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  • 1
    Language: English
    In: Environmental Sciences Europe, 2011, Vol.23(1), pp.1-14
    Description: Byline: Sabine Ulrike Gerbersdorf (1,35), Hendrik Schubert (2,35) Keywords: phytoplankton; vertical migration; UV radiation; PAR; cDOM; underwater light spectrum. Abstract: Background The vertical migration of phytoplankton was investigated in natural waters using in situ fluorescence profiling, chlorophyll a concentrations and life counts at two study sites differing in coloured dissolved organic matter (cDOM) concentrations. The data from the corresponding water depths (50-cm intervals down to 10 m) and times (hourly, before dawn to sunset, several days) were related to the highly resolved (2 nm) underwater ultraviolet radiation (UVR)/photosynthetic active radiation (PAR) transparency (290 to 700 nm). Results Chlorophyll a maxima of mainly motile dinoflagellates were observed in situ at all days and at both study sites (open marine, brackish waters), independent on prevailing weather conditions or cDOM concentrations. Phytoplankton migration was triggered solely by irradiance in the 400- to 700-nm wavelength range (PAR) at the particular water depth, irrespective of PAR/UVR ratios and surface UVR (290 to 400 nm), after an illumination period of about 40 min. Interestingly, the PAR tolerance levels of the phytoplankton, which have been lower in cDOM-rich waters, matched their light acclimation values determined by parallel PAM measurements. Conclusions The response of the phytoplankton to PAR is not a sufficient protection strategy versus increasing UVR levels, which might have wide ecological implications beyond the level of primary producers to impact important ecosystem functions such as the delicate trophic interactions. Author Affiliation: (135) Institute of Hydraulic Engineering, Hydraulic Laboratory, University of Stuttgart, Pfaffenwaldring 61, 70569, Stuttgart, Germany (235) Institute of Biosciences, Aquatic Ecology, University of Rostock, Albert-Einstein Street 3, 18051, Rostock, Germany Article History: Registration Date: 03/08/2011 Received Date: 03/08/2011 Accepted Date: 25/11/2011 Online Date: 25/11/2011
    Keywords: phytoplankton ; vertical migration ; UV radiation ; PAR ; cDOM ; underwater light spectrum.
    ISSN: 2190-4707
    E-ISSN: 1865-5084
    E-ISSN: 21904715
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  • 2
    Language: English
    In: PLoS ONE, 2012, Vol.7(4), p.e31183
    Description: The accumulation of the widely-used antibacterial and antifungal compound triclosan (TCS) in freshwaters raises concerns about the impact of this harmful chemical on the biofilms that are the dominant life style of microorganisms in aquatic systems. However, investigations to-date rarely go beyond effects at the cellular, physiological or morphological level. The present paper focuses on bacterial biofilms addressing the possible chemical impairment of their functionality, while also examining their substratum stabilization potential as one example of an important ecosystem service. The development of a bacterial assemblage of natural composition – isolated from sediments of the Eden Estuary (Scotland, UK) – on non-cohesive glass beads (〈63 µm) and exposed to a range of triclosan concentrations (control, 2 – 100 µg L −1 ) was monitored over time by Magnetic Particle Induction (MagPI). In parallel, bacterial cell numbers, division rate, community composition (DGGE) and EPS (extracellular polymeric substances: carbohydrates and proteins) secretion were determined. While the triclosan exposure did not prevent bacterial settlement, biofilm development was increasingly inhibited by increasing TCS levels. The surface binding capacity (MagPI) of the assemblages was positively correlated to the microbial secreted EPS matrix. The EPS concentrations and composition (quantity and quality) were closely linked to bacterial growth, which was affected by enhanced TCS exposure. Furthermore, TCS induced significant changes in bacterial community composition as well as a significant decrease in bacterial diversity. The impairment of the stabilization potential of bacterial biofilm under even low, environmentally relevant TCS levels is of concern since the resistance of sediments to erosive forces has large implications for the dynamics of sediments and associated pollutant dispersal. In addition, the surface adhesive capacity of the biofilm acts as a sensitive measure of ecosystem effects.
    Keywords: Research Article ; Biology ; Chemistry ; Earth Sciences ; Engineering ; Genetics And Genomics ; Chemistry ; Microbiology ; Ecology ; Marine And Aquatic Sciences ; Developmental Biology ; Biochemistry
    E-ISSN: 1932-6203
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  • 3
    In: Freshwater Biology, June 2016, Vol.61(6), pp.963-978
    Description: Fine sediments (fine sands or silts) are significantly impacted by microbial biostabilisation. This process complicates precise modelling solutions for sediment dynamics and management strategies for riverine sediment. The present publication investigates the effect of seasonality upon biostabilisation. In total, five straight flume experiments with fluvial water were performed during spring, summer and autumn under identical boundary conditions. The extracellular polymeric substances (EPS), microbial biomass and microbial community composition of the developing biofilms were analysed. In addition, biofilm adhesiveness was measured. Highest biostabilisation occurred during spring (up to six times greater than during autumn) and coincided with maximal EPS production – especially extracellular proteins indicating the essential role of adhesive proteins for the stability of the biofilm matrix. Furthermore, not biomass but microbial community composition significantly differed between seasons. For instance, during minimal biostabilszation in autumn, the diatom community was dominated by the motile diatoms Nitzschia fonticola and Nitzschia dissipata var. dissipata. Concurrently, the highest rates of change within the bacterial community were detected. This suggests a disruptive impact of diatom movement upon the biofilm matrix and overall biofilm stability. These findings emphasise the importance of detailed analyses of the microbial community and demonstrate the complex interactions of distinct biofilm features influencing the functionality of the overall biofilm system.
    Keywords: Biofilm ; Biostabilisation ; Diatoms ; Fine Sediment ; Magnetic Particle Induction
    ISSN: 0046-5070
    E-ISSN: 1365-2427
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  • 4
    Language: English
    In: Journal of Soils and Sediments, 2011, Vol.11(6), pp.1099-1114
    Description: Byline: Sabine Ulrike Gerbersdorf (1), Henner Hollert (2), Markus Brinkmann (2), Silke Wieprecht (1), Holger Schuttrumpf (3), Werner Manz (4) Keywords: Biofilm; Freshwater; Interdisciplinary approach; Management of sediments; Pollutants; Risk assessment Abstract: Purpose Freshwater sediments and their attached microbial communities (biofilms) are essential features of rivers and lakes, providing valuable ecosystem services such as nutrient recycling or self-purification which extend beyond the aquatic environment. Anthropogenic pollutants, whether from the industrial era or as a result of our contemporary lifestyles, can negatively affect these functions with hitherto unknown consequences on ecology, the economy and human health. Thus far, the singular view of the involved disciplines such as ecotoxicology, environmental microbiology, hydrology and geomorphology has prevented a deeper understanding of this emerging issue. Main features This paper discusses briefly the progressions and the state-of-the-art methods within the disciplines of concern related to contaminated sediments, ranging from ecotoxicological test systems, microbiological/molecular approaches to unravel changes of microbial ecosystems, up to the modelling of sediment transport and sorption/desorption of associated pollutants. The first bilateral research efforts on contaminated sediments include efforts to assess ecotoxicological sediment risk including sediment mobility (i.e. ecotoxicology and engineering), enhance bioremediation potential (i.e. microbiology and ecotoxicology) or to understand biostabilisation processes of sediments by microbial assemblages (i.e. microbiology and engineering). Conclusions and perspectives In freshwater habitats, acute, chronic and mechanism-specific toxic effects on organisms, shifts in composition, structure and functionality of benthic microbial communities, as well as the obstruction of important ecosystem services by continuously discharged and long-deposited pollutants, should be related to the in situ sediment dynamics. To achieve an improved understanding of the ecology of freshwater sediments and the impairment of their important ecosystem functions by human-derived pollutants, we suggest a "triad plus x" approach combining advanced methods of ecotoxicology, environmental microbiology and engineering science. Author Affiliation: (1) Department of Hydraulic Engineering and Water Resources Management, Institute of Hydraulic Engineering, University Stuttgart, Pfaffenwaldring 61, 70569, Stuttgart, Germany (2) Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringer Weg 1, 52074, Aachen, Germany (3) Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen University, Mies-van-der-Rohe-Strasse 1, 52056, Aachen, Germany (4) Institute for Integrated Natural Sciences, University Koblenz--Landau, Universitatsstrasse 1, 56070, Koblenz, Germany Article History: Registration Date: 25/04/2011 Received Date: 20/11/2010 Accepted Date: 24/04/2011 Online Date: 11/05/2011 Article note: Responsible editor: Ian G. Droppo
    Keywords: Biofilm ; Freshwater ; Interdisciplinary approach ; Management of sediments ; Pollutants ; Risk assessment
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 5
    Language: English
    In: PLoS ONE, 01 January 2010, Vol.5(11), p.e13794
    Description: It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed ("ecosystem engineers") through the secretion of naturally adhesive organic material (EPS: extracellular polymeric substances). However, little is known about the individual...
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 6
    Language: English
    In: Water, 01 September 2015, Vol.7(9), pp.5061-5077
    Description: In contrast to non-cohesive sediments, the incipient motion of cohesive sediments is characterized by much more complex interactions between several sedimentary, biological, and chemical parameters. Thus, site-specific investigations are required to obtain information about the erosion stability...
    Keywords: Cohesive Sediments ; Incipient Motion ; in Situ Measurement Techniques ; Laboratory Measurement Techniques ; Bulk Density ; Particle Size Distribution ; Engineering
    E-ISSN: 2073-4441
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  • 7
    Language: English
    In: Journal of Soils and Sediments, 2018, Vol.18(10), pp.3041-3043
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 8
    Language: English
    In: International Journal of Sediment Research, December 2015, Vol.30(4), pp.273-284
    Description: Biofilm growth may considerably influence the erodibility of river bed sediments and is, thus, an important morphological feature. The extent to which the sediment is stabilized depends on many environmental conditions and even though it is well accepted that these conditions are responsible for the variance of results obtained from field studies, little is known about their impact on biostabilization. In this article, the results from five long-term (4–8 weeks) experiments are presented, investigating the impact of hydrodynamics and light intensity on biostabilization in different seasons. Biofilms are cultivated in a sophisticated setup of six identical straight flumes by circulating natural river water over glass beads with diameters between 0.1 and 0.2 mm. During the course of the experiments biofilm samples are eroded regularly to determine the critical shear stress and to learn more about the erosional behavior of biostabilized sediments. The results indicate a large variance of biostabilization between seasons with the highest values in spring and the lowest in late autumn. Presumably, this is explained by the differences in biofilm growth and composition resulting in mechanically diverse responses to the increased bed shear stress. Higher bed shear stress during cultivation delayed biofilm growth possibly due to reduced net attachment and growth of formerly advected microbes on the sediment surface. Unexpectedly, no substantial biostabilization effect is detected in experiments where biofilms are cultivated in darkness. Another focus in this article is the analysis of the mechanical behavior observed during erosion of the biofilms, that is shown to be an important aspect for the understanding of freshwater biostabilization caused by young growing biofilms.
    Keywords: Biofilm ; Critical Bed Shear Stress ; Erosion Mechanisms ; Environmental Conditions ; Seasonal Variations ; Geology
    ISSN: 1001-6279
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  • 9
    Language: English
    In: Biofouling, 03 July 2018, Vol.34(6), pp.618-629
    Description: The adhesiveness and stability of ubiquitously distributed biofilms is a significant issue in many areas such as ecology, biotechnology and medicine. The magnetic particle induction (MagPI) system allows precise determinations of biofilm adhesiveness at high temporal and spatial resolution...
    Keywords: Biofilm ; Adhesion ; Stability ; Magpi ; Electromagnet ; Oceanography ; Ecology
    ISSN: 0892-7014
    E-ISSN: 1029-2454
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  • 10
    Language: English
    In: Research and Reports in Biology, 2018, Vol.9, p.1(16)
    Description: Biofilms constitute an important issue in microbial ecology, due to their high ecological and economic relevance, but the impact of abiotic conditions and microbial key players on the development and functionality of a natural biofilm is still little understood. This study investigated the effects of light intensity (LI) and bed shear stress (BSS) and the role of dominant microbes during the formation of natural biofilms and particularly the process microbial biostabilization. A comprehensive analysis of microbial biomass, extracellular polymeric substances produced, and the identification of dominant bacterial and algal species was correlated with assessment of biofilm adhesiveness/stability. LI and BSS impacted the biofilms in very different ways: biofilm adhesiveness significantly increased with LI and decreased with BSS. Moreover, microbial biomass and the functional organization of the bacterial community increased with LI, while the dynamics in the bacterial community increased with BSS. Most stable biofilms were dominated by sessile diatoms like Achnanthidium minutissimum or Fragilaria pararumpens and bacteria with either filamentous morphology, such as Pseudanabaena biceps, or a potential high capacity for extracellular polymeric-substance production, such as Rubrivivax gelatinosus. In contrast, microbes with high motility, such as Nitzschia fonticola, Pseudomonas fluorescens, and Caulobacter vibrioides, dominated the least adhesive biofilms. Their movement and potential antibiotic production could have had a disruptive impact on the biofilm matrix, which decreased its stability. This is the first study to unveil the link between abiotic conditions and resulting shifts in key microbial players to impact the ecosystem-service microbial biostabilization. Keywords: microbial biostabilization, natural biofilms, abiotic factors, microbial community, mesocosm
    Keywords: Ecosystem Components – Analysis
    ISSN: 1179-7274
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