TY - JOUR A1 - Blum, Rahel ED - Denz, Rebekka ED - Rudolf, Gabi T1 - Eine Schreibübung als Einblick in die jüdische Lebenswelt auf dem Lande JF - Genisa-Blätter II KW - Genisa KW - Jüdische Studien KW - Geniza KW - Jewish Studies Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-104639 SP - 85 EP - 96 ER - TY - JOUR A1 - Denz, Rebekka A1 - Rudolf, Gabi ED - Denz, Rebekka ED - Rudolf, Gabi T1 - Werkstattbericht: Genisot in Franken JF - Genisa-Blätter II KW - Genisa KW - Jüdische Studien KW - Geniza KW - Jewish Studies Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-104464 SP - 7 EP - 14 ER - TY - JOUR A1 - Weinhold, Beate ED - Denz, Rebekka ED - Rudolf, Gabi T1 - ‚Ma‘oz tsur jeshu‘ati‘ BT - Prolegomenon zu „Chanukka, die sechste“ in fränkischen Genisot JF - Genisa-Blätter II KW - Genisa KW - Jüdische Studien KW - Geniza KW - Jewish Studies Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-104561 SP - 45 EP - 50 ER - TY - JOUR A1 - Müller, Monika ED - Denz, Rebekka ED - Rudolf, Gabi T1 - Vom Handeln und Schmusen BT - ein Zettel aus der Altenschönbacher Genisa JF - Genisa-Blätter II KW - Genisa KW - Jüdische Studien KW - Geniza KW - Jewish Studies Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-104659 SP - 111 EP - 117 ER - TY - JOUR A1 - Reese, Ronja A1 - Gudmundsson, Gudmundur Hilmar A1 - Levermann, Anders A1 - Winkelmann, Ricarda T1 - The far reach of ice-shelf thinning in Antarctica JF - Nature climate change N2 - Floating ice shelves, which fringe most of Antarctica’s coastline, regulate ice flow into the Southern Ocean1,2,3. Their thinning4,5,6,7 or disintegration8,9 can cause upstream acceleration of grounded ice and raise global sea levels. So far the effect has not been quantified in a comprehensive and spatially explicit manner. Here, using a finite-element model, we diagnose the immediate, continent-wide flux response to different spatial patterns of ice-shelf mass loss. We show that highly localized ice-shelf thinning can reach across the entire shelf and accelerate ice flow in regions far from the initial perturbation. As an example, this ‘tele-buttressing’ enhances outflow from Bindschadler Ice Stream in response to thinning near Ross Island more than 900 km away. We further find that the integrated flux response across all grounding lines is highly dependent on the location of imposed changes: the strongest response is caused not only near ice streams and ice rises, but also by thinning, for instance, well-within the Filchner–Ronne and Ross Ice Shelves. The most critical regions in all major ice shelves are often located in regions easily accessible to the intrusion of warm ocean waters10,11,12, stressing Antarctica’s vulnerability to changes in its surrounding ocean. Y1 - 2017 U6 - https://doi.org/10.1038/s41558-017-0020-x SN - 1758-678X SN - 1758-6798 VL - 8 IS - 1 SP - 53 EP - 57 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Sier, Mark J. A1 - Langereis, Cor G. A1 - Dupont-Nivet, Guillaume A1 - Feibel, Craig S. A1 - Joordens, Josephine C. A. A1 - van der Lubbe, Jeroen Fiji. A1 - Beck, Catherine C. A1 - Olago, Daniel A1 - Cohen, Andrew T1 - The top of the Olduvai Subchron in a high-resolution magnetostratigraphy from the West Turkana core WTK13, hominin sites and Paleolakes Drilling Project (HSPDP) JF - Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques N2 - One of the major challenges in understanding the evolution of our own species is identifying the role climate change has played in the evolution of hominin species. To clarify the influence of climate, we need long and continuous high-resolution paleoclimate records, preferably obtained from hominin-bearing sediments, that are well-dated by tephro- and magnetostratigraphy and other methods. This is hindered, however, by the fact that fossil-bearing outcrop sediments are often discontinuous, and subject to weathering, which may lead to oxidation and remagnetization. To obtain fresh, unweathered sediments, the Hominin Sites and Paleolakes Drilling Project (HSPDP) collected a ∼216-meter core (WTK13) in 2013 from Early Pleistocene Paleolake Lorenyang deposits in the western Turkana Basin (Kenya). Here, we present the magnetostratigraphy of the WTK13 core, providing a first age model for upcoming HSPDP paleoclimate and paleoenvrionmental studies on the core sediments. Rock magnetic analyses reveal the presence of iron sulfides carrying the remanent magnetizations. To recover polarity orientation from the near-equatorial WTK13 core drilled at 5°N, we developed and successfully applied two independent drill-core reorientation methods taking advantage of (1) the sedimentary fabric as expressed in the Anisotropy of Magnetic Susceptibility (AMS) and (2) the occurrence of a viscous component oriented in the present day field. The reoriented directions reveal a normal to reversed polarity reversal identified as the top of the Olduvai Subchron. From this excellent record, we find no evidence for the ‘Vrica Subchron’ previously reported in the area. We suggest that outcrop-based interpretations supporting the presence of the Vrica Subchron have been affected by the oxidation of iron sulfides initially present in the sediments -as evident in the core record- and by subsequent remagnetization. We discuss the implications of the observed geomagnetic record for human evolution studies. KW - Paleolake Lorenyang KW - Magnetostratigraphy KW - Olduvai Subchron KW - Vrica Subchron KW - Drill-core reorientation KW - ICDP KW - Paleoclimate KW - Hominin evolution Y1 - 2017 U6 - https://doi.org/10.1016/j.quageo.2017.08.004 SN - 1871-1014 SN - 1878-0350 VL - 42 SP - 117 EP - 129 PB - Elsevier CY - Oxford ER - TY - GEN A1 - Wurzbacher, Christian A1 - Fuchs, Andrea A1 - Attermeyer, Katrin A1 - Frindte, Katharina A1 - Grossart, Hans-Peter A1 - Hupfer, Michael A1 - Casper, Peter A1 - Monaghan, Michael T. T1 - Shifts among Eukaryota, Bacteria, and Archaea define the vertical organization of a lake sediment T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Background Lake sediments harbor diverse microbial communities that cycle carbon and nutrients while being constantly colonized and potentially buried by organic matter sinking from the water column. The interaction of activity and burial remained largely unexplored in aquatic sediments. We aimed to relate taxonomic composition to sediment biogeochemical parameters, test whether community turnover with depth resulted from taxonomic replacement or from richness effects, and to provide a basic model for the vertical community structure in sediments. Methods We analyzed four replicate sediment cores taken from 30-m depth in oligo-mesotrophic Lake Stechlin in northern Germany. Each 30-cm core spanned ca. 170 years of sediment accumulation according to 137Cs dating and was sectioned into layers 1–4 cm thick. We examined a full suite of biogeochemical parameters and used DNA metabarcoding to examine community composition of microbial Archaea, Bacteria, and Eukaryota. Results Community β-diversity indicated nearly complete turnover within the uppermost 30 cm. We observed a pronounced shift from Eukaryota- and Bacteria-dominated upper layers (<5 cm) to Bacteria-dominated intermediate layers (5–14 cm) and to deep layers (>14 cm) dominated by enigmatic Archaea that typically occur in deep-sea sediments. Taxonomic replacement was the prevalent mechanism in structuring the community composition and was linked to parameters indicative of microbial activity (e.g., CO2 and CH4 concentration, bacterial protein production). Richness loss played a lesser role but was linked to conservative parameters (e.g., C, N, P) indicative of past conditions. Conclusions By including all three domains, we were able to directly link the exponential decay of eukaryotes with the active sediment microbial community. The dominance of Archaea in deeper layers confirms earlier findings from marine systems and establishes freshwater sediments as a potential low-energy environment, similar to deep sea sediments. We propose a general model of sediment structure and function based on microbial characteristics and burial processes. An upper “replacement horizon” is dominated by rapid taxonomic turnover with depth, high microbial activity, and biotic interactions. A lower “depauperate horizon” is characterized by low taxonomic richness, more stable “low-energy” conditions, and a dominance of enigmatic Archaea. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1111 KW - Archaea KW - Eukaryota KW - Bacteria KW - community KW - freshwater KW - lake KW - DNA metabarcoding KW - beta-diversity KW - sediment KW - turnover Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-431965 SN - 1866-8372 IS - 1111 ER - TY - THES A1 - Périllon, Cécile T1 - The effect of groundwater on benthic primary producers and their interaction T1 - Der Einfluss von Grundwasser auf benthische Primärproduzenten und ihre Interaktionen N2 - In littoral zones of lakes, multiple processes determine lake ecology and water quality. Lacustrine groundwater discharge (LGD), most frequently taking place in littoral zones, can transport or mobilize nutrients from the sediments and thus contribute significantly to lake eutrophication. Furthermore, lake littoral zones are the habitat of benthic primary producers, namely submerged macrophytes and periphyton, which play a key role in lake food webs and influence lake water quality. Groundwater-mediated nutrient-influx can potentially affect the asymmetric competition between submerged macrophytes and periphyton for light and nutrients. While rooted macrophytes have superior access to sediment nutrients, periphyton can negatively affect macrophytes by shading. LGD may thus facilitate periphyton production at the expense of macrophyte production, although studies on this hypothesized effect are missing. The research presented in this thesis is aimed at determining how LGD influences periphyton, macrophytes, and the interactions between these benthic producers. Laboratory experiments were combined with field experiments and measurements in an oligo-mesotrophic hard water lake. In the first study, a general concept was developed based on a literature review of the existing knowledge regarding the potential effects of LGD on nutrients and inorganic and organic carbon loads to lakes, and the effect of these loads on periphyton and macrophytes. The second study includes a field survey and experiment examining the effects of LGD on periphyton in an oligotrophic, stratified hard water lake (Lake Stechlin). This study shows that LGD, by mobilizing phosphorus from the sediments, significantly promotes epiphyton growth, especially at the end of the summer season when epilimnetic phosphorus concentrations are low. The third study focuses on the potential effects of LGD on submerged macrophytes in Lake Stechlin. This study revealed that LGD may have contributed to an observed change in macrophyte community composition and abundance in the shallow littoral areas of the lake. Finally, a laboratory experiment was conducted which mimicked the conditions of a seepage lake. Groundwater circulation was shown to mobilize nutrients from the sediments, which significantly promoted periphyton growth. Macrophyte growth was negatively affected at high periphyton biomasses, confirming the initial hypothesis. More generally, this thesis shows that groundwater flowing into nutrient-limited lakes may import or mobilize nutrients. These nutrients first promote periphyton, and subsequently provoke radical changes in macrophyte populations before finally having a possible influence on the lake’s trophic state. Hence, the eutrophying effect of groundwater is delayed and, at moderate nutrient loading rates, partly dampened by benthic primary producers. The present research emphasizes the importance and complexity of littoral processes, and the need to further investigate and monitor the benthic environment. As present and future global changes can significantly affect LGD, the understanding of these complex interactions is required for the sustainable management of lake water quality. N2 - Im Uferbereich von Seen bestimmen eine Vielzahl von Prozessen das ökologische Gefüge und die Wasserqualität. Grundwasserzustrom, welcher häufig im Uferbereich eines Sees auftritt, kann zum Import von Nährstoffen führen und so signifikant zur Eutrophierung eines Gewässers beitragen. Darüber hinaus bildet der Uferbereich von Seen das Habitat für benthische Primärproduzenten wie Makrophyten (Wasserpflanzen) und Periphyton (Aufwuchs), welche eine Schlüsselrolle im Nahrungsnetz von Seen einnehmen und deren Wasserqualität beeinflussen können. Der durch Grundwasser gesteuerte Eintrag von Nährstoffen kann sich unterschiedlich auf die um Licht und Nährstoffe konkurrierenden Makrophyten und Periphyton auswirken. Während Makrophyten häufig über Wurzeln verfügen und damit Nährstoffe aus dem Sediment aufnehmen, kann Periphyton zu einer Beschattung der Makrophyten beitragen. Grundwasserzustrom könnte deshalb durch Nährstoffzufuhr das Wachstum von Periphyton fördern und damit zu einer Abnahme der Makrophytenabundanz führen. Die in dieser Doktorarbeit vorgestellten Forschungsergebnisse zeigen den Einfluss von einströmendem Grundwasser in Seen auf Makrophyten und Periphyton, und insbesondere die Interaktionen zwischen diesen beiden benthischen Primärproduzenten. Dafür wurden Laborexperimente, sowie Feldexperimente und Messungen in einem oligo-mesotrophen, kalkreichen See miteinander kombiniert. In der ersten Studie wurden im Rahmen einer Literaturrecherche die Auswirkungen des Einstroms von Grundwasser auf das Wachstum von Makrophyten und Periphyton untersucht. Dafür wurden Einträge von Nährstoffen sowie anorganischem und organischem Kohlenstoff berücksichtigt und abschließend ein Konzept entwickelt, das die Interaktion zwischen benthischen Primärproduzenten betrachtet. Die zweite Studie zeigt den Einfluss von Grundwasser auf das Wachstum von Periphyton im geschichteten, oligo-mesotrophen, kalkreichen Stechlinsee (Brandenburg) auf der Basis von Freilanduntersuchungen und -experimenten. Es konnte nachgewiesen werden, dass einströmendes Grundwasser Phosphor aus dem Sediment mobilisiert und so das Wachstum von Periphyton signifikant fördert. Dies war insbesondere am Ende des Sommers relevant, wenn Phosphor im Epilimnion nur noch in sehr geringer Konzentration vorlag. Der Fokus der dritten Studie liegt auf den potenziellen Auswirkungen des Einstroms von Grundwasser auf die Makrophyten in flachen Litoralbereichen des Stechlinsees. Die in den letzten Jahrzehnten beobachteten Veränderungen in der Abundanz und Artenzusammensetzung der Makrophyten, insbesondere der Rückgang der Armleuchteralgen, könnten auch auf Veränderungen im Einstrom von Grundwasser zurückzuführen sein. In der letzten Studie wurden in einem Laborexperiment der Grundwasserzustrom ins Litoral simuliert, um die kombinierte Auswirkung auf Makrophyten- und Periphytonentwicklung unter kontrollierten Umweltbedingungen zu testen. Die Ergebnisse bestätigen die Hypothese, dass die durch den Grundwasserzustrom mobilisierten Nährstoffe aus dem Sediment das Wachstum von Periphyton fördern. Oberhalb eines Grenzwertes der Periphytonbiomasse wird die Entwicklung von Makrophyten behindert. Die vorliegende Arbeit zeigt, dass einströmendes Grundwasser zur Mobilisierung und zum Import von Nährstoffen in Seen führen kann und damit weitreichende Konsequenzen für das ökologische Gefüge und die Wasserqualität haben kann. Die grundwassergesteuerte Nährstoffzufuhr fördert das Wachstum von Periphyton und führt bei genügend großer Periphytonbiomasse zu Änderungen der Makrophytenpopulation bis hin zum Verlust. Die Arbeit verdeutlicht die Relevanz und Komplexität von Prozessen im Litoral von Seen und zeigt zugleich die Notwendigkeit auf, diese benthische Habitate tiefgreifender zu untersuchen. Da globale Veränderungen des Klimas einen weitreichenden Einfluss auf den Grundwassereinstrom in Seen haben können, ist es von entscheidender Bedeutung, die komplexen Auswirkungen dieser Prozesse zu verstehen, um einen nachhaltigen Schutz dieser Ökosysteme zu gewährleisten. KW - groundwater KW - littoral eutrophication KW - benthic primary producers KW - asymmetric competition KW - macrophytes KW - periphyton KW - Grundwasser KW - Makrophyten KW - Periphyton KW - Eutrophierung KW - Litoral KW - benthische Primärproduzenten KW - asymmetrische Konkurrenz Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-406883 ER - TY - GEN A1 - Hornick, Thomas A1 - Bach, Lennart T. A1 - Crawfurd, Katharine J. A1 - Spilling, Kristian A1 - Achterberg, Eric Pieter A1 - Woodhouse, Jason Nicholas A1 - Schulz, Kai Georg A1 - Brussaard, Corina P. D. A1 - Riebesell, Ulf A1 - Grossart, Hans-Peter T1 - Ocean acidification impacts bacteria–phytoplankton coupling at low-nutrient conditions T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The oceans absorb about a quarter of the annually produced anthropogenic atmospheric carbon dioxide (CO2), resulting in a decrease in surface water pH, a process termed ocean acidification (OA). Surprisingly little is known about how OA affects the physiology of heterotrophic bacteria or the coupling of heterotrophic bacteria to phytoplankton when nutrients are limited. Previous experiments were, for the most part, undertaken during productive phases or following nutrient additions designed to stimulate algal blooms. Therefore, we performed an in situ large-volume mesocosm (similar to 55 m(3)) experiment in the Baltic Sea by simulating different fugacities of CO2 (fCO(2)) extending from present to future conditions. The study was conducted in July-August after the nominal spring bloom, in order to maintain low-nutrient conditions throughout the experiment. This resulted in phytoplankton communities dominated by small-sized functional groups (picophytoplankton). There was no consistent fCO(2)-induced effect on bacterial protein production (BPP), cell-specific BPP (csBPP) or biovolumes (BVs) of either free-living (FL) or particle-associated (PA) heterotrophic bacteria, when considered as individual components (univariate analyses). Permutational Multivariate Analysis of Variance (PERMANOVA) revealed a significant effect of the fCO(2) treatment on entire assemblages of dissolved and particulate nutrients, metabolic parameters and the bacteria-phytoplankton community. However, distance-based linear modelling only identified fCO(2) as a factor explaining the variability observed amongst the microbial community composition, but not for explaining variability within the metabolic parameters. This suggests that fCO(2) impacts on microbial metabolic parameters occurred indirectly through varying physicochemical parameters and microbial species composition. Cluster analyses examining the co-occurrence of different functional groups of bacteria and phytoplankton further revealed a separation of the four fCO(2)-treated mesocosms from both control mesocosms, indicating that complex trophic interactions might be altered in a future acidified ocean. Possible consequences for nutrient cycling and carbon export are still largely unknown, in particular in a nutrient-limited ocean. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 667 KW - northern Baltic Sea KW - inorganic nutrients KW - mesocosm experiment KW - elevated CO2 KW - heterotrophic bacteria KW - organic-carbon KW - bacterioplankton KW - seawater KW - growth KW - temperature Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-417126 SN - 1866-8372 IS - 667 ER - TY - JOUR A1 - Bjorneras, C. A1 - Weyhenmeyer, G. A. A1 - Evans, C. D. A1 - Gessner, M. O. A1 - Grossart, Hans-Peter A1 - Kangur, K. A1 - Kokorite, I. A1 - Kortelainen, P. A1 - Laudon, H. A1 - Lehtoranta, J. A1 - Lottig, N. A1 - Monteith, D. T. A1 - Noges, P. A1 - Noges, T. A1 - Oulehle, F. A1 - Riise, G. A1 - Rusak, J. A. A1 - Raike, A. A1 - Sire, J. A1 - Sterling, S. A1 - Kritzberg, E. S. T1 - Widespread Increases in Iron Concentration in European and North American Freshwaters JF - Global biogeochemical cycles N2 - Recent reports of increasing iron (Fe) concentrations in freshwaters are of concern, given the fundamental role of Fe in biogeochemical processes. Still, little is known about the frequency and geographical distribution of Fe trends or about the underlying drivers. We analyzed temporal trends of Fe concentrations across 340 water bodies distributed over 10 countries in northern Europe and North America in order to gain a clearer understanding of where, to what extent, and why Fe concentrations are on the rise. We found that Fe concentrations have significantly increased in 28% of sites, and decreased in 4%, with most positive trends located in northern Europe. Regions with rising Fe concentrations tend to coincide with those with organic carbon (OC) increases. Fe and OC increases may not be directly mechanistically linked, but may nevertheless be responding to common regional-scale drivers such as declining sulfur deposition or hydrological changes. A role of hydrological factors was supported by covarying trends in Fe and dissolved silica, as these elements tend to stem from similar soil depths. A positive relationship between Fe increases and conifer cover suggests that changing land use and expanded forestry could have contributed to enhanced Fe export, although increases were also observed in nonforested areas. We conclude that the phenomenon of increasing Fe concentrations is widespread, especially in northern Europe, with potentially significant implications for wider ecosystem biogeochemistry, and for the current browning of freshwaters. Y1 - 2017 U6 - https://doi.org/10.1002/2017GB005749 SN - 0886-6236 SN - 1944-9224 VL - 31 SP - 1488 EP - 1500 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Lischke, Betty A1 - Mehner, Thomas A1 - Hilt, Sabine A1 - Attermeyer, Katrin A1 - Brauns, Mario A1 - Brothers, Soren M. A1 - Grossart, Hans-Peter A1 - Koehler, Jan A1 - Scharnweber, Inga Kristin A1 - Gaedke, Ursula T1 - Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes JF - Freshwater biology N2 - The sum of benthic autotrophic and bacterial production often exceeds the sum of pelagic autotrophic and bacterial production, and hence may contribute substantially to whole-lake carbon fluxes, especially in shallow lakes. Furthermore, both benthic and pelagic autotrophic and bacterial production are highly edible and of sufficient nutritional quality for animal consumers. We thus hypothesised that pelagic and benthic transfer efficiencies (ratios of production at adjacent trophic levels) in shallow lakes should be similar. We performed whole ecosystem studies in two shallow lakes (3.5ha, mean depth 2m), one with and one without submerged macrophytes, and quantified pelagic and benthic biomass, production and transfer efficiencies for bacteria, phytoplankton, epipelon, epiphyton, macrophytes, zooplankton, macrozoobenthos and fish. We expected higher transfer efficiencies in the lake with macrophytes, because these provide shelter and food for macrozoobenthos and may thus enable a more efficient conversion of basal production to consumer production. In both lakes, the majority of the whole-lake autotrophic and bacterial production was provided by benthic organisms, but whole-lake primary consumer production mostly relied on pelagic autotrophic and bacterial production. Consequently, transfer efficiency of benthic autotrophic and bacterial production to macrozoobenthos production was an order of magnitude lower than the transfer efficiency of pelagic autotrophic and bacterial production to rotifer and crustacean production. Between-lake differences in transfer efficiencies were minor. We discuss several aspects potentially causing the unexpectedly low benthic transfer efficiencies, such as the food quality of producers, pelagic-benthic links, oxygen concentrations in the deeper lake areas and additional unaccounted consumer production by pelagic and benthic protozoa and meiobenthos at intermediate or top trophic levels. None of these processes convincingly explain the large differences between benthic and pelagic transfer efficiencies. Our data indicate that shallow eutrophic lakes, even with a major share of autotrophic and bacterial production in the benthic zone, can function as pelagic systems with respect to primary consumer production. We suggest that the benthic autotrophic production was mostly transferred to benthic bacterial production, which remained in the sediments, potentially cycling internally in a similar way to what has previously been described for the microbial loop in pelagic habitats. Understanding the energetics of whole-lake food webs, including the fate of the substantial benthic bacterial production, which is either mineralised at the sediment surface or permanently buried, has important implications for regional and global carbon cycling. KW - bacterial production KW - benthic food chain KW - pelagic food chain KW - quantitative food webs KW - trophic transfer efficiency Y1 - 2017 U6 - https://doi.org/10.1111/fwb.12979 SN - 0046-5070 SN - 1365-2427 VL - 62 SP - 1693 EP - 1706 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Attermeyer, Katrin A1 - Grossart, Hans-Peter A1 - Flury, Sabine A1 - Premke, Katrin T1 - Bacterial processes and biogeochemical changes in the water body of kettle holes - mainly driven by autochthonous organic matter? JF - Aquatic sciences : research across boundaries N2 - Kettle holes are small inland waters formed from glacially-created depressions often situated in agricultural landscapes. Due to their high perimeter-to-area ratio facilitating a high aquatic-terrestrial coupling, kettle holes can accumulate high concentrations of organic carbon and nutrients, fueling microbial activities and turnover rates. Thus, they represent hotspots of carbon turnover in the landscape, but their bacterial activities and controlling factors have not been well investigated. Therefore, we aimed to assess the relative importance of various environmental factors on bacterial and biogeochemical processes in the water column of kettle holes and to disentangle their variations. In the water body of ten kettle holes in north-eastern Germany, we measured several physico-chemical and biological parameters such as carbon quantity and quality, as well as bacterial protein production (BP) and community respiration (CR) in spring, early summer and autumn 2014. Particulate organic matter served as an indicator of autochthonous production and represented an important parameter to explain variations in BP and CR. This notion is supported by qualitative absorbance indices of dissolved molecules in water samples and C: N ratios of the sediments, which demonstrate high fractions of autochthonous organic matter (OM) in the studied kettle holes. In contrast, dissolved chemical parameters were less important for bacterial activities although they revealed strong differences throughout the growing season. Pelagic bacterial activities and dynamics might thus be regulated by autochthonous OM in kettle holes implying a control of important biogeochemical processes by internal primary production rather than facilitated exchange with the terrestrial surrounding due to a high perimeter-to-area ratio. KW - Bacterial production KW - Carbon turnover KW - Growth efficiency KW - Ponds KW - Respiration KW - DOC quality KW - LC-OCD Y1 - 2017 U6 - https://doi.org/10.1007/s00027-017-0528-1 SN - 1015-1621 SN - 1420-9055 VL - 79 SP - 675 EP - 687 PB - Springer CY - Basel ER - TY - JOUR A1 - Wurzbacher, Christian A1 - Attermeyer, Katrin A1 - Kettner, Marie Therese A1 - Flintrop, Clara A1 - Warthmann, Norman A1 - Hilt, Sabine A1 - Grossart, Hans-Peter A1 - Monaghan, Michael T. T1 - DNA metabarcoding of unfractionated water samples relates phyto-, zoo- and bacterioplankton dynamics and reveals a single-taxon bacterial bloom JF - Environmental microbiology reports N2 - Most studies of aquatic plankton focus on either macroscopic or microbial communities, and on either eukaryotes or prokaryotes. This separation is primarily for methodological reasons, but can overlook potential interactions among groups. Here we tested whether DNA metabarcoding of unfractionated water samples with universal primers could be used to qualitatively and quantitatively study the temporal dynamics of the total plankton community in a shallow temperate lake. Significant changes in the relative proportions of normalized sequence reads of eukaryotic and prokaryotic plankton communities over a 3-month period in spring were found. Patterns followed the same trend as plankton estimates measured using traditional microscopic methods. The bloom of a conditionally rare bacterial taxon belonging to Arcicella was characterized, which rapidly came to dominate the whole lake ecosystem and would have remained unnoticed without metabarcoding. The data demonstrate the potential of universal DNA metabarcoding applied to unfractionated samples for providing a more holistic view of plankton communities. Y1 - 2017 U6 - https://doi.org/10.1111/1758-2229.12540 SN - 1758-2229 VL - 9 SP - 383 EP - 388 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Hornak, Karel A1 - Kasalicky, Vojtech A1 - Simek, Karel A1 - Grossart, Hans-Peter T1 - Strain-specific consumption and transformation of alga-derived dissolved organic matter by members of the Limnohabitans-C and Polynucleobacter-B clusters of Betaproteobacteria JF - Environmental microbiology N2 - We investigated changes in quality and quantity of extracellular and biomass-derived organic matter (OM) from three axenic algae (genera Rhodomonas, Chlamydomonas, Coelastrum) during growth of Limnohabitans parvus, Limnohabitans planktonicus and Polynucleobacter acidiphobus representing important clusters of freshwater planktonic Betaproteobacteria. Total extracellular and biomass-derived OM concentrations from each alga were approximately 20 mg l(-1) and 1 mg l(-1) respectively, from which up to 9% could be identified as free carbohydrates, polyamines, or free and combined amino acids. Carbohydrates represented 54%-61% of identified compounds of the extracellular OM from each alga. In biomass-derived OM of Rhodomonas and Chlamydomonas 71%-77% were amino acids and polyamines, while in that of Coelastrum 85% were carbohydrates. All bacteria grew on alga-derived OM of Coelastrum, whereas only Limnohabitans strains grew on OM from Rhodomonas and Chlamydomonas. Bacteria consumed 24%-76% and 38%-82% of all identified extracellular and biomass-derived OM compounds respectively, and their consumption was proportional to the concentration of each OM compound in the different treatments. The bacterial biomass yield was higher than the total identifiable OM consumption indicating that bacteria also utilized other unidentified alga-derived OM compounds. Bacteria, however, also produced specific OM compounds suggesting enzymatic polymer degradation or de novo exudation. Y1 - 2017 U6 - https://doi.org/10.1111/1462-2920.13900 SN - 1462-2912 SN - 1462-2920 VL - 19 SP - 4519 EP - 4535 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Kettner, Marie Therese A1 - Rojas-Jimenez, Keilor A1 - Oberbeckmann, Sonja A1 - Labrenz, Matthias A1 - Grossart, Hans-Peter T1 - Microplastics alter composition of fungal communities in aquatic ecosystems JF - Environmental microbiology N2 - Despite increasing concerns about microplastic (MP) pollution in aquatic ecosystems, there is insufficient knowledge on how MP affect fungal communities. In this study, we explored the diversity and community composition of fungi attached to polyethylene (PE) and polystyrene (PS) particles incubated in different aquatic systems in north-east Germany: the Baltic Sea, the River Warnow and a wastewater treatment plant. Based on next generation 18S rRNA gene sequencing, 347 different operational taxonomic units assigned to 81 fungal taxa were identified on PE and PS. The MP-associated communities were distinct from fungal communities in the surrounding water and on the natural substrate wood. They also differed significantly among sampling locations, pointing towards a substrate and location specific fungal colonization. Members of Chytridiomycota, Cryptomycota and Ascomycota dominated the fungal assemblages, suggesting that both parasitic and saprophytic fungi thrive in MP biofilms. Thus, considering the worldwide increasing accumulation of plastic particles as well as the substantial vector potential of MP, especially these fungal taxa might benefit from MP pollution in the aquatic environment with yet unknown impacts on their worldwide distribution, as well as biodiversity and food web dynamics at large. Y1 - 2017 U6 - https://doi.org/10.1111/1462-2920.13891 SN - 1462-2912 SN - 1462-2920 VL - 19 SP - 4447 EP - 4459 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Amalfitano, Stefano A1 - Corno, Gianluca A1 - Eckert, Ester A1 - Fazi, Stefano A1 - Ninio, Shira A1 - Callieri, Cristiana A1 - Grossart, Hans-Peter A1 - Eckert, Werner T1 - Tracing particulate matter and associated microorganisms in freshwaters JF - Hydrobiologia : acta hydrobiologica, hydrographica, limnologica et protistologica N2 - Sediment resuspension represents a key process in all natural aquatic systems, owing to its role in nutrient cycling and transport of potential contaminants. Although suspended solids are generally accepted as an important quality parameter, current monitoring programs cover quantitative aspects only. Established methodologies do not provide information on origin, fate, and risks associated with uncontrolled inputs of solids in waters. Here we discuss the analytical approaches to assess the occurrence and ecological relevance of resuspended particulate matter in freshwaters, with a focus on the dynamics of associated contaminants and microorganisms. Triggered by the identification of specific physical-chemical traits and community structure of particle-associated microorganisms, recent findings suggest that a quantitative determination of microorganisms can be reasonably used to trace the origin of particulate matter by means of nucleic acid-based assays in different aquatic systems. KW - Total suspended solids KW - Resuspended particulate KW - Turbidity KW - Sediment traps KW - Particle-associated microorganisms KW - Pathogens Y1 - 2017 U6 - https://doi.org/10.1007/s10750-017-3260-x SN - 0018-8158 SN - 1573-5117 VL - 800 SP - 145 EP - 154 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Tang, Kam W. A1 - Flury, Sabine A1 - Grossart, Hans-Peter A1 - McGinnis, Daniel F. T1 - The Chaoborus pump: Migrating phantom midge larvae sustain hypolimnetic oxygen deficiency and nutrient internal loading in lakes JF - Water research N2 - Hypolimnetic oxygen demand in lakes is often assumed to be driven mainly by sediment microbial processes, while the role of Chaoborus larvae, which are prevalent in eutrophic lakes with hypoxic to anoxic bottoms, has been overlooked. We experimentally measured the respiration rates of C flavicans at different temperatures yielding a Q(10) of 1.44-1.71 and a respiratory quotient of 0.84-0.98. Applying the experimental data in a system analytical approach, we showed that migrating Chaoborus larvae can significantly add to the water column and sediment oxygen demand, and contribute to the observed linear relationship between water column respiration and depth. The estimated phosphorus excretion by Chaoborus in sediment is comparable in magnitude to the required phosphorus loading for eutrophication. Migrating Chaoborus larvae thereby essentially trap nutrients between the water column and the sediment, and this continuous internal loading of nutrients would delay lake remediation even when external inputs are stopped. (C) 2017 Elsevier Ltd. All rights reserved. KW - Chaoborus KW - Eutrophication KW - Oxygen KW - Nutrient KW - Remediation Y1 - 2017 U6 - https://doi.org/10.1016/j.watres.2017.05.058 SN - 0043-1354 VL - 122 SP - 36 EP - 41 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Ionescu, Danny A1 - Bizic-Ionescu, Mina A1 - De Maio, Nicola A1 - Cypionka, Heribert A1 - Grossart, Hans-Peter T1 - Community-like genome in single cells of the sulfur bacterium Achromatium oxaliferum JF - Nature Communications Y1 - 2017 U6 - https://doi.org/10.1038/s41467-017-00342-9 SN - 2041-1723 VL - 8 SP - 9193 EP - 9205 PB - Nature Publ. Group CY - London ER - TY - GEN A1 - Kalinkat, Gregor A1 - Cabral, Juliano Sarmento A1 - Darwall, William A1 - Ficetola, G. Francesco A1 - Fisher, Judith L. A1 - Giling, Darren P. A1 - Gosselin, Marie-Pierre A1 - Grossart, Hans-Peter A1 - Jaehnig, Sonja C. A1 - Jeschke, Jonathan M. A1 - Knopf, Klaus A1 - Larsen, Stefano A1 - Onandia, Gabriela A1 - Paetzig, Marlene A1 - Saul, Wolf-Christian A1 - Singer, Gabriel A1 - Sperfeld, Erik A1 - Jaric, Ivan T1 - Flagship umbrella species needed for the conservation of overlooked aquatic biodiversity T2 - Conservation biology : the journal of the Society for Conservation Biology Y1 - 2017 U6 - https://doi.org/10.1111/cobi.12813 SN - 0888-8892 SN - 1523-1739 VL - 31 SP - 481 EP - 485 PB - Wiley CY - Hoboken ER - TY - THES A1 - Lachmann, Sabrina C. T1 - Ecophysiology matters: Inorganic carbon acquisition in green microalgae related to different nutrient conditions Y1 - 2017 ER - TY - JOUR A1 - Rojas-Jimenez, Keilor A1 - Wurzbacher, Christian A1 - Bourne, Elizabeth Charlotte A1 - Chiuchiolo, Amy A1 - Priscu, John C. A1 - Grossart, Hans-Peter T1 - Early diverging lineages within Cryptomycota and Chytridiomycota dominate the fungal communities in ice-covered lakes of the McMurdo Dry Valleys, Antarctica JF - Scientific reports N2 - Antarctic ice-covered lakes are exceptional sites for studying the ecology of aquatic fungi under conditions of minimal human disturbance. In this study, we explored the diversity and community composition of fungi in five permanently covered lake basins located in the Taylor and Miers Valleys of Antarctica. Based on analysis of the 18S rRNA sequences, we showed that fungal taxa represented between 0.93% and 60.32% of the eukaryotic sequences. Cryptomycota and Chytridiomycota dominated the fungal communities in all lakes; however, members of Ascomycota, Basidiomycota, Zygomycota, and Blastocladiomycota were also present. Of the 1313 fungal OTUs identified, the two most abundant, belonging to LKM11 and Chytridiaceae, comprised 74% of the sequences. Significant differences in the community structure were determined among lakes, water depths, habitat features (i.e., brackish vs. freshwaters), and nucleic acids (DNA vs. RNA), suggesting niche differentiation. Network analysis suggested the existence of strong relationships among specific fungal phylotypes as well as between fungi and other eukaryotes. This study sheds light on the biology and ecology of basal fungi in aquatic systems. To our knowledge, this is the first report showing the predominance of early diverging lineages of fungi in pristine limnetic ecosystems, particularly of the enigmatic phylum Cryptomycota. Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-15598-w SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Mestre, Mireia A1 - Ferrera, Isabel A1 - Borrull, Encarna A1 - Ortega-Retuerta, Eva A1 - Mbedi, Susan A1 - Grossart, Hans-Peter A1 - Gasol, Josep M. A1 - Sala, M. Montserrat T1 - Spatial variability of marine bacterial and archaeal communities along the particulate matter continuum JF - Molecular ecology N2 - Biotic and abiotic particles shape the microspatial architecture that defines the microbial aquatic habitat, being particles highly variable in size and quality along oceanic horizontal and vertical gradients. We analysed the prokaryotic (bacterial and archaeal) diversity and community composition present in six distinct particle size classes ranging from the pico-to the microscale (0.2 to 200 lm). Further, we studied their variations along oceanographic horizontal (from the coast to open oceanic waters) and vertical (from the ocean surface into the meso-and bathypelagic ocean) gradients. In general, prokaryotic community composition was more variable with depth than in the transition from the coast to the open ocean. Comparing the six size-fractions, distinct prokaryotic communities were detected in each size-fraction, and whereas bacteria were more diverse in the larger size-fractions, archaea were more diverse in the smaller size-fractions. Comparison of prokaryotic community composition among particle size-fractions showed that most, but not all, taxonomic groups have a preference for a certain size-fraction sustained with depth. Species sorting, or the presence of diverse ecotypes with distinct size-fraction preferences, may explain why this trend is not conserved in all taxa. KW - attached KW - free-living KW - particulate matter KW - prokaryotic community KW - spatial variability Y1 - 2017 U6 - https://doi.org/10.1111/mec.14421 SN - 0962-1083 SN - 1365-294X VL - 26 SP - 6827 EP - 6840 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Giling, Darren P. A1 - Staehr, Peter A. A1 - Grossart, Hans-Peter A1 - Andersen, Mikkel Rene A1 - Boehrer, Bertram A1 - Escot, Carmelo A1 - Evrendilek, Fatih A1 - Gomez-Gener, Lluis A1 - Honti, Mark A1 - Jones, Ian D. A1 - Karakaya, Nusret A1 - Laas, Alo A1 - Moreno-Ostos, Enrique A1 - Rinke, Karsten A1 - Scharfenberger, Ulrike A1 - Schmidt, Silke R. A1 - Weber, Michael A1 - Woolway, R. Iestyn A1 - Zwart, Jacob A. A1 - Obrador, Biel T1 - Delving deeper: Metabolic processes in the metalimnion of stratified lakes JF - Limnology and oceanography N2 - Many lakes exhibit seasonal stratification, during which they develop strong thermal and chemical gradients. An expansion of depth-integrated monitoring programs has provided insight into the importance of organic carbon processing that occurs below the upper mixed layer. However, the chemical and physical drivers of metabolism and metabolic coupling remain unresolved, especially in the metalimnion. In this depth zone, sharp gradients in key resources such as light and temperature co-occur with dynamic physical conditions that influence metabolic processes directly and simultaneously hamper the accurate tracing of biological activity. We evaluated the drivers of metalimnetic metabolism and its associated uncertainty across 10 stratified lakes in Europe and North America. We hypothesized that the metalimnion would contribute highly to whole-lake functioning in clear oligotrophic lakes, and that metabolic rates would be highly variable in unstable polymictic lakes. Depth-integrated rates of gross primary production (GPP) and ecosystem respiration (ER) were modelled from diel dissolved oxygen curves using a Bayesian approach. Metabolic estimates were more uncertain below the epilimnion, but uncertainty was not consistently related to lake morphology or mixing regime. Metalimnetic rates exhibited high day-to-day variability in all trophic states, with the metalimnetic contribution to daily whole-lake GPP and ER ranging from 0% to 87% and < 1% to 92%, respectively. Nonetheless, the metalimnion of low-nutrient lakes contributed strongly to whole-lake metabolism on average, driven by a collinear combination of highlight, low surface-water phosphorous concentration and high metalimnetic volume. Consequently, a single-sensor approach does not necessarily reflect whole-ecosystem carbon dynamics in stratified lakes. Y1 - 2017 U6 - https://doi.org/10.1002/lno.10504 SN - 0024-3590 SN - 1939-5590 VL - 62 SP - 1288 EP - 1306 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Giling, Darren P. A1 - Nejstgaard, Jens C. A1 - Berger, Stella A. A1 - Grossart, Hans-Peter A1 - Kirillin, Georgiy A1 - Penske, Armin A1 - Lentz, Maren A1 - Casper, Peter A1 - Sareyka, Joerg A1 - Gessner, Mark O. T1 - Thermocline deepening boosts ecosystem metabolism: evidence from a large-scale lake enclosure experiment simulating a summer storm JF - Global change biology N2 - Extreme weather events can pervasively influence ecosystems. Observations in lakes indicate that severe storms in particular can have pronounced ecosystem-scale consequences, but the underlying mechanisms have not been rigorously assessed in experiments. One major effect of storms on lakes is the redistribution of mineral resources and plankton communities as a result of abrupt thermocline deepening. We aimed at elucidating the importance of this effect by mimicking in replicated large enclosures (each 9 m in diameter, ca. 20 m deep, ca. 1300 m 3 in volume) a mixing event caused by a severe natural storm that was previously observed in a deep clear-water lake. Metabolic rates were derived from diel changes in vertical profiles of dissolved oxygen concentrations using a Bayesian modelling approach, based on high-frequency measurements. Experimental thermocline deepening stimulated daily gross primary production (GPP) in surface waters by an average of 63% for > 4 weeks even though thermal stratification re-established within 5 days. Ecosystem respiration (ER) was tightly coupled to GPP, exceeding that in control enclosures by 53% over the same period. As GPP responded more strongly than ER, net ecosystem productivity (NEP) of the entire water column was also increased. These protracted increases in ecosystem metabolism and autotrophy were driven by a proliferation of inedible filamentous cyanobacteria released from light and nutrient limitation after they were entrained from below the thermocline into the surface water. Thus, thermocline deepening by a single severe storm can induce prolonged responses of lake ecosystem metabolism independent of other storm-induced effects, such as inputs of terrestrial materials by increased catchment run-off. This highlights that future shifts in frequency, severity or timing of storms are an important component of climate change, whose impacts on lake thermal structure will superimpose upon climate trends to influence algal dynamics and organic matter cycling in clear-water lakes. Keywords: climate variability, ecosystem productivity, extreme events, gross primary production, mesocosm, respiration stratified lakes KW - climate variability KW - ecosystem productivity KW - extreme events KW - gross primary production KW - mesocosm KW - respiration stratified lakes Y1 - 2017 U6 - https://doi.org/10.1111/gcb.13512 SN - 1354-1013 SN - 1365-2486 VL - 23 SP - 1448 EP - 1462 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Lau, Maximilian P. A1 - Hupfer, Michael A1 - Grossart, Hans-Peter T1 - Reduction-oxidation cycles of organic matter increase bacterial activity in the pelagic oxycline JF - Environmental microbiology reports N2 - Dissolved organic matter (DOM) in aquatic ecosystems contains redox-active moieties, which are prone to oxidation and reduction reactions. Oxidized moieties feature reduction potentials E-h, so that the moieties may be used as terminal electron acceptors (TEAs) in microbial respiration with a thermodynamic energy yield between nitrate and sulfate reduction. Here, we study the response of pelagic freshwater bacteria to exposure to native DOM with varying availabilities of oxidized moieties and hence redox state. Our results show that the prevalence of oxidized DOM favors microbial production and growth in anoxic waters. Reduced DOM in stratified lakes may be oxidized when fluctuations of the oxycline expose DOM in previously anoxic water to epilimnetic oxygen. The resulting oxidized DOM may be rapidly used as TEAs in microbial respiration during subsequent periods of anoxia. We further investigate if the prevalence of these organic electron sinks in anaerobic incubations can induce changes in the microbial community. Our results reveal that DOM traversing transient redox interfaces selects for species that profit from such spatially confined and cyclically restored TEA reservoirs. Y1 - 2017 U6 - https://doi.org/10.1111/1758-2229.12526 SN - 1758-2229 VL - 9 SP - 257 EP - 267 PB - Wiley CY - Hoboken ER -