Refine
Year of publication
- 2014 (226) (remove)
Document Type
- Article (196)
- Doctoral Thesis (17)
- Preprint (8)
- Review (4)
- Postprint (1)
Is part of the Bibliography
- yes (226) (remove)
Keywords
- Earthquake source observations (7)
- Holocene (6)
- Tibetan Plateau (4)
- Erosion (3)
- Himalaya (3)
- Seismicity and tectonics (3)
- Aleatory variability (2)
- Andes (2)
- Baseline shift (2)
- Body waves (2)
- Cenozoic (2)
- Central Asia (2)
- Climate change (2)
- Connectivity (2)
- Cosmogenic nuclides (2)
- Earthquake (2)
- Earthquake dynamics (2)
- Epistemic uncertainty (2)
- Europe (2)
- Glaciation (2)
- Human impact (2)
- INOPEX (2)
- Indian Monsoon (2)
- Inverse theory (2)
- Lake sediment (2)
- Landslide (2)
- Late Pleistocene (2)
- Nanoscale zero-valent iron (nZVI) (2)
- Neogene (2)
- Ostracoda (2)
- Ostracods (2)
- Palaeolimnology (2)
- Pollen (2)
- Qaidam Basin (2)
- Sediment fingerprinting (2)
- Spectroscopy (2)
- Subduction (2)
- Suspended sediment (2)
- Tight integration (2)
- Time-series analysis (2)
- WA-PLS (2)
- cosmogenic nuclides (2)
- erosion (2)
- floodplain sedimentation (2)
- induced seismicity (2)
- lake sediments (2)
- palaeoenvironmental proxies (2)
- sediment dynamics (2)
- suspended sediment (2)
- tectonics (2)
- 3D geomechanical numerical model (1)
- 3D geomechanisch-nummerische Modellierung (1)
- AHP (1)
- Abundance from Large Sites) model (1)
- Accelerometer records (1)
- Acheulian (1)
- Active volcanism (1)
- Adaptation (1)
- African Humid Period (1)
- Age-depth modelling (1)
- Agricultural management (1)
- Alaska (1)
- Alberta (1)
- Alborz Mountains (1)
- Alborz range (1)
- Algeria (1)
- Alpine hazards (1)
- Amino acid (1)
- Amorphous silica (1)
- Amphibolites (1)
- Ancient DNA (1)
- Ancient forest (1)
- Anisotropy of magnetic remanence (1)
- Antarctic glaciology (1)
- Aptian (1)
- Aquifer systems (1)
- Ar-40/Ar-39 dating (1)
- Arabian Sea (1)
- Arc magmatism (1)
- Artificial catchment (1)
- Artificial mixture (1)
- Asymmetric basin (1)
- Atlantic Ocean (1)
- Attribut-Analysen (1)
- Aufenthaltsdauer (1)
- Badlands (1)
- Bagging (1)
- Basaltic ash-fall deposits (1)
- Baseline error (1)
- Bayesian networks (1)
- Bayesian non-parametrics (1)
- Bergsturz (1)
- Betula pubescens Ehrh. ssp czerepanovii (1)
- Biomarker (1)
- Biosilicification (1)
- Biostratigraphy (1)
- Bodenwassergehalt (1)
- Boron isotopes (1)
- Brazil (1)
- Broad-band seismometers (1)
- Buckingham-Darcy law (1)
- Calibration (1)
- Canada (1)
- Cape Verde (1)
- Cappadocia (1)
- Carbo-Iron (R) (1)
- Carbon and oxygen isotopes (1)
- Carbon colloid (1)
- Carbonate platform response (1)
- Carpholite (1)
- Cation-exchange capacity (1)
- Cenozoic climate transitions (1)
- Central-western Mongolia (1)
- Chemical fractionation (1)
- Chloritoid (1)
- Circular statistics (1)
- Cladocera (1)
- Clay mineralogy (1)
- Climate reconstruction (1)
- Cluster (1)
- Clustering (1)
- Coastal hazards (1)
- Coastal regions (1)
- Coastal sequence of shorelines (1)
- Colloid transport (1)
- Common-Reflection-Surface (1)
- Conductivity (1)
- Congo Air Boundary (1)
- Continental margins: convergent (1)
- Corbicula (1)
- Costs (1)
- Crack opening and closure (1)
- Cratons (1)
- Creep and deformation (1)
- Crop rotation (1)
- Crosshole tomography (1)
- Crustal structure (1)
- Cuora (1)
- Cyprus arc (1)
- Dansgaard-Oeschger oscillations (1)
- Database (1)
- Dead Sea basin (1)
- Debris flows (1)
- Deep percolation flux (1)
- Deformationsquellenmodellierung (1)
- Dehydration (1)
- Denali (1)
- Dendroklimatologie (1)
- Density (1)
- Denudation (1)
- Deposition (1)
- Depositional origin (1)
- Diatoms (1)
- Directivity (1)
- Discontinuity surfaces (1)
- Downscaling socio-economic scenarios (1)
- Droughts (1)
- Dry land degradation (1)
- Dynamics and mechanics of faulting (1)
- ELA (1)
- ENSO (1)
- Early warning (1)
- Earthquake ground motions (1)
- East Africa (1)
- East African Rift System (1)
- Ecological health (1)
- Ecosystem services (1)
- Edough (1)
- Element partitioning (1)
- Empirical ground-motion models (1)
- EnMAP (1)
- Energy crops (1)
- Ensembles (1)
- Ex ante assessment (1)
- Exchangeable Ca (1)
- Experiment (1)
- Extensional duplex (1)
- Extracellular DNA (1)
- F-test (1)
- FEM models (1)
- Fault linkage and interaction (1)
- Fauna (1)
- Finnmark Platform (1)
- Floods (1)
- Flora (1)
- Flower structure (1)
- Fluid-rock interaction (1)
- Focal mechanism (1)
- Forearc dewatering (1)
- Forest ecosystem (1)
- Formalised scenario analysis (1)
- Fossil DNA (1)
- Fractional cover (1)
- GMPE (1)
- GPS (1)
- Gastropods (1)
- Gaussian Process regression (1)
- Generalization error (1)
- Geodynamic (1)
- Geomorphologie (1)
- Geophysik (1)
- Georadar (1)
- Geotechnical parameters (1)
- Glacial (1)
- Glacial buzzsaw (1)
- Global inversion (1)
- Global sensitivity analysis (1)
- Grain for Green Project (1)
- Ground motion and GPS (1)
- Ground-motion models (1)
- Ground-motion prediction equations (1)
- Ground-motion-model (1)
- Groundwater (1)
- Growth zoning (1)
- HP/LT metamorphism (1)
- Heinrich events (1)
- Hiatus (1)
- Hierarchical partitioning (1)
- High-rate GPS (1)
- High-rateGPS (1)
- Himalaya-Tibet Orogen (1)
- Himalaya-Tibet orogen (1)
- Holozän (1)
- Hominin (1)
- Huisman-Olff-Fresco models (1)
- Human evolution (1)
- Hydraulic fracture (1)
- Hydrological balance (1)
- Hydrological model (1)
- Hyperion (1)
- Hyperspectral remote sensing (1)
- Hysteresis index (1)
- IPCC (1)
- Idiosomic Si pool (1)
- Image classification (1)
- Imaging spectroscopy (1)
- In-situ remediation (1)
- InSAR (1)
- Incentives (1)
- Index of connectivity (1)
- Indian monsoon (1)
- Indian summer monsoon (1)
- Indicators (1)
- Induced seismicity (1)
- Indus (1)
- Integration (1)
- Interaction (1)
- Interception (1)
- Interferometry (1)
- Intracellular DNA (1)
- Intraplate seismicity (1)
- Irrigation experiment (1)
- Isabena river (1)
- Isometric feature mapping (1)
- Israel (1)
- Issyk-Kul (1)
- Japan (1)
- Kaghan (1)
- Kalakuli Lake (1)
- Kalman filter (1)
- Krustenstruktur der Süd-Türkei (1)
- Krustenstruktur des Eratosthenes Seeberges (1)
- Lake (1)
- Lake Bayan Nuur (1)
- Lake Kinneret (1)
- Lake Malombe (1)
- Lake Stechlin (1)
- Lake model (1)
- Land reform (1)
- Land use conception (1)
- Landslides (1)
- Larger foraminifera (1)
- Laser fluorination (1)
- Last Glacial Maximum (1)
- Late Holocene (1)
- Late cretaceous (1)
- Levant (1)
- Little Ice Age (1)
- Llaima Vulkan (1)
- Llaima volcano (1)
- Local magnitude scale (1)
- Lonar Crater Lake (1)
- Lonar Lake (1)
- Loppa High (1)
- Lower Palaeolithic (1)
- Lupinus albus (1)
- MAT (1)
- MATLAB (1)
- Macrophytes (1)
- Magnetostratigraphy (1)
- Manifold (1)
- Medieval Climate Anomaly (1)
- Mediterranean-mountainous (1)
- Mekong Delta (1)
- Mekong delta (1)
- Melt (1)
- Metamorphism (1)
- Microbial community analysis (1)
- Microcystis aeruginosa (1)
- Microseismicity (1)
- Middle East (1)
- Military conversion (1)
- Mitigation (1)
- Mixing model (1)
- Mixing models (1)
- Mobility (1)
- Modelling (1)
- Moisture-advection feedback (1)
- Momententensor (1)
- Monsoon (1)
- Mosha Fault (1)
- Mossbauer spectroscopy (1)
- Multi-attribute decision-making (1)
- Multi-variables (1)
- Multifunctionality (1)
- N-acetyl-glucosamine (NAG) (1)
- NAO (1)
- Nanomaterial (1)
- Natura 2000 monitoring (1)
- Natural dam (1)
- Natural hazards (1)
- Near East (1)
- Nested scenarios (1)
- Nianbaoyeze Mountains (1)
- Non-parametric regression (1)
- Non-scalar input factors (1)
- Nonparametric statistics (1)
- North Tehran Fault (1)
- North-eastern Spain (1)
- Northeast Spain (1)
- Northern Europe (1)
- Norway (1)
- Numerical experiment (1)
- OLI (1)
- OSL dating (1)
- Oceanic anoxic event 1a (1)
- Ohalo Site (1)
- Oil sands (1)
- Orbital forcing (1)
- Orbitoides (1)
- Overland flow (1)
- Oxygen and carbon isotopes (1)
- Oxygen isotope compositions (1)
- PAN (1)
- Palaeoclimatology (1)
- Palaeoecology (1)
- Palaeoliminology (1)
- Paleoenvironmental change (1)
- Paleohydrology (1)
- Paleolimnology (1)
- Paleoseismology (1)
- Paläogeographie (1)
- Pamir (1)
- Panama (1)
- Partikel Swarm Optimierung (1)
- Persistence (1)
- Pesticide transport (1)
- Pierson-Moskowitz spectra (1)
- Pleistocene/Holocene transition (1)
- Pollen-climate calibration (1)
- Pollen-climate transfer function (1)
- Precise Point Positioning (1)
- Precise point positioning (1)
- Preferential flow (1)
- Process domains (1)
- Proto-North Atlantic (1)
- Public good game (1)
- Pull-Apart Basin (1)
- Pull-apart basin (1)
- Pulsed climate variability hypothesis (1)
- Punishment (1)
- Qinghai-Tibetan Plateau (QTP) (1)
- Quantitative regional plant abundance (1)
- Quartär (1)
- Quellenumkehr (1)
- REE (1)
- REVEALS (Regional Estimates of VEgetation (1)
- Rangeland management (1)
- Rangifer tarandus (1)
- Rasa (1)
- Rate of compositional change (1)
- Recent forest (1)
- Reclamation (1)
- Regional ecosystem service management (1)
- Regional objectives (1)
- Regional-dependence (1)
- Ringstörungen (1)
- Risk reduction (1)
- Rock magnetism (1)
- Role-play (1)
- Roots (1)
- Russian Arctic (1)
- Salinity (1)
- Sampling strategy (1)
- Satellite geodesy (1)
- Sclerochronology (1)
- Sea of Galilee (1)
- Sediment Transport (1)
- Sediment budget (1)
- Sediment cascade (1)
- Sediment connectivity (1)
- Sediment monitoring (1)
- Sediment redistribution (1)
- Sediment transfer (1)
- Sediment yield (1)
- Sedimentation rate (1)
- Seismic cycle (1)
- Seismic slip distribution (1)
- Seismicity (1)
- Seismologie (1)
- Semi-arid (1)
- Semi-arid savanna (1)
- Semiarid (1)
- Sentinel-2 (1)
- Shell Bar (1)
- Si fractions (1)
- Simulation model (1)
- Site amplification (1)
- Site-adequate land use (1)
- Slip rate (1)
- Slope-area plot (1)
- Smallholder (1)
- Soil heterogeneity (1)
- Source mechanism (1)
- South Africa (1)
- South Pacific Gyre (1)
- Space geodetic surveys (1)
- Spannungsmuster (1)
- Spatial autocorrelation (1)
- Spatial scale (1)
- Spatial structure (1)
- Spectral unmixing (1)
- Sr-87/Sr-86 (1)
- Stabile Sauerstoff- und Kohlenstoffisotope (1)
- Stable carbon isotope (1)
- Stable isotopes (1)
- Statistical seismology (1)
- Strandlines (1)
- Stratigraphy (1)
- Stress pattern (1)
- Strong-motion (1)
- Strong-motion data (1)
- Strong-motion records (1)
- Strontium isotope stratigraphy (1)
- Structural geology (1)
- Style of faulting (1)
- Subarctic North Pacific (1)
- Subduction fluids (1)
- Subduction input (1)
- Subduction zone (1)
- Subduction zone processes (1)
- Submarine sediments (1)
- Suguta Valley (1)
- Sumatran fault (1)
- Susceptibility (1)
- TRMM satellite data (1)
- Tailings ponds (1)
- Taphonomy (1)
- Team (1)
- Tectona grandis (1)
- Tectonic stress (1)
- Tectonic-climate coupling (1)
- Tectonics (1)
- Temperate deciduous forest (1)
- Temperature (1)
- Temporal stability of soil water fluxes (1)
- Tendürek Vulkan (1)
- Tendürek volcano (1)
- Tephrostratigraphy (1)
- Terrestrial ecosystem development (1)
- Testudines (1)
- Th-232 (1)
- Thermo-mechanical modeling (1)
- Thermodynamic modeling (1)
- Thermodynamic-geochemical modeling (1)
- Threshold (1)
- Throughfall (1)
- Tien Shan (1)
- Tien Shan (western Central Asia) (1)
- Time series analysis (1)
- Tomography (1)
- Transfer function (1)
- Transform fault (1)
- Tree-ring (1)
- Tropen (1)
- Tropical forest (1)
- Tso Moriri Lake (1)
- Turkey (1)
- UHP eclogites (1)
- UV-Lasermikrodissektion (1)
- UV-laser microdissection (1)
- Uncertainty (1)
- Untergrund (1)
- Vadose zone (1)
- Valley fills (1)
- Vegetation diversity indices (1)
- Verarbeitung seismischer Daten (1)
- Volcano seismology (1)
- Water depth (1)
- Water quality (1)
- Water yield (1)
- Wave propagation (1)
- Weathering indices (1)
- Weights-of-Evidence (1)
- Wellengeschwindigkeit (1)
- X-radiography (1)
- XRF (1)
- Younger Dryas (1)
- Zypernbogen (1)
- aboveground biomass (1)
- accommodation-space (1)
- actively growing bacteria (AGB) (1)
- afforestation (1)
- aktive Weitewinkel-Seismik (1)
- anatexis (1)
- ant mounds (1)
- assimilation (1)
- atmosphere-only climate model simulations (1)
- bacterial community composition (1)
- beginnende Kontinent-Kontinent Kollision (1)
- belowground biomass (1)
- biogeographic provinces (1)
- boundary scavenging (1)
- box turtles (1)
- breccia (1)
- bromodeoxyuridine (BrdU) immunocytochemistry (1)
- captive breeding (1)
- catchment scale (1)
- central Mongolia (1)
- channel steepness (1)
- circular statistics (1)
- climate (1)
- climate change impact (1)
- climate extremes (1)
- climatic and tectonic forcing (1)
- clustering (1)
- coastal flooding (1)
- coherency (1)
- connectivity (1)
- conservation units (1)
- controlled source wide angle seismic (1)
- convection (1)
- correlations (1)
- crustal stress (1)
- crustal structure of south central Turkey (1)
- crustal structure of the Eratosthenes Seamount (1)
- damage (1)
- deformation source modeling (1)
- delayed fluorescence (1)
- delta O-18 (1)
- dendroclimatology (1)
- denudation (1)
- deposition (1)
- diatoms (1)
- diurnal signal (1)
- drainage network expansion (1)
- drought (1)
- drylands (1)
- eDNA (1)
- earthquake deformation (1)
- earthquake location (1)
- earthworm ecological types (1)
- ecohydrological modelling (1)
- environmental change (1)
- eolian dust (1)
- evapotranspiration (1)
- events (1)
- ex-ante impact assessment (1)
- extinction (1)
- falling sphere viscosimetry (1)
- faulting behavior (1)
- feedback (1)
- fire emissions (1)
- floodplain (1)
- floods (1)
- fluid inclusions (1)
- fluid-induced seismicity (1)
- fluorescence imaging (1)
- fluorescence-activated cell sorting (FACS) (1)
- focal mechanisms (1)
- foreland-basin stratigraphy (1)
- forest (1)
- frictional melt (1)
- garnet (1)
- geochemistry (1)
- geomorphology (1)
- geophyics (1)
- geothermal (1)
- geothermischer Reservoire (1)
- glacier flow (1)
- glacier variation (1)
- glaciolacustrine sediment (1)
- glaciological instruments and methods (1)
- global change (1)
- global climate (1)
- global inversion (1)
- global vegetation model (1)
- globale Inversion (1)
- gold (1)
- grain size (1)
- green algae (1)
- ground-penetrating radar (1)
- ground-penetration radar (1)
- groundwater lysimeter (1)
- helium-4 (1)
- high pressure (1)
- high-precision gravimeter (1)
- high-pressure (1)
- holocene (1)
- human impact (1)
- hyporheic zone (1)
- ice dynamics (1)
- ice-sheet modelling (1)
- ice-shelf tributary glaciers (1)
- incipient continent-continent collision (1)
- indischer Monsun (1)
- induzierten Seismizität (1)
- inelastic properties (1)
- infiltration patterns (1)
- iron feature depth (IFD) (1)
- isotopes (1)
- kosmogene Nuklide (1)
- krustale Spannungen (1)
- lake eutrophication (1)
- land conversion (1)
- land use (1)
- land use functions (1)
- landslide (1)
- late Holocene (1)
- late Quaternary (1)
- littoral zone (1)
- lonar lake (1)
- loss and damage (1)
- lupin (1)
- macropore flow (1)
- macropores (1)
- magnetic parameters (1)
- marine-controlled source electromagnetic method (1)
- melt inclusions (1)
- memory (1)
- meso-scale ecosystems (1)
- microsatellites (1)
- microseismicity (1)
- microseisms (1)
- mid-latitude Westerlies (1)
- mine waste (1)
- model validation (1)
- modelling (1)
- modern pollen (1)
- modern surface pollen (1)
- modern surface sediments (1)
- moisture variations in India (1)
- moment tensor (1)
- monitoring (1)
- monsoon (1)
- mountain birch (1)
- multi-proxy reconstructions (1)
- nanogranites (1)
- nested catchments (1)
- neutron radiography (1)
- olivine (1)
- ordination (1)
- out-of-sequence deformation (1)
- overland flow (1)
- oxygen and carbon stable isotopes (1)
- oxygen dynamics (1)
- pH dynamics (1)
- palaeoclimate reconstruction (1)
- palaeoecology (1)
- palaeolimnology (1)
- paleoaltimetry (1)
- paleoelevation (1)
- paleogeography (1)
- paleovegetation (1)
- particle swarm optimisation (1)
- permafrost (1)
- permafrost carbon feedback (1)
- petrography (1)
- phosphorus (1)
- phreatophytes (1)
- phycocyanin (1)
- plant-animal-soil-system (1)
- platinum (1)
- pollen (1)
- pore pressure (1)
- precipitation (1)
- preferential flow (1)
- process based (1)
- productivity (1)
- prolonged droughts (1)
- protactinium (1)
- pseudotachylyte (1)
- quaternary (1)
- radar imaging (1)
- radio-echo sounding (1)
- reactive oxygen species (1)
- reduction (1)
- regression tree (1)
- reindeer (1)
- relative pollen productivity (1)
- relevant pollen source area (1)
- remote sensing (1)
- reservoir characterization (1)
- rheology (1)
- rhizosphere (1)
- ring-fault (1)
- river networks (1)
- rockslide (1)
- root depth distribution (1)
- root distribution (1)
- sediment output (1)
- sediment supply (1)
- sediment-supply ratio (A /S) (1)
- seismic (1)
- seismic attributes (1)
- seismic sequence stratigraphy (1)
- seismische Attribute (1)
- seismische Sequenzstratigraphie (1)
- seismische Stapelungs-Methode (1)
- seismology (1)
- semi-arid area (1)
- soil erosion (1)
- soil water content (1)
- soil water distribution (1)
- soil-root interaction (1)
- source duration (1)
- source inversion (1)
- spatial extent (1)
- spatial parameterization (1)
- specific yield (1)
- spectrogram (1)
- splay faults (1)
- stable isotopes (1)
- stakeholder participation (1)
- storage-discharge relationship (1)
- stormflow (1)
- stream power (1)
- stress pattern (1)
- subduction zone earthquakes (1)
- subsurface (1)
- surface uplift (1)
- sustainable development (1)
- synthetic aperture radar (SAR) (1)
- tectonic stress (1)
- tektonische Spannungen (1)
- temperature (1)
- thermal effect (1)
- thermochronology (1)
- thorium (1)
- transfer functions (1)
- tropics (1)
- tsunami hazards (1)
- typical steppe (1)
- uncertainty (1)
- upper mantle (1)
- vegetation degradation (1)
- water storage (1)
- wave velocities (1)
- weathering indices (1)
- westernmost Tibetan Plateau (1)
- wetland (1)
- zirkulare Statistik (1)
- zoogeomorphology (1)
Institute
- Institut für Geowissenschaften (226) (remove)
To support scientifically sound water management in dryland environments a modelling system has been developed for the quantitative assessment of water and sediment fluxes in catchments, transport in the river system, and retention in reservoirs. The spatial scale of interest is the mesoscale because this is the scale most relevant for management of water and land resources.
This modelling system comprises process-oriented hydrological components tailored for dryland characteristics coupled with components comprising hillslope erosion, sediment transport and reservoir deposition processes. The spatial discretization is hierarchically designed according to a multi-scale concept to account for particular relevant process scales. The non-linear and partly intermittent run-off generation and sediment dynamics are dealt with by accounting for connectivity phenomena at the intersections of landscape compartments. The modelling system has been developed by means of data from nested research catchments in NE-Spain and in NE-Brazil.
In the semi-arid NE of Brazil sediment retention along the topography is the main process for sediment retention at all scales, i.e. the sediment delivery is transport limited. This kind of deposition retains roughly 50 to 60 % of eroded sediment, maintaining a similar deposition proportion in all spatial scales investigated. On the other hand, the sediment retained in reservoirs is clearly related to the scale, increasing with catchment area. With increasing area, there are more reservoirs, increasing the possibility of deposition. Furthermore, the area increase also promotes an increase in flow volume, favouring the construction of larger reservoirs, which generally overflow less frequently and retain higher sediment fractions. The second example comprises a highly dynamic Mediterranean catchment in NE-Spain with nested sub-catchments and reveals the full dynamics of hydrological, erosion and deposition features. The run-off modelling performed well with only some overestimation during low-flow periods due to the neglect of water losses along the river. The simulated peaks in sediment flux are reproduced well, while low-flow sediment transport is less well captured, due to the disregard of sediment remobilization in the riverbed during low flow.
This combined observation and modelling study deepened the understanding of hydro-sedimentological systems characterized by flashy run-off generation and by erosion and sediment transport pulses through the different landscape compartments. The connectivity between the different landscape compartments plays a very relevant role, regarding both the total mass of water and sediment transport and the transport time through the catchment.
The strong present-day Asian monsoons are thought to have originated between 25 and 22 million years (Myr) ago, driven by Tibetan-Himalayan uplift. However, the existence of older Asian monsoons and their response to enhanced greenhouse conditions such as those in the Eocene period (55-34Myrago) are unknown because of the paucity of well-dated records. Here we show late Eocene climate records revealing marked monsoon-like patterns in rainfall and wind south and north of the Tibetan-Himalayan orogen. This is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from Myanmar, and by aeolian dust deposition in northwest China. Our climate simulations support modern-like Eocene monsoonal rainfall and show that a reinforced hydrological cycle responding to enhanced greenhouse conditions counterbalanced the negative effect of lower Tibetan relief on precipitation. These strong monsoons later weakened with the global shift to icehouse conditions 34 Myr ago.
Members of the acI lineage of Actinobacteria are the most abundant microorganisms in most freshwater lakes; however, our understanding of the keys to their success and their role in carbon and nutrient cycling in freshwater systems has been hampered by the lack of pure cultures and genomes. We obtained draft genome assemblies from 11 single cells representing three acI tribes (acI-A1, acI-A7, acI-B1) from four temperate lakes in the United States and Europe. Comparative analysis of acI SAGs and other available freshwater bacterial genomes showed that acI has more gene content directed toward carbohydrate acquisition as compared to Polynucleobacter and LD12 Alphaproteobacteria, which seem to specialize more on carboxylic acids. The acI genomes contain actinorhodopsin as well as some genes involved in anaplerotic carbon fixation indicating the capacity to supplement their known heterotrophic lifestyle. Genome-level differences between the acI-A and acI-B clades suggest specialization at the clade level for carbon substrate acquisition. Overall, the acI genomes appear to be highly streamlined versions of Actinobacteria that include some genes allowing it to take advantage of sunlight and N-rich organic compounds such as polyamines, di-and oligopeptides, branched-chain amino acids and cyanophycin. This work significantly expands the known metabolic potential of the cosmopolitan freshwater acI lineage and its ecological and genetic traits.
In aquatic environments, community dynamics of bacteria, especially actively growing bacteria (AGB), are tightly linked with dissolved organic matter (DOM) quantity and quality. We analyzed the community dynamics of DNA-synthesizing and accordingly AGB by linking an improved bromodeoxyuridine immunocytochemistry approach with fluorescence-activated cell sorting (BrdU-FACS). FACS-sorted cells of even oligotrophic ecosystems in winter were characterized by 16S rRNA gene analysis. In incubation experiments, we examined community shifts of AGB in response to the addition of N-acetyl-glucosamine (NAG), one of the most abundant aminosugars in aquatic systems. Our improved BrdU-FACS analysis revealed that AGB winter communities of oligotrophic Lake Stechlin (northeastern Germany) substantially differ from those of total bacteria and consist of Alpha-, Beta-, Gamma-, Deltaproteobacteria, Actinobacteria, Candidatus OP10 and Chloroflexi. AGB populations with different BrdU-fluorescence intensities and cell sizes represented different phylotypes suggesting that single-cell growth potential varies at the taxon level. NAG incubation experiments demonstrated that a variety of widespread taxa related to Alpha-, Beta-, Gammaproteobacteria, Bacteroidetes, Actinobacteria, Firmicutes, Planctomycetes, Spirochaetes, Verrucomicrobia and Chloroflexi actively grow in the presence of NAG. The BrdU-FACS approach enables detailed phylogenetic studies of AGB and, thus, to identify those phylotypes which are potential key players in aquatic DOM cycling.
The widely reported paradox of methane oversaturation in oxygenated water challenges the prevailing paradigm that microbial methanogenesis only occurs under anoxic conditions. Using a combination of field sampling, incubation experiments, and modeling, we show that the recurring mid-water methane peak in Lake Stechlin, northeast Germany, was not dependent on methane input from the littoral zone or bottom sediment or on the presence of known micro-anoxic zones. The methane peak repeatedly overlapped with oxygen oversaturation in the seasonal thermocline. Incubation experiments and isotope analysis indicated active methane production, which was likely linked to photosynthesis and/or nitrogen fixation within the oxygenated water, whereas lessening of methane oxidation by light allowed accumulation of methane in the oxygen-rich upper layer. Estimated methane efflux from the surface water was up to 5 mmol m(-2) d(-1). Mid-water methane oversaturation was also observed in nine other lakes that collectively showed a strongly negative gradient of methane concentration within 0-20% dissolved oxygen (DO) in the bottom water, and a positive gradient within >= 20% DO in the upper water column. Further investigation into the responsible organisms and biochemical pathways will help improve our understanding of the global methane cycle.
In aquatic systems, natural organic matter (NOM) and in particular humic substances effectively absorb the ultraviolet (UV)/visible light spectrum of solar radiation and act as a photoprotective filter for organisms. Simultaneously, UV contributes to the generation of potentially harmful reactive oxygen species (ROS). Dose-response experiments were conducted on cyanobacteria and green algae with hydrogen peroxide (H2O2) as a long-lived representative of ROS. Delayed fluorescence (DF) decay kinetics was used as a non-invasive tool to follow changes of phytoplankton activity in real time. In order to investigate phototoxicity and photoprotection by NOM on phytoplankton, we exposed algae to UV-pre-irradiated NOM and direct UV excitation. Cyanobacteria responded to H2O2 concentrations as low as 10(-7) M, while green algae were 2 orders of magnitude less sensitive. UV irradiation of medium with NOM generated H2O2 concentrations of 1.5 x 10(-7) to 3.6 x 10(-7) M. When exposed to these concentrations, only the DF of cyanobacteria led to a measurable effect while that of green algae did not change. The addition of NOM protected all phytoplankton from direct UV irradiation, but cyanobacteria benefitted less. From this we conclude that UV-irradiated water enriched with NOM can adversely affect the physiology of cyanobacteria, but not of green algae, which might control phytoplankton composition and species-specific activities.