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  • Article  (48)
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  • Article  (48)
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  • 1
    Language: English
    In: The Science of the Total Environment, Feb 15, 2015, Vol.506-507, p.353(8)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2014.11.043 Byline: Norbert Kamjunke, Peter Herzsprung, Thomas R. Neu Abstract: Streams and rivers are important sites of organic carbon mineralization which is dependent on the land use within river catchments. Here we tested whether planktonic and epilithic biofilm bacteria differ in their response to the quality of dissolved organic carbon (DOC). Thus, planktonic and biofilm bacterial production was compared with patterns of DOC along a land-use gradient in the Bode catchment area (Germany). The freshness index of DOC was positively related to the proportion of agricultural area in the catchment. The humification index correlated with the proportion of forest area. Abundance and production of planktonic bacteria were lower in headwaters than at downstream sites. Planktonic production was weakly correlated to the total concentration of DOC but more strongly to quality-measures as revealed by spectra indexes, i.e. positively to the freshness index and negatively to the humification index. In contrast to planktonic bacteria, abundance and production of biofilm bacteria were independent of DOC quality. This finding may be explained by the association of biofilm bacteria with benthic algae and an extracellular matrix which represent additional substrate sources. The data show that planktonic bacteria seem to be regulated at a landscape scale controlled by land use, whereas biofilm bacteria are regulated at a biofilm matrix scale controlled by autochthonous production. Thus, the effects of catchment-scale land use changes on ecosystem processes are likely lower in small streams dominated by biofilm bacteria than in larger streams dominated by planktonic bacteria. Article History: Received 4 September 2014; Revised 11 November 2014; Accepted 11 November 2014 Article Note: (miscellaneous) Editor: C.E.W. Steinberg
    Keywords: Bacteria
    ISSN: 0048-9697
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Hydrobiologia, 2010, Vol.649(1), pp.379-383
    Description: To investigate the consequences of increased temperature and enhanced input of dissolved organic matter (DOM) into lakes for heterotrophicic bacteria and for mixotrophic algae which use DOM in addition to photosynthesis, the hypotheses were tested whether (1) both bacteria and mixotrophic algae benefit from increased input of DOM, or (2) increased DOM input enhances bacterial biomass and thereby decreases algal biomass. Growth experiments in batch cultures, exudation measurements, and competition experiments in chemostats were performed at two temperature levels. Increased temperature stimulated the autotrophic growth rate of Chlorella protothecoides . Bacteria and Chlorella increased their heterotrophic growth rates at higher DOM concentration at lower temperature whereas enhanced DOM concentration hardly stimulated their growth at higher temperature. In chemostats, enhanced input of soil extract increased both bacterial and algal biomass at lower temperature whereas bacterial biomass increased only slightly and algal biomass decreased at higher temperature. Thus, the temperature determines the response of microorganisms to enhanced DOM concentration.
    Keywords: Bacteria ; Mixotrophic algae ; Temperature ; DOM ; Climate change ; Chemostat
    ISSN: 0018-8158
    E-ISSN: 1573-5117
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  • 3
    Language: English
    In: Science of the Total Environment, 01 April 2016, Vol.548-549, pp.51-59
    Description: Enhanced concentrations of dissolved organic matter (DOM) in freshwaters are an increasing problem in drinking water reservoirs. In this study we investigated bacterial DOM degradation rates in the tributaries of the reservoirs and tested the hypotheses that (1) DOM degradation is high enough to decrease DOM loads to reservoirs considerably, (2) DOM degradation is affected by stream hydrology, and (3) phosphorus addition may stimulate bacterial DOM degradation. Bacterial biomass production, which was used as a measure of DOM degradation, was highest in summer, and was usually lower at upstream than at downstream sites. An important proportion of bacterial production was realized in epilithic biofilms. Production of planktonic and biofilm bacteria was related to water temperature. Planktonic production weakly correlated to DOM quality and to total phosphorus concentration. Addition of soluble reactive phosphorus did not stimulate bacterial DOM degradation. Overall, DOM was considerably degraded in summer at low discharge levels, whereas degradation was negligible during flood events (when DOM load in reservoirs was high). The ratio of DOM degradation to total DOM release was negatively related to discharge. On annual average, only 0.6–12% of total DOM released by the catchments was degraded within the tributaries.
    Keywords: Bacterial Production ; Doc ; Freshness Index ; Humification Index ; Phosphorus ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: Water Research, 15 October 2017, Vol.123, pp.513-523
    Description: Streams are important sites of transformation of dissolved organic matter (DOM). The molecular characterization of DOM-quality changes requires sophisticated analytical evaluation techniques. The goal of our study was to link molecular DOM transformation with bacterial activity. We measured the degradation of leaf leachate over a gradient of bacterial production obtained by different rates of percolation of sediments in seven experimental flumes on five sampling dates. We developed a new strategy for evaluating molecular formula data sets obtained by ultra-high resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), in which the time-dependent change of component abundance was fitted by a linear regression model after normalization of mass peak intensities. All components were categorized by calculating the slope (change of percent intensity per day) in each of the seven flumes. These slopes were then related to cumulative bacterial production. The concentration of DOM decreased quickly in all flumes. Bacterial activity was higher in flumes with percolated sediment than in those without percolation, whereas plankton bacterial activity was higher in flumes without percolation or without sediment. There were no differences in molecular-DOM characteristics between flumes, but there were distinct changes over time. Positive slopes, i.e. increasing intensities over time, were found for small molecules (MW 〈 450 Da) and high O/C ratios, whereas decreasing intensities were observed less often and only for large molecules and low O/C ratios. The positive slopes of produced components showed a positive relationship to bacterial production for small and for oxygen-rich components. The negative slopes of degraded components were negatively related to bacterial production for large and for oxygen-deficient molecules. Overall, the approach provided new insights into the transformation of specific molecular DOM components.
    Keywords: Bacterial Production ; Biofilm ; DOM ; Fticr MS ; Leaf Leachate ; Stream ; Engineering
    ISSN: 0043-1354
    E-ISSN: 1879-2448
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  • 5
    Language: English
    In: Science of the Total Environment, 15 January 2017, Vol.577, pp.329-339
    Description: Pre-dams are small reservoirs constructed upstream of the main drinking water reservoirs and are used for nutrient removal and sediment trapping. Little is known about the role of pre-dams regarding the production and decomposition of dissolved organic carbon (DOC) in relation to discharge and how this affects the quality of DOC in the water. We combined quantitative and qualitative investigations under different hydrological conditions at three pre-dams exhibiting a gradient from oligotrophic/high-DOC to eutrophic/low-DOC. All pre-dams were mainly autotrophic in their upper water layers. The ratio of OC production to total gained OC (i.e. OC import + OC production) decreased with increasing discharge. On average, 0–30% of the total gained OC was produced within the pre-dams. The amount of microbially decomposed DOC increased with the average water residence time (WRT) and with the trophic status of the pre-dams. Radiocarbon analyses of respired CO revealed that heterotrophic bacteria preferentially utilized old DOC components (195–395 years before present) under base flow conditions, whereas younger components (modern, i.e. OC produced after 1950) were utilized at high discharge. DOC quality changed significantly over the year within the pre-dams: High proportions of algae-derived DOC were observed during base flow in summer, and the freshness index (β/α ratio) decreased significantly with higher discharges. DOC production and quality changes in response to hydrological conditions should be considered for future water quality management in reservoirs, as climate scenarios for temperate regions predict decreased runoffs leading to longer WRT and increased eutrophication and production of algae-derived OC.
    Keywords: Carbon Isotopes ; 14c ; Autotrophy ; Microbial Decomposition ; Fluorescence ; Net Production ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 6
    Language: English
    In: Science of the Total Environment, 15 February 2015, Vol.506-507, pp.353-360
    Description: Streams and rivers are important sites of organic carbon mineralization which is dependent on the land use within river catchments. Here we tested whether planktonic and epilithic biofilm bacteria differ in their response to the quality of dissolved organic carbon (DOC). Thus, planktonic and biofilm bacterial production was compared with patterns of DOC along a land-use gradient in the Bode catchment area (Germany). The freshness index of DOC was positively related to the proportion of agricultural area in the catchment. The humification index correlated with the proportion of forest area. Abundance and production of planktonic bacteria were lower in headwaters than at downstream sites. Planktonic production was weakly correlated to the total concentration of DOC but more strongly to quality-measures as revealed by spectra indexes, i.e. positively to the freshness index and negatively to the humification index. In contrast to planktonic bacteria, abundance and production of biofilm bacteria were independent of DOC quality. This finding may be explained by the association of biofilm bacteria with benthic algae and an extracellular matrix which represent additional substrate sources. The data show that planktonic bacteria seem to be regulated at a landscape scale controlled by land use, whereas biofilm bacteria are regulated at a biofilm matrix scale controlled by autochthonous production. Thus, the effects of catchment-scale land use changes on ecosystem processes are likely lower in small streams dominated by biofilm bacteria than in larger streams dominated by planktonic bacteria.
    Keywords: Bacterial Production ; Doc ; Freshness Index ; Humification Index ; Biofilm ; Confocal Laser Scanning Microscopy (Clsm) ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 7
    Language: English
    In: Environmental Monitoring and Assessment, 2013, Vol.185(11), pp.9221-9236
    Description: The Bode catchment (Germany) shows strong land use gradients from forested parts of the National Park (23 % of total land cover) to agricultural (70 %) and urbanised areas (7 %). It is part of the Terrestrial Environmental Observatories of the German Helmholtz association. We performed a biogeochemical analysis of the entire river network. Surface water was sampled at 21 headwaters and at ten downstream sites, before (in early spring) and during the growing season (in late summer). Many parameters showed lower concentrations in headwaters than in downstream reaches, among them nutrients (ammonium, nitrate and phosphorus), dissolved copper and seston dry mass. Nitrate and phosphorus concentrations were positively related to the proportion of agricultural area within the catchment. Punctual anthropogenic loads affected some parameters such as chloride and arsenic. Chlorophyll a concentration and total phosphorus in surface waters were positively related. The concentration of dissolved organic carbon (DOC) was higher in summer than in spring, whereas the molecular size of DOC was lower in summer. The specific UV absorption at 254 nm, indicating the content of humic substances, was higher in headwaters than in downstream reaches and was positively related to the proportion of forest within the catchment. CO 2 oversaturation of the water was higher downstream compared with headwaters and was higher in summer than in spring. It was correlated negatively with oxygen saturation and positively with DOC concentration but negatively with DOC quality (molecular size and humic content). A principle component analysis clearly separated the effects of site (44 %) and season (15 %), demonstrating the strong effect of land use on biogeochemical parameters.
    Keywords: TERENO ; Land use ; Nutrients ; Heavy metals ; DOC ; Bode
    ISSN: 0167-6369
    E-ISSN: 1573-2959
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  • 8
    Language: English
    In: Science of the Total Environment, 15 December 2015, Vol.537, pp.129-138
    Description: Chile is the second largest producer of salmonids worldwide. The first step in the production of salmonids takes place in land-based aquacultures. However, the effects of the discharge from these aquacultures on stream dissolved organic matter (DOM) content, molecular composition and degradability are unknown. The aim of this study was thus to investigate the inputs of anthropogenic DOM from land-based aquaculture to the predominantly pristine river systems of North Patagonia. We hypothesized, that i) DOM exported from land-based aquaculture mainly consists of protein-like fluorescence (tyrosine and tryptophan) released from fish feces and food remains, and that ii) this DOM is highly degradable and therefore rapidly turned-over within the receiving streams. In the North Patagonian region we conducted a screening of ten land-based aquacultures and an intensive sampling campaign for one aquaculture. This was combined with longitudinal transects and a degradation experiment in order to couple the composition of DOM exported from land-based aquacultures to its degradability in streams. We measured dissolved organic carbon (DOC) concentration by high-temperature catalytic oxidation and DOM composition by fluorescence spectroscopy and parallel factor analysis. In the effluent of the ten screened aquacultures and in the repeated sampling of one aquaculture, we consistently found an increase of DOC concentrations and a dominance of protein-like fluorescence. The protein-like fluorescence rapidly disappeared downstream of the aquacultures, and in the degradation experiment. 21% of the DOC export from the repeatedly sampled aquaculture resulted from food addition and 76% from fish production. We conclude that large amounts of degradable DOM are exported from land-based aquacultures. This probably has strong effects on the ecological structure and function of North Patagonian streams, and similarly affected streams worldwide.
    Keywords: Aquaculture ; Organic Contamination ; Dissolved Organic Matter ; Fluorescence Spectroscopy ; Fish Farms ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 9
    Language: English
    In: Science of the Total Environment, 01 June 2018, Vol.625, pp.519-530
    Description: A large part of the organic carbon in streams is transported by pulses of terrestrial dissolved organic carbon (tDOC) during hydrological events, which is more pronounced in agricultural catchments due to their hydrological flashiness. The majority of the literature considers stationary benthic biofilms and hyporheic biofilms to dominate uptake and processing of tDOC. Here, we argue for expanding this viewpoint to planktonic bacteria, which are transported downstream together with tDOC pulses, and thus perceive them as a less variable resource relative to stationary benthic bacteria. We show that pulse DOC can contribute significantly to the annual DOC export of streams and that planktonic bacteria take up considerable labile tDOC from such pulses in a short time frame, with the DOC uptake being as high as that of benthic biofilm bacteria. Furthermore, we show that planktonic bacteria efficiently take up labile tDOC which strongly increases planktonic bacterial production and abundance. We found that the response of planktonic bacteria to tDOC pulses was stronger in smaller streams than in larger streams, which may be related to bacterial metacommunity dynamics. Furthermore, the response of planktonic bacterial abundance was influenced by soluble reactive phosphorus concentration, pointing to phosphorus limitation. Our data suggest that planktonic bacteria can efficiently utilize tDOC pulses and likely determine tDOC fate during downstream transport, influencing aquatic food webs and related biochemical cycles.
    Keywords: Terrestrial Doc ; Agricultural Catchment ; Flood Pulse ; Hydrology ; Bacteria ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 10
    In: Limnology and Oceanography, May 2000, Vol.45(3), pp.741-743
    Description: In experiments with axenic cultures of , we tested whether this cyanobacterium incorporates leucine, a compound that is often used for the measurement of heterotrophic bacterioplankton production. showed significant leucine incorporation, and the uptake of exponentially growing cells was higher than the uptake of cells in stationary growth phase. Therefore, the leucine method may not be suitable for measuring bacterial production in highly eutrophic waters with a dominance of cyanobacteria.
    Keywords: Oceanography;
    ISSN: 0024-3590
    E-ISSN: 1939-5590
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