Person: Gergs, René
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1979
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Biologe
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Gergs
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René
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Veröffentlichung Is Dikerogammarus villosus (Crustacea, Gammaridae) a 'killer shrimp' in the River Rhine system?(2016) Koester, Meike; Bayer, Bastian; Gergs, René; Sahm, RenéCommunities and food web structures of aquatic ecosystems can be strongly affected by the establishment of alien macroinvertebrate species. In many European waters, the invasion of the Ponto-Caspian amphipod Dikerogammarus villosus has led to displacement of other macroinvertebrates. Predation by D. villosus is often assumed to be the key driver of the displacement based on results of laboratory studies, but this has not been verified in the field. Here, we report our investigation of the relevance of D. villosus predation in the River Rhine system using both stable isotope analyses of d13C and d15N, and molecular analyses of D. villosus gut contents with group-specific primers aiming at macroinvertebrate prey taxa. Stable isotope analyses of D. villosus from ten sites showed mean d15N values comparable to those of primary consumers. Overall, only approximately 1% of all tested primer/gut content combinations revealed DNA of the respective taxa. Both indicate minor importance of predation by D. villosus as a driver of the observed macroinvertebrate displacement. Conceivably, competitive strength due to opportunistic feeding, indicated by different niche widths between and a strong intraspecific variation of d13C values of D. villosus within sites of our study, is much more important for its invasion success. Quelle: http://link.springer.comVeröffentlichung Is The invasive amphipod Dikerogammarus villosus the main factor structuring the benthic community across different types of water bodies in the River Rhine system?(2018) Koester, Meike; Gergs, René; Schneider, Maximilian; Hellmann, Claudia; Sahm, RenéDikerogammarus villosus, one of the most successful invaders in European river systems, is commonly regarded as a threat to native biodiversity and a main factor structuring the benthic community of invaded systems. The impact of D. villosus has been intensively studied in small-scale experiments and field observations, but its impact on natural communities on a larger scale remains unclear. Here, we investigated the benthic community structure at ten sites covering a broad range of habitats along the River Rhine (Central Europe) and its tributaries, to determine whether D. villosus is one of the main factors structuring the benthic community. Community composition was analysed using non-metric multidimensional scaling, distance-based redundancy analysis, and correlation analyses. D. villosus was one of nine relevant taxa present that altogether reflected a large part of the variation in the benthic samples, but further analyses indicated that the species might be less important for the community structure than other relevant taxa. Moreover, all nine relevant taxa together can explain only a similar amount of variation in our samples than the five relevant non-faunal environmental factors (water temperature, pH, conductivity, percentage of medium-sized gravel and macrophytes). Overall, our results suggested that rather a combination of non-faunal environmental factors than D. villosus mainly structure the benthic community composition on this larger spatial scale. © 2018 Elsevier GmbH. All rights reserved.Veröffentlichung Contribution of organic toxicants to multiple stress in river ecosystems(2016) Schäfer, Ralf B.; Gergs, René; Kuehn, Bernhard; Malaj, Egina; Sahm, RenéRiver ecosystems are threatened by multiple stressors, including habitat degradation, pollution and invasive species. However, freshwater ecologists have largely disregarded the contribution of toxicants to stress in rivers, whereas ecotoxicologists have primarily examined toxicant effects in artificial systems. As a result, there is a paucity of information on the co-occurrence of organic toxicants with other stressors and on the relative importance of toxicants for overall ecological risk in rivers. We used monitoring data for German rivers to analyse the individual and joint occurrence of four stressors: habitat degradation, invasive species, nutrient pollution and organic toxicants. All stressors were examined for ecological risks in terms of whether they exceeded low- and high-risk thresholds derived from published studies and regulatory thresholds. Nutrients and habitat degradation exceeded low and high risk thresholds at c. 85% of the sites and invasive species and organic toxicants at c. 50% of the sites. At least one stressor exceeded thresholds at all sites for which data on all four stressors were available. Toxicity showed weak positive correlations with nutrients and habitat degradation (0.2 < Spearman's ? < 0.34, 0.009 < P < 0.08). The risks of ecological effects arising from habitat degradation and invasive species were higher in lowland rivers, particularly for invasive species. Our assessment shows that organic toxicants contribute notably to risks of ecological effects in rivers, to a similar extent as invasive species, although habitat degradation and nutrients are the dominant stressors. Exposure to multiple stressors is the typical situation prevailing in rivers. Consequently, mitigation measures focusing on individual stressors may not be effective at reducing ecological risks. This suggests that integrating concepts and data from freshwater ecology and ecotoxicology is essential to meet the challenge of managing multiple stressors in river ecosystems. Quelle: http://onlinelibrary.wiley.com/Veröffentlichung Effects of copper ions on non-target species: a case study using the Grazer Theodoxus fluviatilis (Gastropoda: Neritidae)(2020) Rothmeier, Louisa Marie; Feibicke, Michael; Martens, Andreas; Gergs, René; Watermann, Burkard; Kullwatz, Jan Christopher; Sahm, RenéThe heavy metal copper has been widely used in industrial processes as well as a pesticide product in agriculture or as biocide. Anthropogenic activities by which copper can enter the environment are rather diverse including mining, metal finishing factories, discharging in industry, or sewage treatment plants. In agriculture, copper compounds are used mainly as fungicides or herbicides (e.g. reviewed by Flemming and Trevors 1989). Furthermore, it was formerly used in reservoirs, streams and ponds for controlling algae blooms and is now commonly used as a biocide in antifouling paintings for ships to protect hulls from corrosion and for fuel efficiency (Piola et al. 2009; Watermann et al. 2017). When copper is released into freshwater systems, for example via agricultural runoff, it exists in surface waters in the form of free ions (Cu2+), complexed with ligands or bound to particles, occurring at median water concentrations often ranging between 4 to 10 Ìg Cu2+/L (ATSDR 2004). As a persistent element, copper is able to accumulate in biofilms (Morin et al. 2008) and sediments of rivers, lakes and estuaries, from where it can also be remobilised (Watermann et al. 2017). Absorption of copper ions into biofilms increases with increasing ion concentration (Bhaskar and Bhosle 2006), leading to highly contaminated biofilms in polluted environments. © 2020 Springer Nature Switzerland AGVeröffentlichung Laboratory conditions can change the complexity and composition of the natural aquatic mycobiome on Alnus glutinosa leaf litter(2022) Carl, Steffen C.; Gergs, René; Sahm, René; Mohr, SilviaCommunity structure is of major interest when aquatic fungi are studied, particularly in leaf decomposition experiments. Although such studies are often conducted as laboratory experiments with microbial communities taken from the field, it remains unclear to what extent natural fungal communities can be sustained under experimental conditions. Here, we used DNA metabarcoding to investigate the development of fungal communities on alder leaves both under laboratory and field conditions. Five leaf conditioning treatments were compared by colonizing leaves in a stream, exposing stream colonized leaves to a defined medium or filtered stream water and using stream colonized leaves to inoculate sterile leaves in the defined medium or stream water. Fewer species were found on leaves that were inoculated under laboratory conditions, whereas differences in fungal community composition were comparably low in the other treatments, irrespective of the chosen medium. Possible shifts in fungal communities should therefore be considered in laboratory experiments. © 2021 The AuthorsVeröffentlichung Combined Surface-Subsurface Stream Restoration Structures Can Optimize Hyporheic Attenuation of Stream Water Contaminants(2023) Herzog, Skuyler P.; Galloway, Jason; Banks, Eddie W.; Gergs, René; Sahm, René; Kusebauch, BjörnThere is a design-to-function knowledge gap regarding how engineered stream restoration structures can maximize hyporheic contaminant attenuation. Surface and subsurface structures have each been studied in isolation as techniques to restore hyporheic exchange, but surface-subsurface structures have not been investigated or optimized in an integrated manner. Here, we used a numerical model to systematically evaluate key design variables for combined surface (i.e., weir height and length) and subsurface (i.e., upstream and downstream baffle plate spacing) structures. We also compared performance metrics that place differing emphasis on hyporheic flux versus transit times. We found that surface structures tended to create higher flux, shorter transit time flowpaths, whereas subsurface structures promoted moderate-flux, longer transit time flowpaths. Optimal combined surface-subsurface structures could increase fluxes and transit times simultaneously, thus providing conditions for contaminant attenuation that were many times more effective than surface or subsurface structures alone. All performance metrics were improved by the presence of an upstream plate and the absence of a downstream plate. Increasing the weir length tended to improve all metrics, whereas the optimal weir height varied based on metrics. These findings may improve stream restoration by better aligning specific restoration goals with appropriate performance metrics and hyporheic structure designs. © https://pubs.acs.org/Veröffentlichung The role of behavioral ecotoxicology in environmental protection(2021) Ford, Alex; Ågerstrand, Marlene; Brooks, Bryan W.; Duquesne, Sabine; Sahm, René; Gergs, René; Jacob, Stefanie; Maack, Gerd; Mohr, SilviaFor decades, we have known that chemicals affect human and wildlife behavior. Moreover, due to recent technological and computational advances, scientists are now increasingly aware that a wide variety of contaminants and other environmental stressors adversely affect organismal behavior and subsequent ecological outcomes in terrestrial and aquatic ecosystems. There is also a groundswell of concern that regulatory ecotoxicology does not adequately consider behavior, primarily due to a lack of standardized toxicity methods. This has, in turn, led to the exclusion of many behavioral ecotoxicology studies from chemical risk assessments. To improve understanding of the challenges and opportunities for behavioral ecotoxicology within regulatory toxicology/risk assessment, a unique workshop with international representatives from the fields of behavioral ecology, ecotoxicology, regulatory (eco)toxicology, neurotoxicology, test standardization, and risk assessment resulted in the formation of consensus perspectives and recommendations, which promise to serve as a roadmap to advance interfaces among the basic and translational sciences, and regulatory practices. © 2021 The AuthorsVeröffentlichung Life under exceptional conditions̶isotopic niches of benthic invertebrates in the estuarine maximum turbidity zone(2017) Taupp, Thomas; Gergs, René; Hellmann, Claudia; Sahm, RenéVeröffentlichung The Danubian cryptic invader Theodoxus fluviatilis (Gastropoda: Neritidae) in the River Rhine: a potential indicator for metal pollution?(2021) Rothmeier, Louisa Marie; Bartz, Jennifer; Martens, Andreas; Gergs, René; Watermann, Burkard; Sahm, RenéMetal pollution poses a major threat to aquatic systems especially in anthropogenic influenced areas, in as much as metals are persistent in the environment. The freshwater snail Theodoxus fluviatilis has often been used as an indicator species for the ecological status in river monitoring. In the River Rhine, the native Northern-European form of T. fluviatilis is nowadays extinct, whilst the Danubian form is spreading along the river. The aim of our study was to investigate if the cryptic invader is affected by metal exposure present in the River Rhine and to discuss its potential as an indicator for metal pollution. Several environmental abiotic (14 water environmental variables plus five common metal concentrations in water and biofilm) and biotic parameters (biofilm mass) were measured across 23 sites along the River Rhine. Five population and six histopathological parameters were evaluated on snails collected at all 23 sites. Aqueous chromium concentration was positively correlated to the damage of male reproductive organs of T. fluviatilis, and higher ammonium concentration was correlated to a decrease in snail size and an increase in the proportion of juveniles. None of the analysed snail parameters was negatively correlated to concentrations of other metals measured, like copper and zinc. Therefore, based on the parameters evaluated, our results indicate that the Danubian form of T. fluviatilis is only restrictedly suitable as an indicator for metal pollution in the River Rhine system. Further field and laboratory investigations including other stressors are necessary to evaluate the indicator potential of the cryptic invader holistically. © The Author(s) 2021Veröffentlichung The auxin herbicide mecoprop-P in new light: Filling the data gap for dicotyledonous macrophytes(2021) Feibicke, Michael; Gergs, René; Sahm, René; Hönemann, Linda; Kusebauch, Björn; Mohr, Silvia; Périllon, CécileMecoprop-P (MCPP-P) is an auxin herbicide which has been used against dicotyledonous weed plants since the 1980s. While fate and monitoring data of MCPP-P in the aquatic environment revealing concentrations up to 103 ÎÌg/L in freshwaters are well documented, only very few toxicity data and no studies with dicotyledonous macrophytes have been published in open literature so far. To fill up this essential data gap, a microcosm study was conducted in order to test the sensitivity of nine dicotyledonous and one Ceratophyllales macrophyte species. The plant species were exposed to seven MCPP-P concentrations ranging from 8 to 512 (micro)g/L for 21/22 days in one microcosm per concentration, and two further microcosms served as controls. Plant preparation was adapted to each species and endpoints were measured to calculate growth rates. Data were generated to obtain effect concentrations (ECX) which then were used to construct species sensitivity distribution curves (SSD). Eight species proved to be sensitive to MCPP-P in the tested concentration range with EC50 values ranging from 46.9 (micro)g/L for Ranunculus aquatilis to 656.4 (micro)g/L MCPP-P for Ludwigia repens. Taking the EC50 values of this study and published data for autotrophic organisms into account, a hazard concentration (HC5) of 2.7 (micro)g/L was derived from the SSD curve, while an SSD curve without dicotyledonous macrophytes resulted in an about 100 times higher HC5 (360.8 (micro)g/L MCCP-P). This confirms that a re-evaluation for old auxin herbicides by including dicotyledonous test species into the environmental risk assessment may be indicated. Furthermore, the use of MCPP-P in bitumen felts as protection against rooting by plants is not in the focus of any risk regulation so far. This application, however, can lead to high run-off concentrations that can enter surface waters easily, exceeding the new regulatory acceptable concentration values. © 2021 The Authors