Trace element bioaccumulation in benthic organisms is important part of aquatic environment pollution research, since water and sediment analysis itselfs do not provide significant information about bioavailability of contaminants and the results mostly shows just current pollution at the time of sampling. This study focuses on urban streams contamination which are currently significant source of trace elements. Botic stream was chosen as exemplary, because it is affected by many combined sewer system overflows which are sources of contamination in times of heavy rain and flood. Load several sampling took place on 10 stream sites during the year of 2012. This thesis deals with 11 trace elements concretelly Cd, Co, Cr, Cu, Hg, Ni, Zn, As, Fe, Pb and Al. Trace elements were assessed in both benthic organisms and sediment. As well taxons were selected from benthic organisms, which are widely found at any time of the reference year: caddisflies of family Hydropsychidae, leeches Erpobdella sp. and mayflies of Baetidae family. Sediment analysis included sequential extraction which divided trace elements into 4 fractions according to mobility. Based on the results, bioavailability was assessed on observed elements and correlation between concentration in bethos and sediment was tested. Finally, impact of...

The thesis deals with the status assessment of the stream in urban areas. The study area is the stream Rokytka in Prague. The method Hydroecological monitoring HEM (Langhammer, 2007, 2013) was used for the thesis based on field hydromorphological survey. This method is compatible with the Water Framework Directive 2000/60/EC. The thesis also includes assessement of the rainoff regime and water quality based on the available hydrological and hydrochemical data. As a final result, it was found out the stream Rokytka achieves III. hydromophological state - average state. The water quality state does not meet the requirements of the environmental standards quality. In the urban landscape, it is necessary to find a suitable compromise between flood protection and good environmental conditions. Powered by TCPDF (www.tcpdf.org)

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Rivers and their catchments are under mounting pressure from direct channel modification, intensification of land use, and from a legacy of decades of channelisation. Recent legislation, in the form of the EU Water Framework Directive, places a greater emphasis on the management of water bodies as holistic systems, and includes the explicit consideration of hydromorphological quality, which describes the hydrologic and geomorphic elements of river habitats. These are defined specifically as hydrological regime, river continuity and river morphology. This appreciates that sediment and flow regimes, along with the channel structure, provides the 'template' on which stream ecological structure and function is built. Invertebrate fauna contribute significantly to the biodiversity of rivers, and often form the basis of monitoring river health. However much of the fundamental ecological knowledge base on the response of invertebrates to hydromorphological change needed to make informed decisions and accurate predictions, is either lacking, inadequate or contradictory. This thesis addresses some of the key potential shortcomings in recent bio-assessment that others have alluded to, but which have rarely been explored in the context of direct channel manipulations. By using two case studies of, realignment in a natural upland catchment, and flood protection engineering in an urban stream, this study investigates the sensitivity of hydromorphological impact assessment methods that rely on biodiversity patterns of benthic riverfly (Ephemeroptera, Plecoptera and Trichoptera) larva. This work employed widely used biomonitoring indices of benthic riverfly larva abundance, species richness, alpha and beta diversity, and community composition, applied over a range of spatial scales, in combination with spatially contemporaneous physical habitat data, to describe and explain community changes in response to disturbance, and patterns of natural variation. The effects of restoration were investigated using a high degree of sample replication within channels and across the wider catchment, as well as contrasting spring and autumn seasons. To assess change in a small urban channel, approaches that explicitly consider spatial elements of community data, using spatial eigenvectors analysis, were applied to spatially detrend community data and directly investigate spatial patterns. Restoration of the Rottal Burn was found to be successful in restoring habitat diversity and geomorphic processes, and in turn increasing reach scale species richness and beta diversity through the gradual arrival of rare and specialist taxa into novel habitats. Catchment scale replication revealed high variation in diversity indices of modified and undisturbed streams, and a strong temporal pattern related to antecedent flow conditions. Channels with greater habitat heterogeneity were able to maintain high gamma diversity during times of high flow stress by providing a number of low flow refuges along their length. The urban Brox Burn had surprisingly high riverfly richness and diversity driven by small scale hydraulic heterogeneity, created by bed roughness resulting in a range of microhabitats. Riverfly community responses to direct channel dredging could not be detected by measurements of average richness and diversity, however distinct changes were seen in gamma diversity, the identity of community members and their arrangement among sample patches. Impacts of sediment pollution release due to engineering were short lived and apparently had little detrimental impact on biodiversity. Strong spatial patterns of community assembly on the stream bed were uncovered, relating to longitudinal, edge and patchy patterns. Significant habitat drivers of community composition were confounded by high amounts of spatial autocorrelation, especially hydraulic variables. Due to the strongly physical and spatial nature of hydromorphological disturbance, turnover of species between sample locations at a range of scales, and the spatial arrangement of habitats and communities is of more use for detecting these types of subtle changes compared to mean richness or diversity. These findings have implications for the targeting of resources for monitoring of restoration, or engineering disturbances, in order to be sensitive to hydromorphological change. Efforts should target the main area of natural variability within the system, either replicating sampling in time or space to distinguish effects of impact. Spatial patterns, measures of beta diversity and species identity can be better exploited to identify systems with functioning geomorphological processes. Channel typologies proved misleading, and quantification of habitat and selection of control sites using multiple pre-defined criteria should be carried out. Studies of restoration operations and engineering impacts provide considerable opportunities for advancing our knowledge of the mechanisms that drive community response under a range of conditions to improve impact detection.

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