Freiberg (Sachsen), Techn. Universiẗat, Diss., 2007.

This thesis handle with the ecological status of Smržovka stream, respectively handle with change of the ecological state of stream due to urbanization. Smržovka stream, concretely the right tributary of significant river Kamenice Jizerské hory Mountains rises in the Jizerské hory Mountains protected landscape area, which is almost intact due to water pollution and gradually flows through an urbanized area with a relatively high level of infrastructure and sources of pollution. For the ecological status assessment of stream were used the following three indicators: hydromorphological mapping, physico-chemical water analysis and evaluation of biological components of makrozoobenthos in terms of saprobity. The work provides information on water quality in the stream with that this unique data can be the basis for the study of other small streams that spring in urban mountainous areas.

Das Verständnis über die Ausprägung der Lebensgemeinschaften von benthischen Invertebraten in aquatischen Ökosystemen in Abhängigkeit von abiotischen Faktoren ist von grundlegender wissenschaftlicher Bedeutung und eine Voraussetzung für die Bewertung, den Schutz und die Wiederherstellung der ökologischen Integrität in Fließgewässern. Für die Erarbeitung von Abhängigkeiten zwischen der benthischen Lebensgemeinschaft, der Hydromorphologie und der Saprobie standen insgesamt 409 Datensätze in Form von Taxalisten des Makrozoobenthos zur Verfügung. Diese wurden mit Strukturgütedaten verschnitten und anhand uni- und multivariater statistischer Methoden analysiert. Folgende Ergebnisse konnten dabei erzielt werden: (a) es können sieben Einzelparameter der Gewässerstruktur identifiziert werden, die einen signifikanten Einfluss auf die benthische Biozönose ausüben, (b) die Fließgewässertypen 5 und 5.1 unterscheiden sich auf Basis des vorliegenden Datensatzes weder in der taxonomischen noch in der funktionalen Zusammensetzung der Makrozoobenthoszönose und (c) bei einer erhöhten saprobiellen Belastung überlagert der Einfluss der organischen Belastung die strukturellen Gegebenheiten. Für die Entwicklung und Anpassung effizienter Strukturgüteverfahren und die daraus resultierenden Monitoring- und Maßnahmenprogramme für ein integriertes Fließgewässermanagement ist die Auswahl ökologisch relevanter Parameter von immenser Bedeutung. / The understanding about the development of benthic invertebrate communities as a function of abiotic influencing factors in aquatic ecosystems is of essential scientific relevance for the assessment of the ecological status of rivers and streams. For the development of interdependencies between benthic invertebrates, hydromorphology and saprobity, 409 species lists of the macroinvertebrates were provided. They were aggregated with morphological features and analysed with different uni- and multivariate statistical methods. On the basis of the used analyses, the following results were achieved: (a) seven ecological relevant morphological features with significant influence to benthic invertebrate community could be identified, (b) on the basis of the present database, the structural and functional composition of the benthic invertebrates can not be differ river type specific (type 5 and 5.1) and (c) if the saprobic pressure decrease, the organic pressure superpose the hydromorphology. The values of the biological attributes are low in spite of near natural morphological conditions. For an ecological efficiency stream habitat assessment, the identified relevant morphological parameters have to consider. The “morphological characteristic curves” are well describing the results of a local monitoring. This application-oriented instrument can be used for (a) the operationalisation of environmental objectives, (b) the development and adaption of monitoring strategies and (c) the derivation and prioritisation of ecological and economic efficiency measurements for an integrated river management.

Biologische und chemische Monitoringdaten wurden im Hinblick auf insektizid wirkende Stoffe ausgewertet. Im Zeitraum 2009 bis 2017 wurden 28 Wirkstoffe nachgewiesen. Die 44 am stärksten belasteten Wasserkörper-Messstellen wurden identifiziert und tabellarisch dargestellt. Die Auswertung unterstützt den Nationalen Aktionsplan zur nachhaltigen Anwendung von Pflanzenschutzmitteln. Redaktionsschluss: 30.11.2018

The prey consumption by benthivorous fish predators can have profound top-down effects in stream food webs. To analyse this effects in small temperate stream ecosystems, a long-term field experiment was conducted in two streams in South-eastern Germany, Gauernitzbach and Tännichtgrundbach, from 2004 to 2011. The densities of two small-bodied benthivorous fish species, gudgeon (Gobio gobio) and stone loach (Barbatula barbatula), were manipulated following a Before-After-Control-Impact design. The top predator regime affected the benthic community composition of the streams mainly in pools, whereas the total benthic invertebrate biomass was not affected in any mesohabitat. The present work describes a causal analysis of the observed food web effects using additional field analyses and laboratory experiments, with a special focus on the habitat use and foraging behaviour of the fish as top predators. The probably most important of the analysed mechanisms was mesohabitat-specific predation by the fish. Three 24-h field video surveys combined with benthic invertebrate sampling showed that constraints in habitat use, especially for gudgeon, induced a differential predator-prey habitat overlap which resulted in a higher predation risk for the invertebrate prey in pools than in riffles. Another important mechanism was selective predation of both fish species. Their prey selectivity was largely explained by a small number of prey variables being connected to the partly non-visual foraging mode of these benthic predators. Besides the traits body size and feeding type, long-term mean abundance played a central role, small and highly abundant invertebrates, grazers and sediment feeders being preferred by gudgeon and stone loach. The preference for small and abundant prey taxa (chironomids) exceeded purely opportunistic feeding and probably facilitated resource partitioning between the two fish species having very similar diets. In addition to active selectivity, different predator avoidance strategies of the invertebrates analysed in laboratory experiments explained the passive selectivity of the fish predators for certain prey taxa in the streams. This could be shown for two abundant taxa being consumed by the fish predators in very different quantities, Gammarus pulex and Hydropsyche instabilis. These three mechanisms, although probably interacting with several other factors, could explain a large part of the effects the top-down food web manipulation had on the benthic community, especially the observed high degree of mesohabitat and species specificity. Confirming this, quantitative characteristics of predation food webs, for instance the importance of intraguild predation, differed markedly between pool and riffle mesohabitats. From the results of this study it can be concluded that the benthivorous fish affected benthic community structure mainly by mesohabitat-specific and selective predation. A manipulation of this (native) top predator type therefore will probably have such rather subtle but not catastrophic consequences in ecosystems with a high biotic diversity and a rich natural habitat structure and connectivity.

Structural changes in macrozoobenthic communities and changes in chemistry in longitudinal profiles of two acidified streams in the Bohemian Forest (Czech Republic) were investigated in 2007. The progress in chemical recovery was evident in both streams, whereas zoobenthos recovery was obvious only in less acidified stream.

The prey consumption by benthivorous fish predators can have profound top-down effects in stream food webs. To analyse this effects in small temperate stream ecosystems, a long-term field experiment was conducted in two streams in South-eastern Germany, Gauernitzbach and Tännichtgrundbach, from 2004 to 2011. The densities of two small-bodied benthivorous fish species, gudgeon (Gobio gobio) and stone loach (Barbatula barbatula), were manipulated following a Before-After-Control-Impact design. The top predator regime affected the benthic community composition of the streams mainly in pools, whereas the total benthic invertebrate biomass was not affected in any mesohabitat. The present work describes a causal analysis of the observed food web effects using additional field analyses and laboratory experiments, with a special focus on the habitat use and foraging behaviour of the fish as top predators. The probably most important of the analysed mechanisms was mesohabitat-specific predation by the fish. Three 24-h field video surveys combined with benthic invertebrate sampling showed that constraints in habitat use, especially for gudgeon, induced a differential predator-prey habitat overlap which resulted in a higher predation risk for the invertebrate prey in pools than in riffles. Another important mechanism was selective predation of both fish species. Their prey selectivity was largely explained by a small number of prey variables being connected to the partly non-visual foraging mode of these benthic predators. Besides the traits body size and feeding type, long-term mean abundance played a central role, small and highly abundant invertebrates, grazers and sediment feeders being preferred by gudgeon and stone loach. The preference for small and abundant prey taxa (chironomids) exceeded purely opportunistic feeding and probably facilitated resource partitioning between the two fish species having very similar diets. In addition to active selectivity, different predator avoidance strategies of the invertebrates analysed in laboratory experiments explained the passive selectivity of the fish predators for certain prey taxa in the streams. This could be shown for two abundant taxa being consumed by the fish predators in very different quantities, Gammarus pulex and Hydropsyche instabilis. These three mechanisms, although probably interacting with several other factors, could explain a large part of the effects the top-down food web manipulation had on the benthic community, especially the observed high degree of mesohabitat and species specificity. Confirming this, quantitative characteristics of predation food webs, for instance the importance of intraguild predation, differed markedly between pool and riffle mesohabitats. From the results of this study it can be concluded that the benthivorous fish affected benthic community structure mainly by mesohabitat-specific and selective predation. A manipulation of this (native) top predator type therefore will probably have such rather subtle but not catastrophic consequences in ecosystems with a high biotic diversity and a rich natural habitat structure and connectivity.