Auflistung nach Autor:in "Sahm, René"

Gerade angezeigt 1 - 20 von 20

Altes Herbizid - neu beleuchtet: Wirkung von Mecoprop-P auf Wasserpflanzen
(2019) Périllon, Cécile; Mohr, Silvia; Alscher, Bonny; Sahm, René; Janthur, Ina; Schmiediche, Ronny; Feibicke, Michael; Pabst, Silke; Hönemann, Linda
Are laboratory transferred fungal communities representative for the evaluation of xenobiotic stressors?
(2021) Carl, Steffen C.; Mohr, Silvia; Sahm, René
Better define beta-optimizing MDD (minimum detectable difference) when interpreting treatment-related effects of pesticides in semi-field and field studies
(2020) Alalouni, Urwa; Duquesne, Sabine; Egerer, Sina Elisabeth; Frische, Tobias; Gergs, René; Gräff, Thomas; Sahm, René; Pieper, Silvia; Wogram, Jörn
The minimum detectable difference (MDD) is a measure of the difference between the means of a treatment and the control that must exist to detect a statistically significant effect. It is a measure at a defined level of probability and a given variability of the data. It provides an indication for the robustness of statistically derived effect thresholds such as the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC) when interpreting treatment-related effects on a population exposed to chemicals in semi-field studies (e.g., micro-/mesocosm studies) or field studies. MDD has been proposed in the guidance on tiered risk assessment for plant protection products in edge of field surface waters (EFSA Journal 11(7):3290, 2013), in order to better estimate the robustness of endpoints from such studies for taking regulatory decisions. However, the MDD calculation method as suggested in this framework does not clearly specify the power which is represented by the beta-value (i.e., the level of probability of type II error). This has implications for the interpretation of experimental results, i.e., the derivation of robust effect values and their use in risk assessment of PPPs. In this paper, different methods of MDD calculations are investigated, with an emphasis on their pre-defined levels of type II error-probability. Furthermore, a modification is suggested for an optimal use of the MDD, which ensures a high degree of certainty for decision-makers. © 2020 Springer Nature Switzerland AG
Can the fungicide penconazole alter the community composition of the aquatic mycobiome on Alnus glutinosa leaf litter?
(2023) Carl, Steffen C.; Baschien, Christiane; Mohr, Silvia; Kusebauch, Björn; Sahm, René
Excerpt of an upcoming publication. Abstract: Aquatic fungi (AF) play a key role in the turnover of organic matter in freshwater ecosystems, such as leaf litter in streams. Fungicides that reach streams via spray drift or surface runoff from agricultural activities may endanger the diversity of AF. In the present proof-of-principle study, we used high throughput sequencing (HTS) of total DNA to investigate composition changes of a natural leaf litter associated aquatic mycobiome in stream channels and in flask microcosms that were treated with 250 (micro)g/L of the azole fungicide penconazole. Treated samples were compared with control samples from untreated systems and samples from the reference stream over a period of three weeks. The community composition (in terms of presence/absence) in fungicide treated and control samples was comparable on leaves, which were conditioned for two weeks in the reference stream prior to fungicide exposure. Here, only the read numbers of two key taxa indicated an abundance shift that was most likely related to the fungicide effect. However, strong diversity effects were observed during the following long-term recolonization (85d) of sterilized leaves under penconazole influence (starting with 160 (micro)g/L a. s.), in which key taxa were significantly reduced in their presence or even absent in fungicide treated stream channels. Results imply, that HTS of total DNA seems to be particularly effective to detect changes in AF communities during the colonization of leaf litter. Future effect studies could consider recolonization under different conditions and RNA sequencing of preconditioned leaves to corroborate the findings of the present study. Quelle: https://www.researchgate.net/
Can the fungicide penconazole alter the community composition of the aquatic mycobiome on Alnus glutinosa leaf litter?
(2023) Carl, Steffen C.; Baschien, Christiane; Mohr, Silvia; Kusebauch, Björn; Sahm, René
Excerpt of an upcoming publication. Abstract: Aquatic fungi (AF) play a key role in the turnover of organic matter in freshwater ecosystems, such as leaf litter in streams. Fungicides that reach streams via spray drift or surface runoff from agricultural activities may endanger the diversity of AF. In the present proof-of-principle study, we used high throughput sequencing (HTS) of total DNA to investigate composition changes of a natural leaf litter associated aquatic mycobiome in stream channels and in flask microcosms that were treated with 250 (micro)g/L of the azole fungicide penconazole. Treated samples were compared with control samples from untreated systems and samples from the reference stream over a period of three weeks. The community composition (in terms of presence/absence) in fungicide treated and control samples was comparable on leaves, which were conditioned for two weeks in the reference stream prior to fungicide exposure. Here, only the read numbers of two key taxa indicated an abundance shift that was most likely related to the fungicide effect. However, strong diversity effects were observed during the following long-term recolonization (85d) of sterilized leaves under penconazole influence (starting with 160 (micro)g/L a. s.), in which key taxa were significantly reduced in their presence or even absent in fungicide treated stream channels. Results imply, that HTS of total DNA seems to be particularly effective to detect changes in AF communities during the colonization of leaf litter. Future effect studies could consider recolonization under different conditions and RNA sequencing of preconditioned leaves to corroborate the findings of the present study. Quelle: https://www.researchgate.net/
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, Björn
There 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/
Contribution of organic toxicants to multiple stress in river ecosystems
(2016) Schäfer, Ralf B.; Gergs, René; Kuehn, Bernhard; Malaj, Egina; Sahm, René
River 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/
Ecological concepts of complex trophic interactions - bottom-up and top-down regulation of food web and community structures
(2021) Sahm, René
Effects of a realistic pesticide spraying sequence for apple crop on stream communities in mesocosms: negligible or notable?
(2023) Duquesne, Sabine; Feibicke, Michael; Frische, Tobias; Gergs, René; Meinecke, Stefan; Sahm, René; Mohr, Silvia
Background Several large-scale studies revealed impacts and risks for aquatic communities of small rural lakes and streams due to pesticides in agricultural landscapes. It appears that pesticide risk assessment based on single products does not offer sufficient protection for non-target organisms, which are exposed repeatedly to pesticide mixtures in the environment. Therefore, a comprehensive stream mesocosm study was conducted in order to investigate the potential effects of a realistic spraying sequence for conventional orchard farmed apples on a stream community using pesticides at their regulatory acceptable concentrations (RACs). Eight 74-m-long stream mesocosms were established with water, sand, sediment, macrophytes, plankton and benthic macroinvertebrates. In total, nine fungicidal, four herbicidal and four insecticidal pesticides were applied in four of the eight stream mesocosms on 19 spraying event days in the period from April to July while the remaining four stream mesocosms served as controls. The community composition, the abundance of benthos, periphyton and macrophytes, the emergence of insects, physico-chemical water parameters, and drift measurements of aquatic invertebrates were measured. Results The pesticide spraying sequence induced significant effects on invertebrates, periphyton, and macrophytes as well as on the water ion composition especially in the second half of the experiment. It was not possible to relate the observed effects on the community to specific pesticides applied at certain time points and their associated toxic pressure using the toxic unit approach. The most striking result was the statistically significant increase in variation of population response parameters of some taxa in the treated mesocosms compared to the controls. This inter-individual variation can be seen as a general disturbance measure for the ecosystem. Conclusions The pesticide spraying sequence simulated by using RAC values had notable effects on the aquatic stream community in the conducted mesocosm study. The results indicate that the current risk assessment for pesticides may not ensure a sufficient level of protection to the field communities facing multiple pesticide entries due to spraying sequences and other combined stress. Hence, there is still room for improvement regarding the prospective risk assessment of pesticides to further reduce negative effects on the environment. © The Author(s) 2023
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, René
The 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 AG
Effects of laboratory conditions on the composition of leaf detached fungal communities on Alnus glutinosa leaf litter
(2021) Carl, Steffen C.; Mohr, Silvia; Sahm, René; Baschien, Christiane
How to implement stable isotope analyses into ecotoxicological risk assessment of chemicals using aquatic mesocosm experiments?
(2018) Sahm, René; Bayer, Bastian; Feibicke, Michael; Mohr, Silvia; Schmidt, Ralf
Is Dikerogammarus villosus (Crustacea, Gammaridae) a 'killer shrimp' in the River Rhine system?
(2016) Koester, Meike; Bayer, Bastian; Gergs, René; Sahm, René
Communities 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.com
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, René
Dikerogammarus 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.
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, Silvia
Community 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 Authors
Life under exceptional conditions̶isotopic niches of benthic invertebrates in the estuarine maximum turbidity zone
(2017) Taupp, Thomas; Gergs, René; Hellmann, Claudia; Sahm, René
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, Cécile
Mecoprop-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
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, René
Metal 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) 2021
The Ponto-Caspian parasite Plagioporus cf. skrjabini reaches the River Rhine system in Central Europe: higher infestation in the native than in the introduced Danubian form of the gastropod Theodoxus fluviatilis
(2021) Rothmeier, Louisa Marie; Gergs, René; Sahm, René; Watermann, Burkard
The introduction of non-indigenous organisms in new areas in the context of host-parasite interactions is still poorly understood. This study aimed at a parasitological and histopathological comparison of two phylogenetically distinct forms of the freshwater snail Theodoxus fluviatilis in the River Rhine system: the native Northern-European form, which showed a decline for unknown reasons and is nowadays extinct in the River Rhine, and the non-indigenous Danubian form, which was introduced via the Mainâ€ÌDanube canal. We histopathologically examined populations of Northern-European T. fluviatilis from three smaller rivers of the Rhine system and of Danubian T. fluviatilis from the River Rhine, after confirming the phylogenetic background of the respective population genetically. Results showed differences in the prevalence of trematodes and histopathologic organic alterations between the two snail forms. Both were infected with an opecoelid trematode Plagioporus cf. skrjabini, whereby its prevalence was significantly higher in the Northern-European than in the Danubian form. The parasitic trematode is, to our knowledge, a new trematode species in the River Rhine system, presumably co-introduced through the invasion of its second intermediate and final hosts, i.e. Ponto-Caspian amphipods and gobies. Its impact on native populations of Northern-European T. fluviatilis needs to be subject of future studies. The Author(s) 2021
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, Silvia
For 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 Authors