental indicator values were considered in assessing the potential habitat’s sensitivity. The results support the evidence that sensitivity to temperature may be potentially higher for habitats at alpine and subalpine levels (bushes and grasslands) and medium for forest habitats. Sensitivity to moisture was detected as potentially high for forest habitats and as medium for bushes and grasslands at high mountain elevation. Microthermophilic plants have shown a greater share (76-79%) in alpine and subalpine communities, and the hydrophilic plants (86-96%) in forest communities. About 80% of plants of conservation value (microthermophilic or hydrophilic plants) may be potentially sensitive to predicted warming and drought and 44% of them (microthermophilic and hydrophilic plants) to the changes of both parameters. Climate scenarios (2011-2100) and sensitivity maps (Sat – image interpretation with GIS for the whole mountain area) are included.

© 2018 We hypothesize that the physical features of river habitats and anthropogenic hydromorphological alterations influence macrophyte communities and lead to habitat fragmentation. Sampling included 1081 contiguous survey units positioned in the main channel and side arms along 588 km of the Danube River, along its middle course. To identify habitat fragments, Multivariate Regression Tree analysis (MRT) was applied on macrophyte and environmental data. Indicator species analyses were combined with MRT. To identify habitat fragments on a scale larger than final MRT groups, we set thresholds for an MRT complexity parameter. We identified 20 fine, 7 medium, and 3 large scale habitat fragments. Damming was the main fragmentation agent. Macrophyte communities show continuous variation at all scales of habitat fragmentation. High species diversity indicates major anthropogenic alteration of the river's hydrology and decline of the natural riparian zone. Future studies of the macrophyte communities, and their habitat fragmentation must include more factors (e.g. nutrient status, physicochemical quality of the water, etc.), as well as assessment of the importance of tributaries.

Our objectives were to offer insight into the characteristics of the physical environment in the River Danube in Serbia; and to show the relationship between selected environmental factors and the composition and abundance of macrophyte species. The macrophyte survey method followed the European Standard EN 14184, applying Kohler’s five-level descriptive scale. Principal component analysis was carried out to examine the variation in aquatic vegetation, and to analyze the effect of environmental variables on the aquatic vegetation, redundancy analysis was used. To build a simpler model with fewer explanatory variables, yet sufficiently explaining species variability, forward selection of environmental variables was done. Our results confirmed that physical environmental factors significantly influence the establishment and structure of macrophyte vegetation, with the level of hydrological connectivity to the main river channel being the most important, followed by the transparency of the water column, sediment texture and water-flow velocity. In order to inspect the individual relation between best-fitted plant species and each of selected environmental variables, Spearman’s rank correlation coefficients were calculated. We have distinguished plant species with preferences to specific combinations of analyzed factors. Our results provide a background for future, more specific studies on the macrophyte/habitat relationship. https://doi.org/10.2298/ABS160516116V Received: May 16, 2016; Accepted: June 21, 2016; Published online: October 31, 2016 How to cite: Vukov D, Ilic M, Cuk M, Igic R, Janauer GA. The relationship between habitat factors and aquatic macrophyte assemblages in the Danube river in Serbia. Arch Biol Sci. 2017;69(3):427-37.

The Lobau wetland and oxbow ensemble is part of the large Danube River floodplain area between Vienna (Austria) and Bratislava (Slovakia). The Danube River regulation scheme implemented in the late 19th century considerably affected the Lobau area, which is part of the Danube National Park today. Terrestrialization processes in the floodplain started with the river regulation and pose an increasing threat to the aquatic and wetland vegetation of this ecosystem. Former vegetation studies were either directed toward phytosociological description of associations or to a general vegetation inventory and mapping, where transitions between vegetation types are not accounted for. Our purpose is to provide a detailed insight into the vegetation zonation pattern along the aquatic-terrestrial inundation gradient in the Lobau floodplain area. We sampled a total of 49 belt transects. Samples in each transect were classified into groups using two-way indicator species analysis (TWINSPAN). Resulting groups of all transects were subjected to fuzzy c-mean clustering (FCM), defining ‘community types’ by means of indicator species analysis (ISA). We found 36 significant indicator species typifying 14 community types. Nine types belong to the shoreline vegetation and five types characterize the aquatic habitats. In addition to these community types, two transitional zones were found, one defined as open water/wetland transition and one as wetland/upland transition. Along the aquatic-terrestrial environmental gradient, different floristic and quantitative relations of community types and transition zones were identified. Finally, the importance of such a fine-scale description of zonation patterns along the inundation gradient is discussed in relation to long-term monitoring programmes as the basis for rehabilitation or wetland conservation measures.

There is general agreement among scientists that global temperatures are rising and will continue to increase in the future. It is also agreed that human activities are the most important causes of these climatic variations, and that water resources are already suffering and will continue to be greatly impaired as a consequence of these changes. In particular, it is probable that areas with limited water resources will expand and that an increase of global water demand will occur, estimated to be around 35-60 % by 2025 as a consequence of population growth and the competing needs of water uses. This will cause a growing imbalance between water demand (including the needs of nature) and supply. This urgency demands that climate change impacts on water be evaluated in different sectors using a cross-cutting approach (Contestabile in Nat Clim Chang 3:11-12, 2013). These issues were examined by the EU FP7-funded Co-ordination and support action "ClimateWater" (bridging the gap between adaptation strategies of climate change impacts and European water policies). The project studied adaptation strategies to minimize the water-related consequences of climate change and assessed how these strategies should be taken into consideration by European policies. This article emphasizes that knowledge gaps still exist about the direct effects of climate change on water bodies and their indirect impacts on production areas that employ large amounts of water (e.g., agriculture). Some sectors, such as ecohydrology and alternative sewage treatment technologies, could represent a powerful tool to mitigate climate change impacts. Research needs in these still novel fields are summarized.

Intensively used urban water bodies are vulnerable to eutrophication. The shallow lake Alte Donau (Vienna) can be seen as an example for the extent of anthropogenic influence. Human impacts paired with changes in environmental conditions gave way to eutrophication processes in Alte Donau. Due to the great public interest restoration concepts and subsequently management programs were established. This chapter provides a synthesis of the key aspects to evolve and implement a successful water management plan. An attempt is made to generalise our specific solutions to serve as a basis for the development of similar strategies for other urban lakes.

Seasonal and inter-annual macrophyte assemblage dynamics were surveyed in ten nursery and ten main fishponds stocked primarily with common carp Cyprinus carpio fry and with common carp being reared to market size, respectively. The results indicate a significant difference in macrophyte species number and abundance between the nursery and main fishponds, with up to 24.5% of the variation in macrophyte species distribution patterns explained by fishpond management type (nursery or main) and up to 6.7% by water transparency. Fish biomass used as a fish stock proxy explained up to 13.9% of variability. Although not significant, differences in species number and abundance were found (i) between spring and summer survey periods during the growing season with both species number and abundance usually decreasing in summer, and (ii) between years of the farming production cycle with a higher species number and abundance typically found in the first year of the farming cycle in the nursery fishponds. The results increase knowledge of fishpond macrophyte assemblages and may be of interest for conservation of aquatic habitats.

The complexity of water bodies in the eu-potamal river corridor and the main delta channels of the Romanian Danube is exemplified by the macrophyte vegetation. Two hypotheses provided the background for our study: (a) is the macrophyte vegetation of large, permanently connected branches significantly separated from that of the main river channel; (b) is the macrophyte composition of the Danube main stem significantly altered when the river divides into the three large navigable Delta channels. Water bodies considered were two contiguous sections of the main river channel, two large branches remaining from the historical floodplain, and the three main Delta channels. We quantified macrophyte diversity and floristic variation. Our data set was prepared from the MIDCC-project data base, in which macrophyte occurrence, abundance and habitat parameters are stored for contiguous survey units of the whole Danube river corridor. Field survey method followed that of Kohler and the European Standard EN14184. Results confirmed our first hypothesis: permanently connected side branches still support significantly different macrophyte assemblages, making them important indicators of floodplain connectivity. The diversion of the Danube into its three large navigable delta channels significantly alters the macrophyte vegetation from the c. 300 km of main stem up-river, substantially supporting our second hypothesis. Our results largely enhance the knowledge on aquatic plant biodiversity in the eu-potamal Danube, forming a solid base for long-term studies. We also discuss the relevance of our results regarding the ecological, as well as the conservational, quality of rivers and their floodplains.

A comprehensive understanding of the interplay between the natural environment and the human dimension is one of the prerequisites to successful and sustaining IWRM practises in large river basins such as the Upper Brahmaputra river basin or the Upper Danube river basin. These interactions, their dynamics and changes, and the likely future scenarios were investigated in the BRAHMATWINN project with a series of tools from remote sensing and geoinformatics. An integrated assessment of main components of the natural environment in the two river basins as well as in five reference catchments within those basins, has led to the delineation of hydrological response units (HRUs). HRUs are spatial units bearing a uniform behaviour in terms of the hydrological response regime, as a function of physical parameters land use, soil type, water, vegetation cover and climate. Besides the delineated HRUs which are available in a spatially exhaustive manner for all reference catchments, the following information were provided as spatial layers: (1) uniform digital surface models of both the twinned basins and the reference catchments; (2) glacier areas and the magnitude of glacier loss; (3) mountain permafrost distribution and identification of areas particularly affected by permafrost thaw; (4) a consistent land use/land cover information in all reference catchments; and (5) the vulnerabilities of wetlands and groundwater in terms of anthropogenic impact and climate change.

Water currents are among the strongest environmental variables determining the occurrence and/or abundance of aquatic plants and the European Water Framework Directive (WFD) considers river morphology and current conditions important aspects of reference conditions. We used the database of the Joint Danube Survey JDS-2, organised by the International Commission for the Protection of the Danube River (ICPDR, Vienna), to assess the relationship between water flow velocity and the occurrence and abundance of aquatic macrophyte to be species along the navigable reach of the Danube River. Species abundance was assessed in accordance with European Standard EN 14184-2003. Flow velocities were assessed close to the plant stands and estimated in 4 classes, worked out in earlier studies in combination with flow meter measurements, which is appropriate for the conditions in this large river. Statistical analysis revealed that only survey units with either no visible flow or those with fast flow were characterised by indicator species with high significance. Still water conditions or barely visible flow (flow class 1) were indicated by Potamogeton friesii , Nitellopsis obtusa and Trapa natans , and by Potamogeton perfoliatus , Potamogeton nodosus and Stuckenia pectinata . Lemna minor , indicative for flow class 1 as well, was detected in all the other flow classes, too: in all these cases it established its stands closely intermingled with other aquatic species. For survey units with slow (flow class 2) or intermediate flow (flow class 3). No statistically significant indicator species could be determined. The highest flow velocities (flow class 4) were significantly indicated by Fissidens rufulus , Cinclidotus fontinaloides and Cinclidotus riparius . Occurrence of aquatic mosses was also highly related to the Berger–Parker dominance index in NMDS analysis. In the same analysis, but towards the smallest flow velocities, the majority of vascular species and the Simpson diversity index were closely related. The spectrum of life forms was considerably reduced under medium and high flow velocity conditions. With regard to Simpson species diversity, our analysis indicates an agglomeration of diversity in the Middle Danube reach that includes the Iron Gates impoundment. Our results offer a first look at the macrophyte/water flow relationship of a very large river in Europe, the Danube.

The UNESCO Biosphere Reserve Lobau (Austria), established in 1977 within the city limits of Vienna, is part of the Danube National Park and one of the ecologically richest parts of the Danube River Corridor. Hardly noticed by diverging stakeholder interests the smaller aquatic habitats in the floodplain area are acutely threatened by wetland ageing and terrestrialisation processes. In 2007 an aquatic plant survey was carried out in the water bodies of the active floodplain on the left bank of the Danube main river channel as well as in the semi-separated water bodies of the Lobau. Results clearly show the impact of through-flow on aquatic plant species composition and abundance, as these metrics are significantly higher in the semiseparated location. Suitable water regime for all sensitive aquatic plants is an essential prerequisite for sustaining aquatic macrophyte diversity in the Lobau Biosphere Reserve, and could provide an ecohydrological basis for rehabilitation activities in other regulated river floodplains located in cultivated landscapes.

The Krka River is a lowland karstic watercourse with an extended underground hydrological net. Travertine cascades, blocks and dams in the riverbed influence the river flow and depth, creating a variety of habitats. The watershed landscape is a mosaic of agricultural and natural patches with some urban areas. Macrophyte and habitat survey was made on the whole river length. Macrophyte community consisted of 33 vascular plant species. Among them Ceratophyllum demersum, Myriophyllum spicatum, Potamogeton filiformis, P. natans, P. nodosus and Najas marina were abundant. RDA analysis distributed species and reaches of the river in three distinct groups. The first group comprises survey units from the source to the middle of the river, near the industrial city of Novo Mesto. The second group consists of survey units in the city, and the third group the units located from Novo Mesto. The importance of water flow, which is the highest in the upper part of the river, and the relation between sediment type and species colonizing habitats with lower flow velocities are clearly shown.

Ecological compensation structures in the reservoir of the Freudenau hydro-electric power plant (River Danube, Vienna, Austria) developed into habitats dominated by aquatic macrophytes. Ecological functioning of the macrophytes is documented by their attractiveness to several fish guilds, including the rheophilic group and by their ability to restrict phytoplankton growth. However, in comparison with different types of natural floodplain water bodies in the Danube River corridor, with other power plant reservoirs and with the free flowing reach of the Austrian Danube between Vienna and Bratislava the composition of the indicator species among the aquatic plants was significantly different, as proven by statistical analysis. This puts the compensation structures at an intermediate position between the macrophyte vegetation of power plant reservoirs without such constructions and certain floodplain water ensembles as well as the free flowing reach. Some similarities exist especially with respect to the distribution of growth forms of the aquatic plants. Based on these results it can be concluded that with regard to the Water Framework Directive such compensation structures may serve as a means to provide conditions to meet the “good ecological potential”.

The quality of the aquatic environment and macrophytes were surveyed in the case of the remarkable karstic river Ljubljanica s. lat. (Slovenia). It consists of seven intermittent and permanent surface watercourses, connected by groundwater flows. We assessed 11 parameters describing the land use beyond the riparian zone, the structure of the riparian zone and stream channel morphology, as well as the distribution and abundance of macrophytes. The intermittent watercourses exhibited a relatively high level of naturalness, because the variable water regime prevents intensive human activity. Greater influence of the human activity on the permanent watercourses resulted in a modified riverine environment. The share of different ecological groups of macrophytes, i.e. submerged, emerged and amphibious species, reflected the water regimes of the different watercourses. A total of 62 taxa of macrophytes were identified in about 100 km of length examined. Of these, amphibious macrophytes dominated as a consequence of intermittent water regime. The relationship between environmental parameters and macrophytes, and the effects of the intermittent hydrology were investigated. All environmental parameters explained 28% of the variance in the distribution of macrophytes in watercourses, as determined by canonical correspondence analysis. Completeness of the riparian zone, bank undercutting and sediment accumulation were found to be the most influential.

The current status of the aquatic vegetation in significant Tisza River oxbows is described. Aspects of dominance and possible problems raised by protected, but aggressively competitive, species are highlighted. The gap between some stakeholder interests and the needs for sustaining biological quality in the oxbows is indicated. Predictive GIS scenarios for the Csatloi oxbow, which is a natural sanctuary in the middle reach of the Hungarian Tisza, show the results of possible management strategies. Sensible ecohydrological planning, and focussing stakeholder interests on different reaches of the floodplain, without sacrificing flood protection, are presented as the solution to urgent problems of river restoration.

Jegricka is a typical lowland river in Vojvodina. The agricultural area surrounding the river has significant influence on its water quality, and on the aquatic vegetation, too, through different artificial measures and pesticides draining into the river. During the first year of investigations a 34 km long reach, between the villages Temerin and Gospodinci was surveyed. Fine inorganic material builds most of the flat slopes in the upper littoral, and detritus is the most common sediment type in the littoral zone, where aquatic macrophytes are growing. Flow velocity is very low. Transparency varied between 40 and 85 cm. Land use along the banks of the Jegricka is mainly agricultural crops. A total number of 22 aquatic species was recorded. The metric Relative Plant Mass, the species distribution pattern, and some ecological indicators were analysed.

Floodplain lakes are one of the most essential habitats for aquatic macrophytes in the modern cultural landscape. Their maintenance and support calls for ecohydrological strategies, as river development, enhanced flood control and other stakeholder interests may have negative impact on the present oxbow ecosystems. Three examples are given to present the situation of macrophytes in floodplain water bodies on the Danube, and the Tisza River. The importance of ecohydrology as a sustainable strategy and a look back to its sources in the Ecotone MaB program are presented. Finally conclusions point to regionalisation of planning goals as the solution for many aspects in floodplain water management.

This is a descriptive account of the impact of the Gabcikovo hydro-electric power plant (HEP) and other man-induced changes on the aquatic vegetation of the Szigetkoz area. Today the environmental complex of water bodies in the Szigetkoz supports 26 aquatic macrophyte species, which occur in the main river channel, and in different flood plain habitats. Prior to the construction of the Gabcikovo HEP almost no macrophytes existed in the main river channel. The HEP takes in most of the water today, reducing the discharge in the main river to a few hundred cubic-metres per second, compared with about 2000 m 3 .s -1 before. The water level has also decreased in the flood plain. Some parts of the channel and oxbow systems are irrigated through the complex Active Floodplain Water-Supply System (AFWSS), today. Several aquatic and amphiphytic species have invaded in the abandoned river bed and in shallow reaches with little flow or even stagnant character. Flood plain water bodies show a different successional development. In some side arm systems the lack of water has led to a near or full extinction of aquatic vegetation. Other parts, receiving compensation flow water by the AFWSS were transformed from marshlands to fully aquatic environments. Where algal production increased no macrophytes are present. Other water bodies have clear water, but only a few eutrophic species remain there, and in many survey units rare species have disappeared. A striking feature of the aquatic vegetation is the clumped distribution of many species: they develop large stands in some habitats, but they are not widely distributed over the whole water body system. The whole system is still in a state of change and the decrease in species richness may continue.

In Austria the character of the River Danube is dominated by the alpine-born tributaries, especially the River Inn, by a series of hydro-electric power plants, and by the traffic of large barges, mainly tug-pushed multiple barge units. As a consequence, transparency of the water is low due to the large load of suspended solids and wave action on the rip-rap-lined banks is strong. Under such conditions, a species-rich moss flora has developed predominantly in the upper reach of the Abwinden-Asten impoundment whilst phanerogams are more prevalent in the reach closer to the barrage. However, the plant mass development in this Austrian impoundment is much less than in comparable sections of the upper German reach.

This study has, for the first time made it possible to describe the aquatic vegetation of the Danube River on the basis of a unified methodology for field surveying, data processing and the display of results. Some features of species richness, species composition and dominance are presented. As the surveyed reaches of the river and the flood plain water body systems represent only a miniature section of the river a complete picture is far away, although surveys were made in all important parts of the Danube. Yet, some aspects are very clear and may not change much in any future, more detailed surveys. The total number of aquatic macrophyte species was high and made up of 4 charaphytes, 10 mosses and liverworts and 66 vascular species (only hydrophytes and amphiphytes were counted; filamentous algae and helophytes were excluded). The occurrence of mosses is almost exclusively restricted to the upper reach. With respect to species richness, habitats outside the main river channel such as side channels, oxbows, and artificial canals have an inherently high value. The occurrence of classical rheophilic species is rather limited in the main channel and last but not least, the frequency of Ceratophyllum demersum is surprisingly high for a species supposedly confined to still water habitats. All this information forms a new, and at least in part, unexpected picture of the aquatic flora of the largest river of Central Europe, the Danube.

Aquatic vegetation was surveyed in the main channel of the River Danube near Baja (southern Hungary) in the Gemenc National Park and in an irrigation and drainage canal system on the left bank of the river. The main river was species-poor, compared to the oxbows and the canals, in which more species and much greater plant mass developed. Characteristic features were identified with regard to Relative Plant Mass, a measure of dominance, and the Mean Mass Index, which indicates the distribution pattern of species in a system. This is the first quantitative survey, which may form the baseline for future comparative investigations of the development of the aquatic vegetation in this section of the River Danube.

South of Budapest an irrigation and drainage canal system extends from the left bank of the main river into the Kiskunsag area. The canals differ in size, discharge and salinity. Management includes mowing of aquatic vegetation and dredging. Macrophyte surveys were carried out in part of the main canal (Dunavolgyi-focsatornat), in the medium-sized Harmincas-Canal, and in the smaller Apaji-Canal. The main canal receives its water directly from the Danube River. Water flow is slow, there is no shading by riparian vegetation and the water is rich in nutrients, but usually clear. Water temperatures are relatively high in summer and are beneficial for species like Ceratophyllum demersum, C. submersum, Trapa natans, Cabomba caroliniana and Najas marina. For the first time a floristic-ecological characterization was possible for part of the canal system. The occurrence of the neophyte C. caroliniana, and the high species richness found in the canals make them interesting and valuable habitats for the aquatic vegetation, despite their anthropogenic origin.

The macrophyte vegetation of the eutrophic River Vils (Oberpfalz, Bavaria) was surveyed and mapped in summer 1999. Regarding carbonate content, the river is of medium to rather hard. The macrophyte diversity is relatively high. In the Vils 26 tracheophytic hydrophytes, 24 tracheophytic amphiphytes and 37 helophytic species were found. The picture is dominated by eutrophent elements like Potamogeton pectinatus, Ceratophyllum demensum, Sparganium emersum and others. Floristic specialities in the Vils are the hybrids Potamogeton x fluitans and Potamogeton x schreberi. The distribution diagram shows patterns for several species in the river course. According to changes in the floristic composition and river-morphological structures, the river could be divided into five reaches (A-E). These reaches were characterized regarding Relative Plant Mass (RPM) and species numbers as well as Mean Mass Index and Relative Range Length. The RPM values in combination with species numbers revealed important new aspects regarding biodiversity and the dominance of macrophyte species. Additionally the macrophyte distribution across the river was described by five transects.

Numerous hydro-electric power stations and their retainments form a characteristic feature of the upper reaches of the River Danube in Germany and Austria. The aquatic vegetation was assessed in one retainment, which is part of a contiguous set of five power plants. Three reaches were recognised in the impoundment based on characterstic species. In the upper part only rheophilic mosses and Ranunculus fluitans were present. In the middle reach one moss is still present and several new phanerogam species occur, but the plant mass is low. In the lower reach no mosses are present any more and phanerogams become very abundant. Upon comparison the latter situation is close to that found in reaches of the Danube (e.g. in Hungary) where the natural gradient of the river is much lower than in Germany.

The EU water framework directive (WFD) is intensively connected with other European legal regulations and supporting documents. This close interrelationship calls for deeper considerations when WFD is implemented in locations of high conservation value, e.g. Natura 2000 sites. A comprehensive, but specific comparison of the goals of WFD with the aims of habitats directive (HD) and birds directive (BD) provides a sensitive overview on their peculiarities, with an outlook on potential synergies and conflicts. The sometimes complex guidance for solving complicated situations in the practical application of these differing legal provisions is also described. The representation of requirements for Natura 2000 sites as part of river basin management plans, and related up-to-date experience are given special attention. Finally recommendations and conclusions provide the reader with a complete view of this challenging chapter in European Policy. In the end, considerably more synergies than conflicts are identified between the objectives of WFD, HD and BD. Whenever conflicts should arise these directives prevent derogating from their requirements by cross-references. Therefore, firm and timely coordination between water and nature conservation authorities is necessary.

In BRAHMATWINN the upper Danube river basin (UDRB) and the upper Brahmaputra river basin (UBRB) were selected as the representative catchments in two mountain-dominated geographical regions. Three test sites were selected in the UBRB: the Lhasa River catchment in Tibet/China, the Wang Chu river catchment in Bhutan, and the Assam reach of the Brahmaputra river. In the UDRB the Lech river and Salzach river catchments were studied. This chapter focuses primarily on the vegetation of wetlands, which are dynamic ecosystem elements, depending on their hydrological resources and thus prone to suffer from climate change impacts. Location, hydrological ecosystem functions (ESF), and ecosystem services (ESS) together with the vulnerability of wetlands were assessed.

A multi-model-based study was performed in order to unravel valuable fen meadow habitats' possible exposure to eutrophication, which is expected to occur as a result of the re-saturation of degraded peat soils. The framework was tested in a 3000-ha fen-drain system to be restored in the Middle Biebrza Basin (northeast Poland), where the datasets and related models were used to delineate prospective eutrophication hotspots and nutrient transport. A 1-d hydrodynamic model and a 3-d groundwater flow model were applied to constitute the hydrological response of the fen-drain system to the prospective construction and function of weirs and spillways, which are expected to induce the increase of groundwater levels in degraded fens. A groundwater particle-tracking postprocessor was applied to delineate flow pathways and discharge zones and to determine water residence time in modelled layers. Soil and habitat maps, a high-resolution digital elevation model and historic groundwater level observations were applied to the model performance, calibration and spatial analysis of prospective eutrophication hotspots where increased eutrophication of groundwater can be expected due to the re-saturation of degraded peat soils. The study revealed that the large-scale fen rewetting that occurred as a result of surface water bodies' damming can potentially result in groundwater-driven nutrient dispersion along with an enhanced nutrient transport from a fen to the adjacent water bodies. Spatial analyses showed that, although the rewetting-driven eutrophication of Molinia fen meadows located in the study area is not likely, one can expect increased nutrient discharges to adjacent drains, inducing the contamination of ox-bow lakes located along the rivers. We propose the presented methodology to be applied ex-ante to fen-rewetting projects in strategic environmental assessments of restoration projects in order to manage the potentially negative environmental consequences of fen and river eutrophication with special regard to nutrient hotspots that are likely to occur within the rewetted fens.

'Hydrology and Water Resources Development in a Vulnerable Environment’ is the topic of the current phase of IHP-V. To ascertain sustainable use of landscape resources, ecohydrological processes in the surficial environment must be studied. The objectives of Project 2.3 are the interactions between river systems, floodplains, and wetlands. The gap between hydrology and ecology must be closed to understand the hydrological cycle in different ecosystems and to gain more detailed information on the plant and animal communities that influence the flow of water and its contents. Project 2.4 aims at the comprehensive assessment of the surficial ecohydrological processes on a global scale. Through experimental research, flow of water, sediments, nutrients, and pollutants in different scales, climates and geographic regions must be studied. Non-structural measures for construction and management should be evaluated with respect to environmental quality enhancement, and water ecosystem vulnerability should be assessed. It is the incitement to collect hydrological and ecological data in a more balanced way. Efficient lines of research in ecohydrology start with getting to know the partner's concepts and to begin to think in the partner's scales. This will indicate the start of genuine integrated research with all partners joined in an interdisciplinary network.

In the flood-relief channel New Danube, waterplants are the visually dominant life-form, supporting a varied aquatic biota. Their positive ecological value is partly counteracted in public opinion by the restraint on recreational activities exerted by macrophytes. Formulation of a balanced management plan taking into consideration ecological values and the nutrient buffering ability of the waterplants, as well as the comfort of swimmers and surfers, was a major objective for research. Although it is a man-made channel, the aquatic macrophyte vegetation of the New Danube resembles closely that of other, more natural water bodies in the floodplains of the Danube in Austria. Species number and composition are briefly considered; more than 75 % of the species occurred regularly throughout eleven years of investigation (1987-1997). Macrophytes are a key factor in the phosphorus regime of the New Danube, competing with the phytoplankton for a limited supply of the nutrient and thus supporting a high water quality. Two severe floods resulted in considerable biomass reduction, but the aquatic plant stands recovered quickly each time, evidence of the high resilience potential for macrophyte growth in the New Danube. Estimated biomass for preceding years and initial biomass values for following years correlated well when inter-annual relationships were studied. Therefore, avoidance of over-controlling macrophytes by weed-cutting must be a major management objective, as intensive reduction could trigger a shift into an alternative state dominated by phytoplankton The result would be a substantially decreased water quality with numerbus negative features, including algal blooms and possible loss of animals such as fish.

Recording and assessment of aquatic macrophytes was a request for the Joint Danube Survey 2 (JDS2). New insight regarding occurrence, abundance and specific distribution of macrophytes was based on methodological adaptations better adjusted to the size of this large European river and permitted more appropriate statistical interpretation. Regarding the ecological status of sampling stretches, an intentional, preliminary way of interpretation is provided, respecting trendsetting new international literature. Due to longer river stretches recorded, a higher number of species was detected in JDS2. Each of the ten official river sections showed an individual character of the macrophyte vegetation. Results of JDS2 macrophyte survey are put in relation with international literature and side effects are discussed, which are of relevance when assessing macrophytes in large rivers for purposes of science, European Water Framework Directive or regarding conservation issues.

The detection of macrophyte-dependent ecotones, the characterization of different hydrological regimes and aspects of sports fishing activities were the main objectives studied in a backwater system of the River Danube in Austria. The macrophyte survey, a dynamic hydrological model and a socio-economic study were all part of the Austrian Ecotone Project. Conclusions were drawn from this database by GIS thematic map interpretation and overlay techniques. Significant transitions existed between stretches of macrophyte vegetation as far as species number and plant mass are concerned. These transitions can be attributed as macrophyte-dependent aquatic/aquatic ecotones. Some plant species and the structural diversity of the aquatic vegetation were found to be characteristic for backwater reaches with different hydrological regimes. In contrast to a hypothesis worked out earlier in the ecotone project the GIS overlays revealed spatial coincidence between the centres of sports fishing activities and survey stretches with high densities of macrophyte vegetation.

This chapter deals with several potential effects of climate change, addressed to Natura 2000 habitats from the following categories: woodlands, grasslands, brushwoods, rocky habitats, coastal and dune habitats, surface water habitats, peat bogs and moorlands. For these categories seven impact classes were identified: seasonal impact, sea level rise, hydrology, soil, extreme events, CO2 concentration, cumulative effects that change the quality of environmental conditions. The chapter provides information and examples regarding the actual and anticipated types of impacts on Natura 2000 habitats and underlines some trends which can be predicted for the future.

Climate change impacts biota from individual level to whole habitats. Changing regional climate conditions let individuals be more prone to catastrophic disturbances (e.g. disease, insects, or fires). Climate change exposures and the sensitivity of species and habitats against these exposures can be used to assess the potential impacts on habitats. The exposure was evaluated in terms of “magnitude of changes” by comparing climatic conditions from the past to the future during the vegetation periods. The sensitivity included the ecological envelope of the habitat by assessing indicator values based on the species composition, and the regional expert-knowledge evaluated different criteria ranging from regeneration or distribution to invasive species. If-then rules combined the exposure magnitudes with the sensitivity categories to potential impacts. Results are presented for the Alpine, Continental and Pannonian biogeographical region. Freshwater habitats, raised bogs and mires and fens, as well as forest are most sensitive, whereas the very specialised azonal rocky habitats show the lowest sensitivity. Highest impacts can be expected in the dormant season of the vegetation period. Utilising categories and rules for the assessment of impacts instead of modelling approaches has the advantage of a simple framework transferrable to other biogeographical regions.

The implementation of adaptation actions in local conservation management is a new and complex task with multiple facets, influenced by factors differing from site to site. A transdisciplinary perspective is therefore required to identify and implement effective solutions. To address this, the Inter- national Conference on Managing Protected Areas under Cli- mate Change brought together international scientists, conservation managers, and decision-makers to discuss current experiences with local adaptation of conservation manage- ment. This paper summarizes the main issues for implementing adaptation that emerged from the conference. These include a series of conclusions and recommendations on monitoring, sensitivity assessment, current and future management prac- tices, and legal and policy aspects. A range of spatial and temporal scales must be considered in the implementation of climate-adapted management. The adaptation process must be area-specific and consider the ecosystem and the social and economic conditions within and beyond protected area boundaries. However, a strategic overview is also needed: management at each site should be informed by conservation priorities and likely impacts of climate change at regional or even wider scales. Acting across these levels will be a long and continuous process, requiring coordination with actors outside the ''traditional'' conservation sector. To achieve this, a range of research, communication, and policy/legal actions is required. We identify a series of important actions that need to be taken at different scales to enable managers of protected sites to adapt successfully to a changing climate.

Climate change is one of the most severe threats to the environment in this century. Its possible effects on the aquatic vegetation in river and floodplain habitats are described by relation to carbon dioxide, temperature, precipitation and water discharge, as well as species migration and alien aquatic plants. Potential conflicts between river restoration and habitat conservation are briefly explained. Sensible solutions need approaches that include ecohydrology principles and mediate between diverging stakeholder interests.