The hyporheic interstitial was recognized as an integral zone within the aquatic ecosystem bearing important functions for both adjacent compartments, surface and ground water, about 50 years ago. Since then, rather disciplinary works gained knowledge on the organismic community of this ecotone, its spatial extent, the role of distinct parameters such as hydrology and morphology, temporal characteristics, process dynamics, the role for stream or groundwater quality and restoration measures. However, a systematic study on the risks to the hyporheic functions was missing to date. This thesis combined existing methods in order to gather an integrated set of information allowing for the assessment of the ecotonal status. This approach was applied to investigate the functional behavior towards stressors like increasing nutrient and fine sediment input into a rather pristine environment. An interdisciplinary risk assessment and the establishment of adapted measures was called for as land-use scenarios for the studied catchment area indicated progressive onland erosion. Therefore firstly, an integrated monitoring scheme was drawn up and conducted at three sites along a river that underlay a stressor gradient such as mentioned before. Secondly, the data sets were analysed in order to evaluate the status of the hyporheic funtions at the riffles. Thirdly, a coupled surface-subsurface modelling approach was set up to further study the impact of the stressors on the ecotonal integrity. And fourthly, an interdisciplinary consideration combined with studies on the catchments sediment budget and the rivers ecological status was applied to identify measures for the restoration and protection of the aquatic ecosystem. The analysis of the data gathered with the help of the established monitoring scheme revealed that elevated nutrient or fine sediment input lead to biological or physical clogging, respectively, with consequences for the hyporheic zone functions. The surface - ground water connectivity was either lowered in summer months, when biofilm growth was highest, or permanently, as fine sediment particles infiltrated into the interstices of the riverbed sediment. Scouring did not seem to take place as high amounts of fine particles were found in the matrix after discharge events of snowmelt and summer precipitation. With respect to the biogeochemical regulation function, biofilm material appeared to provide an autochthonous carbon source boosting microbial substance turnover. The sediment underneath the physical clogged layer was cut off from carbon and oxygen rich surface water and thus was not reactive. However, the enhanced surface area provided by the fine sediment within the topmost sediment layer seemed to support microbial processing. The inclusion of the results of a study concerning the ecological status at the investigated reaches lead to the deduction that biological clogging at the present degree was not affecting habitat quality. Whereas the physical clogging had tremendeous and lasting effects on the macroinvertebrate community which carries to the conclusion that sediment management within the studied catchment is of uttermost importance. A scenario analysis reflecting distinct clogging degrees and types with a calibrated model of a studied riffle within a pristine reach proved the observed loss of hydrologic connectivity due to physical and biological clogging. Further, a treshold of oxygen consumption rates above which the reproduction of salmonid fish would be unsuccessful was identified for the settings of the middle reaches. In summer month with low discharge it seemed to be likely that this treshold might be reached. Following, a dynamic discharge may be decisive to protect the ecotonal integrity. The integration with the outcome of an investigation regarding the sediment sources within the catchment allowed for two suggestions. On the one hand, river bank restoration and protection within the middle reaches need to be prioritised, and on the other hand, the conservation of the natural vegetation at the steep slopes within the mountaineous areas need to be undertaken in order to secure the pristine aquatic environment of this area. Hyporheic zone research of the last decade was driven by testing hypotheses on the functional significance of distinct spatial and temporal configurations in the field and by new modelling approaches. However, data on the quantification of the ecological impact of clogging processes were lacking. The thesis contributed to the systemic understanding of the hyporheic zone being affected by physical and biological clogging and new field data within a degrading pristine environment were generated, accessible for further hyporheic research. The interdisciplinarity enabled comprehensive statements for the usage of an Integrated Water Resources Management plan.

The hyporheic interstitial was recognized as an integral zone within the aquatic ecosystem bearing important functions for both adjacent compartments, surface and ground water, about 50 years ago. Since then, rather disciplinary works gained knowledge on the organismic community of this ecotone, its spatial extent, the role of distinct parameters such as hydrology and morphology, temporal characteristics, process dynamics, the role for stream or groundwater quality and restoration measures. However, a systematic study on the risks to the hyporheic functions was missing to date. This thesis combined existing methods in order to gather an integrated set of information allowing for the assessment of the ecotonal status. This approach was applied to investigate the functional behavior towards stressors like increasing nutrient and fine sediment input into a rather pristine environment. An interdisciplinary risk assessment and the establishment of adapted measures was called for as land-use scenarios for the studied catchment area indicated progressive onland erosion. Therefore firstly, an integrated monitoring scheme was drawn up and conducted at three sites along a river that underlay a stressor gradient such as mentioned before. Secondly, the data sets were analysed in order to evaluate the status of the hyporheic funtions at the riffles. Thirdly, a coupled surface-subsurface modelling approach was set up to further study the impact of the stressors on the ecotonal integrity. And fourthly, an interdisciplinary consideration combined with studies on the catchments sediment budget and the rivers ecological status was applied to identify measures for the restoration and protection of the aquatic ecosystem. The analysis of the data gathered with the help of the established monitoring scheme revealed that elevated nutrient or fine sediment input lead to biological or physical clogging, respectively, with consequences for the hyporheic zone functions. The surface - ground water connectivity was either lowered in summer months, when biofilm growth was highest, or permanently, as fine sediment particles infiltrated into the interstices of the riverbed sediment. Scouring did not seem to take place as high amounts of fine particles were found in the matrix after discharge events of snowmelt and summer precipitation. With respect to the biogeochemical regulation function, biofilm material appeared to provide an autochthonous carbon source boosting microbial substance turnover. The sediment underneath the physical clogged layer was cut off from carbon and oxygen rich surface water and thus was not reactive. However, the enhanced surface area provided by the fine sediment within the topmost sediment layer seemed to support microbial processing. The inclusion of the results of a study concerning the ecological status at the investigated reaches lead to the deduction that biological clogging at the present degree was not affecting habitat quality. Whereas the physical clogging had tremendeous and lasting effects on the macroinvertebrate community which carries to the conclusion that sediment management within the studied catchment is of uttermost importance. A scenario analysis reflecting distinct clogging degrees and types with a calibrated model of a studied riffle within a pristine reach proved the observed loss of hydrologic connectivity due to physical and biological clogging. Further, a treshold of oxygen consumption rates above which the reproduction of salmonid fish would be unsuccessful was identified for the settings of the middle reaches. In summer month with low discharge it seemed to be likely that this treshold might be reached. Following, a dynamic discharge may be decisive to protect the ecotonal integrity. The integration with the outcome of an investigation regarding the sediment sources within the catchment allowed for two suggestions. On the one hand, river bank restoration and protection within the middle reaches need to be prioritised, and on the other hand, the conservation of the natural vegetation at the steep slopes within the mountaineous areas need to be undertaken in order to secure the pristine aquatic environment of this area. Hyporheic zone research of the last decade was driven by testing hypotheses on the functional significance of distinct spatial and temporal configurations in the field and by new modelling approaches. However, data on the quantification of the ecological impact of clogging processes were lacking. The thesis contributed to the systemic understanding of the hyporheic zone being affected by physical and biological clogging and new field data within a degrading pristine environment were generated, accessible for further hyporheic research. The interdisciplinarity enabled comprehensive statements for the usage of an Integrated Water Resources Management plan.

Sewage exfiltration from a sanitary and combined sewer systems and its percolation into porous medium results in a clogged or colmation layer in the nearby soil. In order to develop a comprehensive understanding of raw sewage transport mechanisms in porous media, investigations were carried out on the micro-scale properties of the multiphase system. In our laboratory experiments, the role of surfactants as a major organic chemical compound in wastewater was evaluated by using a surfactant solution as an artificial wastewater percolating into a porous media, represented by using columns and Plexiglas model. We studied flows of water and surfactants solution in saturated porous medium to detect the dynamic effects by means of measuring pressure and permeability as well as by visualization of flow regions and consequence for porosity along interfaces between water and surfactants solution. The tests revealed that mechanisms at interfaces between fluids and solids as well as between water and surfactants solution (i.e. wastewater) are significantly influencing the flow behavior. At the interfaces surfactant molecules are adsorbed or accumulate, respectively, and subsequently inducing electrical charges to those layers, altering the properties of fluids and these interfaces. Depending on the conditions, channels might be narrowed and thus decreasing the flow rate with a later erosion and increase of flow rates, or the flow and thus the erosive capacity might become intensified along the interface between surfactants solution and neighbouring water. In conclusion, the results of tests proved the surfactants to be an important controlling factor in the hydraulic properties of wastewater percolating into soil.

Die Eutrophierung von Fließgewässern führt besonders im Frühjahr zur Zunahme der Biomasse des benthischen Aufwuchses. Dies kann zur reduzierter Infiltration von Wasser in die Gewässersohle führen und wichtige Funktionen von Fließgewässerökosystems stören. Verschiedene Studien konnten zeigen, dass invertebrate Weidegänger (Grazer) in der Lage sind die Biomasse des Aufwuchses in Fließgewässern effektiv zu reduzieren. Diese wichtige ökologische Funktion, das benthische Grazing, kann dazu beitragen negative Effekte der Eutrophierung in Fließgewässern zu kompensieren. Relevante invertebrate Grazer sind unter anderem die Larven der Eintagsfliege Rhithrogena semicolorata, die hohe Biomassen in Fließgewässern erreichen und eine hohe Spezialisierung auf Aufwuchs zeigen. Die Larven von R. semicolorata sind während ihres einjährigen Lebenszykluses Pestiziden ausgesetzt, welche ihre Entwicklung beeinträchtigen können. Um die Effekte von Pestiziden auf die Entwicklung dieser wichtigen Grazer zu untersuchen wurden drei Expositionsszenarien in Anlehnung an reale Bedingungen im Freiland untersucht. Das erste Szenario untersucht die Effekten einer Exposition mit dem Herbizid Terbutryn auf die Grazer-Aufwuchs-Interaktion, wie sie im Herbst und zeitigen Frühjahr anzutreffen ist. Terbutryn verursachte ab 6 µg/L eine deutliche Reduktion der Aufwuchsquantität, was indirekt das Wachstum und die Fettreserven der Grazer verringerte. Die Grazer zeigten ab 0,6 µg/L eine deutliche erhöhte Drift. Da bei dieser Konzentration noch keine Effekte auf die Aufwuchsbiomasse detektiert wurde, ist dies ein Indiz für verringerte Qualität des Aufwuchses. Insektzide werden verstärkt im Frühjahr ausgebracht und beeinflussen die Entwicklung der Grazer direkt. Das zweite Szenario untersuchte die Effekte des Insektizids lambda-Cyhalotrhin (LCH) auf die Grazer-Aufwuchs-Interaktion. LCH ist stark lipophil und adsorbiert schnell an organisches Material und Aufwüchse in Gewässer, weshalb es besonders für aufwuchsfressende Organismen bioverfügbar ist. Neben den erwarteten letalen Effekten wurden in Bereichen um 1 µg/g OC bereits subletale Effekte auf das Driftverhalten sowie das Wachstum der Grazer gefunden. Die Fettreserven waren ab ca. 0,01 µg/g OC reduziert, was auf verringerte Fraßaktivität in diesen niedrigen Konzentrationsbereichen schließen lässt. Die Analyse des Aufwuchses zeigte einen indirekt Effekt von LCH auf die Aufwuchsentwicklung, der einerseits auf die erhöhte Mortalität der Grazer aber auch auf LCH-induzierte Verhaltensänderungen zurückgeführt werden konnte. Das finale Szenario befasste sich mit den Effekten der kombinierten Exposition von Herbizid und Insektizid, wie sie im Lebenszyklus von R. semicolorata auftreten. Dabei zeigte sich entgegen der Erwartung keine erhöhte Mortalität durch die kombinierte Exposition. Die Ergebnisse weisen jedoch daraufhin, dass die Reduzierung der physiologischen Kondition der Grazer, durch die indirekten Effekte von Terbutryn, in subletalen Konzentrationsbereichen von LCH die Dauer bis zur Wiedererholung verlängert. Außerdem zeigte sich am Ende eine erhöhte Aufwuchsbiomasse, was eine reduzierte Leistung des Grazings durch die kombinierte Exposition indiziert. / The eutrophication of running water ecosystems leads especially in spring to an increase of benthic biofilms or aufwuchs, which reduces the infiltration of water into the river bed and, hence, disturb important ecological functions. Different studies already showed that invertebrate grazers of running water ecosystems are able to reduce the aufwuchs biomass effectively. This important ecological function, the benthic grazing, can therefore contribute to compensate the negative effects of eutrophication in lotic ecosystems. Relevant grazers are for instance the larvae of the mayfly Rhithrogena semicolorata, which reach high biomasses in streams and show a high feeding specialisation on aufwuchs. During their on year lasting life cycle the larvae of R. semicolorata are exposed to different pesticides, which can disturb their development. To evaluate the effects of pesticides on the development of this important grazer three exposition scenarios were performed following real exposure patterns from the environment. In the first scenarios the effects of a solely exposure with the herbicide Terbutryn on the grazer-aufwuchs-interaction was investigated, as it occurs preferably during autumn and spring. Terbutryn induced a clear reduction of aufwuchs quantity at 6 µg/L, which indirectly affected the growth and the energy storages of the grazers. Furthermore, the grazers showed an increased drift activity at 0.6 µg/L. Considering that the aufwuchs biomass was not affected at this low concentrations, the increased drift was interpreted as an indirect effect of reduced aufwuchs quantity. Inseciticides are preferably applied during spring and are able to disturb the development of grazers directly. The second scenario investigated therefore the effects of the insecticide lambda-Cyhalothrin (LCH) on the grazer-aufwuchs-interaction. LCH has a high lipophilicity and thus rapidly binds to organic matter or aufwuchs after entering aquatic ecosystems. This behaviour leads to a increased bioavailability of this substance to aufwuchs feeding organisms. Apart from the expected lethal effects, sublethal effects in form of increased drift and reduced grazer growth were found in a range of 1 µg/g OC LCH. Moreover, the energy storages of grazers were reduced at 0,01 µg/g OC, which is an indication of disturbed feeding behaviour at this low concentration. The analysis of the aufwuchs revealed additionally an indirect effect of LCH on the aufwuchs development, which was caused by increased grazer mortality and behavioural changes of the grazers induced by sublethal LCH concentrations. The final scenario aimed on the effects of a combined exposure of herbicide and insecticide, as it occurs during the life cycle of R. semicolorata. A increased mortality of grazers, due to the combinded exporsure, was not found. However, the results indicate that the reduction of the physiological condition by the indirect effect of Terbutryn extends the time until grazers recover from sublethal LCH exposure. Finally, also an increased aufwuchs biomass was found in treatments with combined exposure, indicating a reduced performance of grazers exposed to both substances.

Die Eutrophierung von Fließgewässern führt besonders im Frühjahr zur Zunahme der Biomasse des benthischen Aufwuchses. Dies kann zur reduzierter Infiltration von Wasser in die Gewässersohle führen und wichtige Funktionen von Fließgewässerökosystems stören. Verschiedene Studien konnten zeigen, dass invertebrate Weidegänger (Grazer) in der Lage sind die Biomasse des Aufwuchses in Fließgewässern effektiv zu reduzieren. Diese wichtige ökologische Funktion, das benthische Grazing, kann dazu beitragen negative Effekte der Eutrophierung in Fließgewässern zu kompensieren. Relevante invertebrate Grazer sind unter anderem die Larven der Eintagsfliege Rhithrogena semicolorata, die hohe Biomassen in Fließgewässern erreichen und eine hohe Spezialisierung auf Aufwuchs zeigen. Die Larven von R. semicolorata sind während ihres einjährigen Lebenszykluses Pestiziden ausgesetzt, welche ihre Entwicklung beeinträchtigen können. Um die Effekte von Pestiziden auf die Entwicklung dieser wichtigen Grazer zu untersuchen wurden drei Expositionsszenarien in Anlehnung an reale Bedingungen im Freiland untersucht. Das erste Szenario untersucht die Effekten einer Exposition mit dem Herbizid Terbutryn auf die Grazer-Aufwuchs-Interaktion, wie sie im Herbst und zeitigen Frühjahr anzutreffen ist. Terbutryn verursachte ab 6 µg/L eine deutliche Reduktion der Aufwuchsquantität, was indirekt das Wachstum und die Fettreserven der Grazer verringerte. Die Grazer zeigten ab 0,6 µg/L eine deutliche erhöhte Drift. Da bei dieser Konzentration noch keine Effekte auf die Aufwuchsbiomasse detektiert wurde, ist dies ein Indiz für verringerte Qualität des Aufwuchses. Insektzide werden verstärkt im Frühjahr ausgebracht und beeinflussen die Entwicklung der Grazer direkt. Das zweite Szenario untersuchte die Effekte des Insektizids lambda-Cyhalotrhin (LCH) auf die Grazer-Aufwuchs-Interaktion. LCH ist stark lipophil und adsorbiert schnell an organisches Material und Aufwüchse in Gewässer, weshalb es besonders für aufwuchsfressende Organismen bioverfügbar ist. Neben den erwarteten letalen Effekten wurden in Bereichen um 1 µg/g OC bereits subletale Effekte auf das Driftverhalten sowie das Wachstum der Grazer gefunden. Die Fettreserven waren ab ca. 0,01 µg/g OC reduziert, was auf verringerte Fraßaktivität in diesen niedrigen Konzentrationsbereichen schließen lässt. Die Analyse des Aufwuchses zeigte einen indirekt Effekt von LCH auf die Aufwuchsentwicklung, der einerseits auf die erhöhte Mortalität der Grazer aber auch auf LCH-induzierte Verhaltensänderungen zurückgeführt werden konnte. Das finale Szenario befasste sich mit den Effekten der kombinierten Exposition von Herbizid und Insektizid, wie sie im Lebenszyklus von R. semicolorata auftreten. Dabei zeigte sich entgegen der Erwartung keine erhöhte Mortalität durch die kombinierte Exposition. Die Ergebnisse weisen jedoch daraufhin, dass die Reduzierung der physiologischen Kondition der Grazer, durch die indirekten Effekte von Terbutryn, in subletalen Konzentrationsbereichen von LCH die Dauer bis zur Wiedererholung verlängert. Außerdem zeigte sich am Ende eine erhöhte Aufwuchsbiomasse, was eine reduzierte Leistung des Grazings durch die kombinierte Exposition indiziert. / The eutrophication of running water ecosystems leads especially in spring to an increase of benthic biofilms or aufwuchs, which reduces the infiltration of water into the river bed and, hence, disturb important ecological functions. Different studies already showed that invertebrate grazers of running water ecosystems are able to reduce the aufwuchs biomass effectively. This important ecological function, the benthic grazing, can therefore contribute to compensate the negative effects of eutrophication in lotic ecosystems. Relevant grazers are for instance the larvae of the mayfly Rhithrogena semicolorata, which reach high biomasses in streams and show a high feeding specialisation on aufwuchs. During their on year lasting life cycle the larvae of R. semicolorata are exposed to different pesticides, which can disturb their development. To evaluate the effects of pesticides on the development of this important grazer three exposition scenarios were performed following real exposure patterns from the environment. In the first scenarios the effects of a solely exposure with the herbicide Terbutryn on the grazer-aufwuchs-interaction was investigated, as it occurs preferably during autumn and spring. Terbutryn induced a clear reduction of aufwuchs quantity at 6 µg/L, which indirectly affected the growth and the energy storages of the grazers. Furthermore, the grazers showed an increased drift activity at 0.6 µg/L. Considering that the aufwuchs biomass was not affected at this low concentrations, the increased drift was interpreted as an indirect effect of reduced aufwuchs quantity. Inseciticides are preferably applied during spring and are able to disturb the development of grazers directly. The second scenario investigated therefore the effects of the insecticide lambda-Cyhalothrin (LCH) on the grazer-aufwuchs-interaction. LCH has a high lipophilicity and thus rapidly binds to organic matter or aufwuchs after entering aquatic ecosystems. This behaviour leads to a increased bioavailability of this substance to aufwuchs feeding organisms. Apart from the expected lethal effects, sublethal effects in form of increased drift and reduced grazer growth were found in a range of 1 µg/g OC LCH. Moreover, the energy storages of grazers were reduced at 0,01 µg/g OC, which is an indication of disturbed feeding behaviour at this low concentration. The analysis of the aufwuchs revealed additionally an indirect effect of LCH on the aufwuchs development, which was caused by increased grazer mortality and behavioural changes of the grazers induced by sublethal LCH concentrations. The final scenario aimed on the effects of a combined exposure of herbicide and insecticide, as it occurs during the life cycle of R. semicolorata. A increased mortality of grazers, due to the combinded exporsure, was not found. However, the results indicate that the reduction of the physiological condition by the indirect effect of Terbutryn extends the time until grazers recover from sublethal LCH exposure. Finally, also an increased aufwuchs biomass was found in treatments with combined exposure, indicating a reduced performance of grazers exposed to both substances.

Sewage exfiltration from a sanitary and combined sewer systems and its percolation into porous medium results in a clogged or colmation layer in the nearby soil. In order to develop a comprehensive understanding of raw sewage transport mechanisms in porous media, investigations were carried out on the micro-scale properties of the multiphase system. In our laboratory experiments, the role of surfactants as a major organic chemical compound in wastewater was evaluated by using a surfactant solution as an artificial wastewater percolating into a porous media, represented by using columns and Plexiglas model. We studied flows of water and surfactants solution in saturated porous medium to detect the dynamic effects by means of measuring pressure and permeability as well as by visualization of flow regions and consequence for porosity along interfaces between water and surfactants solution. The tests revealed that mechanisms at interfaces between fluids and solids as well as between water and surfactants solution (i.e. wastewater) are significantly influencing the flow behavior. At the interfaces surfactant molecules are adsorbed or accumulate, respectively, and subsequently inducing electrical charges to those layers, altering the properties of fluids and these interfaces. Depending on the conditions, channels might be narrowed and thus decreasing the flow rate with a later erosion and increase of flow rates, or the flow and thus the erosive capacity might become intensified along the interface between surfactants solution and neighbouring water. In conclusion, the results of tests proved the surfactants to be an important controlling factor in the hydraulic properties of wastewater percolating into soil.

In der vorliegenden Arbeit wurde die Beeinflussung der Wechselwirkungen zwischen Oberflächenwasser, Interstitial und Grundwasser durch eutrophierungsbedingte Kolmationszyklen in einem anthropogen belasteten Fließgewässer (Lahn, Hessen) untersucht. Dabei wurden Mesokosmosexperimente und Freilanduntersuchungen an einer hyporhithralen Pool-Riffle-Sequenz miteinander kombiniert und die Ergebnisse vergleichend interpretiert. Im Rahmen der Arbeit wurde ein experimenteller Versuchsstand aufgebaut, der aus einer kontinuierlich durchströmten Sedimentsäule bestand und in einem mobilen Laborcontainer an der Lahn installiert war. Mit Hilfe dieses mesoskaliges Sedimentkörperexperimentes wurden jahreszeitliche Verlaufsmuster der inneren Kolmation analysiert, parametrisiert und mit physikalischen (Schwebstoffdynamik) und biologischen Kolmationskomponenten in Beziehung gesetzt. Besonderer Fokus lag dabei auf der Entwicklung des Periphytons, das in eutrophierten Fliessgewässern verstärkender Faktor der Kolmation werden kann. Ferner ließ sich mit dem aufgebauten Sedimentkörperexperiment der Einfluss von Kolmation auf Stoffumsetzungsprozesse (O2) im Interstitial modellhaft erfassen. In einem zweiten mesoskaligen Versuchsstand wurde die Bedeutung der hyporheischen Meiofauna für biogene Dekolmationsvorgänge (Fraß und Bioturbation) untersucht.

In der vorliegenden Arbeit wurde die Beeinflussung der Wechselwirkungen zwischen Oberflächenwasser, Interstitial und Grundwasser durch eutrophierungsbedingte Kolmationszyklen in einem anthropogen belasteten Fließgewässer (Lahn, Hessen) untersucht. Dabei wurden Mesokosmosexperimente und Freilanduntersuchungen an einer hyporhithralen Pool-Riffle-Sequenz miteinander kombiniert und die Ergebnisse vergleichend interpretiert. Im Rahmen der Arbeit wurde ein experimenteller Versuchsstand aufgebaut, der aus einer kontinuierlich durchströmten Sedimentsäule bestand und in einem mobilen Laborcontainer an der Lahn installiert war. Mit Hilfe dieses mesoskaliges Sedimentkörperexperimentes wurden jahreszeitliche Verlaufsmuster der inneren Kolmation analysiert, parametrisiert und mit physikalischen (Schwebstoffdynamik) und biologischen Kolmationskomponenten in Beziehung gesetzt. Besonderer Fokus lag dabei auf der Entwicklung des Periphytons, das in eutrophierten Fliessgewässern verstärkender Faktor der Kolmation werden kann. Ferner ließ sich mit dem aufgebauten Sedimentkörperexperiment der Einfluss von Kolmation auf Stoffumsetzungsprozesse (O2) im Interstitial modellhaft erfassen. In einem zweiten mesoskaligen Versuchsstand wurde die Bedeutung der hyporheischen Meiofauna für biogene Dekolmationsvorgänge (Fraß und Bioturbation) untersucht.