The southern limits of the Zagros Mountains (Iran) include various aquatic habitats ranging from cold purely fresh to warm saline springs, many of them in isolated watershed basins. Diverse habitats could be correlated with morphological variation in freshwater taxa, as in for example, highly variable patterns of setation in amphipods. We measured length and density of the setae on selected appendages in six species of Gammarus Fabricius, 1775 collected from 14 locations (two species being sympatric) and tested for correlation with seasonal mean water temperature, dissolved oxygen, salinity, and pH of their respective habitats. The results were analyzed using analysis of variance, linear model, and correlation analysis. These regions showed significant variation in the selected ecological factors, and the species had significantly different patterns of setation. It may be supposed that increasing setation in gammarids can improve ventilating activity and hence their respiratory efficiency at higher temperatures and salinity conditions. This correlation may reflect selective pressure on the speciation of gammaridean amphipods in the southern Zagros region.

The European eel (Anquilla anquilla) has been declining throughout its area of distribution, is addressed in several pieces of legislation, and is the target of extensive restoration efforts. Therefore, investigating and conserving natural eel habitats is urgently needed. Large, near-natural rivers have become rare in Europe but the Balkans host some of the extant examples. However, several Balkan rivers–among them the transboundary river Vjosa/Aoos of Albania and Greece–are under threat from planned hydropower constructions. This study synthesizes European eel catch data from four institutions and the results of a recent electrofishing survey. Population density and structure as well as habitat choice were studied at different spatial scales. We calculated densities for each meso-habitat (0–1303 ind./ha) and extrapolated these values across three different hydromorphological channel sections (meandering: 70 ind./ha, braided: 131 ind./ha, constrained: 334 ind./ha), resulting in an overall mean density of 168 ind./ha. Proposed hydropower plants would cut off about 80% of the catchment currently accessible and impact river sections downstream of the dams by disturbing hydrological dynamics. By linking study results to relevant legislation and literature we provide evidence-based data for water management decisions. We call for the Vjosa/Aoos to be protected in order to secure its outstanding conservation value.

AbstractAlong the Upper Danube, almost all former floodplain areas have been lost due to river regulation, large-scale land-use changes, and terrestrialization processes. In the Lobau floodplain near the City of Vienna, ongoing terrestrialization leads to a dramatic loss of aquatic and semiaquatic habitats. Although the ecological values of the remaining floodplain area, such as high productivity and high biodiversity, are widely acknowledged, the implementation of restoration measures is difficult. In urban environments such as the Lobau, planning and decision-making for floodplain restoration inevitably involves tradeoffs, uncertainties, and conflicting objectives and value judgments. Beyond ecological values, the main socioeconomic aspects are flood control, drinking water supply for Vienna, and recreation.The aim of this chapter is to present the current ecological situation and the major development tendencies of the Lobau floodplain and to show the effects of potential management measures on the ecological situation.

This paper highlights the challenges of distilling generalizable principles and guidelines for sustainable co-management arrangements and demonstrating the practical impact of the underlying research. We explore the complexities of multicountry, socio-ecological research and address the challenges of moving beyond pure research to engage with the science-policy- practice interfaces. Growing demand for such applied research by official funding agencies is linked to the requirements of policy relevance and ` research impact'. Successful applied research requires ongoing user engagement throughout a project, which is often hard to achieve, especially when diverse stakeholders have sharply different power, knowledge and interests. The arguments are exemplified by our personal experience on such a complex project. Clear impact agendas could be useful for strengthening efforts to achieve transdisciplinarity but research applications should not be penalised on account of inherent potential uncertainties and risks.

Summary Metacommunity ecology predicts the relative importance of environmental and spatial processes in the structure of species assemblages. Such processes may act differentially on subsets of the community characterised by specific traits. To gain a deeper insight into these mechanisms, we supplemented a common method of studying metacommunities with an analysis of individual species and their traits. River floodplains are challenging environments for metacommunity analysis due to their spatial heterogeneity, temporal stochasticity and configurations of the networks of waterbodies. An analysis of aquatic gastropods showed that both environmental and spatial factors had significant influence. Within the spatial variables tested, the configuration of the floodplain network upstream of a sampling site was particularly important. An analysis of individual species revealed that traits related to niche breadth and drift propensity were significant for structuring the assemblages: species with a broad niche width (i.e. generalist, or neutral species) and a high drift propensity were governed more by the spatial configuration, whereas environmental conditions mainly determined the distribution of specialists having traits that prevented drift. These results can be interpreted as a trade‐off between habitat specialisation and colonisation ability: specialists succeed locally due to competitiveness and a strategy of reducing risks by preventing drift, whereas generalists may succeed regionally due to a strategy of spreading risks, by high levels of reproductive output, dispersal rates and adaptability. Our findings have implications for schemes to restore river floodplains that affect the aquatic network, with subsequent effects on community assembly and thus on biodiversity.

Disease outbreaks constrain aquaculture development. Knowledge on the potential risks of pathogens to farmed fish can help in designing management strategies for increased aquaculture productivity and sustainability. This study compares the helminth infections in reservoirs and therein operated cages as well as earthen fish ponds and the feeding stream in order to assess the significance of life cycle style and water sources in parasite transmission. In addition field experiments were setup to determine loading time and transmission rate. From 650 fish examined, 8 helminth species were recorded (3 from caged- and all 8 from pond-raised fish). The parasite community was dominated by trophically-transmitted species in both culture systems indicating the importance of trophic pathway in helminth transmission. The occurrence of trophically-transmitted helminths in caged-fish was positively related to their prevalence in reservoir-dwelling hosts indicating the importance of water supply in spread of helminths. The prevalence in pond-raised fish was higher than in stream-dwelling ones suggesting the presence of local sources of infective stages within ponds. Risk assessment revealed that monogeneans are high-risk parasites while heteroxenous helminths pose low to negligible threats to farmed fish. Although, cages appeared safer to heteroxenous parasites than ponds, their location in the water body, especially the distance from shores and depth is critical.

The infection dynamics of the gill monogeneans Cichlidogyrus tilapiae and C. sclerosus on Oreochromis niloticus with respect to habitat type (reservoir, stream, ponds and cages), host sex, size and seasons was determined between January and November 2008. During the study period, 45.2% of the 650 fish examined were infected with Cichlidogyrus spp. The infected hosts harboured an average of 8.6 ± 3.4 parasites/fish. Across habitat types, the proportion of infected fish was not statistically different. In contrast, the number of parasites recorded on infected fish from different habitat types differed significantly. The highest parasite number was recorded in reservoir-dwelling fish and lowest in stream-dwelling hosts. Concerning sex, more female O. niloticus were infected and harboured a high number of parasites than male and sexually undifferentiated fish. A weak negative relationship was found between rainfall and monthly parasite infections. However, a higher number of parasites and proportion of infected hosts were found during dry than in wet seasons, except in ponds. Results of this study show that differential exposure due to changes in fish behaviour associated with habitat modification and sex may account for the infection difference across the sampled sites. Meanwhile, rainfall and the associated hydrological events are important factors regulating monogenean infections in tropical aquatic environments. The continuous presence of Cichlidogyrus spp. in fish provides evidence of possible parasite outbreaks, indicating the application of biosecurity measures as crucial for the success of intensive fish farming.

The Lobau near Vienna used to be a dynamic floodplain which was cut off from the Danube River in the course of regulation measures in the 19th century. In order to compensate for deficits in the water budget, a water enhancement scheme for the upstream part of the floodplain, the Obere Lobau, was initiated in 2001. The aims of this scheme were to increase water levels in the floodplain and to discharge nutrients from the area's highly eutrophic water bodies by imposing a controlled surface water exchange through the main side arm. Our study evaluates the effects of this artificial water supply on the hydrological and trophic state of the backwaters.The effects of the water enhancement scheme were partly overlaid by the impoundment of the Danube after the construction of a power plant. Both the artificial water enhancement and the Danube impoundment improved the hydrological and trophic condition of the backwaters through an increased surface or sub-surface water supply. In addition, the water enhancement scheme provided a surface water exchange through the chain of backwaters, creating uniformity among the connected water bodies and leading to a significant decrease in temporal variability. However, spatial and temporal restrictions in the scheme ensured that the individual backwaters could maintain their specific biogeochemical character. Our long-term observations of mitigation effects in degraded urban wetlands demonstrate the need for a steady and well controlled water supply in order to achieve successful long-term maintenance of such systems. (C) 2011 Elsevier B.V. All rights reserved.

The paper summarizes current knowledge upon taxonomy and distribution of the freshwater Gammarus Fabricius, 1775 in Iran. Based on the literature data, 24 species were recorded so far from the fresh waters in the country. Revision of previously published materials including type collections, and analysis of new materials, revealed presence of 18 valid freshwater Gammarus species in Iran (G. anodon, G. bakhteyaricus, G. baloutchi, G. crinicaudatus, G. hegmatanensis, G. komareki, G. lacustris, G. lobifer, G. loeffleri, G. lordeganensis, G. paricrenatus, G. parthicus, G. pretzmanni, G. pseudosyriacus, G. sepidannus, G. shirazinus, G. sirvannus and G. zagrosensis). Among the remaining six species, three (G. arduus, G. laticoxalis, G. syriacus) were reported as a result of misidentification and further three (G. miae, G. plumipes, G. projectus) appeared to be junior synonyms of other already described species. Distribution ranges of most of the species are restricted usually to only few localities in the mountainous terrain, so they may be treated as Iranian endemics. The only exceptions are: G. lacustris (widely distributed in Holarctic, with only few populations in Iran), G. komareki (widely distributed in the Balkan Peninsula and Asia Minor, in Iran recorded from the entire Alborz region) and G. pseudosyriacus (widely distributed in Asia Minor, in Iran found in the entire Zagros region). A brief remark on taxonomy of each species is presented, with emphasis on misidentifications, synonymies and similar species, supplemented by distribution data, and ecological details if available. An identification key for the freshwater Gammarus of Iran is provided.

Despite the prospering results emerging from some recent works on Iranian amphipod fauna, continental waters in the south-east edges of the Zagros Mountain ranges had not been investigated for gammarids before. This paper introduces two new epigean species, G. shirazinus and G. loeffleri, distributed in many running waters of four catchment areas in a broad region in the south of Iran. The most important ecological features of the habitats of these species in comparison with previously studied gammarids are higher water temperature and salinity, and lower dissolved oxygen in their habitats, coinciding with decreasing elevation. A comparison of the ultra-structure of the cuticle of the head capsule by scanning electron microscopy between these two new species, and some other species is given. A detailed species description is provided. In addition, the geographical and ecological range of the new species is discussed.

Current shifts in ecosystem composition and function emphasize the need for an understanding of the links between environmental factors and organism fitness and tolerance. The examples discussed here illustrate how recent progress in the field of comparative physiology may provide a better mechanistic understanding of the ecological concepts of the fundamental and realized niches and thus provide insights into the impacts of anthropogenic disturbance. Here we argue that, as a link between physiological and ecological indicators of organismal performance, the mechanisms shaping aerobic scope and passive tolerance set the dimensions of an animal’s niche, here defined as its capacity to survive, grow, behave, and interact with other species. We demonstrate how comparative studies of cod or killifish populations in a latitudinal cline have unraveled mitochondrial mechanisms involved in establishing a species’ niche, performance, and energy budget. Riverine fish exemplify how the performance windows of various developmental stages follow the dynamic regimes of both seasonal temperatures and river hydrodynamics, as synergistic challenges. Finally, studies of species in extreme environments, such as the tilapia of Lake Magadi, illustrate how on evolutionary timescales functional and morphological shifts can occur, associated with new specializations. We conclude that research on the processes and time course of adaptations suitable to overcome current niche limits is urgently needed to assess the resilience of species and ecosystems to human impact, including the challenges of global climate change.

This study evaluated the effects of a controlled surface water connectivity scheme on several backwaters in an urban floodplain within the city limits of Vienna, the Upper Lobau. A phosphorus budget and ecosystem metabolism measurements were used to assess the reaction of two trophically distinct floodplain backwater sections on changed connectivity conditions. The surface water connection led to a reduction of the retention times in the backwater system. The water column nutrient concentrations in the individual backwater sections approached those of the source water body. The significance of these effects, however, depends on the historical and current trophic situation of the respective water bodies. Generally, the surface water connectivity introduced particulate phosphorus export up to 30% increase over the influent loading and dissolved phosphorus up to 14% increase over the influent loading. However, in sections with submersed macrophyte development, which provided enhanced filtering capacities for particulate matter, sediment and phosphorus accumulation rates were increased. At the same time, water transparency increased resulting in a positive feedback supporting further macrophyte development. Based on these findings, the evaluation of restoration measures in urban floodplains needs to consider the spatial and temporal dynamics of nutrients and ecosystem processes such as gross primary production and community respiration to predict long-term development.

Navigation alters the ecology of large inland waterways via engineering and more directly by emission of hazardous substances and wave wash. We investigated the potential effects of the latter on the early life history stages of riverine fish, which have their nursery zones generally located in shallow areas with low current and higher water temperatures. Ship induced wave wash causes the following impacts on fish during their early life history stages: i) short-term dislocation of suitable larval and juvenile fish habitats due to wake and splash; ii) water velocities during ship passages frequently exceed maximum swimming performances of 0+fish; and iii) suspended solids concentrations in the inshore habitats increase dramatically and limit the foraging efficiency of young of the year fish (YOY).In situ conditions during ship passages were investigated in three different inshore zones of the Austrian Danube with respect to wake and splash patterns, changes in water velocity and turbidity. These navigation induced conditions in the main nursery zones of riverine fish were set in comparison to results on swimming performances and capacities of larval and juvenile fish obtained in experimental studies.Engineering in large river systems in Europe and USA has resulted in a strong reduction of natural shoreline structures. Within this altered situation, navigation induced wave wash has a strong and cumulative effect on riverine fish recruitment and, hence, contributes to the general ongoing decline of native fish stocks in inland waterways. These aspects require particular consideration in river restoration programs to mitigate the effects of navigation, especially with respect to the intended expansion of European water ways within EC projects like TEN-T and NAIADES.

Gammarus zagrosensis n. sp. and Gammarus sepidannus n. sp., both from Gammarus pulex–group, are described from Sepidan County, Fars Province. They inhabit mountainous springs and were found co-occuring in some localities. Many clear morphological differences were recognized, including the setation of the second antenna and pereopods, length of antennal gland cone, postero-inferior protruding lobe and postero-distal corner setation in the basis of P6–7, endopodite/ exopodite ratios of uropod 3, dorsal elevation of urosomites, and setation of lower distal margin of epimeral plates 2 and 3. Gammarus zagrosensis is distinguished from G. pseudosyriacus by having setae on the distal segments of pereopod 5–7, a less pointed epimeral plate 2, posterior-inferior corner setae, and the longer setae on uropod 3. The closest species to G. sepidannus are G. balutchi and G. lobifer, the most evident differences of which are the eye size, setosity of first antennal peduncles and flagellum of second antenna, length of gland cone, and uropod rami length ratios. Comparison of the head cuticular micro-structures gives more arguments for separating the two new species from each other, as well as from the previously studied, related species.

The impact of the Kihansi Dam on electrical conductivity, pH, temperature and dissolved oxygen in the Kihansi River was assessed in 2005 after 85% of the original river flow had been diverted to the Lower Kihansi power plant. The results are compared with the data obtained in 1995 before the dam was constructed. Primary production and nitrogen and phosphorus concentrations from sites upstream and downstream of the dam as well as in the reservoir were compared. Phosphorus fractions were determined in the reservoir's sediment. Electrical conductivity and pH values were higher in 2005 than in 1995, whereas oxygen concentrations were lower. Primary production, nitrogen and phosphorus concentrations were lower at stations downstream of the dam than at upstream stations. High fractions of iron- and manganese-bound phosphorus in the reservoir sediment suggest a potential for phosphorus retention. Concentrations of nitrogen and phosphorus along the Kihansi River were higher during the dry season than in the wet season. These results contribute to the documented baseline data on environmental changes in tropical river systems after flow diversion and reservoir development.

Summary 1. Side‐arms connected to the main stem of the river are key areas for biogeochemical cycling in fluvial landscapes, exhibiting high rates of carbon processing. 2. This work focused on quantifying autochthonous and allochthonous carbon pools and, thereby, on comparing transport and transformation processes in a restored side‐arm system of the River Danube (Regelsbrunn). We established a carbon budget and quantified carbon processing from March to September 2003. In addition, data from previous studies during 1997 to 1999 were assessed. 3. Gross primary production (GPP) and community respiration were estimated by diel oxygen time curves and an oxygen mass balance. Plankton primary production was determined to estimate its contribution to GPP under different hydrological conditions. 4. Based on the degree of connectivity, three hydrological phases were differentiated. Most of the organic matter, dominated by allochthonous carbon, was transported in the main channel and through the side‐arm during floods, while at intermediate and low flows (and thus connectivity), transformation processes became more important and autochthonous carbon dominated the carbon pool. The side‐arm system functioned as a sink for particulate matter [total suspended solids and particulate organic carbon (POC)] and a source of dissolved organic carbon (DOC) and chlorophyll‐ a . 5. Autochthonous primary production of 4.2 t C day −1 in the side‐arm was equivalent to about 20% of the allochthonous inputs of 20 t C day −1 (POC and DOC) entering the area at mean flow (1% of the discharge of the main channel). Pelagic photosynthesis was generally high at mean flow (1.3–3.8 g C m −2 day −1 ), and contributed up to 90% of system productivity. During long stagnant periods at low discharge, the side‐arm was controlled by biological processes and a shift from planktonic to benthic activity occurred (benthic primary production of 0.4–14 g C m −2 day −1 ). 6. The transformation of the organic matter that passes through the side‐arm under different hydrological conditions, points to the importance of these subsystems in contributing autochthonous carbon to the food web of the main channel.

This chapter contains sections titled: Introduction Geomorphology and Patch Dynamics Creating Retention Zones Retention, Hydraulics and Physiographic Conditions Habitat Conditions for Characteristic Biota Retention and Water Column Processes The Significance of Retention Zones for the River Network Implications for River Management References

Due to human impacts, floodplains in urban regions are often simultaneously affected by eutrophication, loss of hydrological dynamics and even land use change. In order to mitigate some of these effects in a degraded floodplain within the city limits of Vienna, the "Dotation Lobau" a water enhancement scheme, was initiated in 2001. The present contribution demonstrates the effects of surface reconnection, with a low discharge (mean 0.2 m(3) s(-1)), on the phosphorus budget, by comparing connected and isolated backwaters. The surface water supply resulted in a decrease of mean trophic levels due to a decreased hydrological retention time and the establishment of a transport phase (phosphorus output). Furthermore, the study indicated that primarily sediment-associated processes, such as the accumulation or release of phosphorus, will influence the long term development of the floodplain.