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  • 1
    Language: English
    In: Microbial Ecology, 2002, Vol.44(1), pp.19-29
    Description: Heterotrophic nanoftagellates (HNF) make up a large fraction of the Zooplankton biomass of rivers. Their abundance can be strongly affected by water discharge, but the consequences of this highly dynamic factor for their main prey, the bacteria, is still unknown. The focus of this study was on bacterial-HNF interactions in the Lower River Rhine (Germany) with respect to the discharge-dependent dynamics. The bacterial and HNF abundances and biomasses were determined over the course of 17 months. The potential consumption of bacteria by HNF was calculated based on the biomass data and on data on the HNF production. The mean bacterial abundance in the Rhine at Cologne ranged from 0.3×10 6 to 3.5×10 6 cells mL −1 with lowest abundances in winter and highest in late spring. No significant changes in abundance during the downstream passage were found. Neither could a significant correlation be found between bacterial and HNF abundance. The ratio of bacterial to HNF abundance showed high variations which lay between 166 and 19,055 and was negatively dependent on water discharge. Monthly routine calculations on the potential bacterial consumption by HNF revealed a clearance of between 2 and 66% of the bacterial standing stock d −1 . The values increased greatly with water discharge and could exceed 100% d −1 at times of high water flow. The presented data suggests a change in the top-down control of the planktonic bacteria due to the water discharge: The importance of benthic predation at low water flow (high contact probability to benfhic predators) gives way to an increased importance in predation by planktonic HNF at high water flow.
    Keywords: Freshwater ; Freshwater ; Species Interactions: General;
    ISSN: 0095-3628
    E-ISSN: 1432-184X
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  • 2
    Language: English
    In: Proceedings of the National Academy of Sciences of the United States of America, 1 January 2010, Vol.107(1), pp.115-120
    Description: Eukaryotic microbial life at abyssal depths remains "uncharted territory" in eukaryotic microbiology. No phylogenetic surveys have focused on the largest benthic environment on this planet, the abyssal plains. Moreover, knowledge of the spatial patterns of deep-sea community structure is scanty, and what little is known originates primarily from morphology-based studies of foraminiferans. Here we report on the great phylogenetic diversity of microbial eukaryotic communities of all 3 abyssal plains of the southeastern Atlantic Ocean—the Angola, Cape, and Guinea Abyssal Plains—from depths of 5,000 m. A high percentage of retrieved clones bad no close representatives in genetic databases. Many clones were affiliated with parasitic species. Furthermore, differences between the communities of the Cape Abyssal Plain and the other 2 abyssal plains point to environmental gradients apparently shaping community structure at the landscape level. On a regional scale, local species diversity showed much less variation. Our study provides insight into the community composition of microbial eukaryotes on larger scales from the wide abyssal sea floor realm and marks a direction for more detailed future studies aimed at improving our understanding of deep-sea microbes at the community and ecosystem levels, as well as the ecological principles at play.
    Keywords: Physical sciences -- Earth sciences -- Geography ; Behavioral sciences -- Anthropology -- Applied anthropology ; Biological sciences -- Ecology -- Population ecology ; Biological sciences -- Biology -- Evolutionary studies ; Biological sciences -- Biology -- Cytology ; Biological sciences -- Ecology -- Population ecology ; Business -- Industry -- Industrial sectors ; Physical sciences -- Earth sciences -- Geography ; Mathematics -- Pure mathematics -- Discrete mathematics ; Biological sciences -- Ecology -- Ecological processes ; Physical sciences -- Earth sciences -- Geography ; Behavioral sciences -- Anthropology -- Applied anthropology ; Biological sciences -- Ecology -- Population ecology ; Biological sciences -- Biology -- Evolutionary studies ; Biological sciences -- Biology -- Cytology ; Biological sciences -- Ecology -- Population ecology ; Business -- Industry -- Industrial sectors ; Physical sciences -- Earth sciences -- Geography ; Mathematics -- Pure mathematics -- Discrete mathematics ; Biological sciences -- Ecology -- Ecological processes
    ISSN: 00278424
    E-ISSN: 10916490
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  • 3
    Language: English
    In: Applied and Environmental Microbiology, 02/11/2011
    Description: This article has been withdrawn.
    Keywords: Engineering ; Biology ; Economics;
    ISSN: 0099-2240
    ISSN: 10985336
    E-ISSN: 10985336
    Source: American Society for Microbiology (via CrossRef)
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  • 4
    Language: English
    In: Biogeosciences Discussions, 2012, Vol.9(12), pp.18253-18293
    ISSN: Biogeosciences Discussions
    E-ISSN: 1810-6285
    Source: CrossRef
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  • 5
    Language: English
    In: Aquatic Microbial Ecology, 05/30/2011, Vol.63(3), pp.299-309
    Description: The role of benthic versus planktonic algae in shaping semi-natural ciliate biofilms was studied using miniature flow cells fed by a permanent flow of natural field water from the River Rhine, Germany. Increased food availability for the ciliates was achieved either by supplementation with planktonic algae or by artificial illumination (to stimulate benthic algal growth). Manipulation of both resources significantly increased the total abundance of ciliates and caused significant shifts in the structure of the ciliate community. Supplementation with planktonic algae particularly stimulated suspension-feeding Peritrichia, whereas Choreotrichia were reduced, probably due to indirect effects such as competition or interference. Increased density of benthic algae especially stimulated surface-feeding groups (e.g. Stichotrichia, Nassophorea), causing the establishment of seasonally atypical structures in the ciliate community, as has been observed in late fall. Ciliates generally responded faster to increased resources during the summer, as compared with winter, suggesting that temperature, as well as the availability of resources, has an important role in shaping ciliate biofilms. Our results are among the first that demonstrate the different contributions of planktonic and benthic algae in shaping ciliate biofilms. Furthermore, they accentuate the need for studies with a higher taxonomic resolution when addressing the responses of microbial biofilms to the increased availability of food.
    Keywords: Biology;
    ISSN: 0948-3055
    E-ISSN: 1616-1564
    Source: CrossRef
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  • 6
    Language: English
    In: Biogeosciences, August 19, 2013, Vol.10(8), p.5555
    Description: Dissolved organic matter (DOM) is an important resource for microbes, thus affecting whole-stream metabolism. However, the factors influencing its chemical composition and thereby also its bio-availability are complex and not thoroughly understood. It was hypothesized that whole-stream metabolism is linked to DOM composition and that the coupling of both is influenced by seasonality and different land-use types. We tested this hypothesis in a comparative study on two pristine forestry streams and two non-forestry streams. The investigated streams were located in the Harz Mountains (central Europe, Germany). The metabolic rate was measured with a classical two-station oxygen change technique and the variability of DOM with fluorescence spectroscopy. All streams were clearly net heterotrophic, whereby non-forestry streams showed a higher primary production, which was correlated to irradiance and phosphorus concentration. We detected three CDOM components (C1, C2, C3) using parallel factor (PARAFAC) analysis. We compared the excitation and emission maxima of these components with the literature and correlated the PARAFAC components with each other and with fluorescence indices. The correlations suggest that two PARAFAC components are derived from allochthonous sources (C1, C3) and one is derived autochthonously (C2). The chromophoric DOM matrix was dominated by signals of humic-like substances with a highly complex structure, followed by humic-like, fulfic acids, low-molecular-weight substances, and with minor amounts of amino acids and proteins. The ratios of these PARAFAC components (C1 : C2, C1 : C3, C3 : C2) differed with respect to stream types (forestry versus non-forestry). We demonstrated a significant correlation between gross primary production (GPP) and signals of autochthonously derived, low-molecular-weight humic-like substances. A positive correlation between P / R (i.e. GPP/daily community respiration) and the fluorescence index FI suggests that the amount of autochthonously produced DOM increased overall with increasing GPP. In accordance with the coupling between DOM and the metabolism, our data also indicate that the composition of DOM is subject to seasonal fluctuations. We concluded that temporal and spatial differences in DOM composition are driven by whole-stream metabolism, in addition to pronounced effects coming from allochthonous sources.
    Keywords: Fluorescence Spectroscopy – Physiological Aspects ; Fluorescence Spectroscopy – Comparative Analysis ; Forestry – Physiological Aspects ; Forestry – Comparative Analysis
    ISSN: 1726-4170
    E-ISSN: 17264189
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  • 7
    In: River Research and Applications, July 2016, Vol.32(6), pp.1264-1278
    Description: We compared the longitudinal plankton development in the two large rivers Rhine and Elbe by means of four Lagrangian sampling campaigns performed within the time span 2009–2011. The campaigns revealed low chlorophyll concentrations in the Rhine along a long river stretch (Rhine‐km 170 to 854) with maximum values below 5 µg L in 2010. In contrast, the Elbe (Elbe‐km 4 to 582) showed high and longitudinally increasing chlorophyll concentrations with maximal values of 174 µg L in 2009 and 123 µg L in 2011. Additional samples of the benthic bivalves along the river stretches revealed high densities of the filter feeders in the Rhine that could potentially explain losses of plankton production. Their densities in the Elbe were significantly lower, making important losses to benthic filter feeders unlikely. However, strong phytoplankton growth was observed during the sampling campaign in 2011 in the Rhine coinciding with a low discharge event. This resulted in an exceptionally high chlorophyll value of up to 244 µg L in the lower river sections, a value that was not reached in the last two decades of continuous water quality monitoring in the Rhine. Even though we cannot fully explain this phenomenon, it shows that phytoplankton has a high growth potential in the Rhine but is usually controlled by other mechanisms. Tributaries represented an additional and important source of plankton biomass and suspended substances in the Rhine, whereas they primarily diluted the plankton concentrations in the Elbe. Copyright © 2015 John Wiley & Sons, Ltd.
    Keywords: Phytoplankton ; Zooplankton ; Plankton Dynamics ; Potamoplankton ; Eutrophication ; Lagrangian Approach ; Large Rivers ; Bivalves
    ISSN: 1535-1459
    E-ISSN: 1535-1467
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  • 8
    Language: English
    In: Aquatic Microbial Ecology, 05/25/2012, Vol.66(2), pp.133-147
    Description: Aquatic heterotrophic protists structure biofilm morphology and stimulate organic matter processing, but knowledge about their effects on the activity of surface-associated communities is still missing. Microcosm experiments revealed that the community respiration of young biofilms (7 d old) at mineral surfaces was not affected by co-cultivation with the raptorial feeder Chilodonella uncinata or the suspension feeder Tetrahymena pyriformis. However, grazing by both ciliates reduced the bacterial abundance and probably enhanced nutrient availability by recycling. Our data indicated an increased individual bacterial activity under grazing pressure, resulting in no net effect on the community respiration. In a second experiment, the respiration of leaf-associated microbial communities composed of the fungus Heliscus lugdunensis and a multi-species bacterial assemblage was significantly enhanced in the presence of T. pyriformis after 7 d of incubation. The stimulation was observed under both normoxic (turbulent) and hypoxic (turbulent and stagnant) conditions. After longer incubation, presumably matching an advanced phase of leaf degradation, T. pyriformis did not affect community respiration exposed to hypoxic stagnant conditions. In contrast to former studies, no impact of protists on leaf mass loss was observed. By stimulating leaf-associated community respiration, protists seem to affect processes involved in the initial phase of leaf processing.
    Keywords: Biology;
    ISSN: 0948-3055
    E-ISSN: 1616-1564
    Source: CrossRef
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  • 9
    Language: English
    In: Journal of Plankton Research, 04/01/2010, Vol.32(4), pp.491-502
    Description: The development of the planktonic microbial community [bacteria, heterotrophic nanoflagellates (HNF) and ciliates] was investigated along a 660 km stretch of the River Rhine using Lagrangian sampling in May 2000, and by taking the influence of the main tributaries into account. The relative importance of the components of the microbial food web (HNF, ciliates) increased in the course of the German river stretch, whereas the absolute abundance of protozooplankton decreased and phytoplankton abundance increased. Bacterial abundance remained relatively constant throughout the river stretch investigated. The taxonomic composition of phytoplankton changed from a dominance of cryptophytes to a dominance of diatoms, whereas flagellates, ciliates and metazooplankton showed no shift in species composition. Some tributaries had higher abundances of planktonic organisms than the Rhine itself, but only the River Moselle contributed significantly to the plankton load of the Rhine. However, even after its confluence with the River Rhine abundances of the heterotrophic plankton (HNF and ciliates) remained low and decreased further downstream. The shifts in the composition of the pelagic microbial food web along the river stretch are discussed in the context of group-specific growth and loss processes.
    Keywords: Biology ; Oceanography ; Ecology;
    ISSN: 0142-7873
    E-ISSN: 1464-3774
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  • 10
    Language: English
    In: Applied and Environmental Microbiology, 10/01/2006, Vol.72(10), pp.6638-6643
    Description: Heterotrophic flagellates are key components of all ecosystems. Understanding the patterns of biodiversity of these organisms is thus particularly important. Here we analyzed the intraspecific diversity of 10 morphospecies of heterotrophic flagellates comprising representatives of the Apusozoa (2 morphospecies) and Kinetoplastea (8 morphospecies), all belonging to the most common flagellates with worldwide distribution. Most morphospecies showed a mixing of lineages isolated from diverse habitats, indicating that some lineages of these morphospecies had been able to colonize different habitats several times. Furthermore, our results revealed remarkable levels of genetic divergence within most of the morphospecies studied, underlining the difficulty of correctly determining species by means of morphology alone. Many cryptic or pseudocryptic species seem to occur. Our results revealed clear divergence between marine and freshwater lineages of the morphospecies Ancyromonas sigmoides, showing that freshwater lineages have not been able to colonize marine environments and marine lineages have not been able to colonize freshwater environments for a long time.
    Keywords: Engineering ; Biology ; Economics;
    ISSN: 0099-2240
    E-ISSN: 10985336
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