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  • 1
    Keywords: Forschungsbericht
    Type of Medium: Online Resource
    Pages: Online-Ressource (11 S., 1,08 MB) , Ill., graph. Darst.
    Language: English
    Note: Förderkennzeichen BMBF 02WA0902. - [Dt. T.: Stickstoff-Eliminierung aus salinen und hypersalinen Abwässern aus Entsalzungsanlagen] , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden. - Auch als gedr. Ausg. vorhanden , Systemvoraussetzungen: Acrobat reader.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The impact of burrowing larvae of Ephoron virgo (Ephemeroptera, Polymitarcidae) on sediment microbiology has not been previously investigated because of difficulties in sampling the sediment of large rivers under in situ conditions. Therefore, we conducted experiments in the on-ship Ecological Rhine Station of the University of Cologne (Germany), in which ambient conditions of the River Rhine can be closely mimicked.2. In two consecutive seasons, experimental flow channels were stocked with Ephoron larvae and continuously supplied with water taken directly from the River Rhine. Sediment from the immediate vicinity of Ephoron burrows (i.e. U-shaped cavities reaching 10–80 mm deep into the sediment) and bulk sediment samples were analysed for (i) particulate organic matter content, (ii) microscale in situ distribution of O2, NO〈inlineGraphic alt="inline image" href="urn:x-wiley:00465070:FWB1258:FWB_1258_mu1" location="equation/FWB_1258_mu1.gif"/〉, and NH〈inlineGraphic alt="inline image" href="urn:x-wiley:00465070:FWB1258:FWB_1258_mu2" location="equation/FWB_1258_mu2.gif"/〉, and (iii) potential activities of exoenzymes.3. Sediment surrounding the Ephoron burrows had markedly higher organic matter contents and exoenzyme activities compared with the bulk sediment. Microsensor measurements demonstrated that local O2 and NO〈inlineGraphic alt="inline image" href="urn:x-wiley:00465070:FWB1258:FWB_1258_mu3" location="equation/FWB_1258_mu3.gif"/〉 penetration into the sediment were greatly enhanced by larval ventilation behaviour. Volumetric O2 and NO〈inlineGraphic alt="inline image" href="urn:x-wiley:00465070:FWB1258:FWB_1258_mu4" location="equation/FWB_1258_mu4.gif"/〉 turnover rates that were calculated from steady state concentration profiles measured directly in the burrow lining were considerably higher than at the sediment surface.4. In the sediment of the fast flowing River Rhine Ephoron burrows are preferential sites of organic matter accumulation and dissolved oxidant penetration. Our data suggest that the burrows are surrounded by a highly active microbial community that responds to the inputs from the water column with elevated O2 and NO〈inlineGraphic alt="inline image" href="urn:x-wiley:00465070:FWB1258:FWB_1258_mu5" location="equation/FWB_1258_mu5.gif"/〉 turnover, and release of exoenzymes into the sediment pore water. Especially during periods of mass occurrence, the larvae of E. virgo may thus significantly contribute (i) to the ecological connection between the water column and the sediment and (ii) to biogeochemical processing of organic matter in the riverbed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 46 (2003), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Two freshwater sediments (organic-poor and organic-rich) that contained their distinct natural microbial communities were incubated in experimental microcosms with either NH4+ or NO2− in the overlying water. Microsensor measurements revealed the thin oxic surface layer as a site of initially high rates of nitrification, i.e. O2, NH4+, and NO2− consumption, and NO3− production. Unexpectedly, during the subsequent 4-week incubation NH4+ consumption decreased in both sediment types and NO2− consumption decreased in the organic-rich sediment. In the organic-rich sediment O2 consumption and NO3− production paralleled these decreases, i.e. the reduced NH4+ and NO2− consumption rates were most probably due to reduced activity of nitrifiers. These microsensor data imply factors other than frequently suggested competition between nitrifiers and heterotrophs for NH4+, NO2− or O2 as causes for the loss of nitrification activity. We hypothesize that experimental manipulations (e.g. removal of macrofauna, redistribution of particulate organic matter, permanent nutrient enrichment) rendered the performance of the microbial community unstable. It is thus recommendable to restrict experiments in such commonly used model systems to the period of highest stability.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2024-02-07
    Description: In the hadal zone of the ocean (6–11 km), the characteristics of sinking marine snow particles and their attached microbial communities remain elusive, despite their potential importance for benthic life thriving at extreme pressures (60–110 MPa). Here, we used simulation experiments to explore how increasing pressure levels modify the microbial degradation, organic matter composition, and microbiome of sinking diatom aggregates. Individual aggregates were incubated in rotating tanks in which pressure was incrementally increased to simulate a descent from surface to hadal depth within 20 days. Incubations at atmospheric pressure served as controls. With increasing pressure, microbial respiration and diatom degradation decreased gradually and ceased completely at 60 MPa. Dissolved organic carbon leaked substantially from the aggregates at ≥40 MPa, while diatom lipid and pigment contents decreased moderately. Bacterial abundance remained stable at 〉40 MPa, but bacterial community composition changed significantly at 60–100 MPa. Thus, pressure exposure reduces microbial degradation and transforms both organic matter composition and microbiomes of sinking particles, which may seed hadal sediments with relatively fresh particulate organic matter and putative pressure-tolerant microbes.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 5
    Publication Date: 2022-07-06
    Description: Identifying and quantifying nitrogen pools is essential for understanding the nitrogen cycle in aquatic ecosystems. The ubiquitous diatoms represent an overlooked nitrate pool as they can accumulate nitrate intracellularly and utilize it for nitrogen assimilation, dissipation of excess photosynthetic energy, and Dissimilatory Nitrate Reduction to Ammonium (DNRA). Here, we document the global co-occurrence of diatoms and intracellular nitrate in phototrophic microbial communities in freshwater (n = 69), coastal (n = 44), and open marine (n = 4) habitats. Diatom abundance and total intracellular nitrate contents in water columns, sediments, microbial mats, and epilithic biofilms were highly significantly correlated. In contrast, diatom community composition had only a marginal influence on total intracellular nitrate contents. Nitrate concentrations inside diatom cells exceeded ambient nitrate concentrations ∼100–4000-fold. The collective intracellular nitrate pool of the diatom community accounted for 〈1% of total nitrate in pelagic habitats and 65–95% in benthic habitats. Accordingly, nitrate-storing diatoms are emerging as significant contributors to benthic nitrogen cycling, in particular through Dissimilatory Nitrate Reduction to Ammonium activity under anoxic conditions.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
    Format: application/pdf
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  • 6
    Publication Date: 2022-05-26
    Description: © The Author(s), 2014. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS Biology 12 (2014): e1001889, doi:10.1371/journal.pbio.1001889.
    Description: Microbial ecology is plagued by problems of an abstract nature. Cell sizes are so small and population sizes so large that both are virtually incomprehensible. Niches are so far from our everyday experience as to make their very definition elusive. Organisms that may be abundant and critical to our survival are little understood, seldom described and/or cultured, and sometimes yet to be even seen. One way to confront these problems is to use data of an even more abstract nature: molecular sequence data. Massive environmental nucleic acid sequencing, such as metagenomics or metatranscriptomics, promises functional analysis of microbial communities as a whole, without prior knowledge of which organisms are in the environment or exactly how they are interacting. But sequence-based ecological studies nearly always use a comparative approach, and that requires relevant reference sequences, which are an extremely limited resource when it comes to microbial eukaryotes. In practice, this means sequence databases need to be populated with enormous quantities of data for which we have some certainties about the source. Most important is the taxonomic identity of the organism from which a sequence is derived and as much functional identification of the encoded proteins as possible. In an ideal world, such information would be available as a large set of complete, well-curated, and annotated genomes for all the major organisms from the environment in question. Reality substantially diverges from this ideal, but at least for bacterial molecular ecology, there is a database consisting of thousands of complete genomes from a wide range of taxa, supplemented by a phylogeny-driven approach to diversifying genomics. For eukaryotes, the number of available genomes is far, far fewer, and we have relied much more heavily on random growth of sequence databases, raising the question as to whether this is fit for purpose.
    Description: This project was funded by the Gordon and Betty Moore Foundation (GBMF; Grants GBMF2637 and GBMF3111) to the National Center for Genome Resources (NCGR) and the National Center for Marine Algae and Microbiota (NCMA).
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/msword
    Format: application/pdf
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  • 7
    Publication Date: 2023-12-01
    Description: The effect of increasing hydrostatic pressure on the microbial degradation, the organic matter composition, and the microbiome of 'marine snow' particles was studied in laboratory incubation experiments. Model aggregates were produced from the diatom Skeletonema marinoi and the natural microbial community of surface seawater collected in the Kattegat. The aggregates were incubated individually in rotating pressure and control tanks to keep them suspended during 20-day incubations in the dark and at 3°C. In the pressure tanks, hydrostatic pressure was increased at increments of 5 MPa per day to finally reach 100 MPa. This pressure scheme simulates the descent of diatom aggregates from the surface ocean down into a 10-km deep hadal trench. In the control tanks, pressure was always left at atmospheric level. To answer the question, if the observed pressure-induced leakage of dissolved organic carbon (DOC) from S. marinoi occurs during pressurization or depressurization, 3 additional experiments were carried out: 1) S. marinoi suspended in seawater were rotated at 0.1 MPa for 24 h and then allowed to settle for 3 h. 2) S. marinoi suspended in seawater were rotated at 60 MPa for 24 h, then allowed to settle for 3 h, and then depressurized. 3) S. marinoi suspended in seawater were first allowed to settle for 3 h, then incubated without rotation at 60 MPa for 1 h, and then depressurized. At the end of each experiment, vertical profiles of diatom cell abundance and DOC were determined, which revealed during which phase of the pressure experiment S. marinoi was leaking DOC into the surrounding seawater.
    Keywords: biological carbon pump; Carbon, organic, dissolved; Carbon, organic, dissolved, standard deviation; Date/time end, experiment; Date/time start, experiment; Deep sea; Diatom; Diatoms; Diatoms, standard deviation; Digital manometer, Keller AG, LEO5; DISTANCE; Experiment; Experimental treatment; HADAL_aggregates; Hadal trench; hydrostatic pressure; Laboratory; Laboratory experiment; lipids; marine carbon cycle; marine snow; microbial community; Microscopic cell count, Fuchs-Rosenthal, Fuchs-Rosenthal counting chamber; pigments; Replicate; Respiration; RULER; Ruler stick; Shimadzu TOC-L total organic carbon analyzer; Treatment: pressure; Type of study
    Type: Dataset
    Format: text/tab-separated-values, 216 data points
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  • 8
    Publication Date: 2024-03-02
    Description: The effect of increasing hydrostatic pressure on the microbial degradation, the organic matter composition, and the microbiome of 'marine snow' particles was studied in laboratory incubation experiments. Model aggregates were produced from the diatom Skeletonema marinoi and the natural microbial community of surface seawater collected in the Kattegat. The aggregates were incubated individually in rotating pressure and control tanks to keep them suspended during 20-day incubations in the dark and at 3°C. In the pressure tanks, hydrostatic pressure was increased at increments of 5 MPa per day to finally reach 100 MPa. This pressure scheme simulates the descent of diatom aggregates from the surface ocean down into a 10-km deep hadal trench. In the control tanks, pressure always remained at atmospheric level. Aerobic respiration was continuously measured as a proxy for oxidative carbon mineralization in the aggregates (Stief et al. 2021, https://doi.org/10.1002/lno.11791). Leakage of dissolved organic carbon was monitored as an additional carbon loss term. The contents of different diatom lipids and photopigments were measured throughout the incubation. The succession of microbial (mainly bacterial) communities associated with the sinking diatom aggregates was followed by 16S rRNA gene amplicon sequencing throughout the incubation; the corresponding data are deposited in the NCBI short-read archive under the accession number PRJNA976707.
    Keywords: biological carbon pump; Deep sea; Diatom; Hadal trench; hydrostatic pressure; lipids; marine carbon cycle; marine snow; microbial community; pigments; Respiration
    Type: Dataset
    Format: application/zip, 15 datasets
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  • 9
    Publication Date: 2024-01-26
    Description: The effect of increasing hydrostatic pressure on the microbial degradation, the organic matter composition, and the microbiome of 'marine snow' particles was studied in laboratory incubation experiments. Model aggregates were produced from the diatom Skeletonema marinoi and the natural microbial community of surface seawater collected in the Kattegat. The aggregates were incubated individually in rotating pressure and control tanks to keep them suspended during 20-day incubations in the dark and at 3°C. In the pressure tanks, hydrostatic pressure was increased at increments of 5 MPa per day to finally reach 100 MPa. This pressure scheme simulates the descent of diatom aggregates from the surface ocean down into a 10-km deep hadal trench. In the control tanks, pressure was always left at atmospheric level. Volumetric oxygen consumption rates of sinking diatom aggregates were calculated from the temporal change in oxygen concentration in the water surrounding the aggregates and the individual aggregate volume and served as a proxy for aerobic microbial aggregate degradation.
    Keywords: biological carbon pump; Date/time end, experiment; Date/time start, experiment; Deep sea; Diatom; Digital manometer, Keller AG, LEO5; Experiment; Experimental treatment; HADAL_aggregates; Hadal trench; hydrostatic pressure; Laboratory; Laboratory experiment; lipids; marine carbon cycle; marine snow; microbial community; Optical Oxygen Meter (FireSting, PyroScience GmbH, Germany); Oxygen consumption; pigments; Replicate; Respiration; Treatment: pressure; Treatment: time after; Type of study
    Type: Dataset
    Format: text/tab-separated-values, 2940 data points
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  • 10
    Publication Date: 2024-01-26
    Description: The effect of increasing hydrostatic pressure on the microbial degradation, the organic matter composition, and the microbiome of 'marine snow' particles was studied in laboratory incubation experiments. Model aggregates were produced from the diatom Skeletonema marinoi and the natural microbial community of surface seawater collected in the Kattegat. The aggregates were incubated individually in rotating pressure and control tanks to keep them suspended during 20-day incubations in the dark and at 3°C. In the pressure tanks, hydrostatic pressure was increased at increments of 5 MPa per day to finally reach 100 MPa. This pressure scheme simulates the descent of diatom aggregates from the surface ocean down into a 10-km deep hadal trench. In the control tanks, pressure was always left at atmospheric level. Oxygen concentrations in the water surrounding the diatom aggregates were continuously measured using an optode-based pressure-tank setup introduced by Stief et al. 2021 (https://doi.org/10.1002/lno.11791) and were used to calculate oxygen consumption rates.
    Keywords: biological carbon pump; Date/time end, experiment; Date/time start, experiment; Deep sea; Diatom; Digital manometer, Keller AG, LEO5; Experiment; Experimental treatment; HADAL_aggregates; Hadal trench; hydrostatic pressure; Laboratory; Laboratory experiment; lipids; marine carbon cycle; marine snow; microbial community; Optical Oxygen Meter (FireSting, PyroScience GmbH, Germany); Oxygen; pigments; Replicate; Respiration; Treatment: pressure; Treatment: time after; Type of study
    Type: Dataset
    Format: text/tab-separated-values, 14683 data points
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