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  • 1
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    Influence of hydro-climatic variation on marine phytoplankton phenology: species-specific responses on the decadal scale (2017)
    In:  EPIC3ASLO Aquatic Sciences Meeting, Honululu, Hawaii, 2017-02-26-2017-03-03
    Details
    Publication Date: 2017-03-28
    Description: The range of environmental conditions in marine pelagic ecosystems is characterized by seasonality, particularly in mid and high latitudes. Annual cycles of light availability and water temperature are central to processes in pelagic food webs and drive the phenology of planktonic organisms. Using high resolution data of 24 phytoplankton species observed at Helgoland Roads (North Sea) during the period from 1962 to 2014, we analyzed the phenological response to long-term changes in the hydro-climatic conditions. We estimated timing by calculating the date of 50th percentile of cumulative abundance by taking into account both unimodal and bimodal (spring and autumn) peak structures. We show that species-specific preferences in combination with seasonally varying trends in environmental parameters led to a complex phenological response pattern. Species showing widely overlapping timing windows can exhibit different phenological responses. Both diatoms and dinoflagellates exhibit significant changes in seasonal peak timing (earlier/later), but some species show a remarkable constancy over the entire period. The intra-annual variability of timing strongly differs between different species, also due to basic differences in the environmental variability during the year. Shifts of the majority of species reflect long-term displacements in the occurrence of water temperature ranges within the year. On the long-term, only a few species show significant relationships between annual timing and peak abundance. Such complexity illustrates the uncertainty of making conclusions about potential future ecological development related to climate change.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 2
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    Klimawandel aktuell: Daten von Sylt und Helgoland (2018)
    In:  EPIC3Vortragsreihe Erlebniszentrum Naturgewalten
    Details
    Publication Date: 2018-09-27
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    Short-term changes in polysaccharide utilization mechanisms of marine bacterioplankton during a spring phytoplankton bloom (2020)
    In:  EPIC3Journal of Sea Research
    Details
    Publication Date: 2020-08-03
    Description: Spring phytoplankton blooms in temperate environments contribute disproportionately to global marine productivity. Bloom-derived organic matter, much of it occurring as polysaccharides, fuels biogeochemical cycles driven by interacting autotrophic and heterotrophic communities. We tracked changes in the mode of polysaccharide utilization by heterotrophic bacteria during the course of a diatom-dominated bloom in the German Bight, North Sea. Polysaccharides can be taken up in a ‘selfish’ mode, where initial hydrolysis is coupled to transport into the periplasm, such that little to no low-molecular weight (LMW) products are externally released to the environment. Alternatively, polysaccharides hydrolyzed by cell-surface attached or free extracellular enzymes (external hydrolysis) yield LMW products available to the wider bacterioplankton community. In the early bloom phase, selfish activity was accompanied by low extracellular hydrolysis rates of a few polysaccharides. As the bloom progressed, selfish uptake increased markedly, and external hydrolysis rates increased, but only for a limited range of substrates. The late bloom phase was characterized by high external hydrolysis rates of a broad range of polysaccharides and reduced selfish uptake of polysaccharides, except for laminarin. Substrate utilization mode is related both to substrate structural complexity and to the bloom-stage dependent composition of the heterotrophic bacterial community.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    Short‐term changes in polysaccharide utilization mechanisms of marine bacterioplankton during a spring phytoplankton bloom (2020)
    In:  EPIC3Environmental Microbiology, 22(5), pp. 1884-1900, ISSN: 1462-2912
    Details
    Publication Date: 2020-07-22
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Control of phytoplankton in a shelf sea: Determination of the main drivers based on the Helgoland Roads Time Series (2015)
    In:  EPIC3Journal of Sea Research, 105, pp. 42-52, ISSN: 13851101
    Details
    Publication Date: 2017-02-02
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Klimawandel und Plankton (2014)
    Verlag Wissenschaftliche Auswertungen
    In:  EPIC3Warnsignal Klima: Gefahren für Pflanzen, Tiere und Menschen., Verlag Wissenschaftliche Auswertungen
    Details
    Publication Date: 2017-02-02
    Description: Ein besseres Verständnis der Auswirkungen des Klimawandels auf die marinen Ökosysteme ist für den Menschen sowohl aus ökologischer wie auch ökonomischer Sicht von herausragender Bedeutung. Die Reaktion von Phyto- und Zooplanktern auf klimatische Veränderungen spielt aufgrund ihrer Funktion als Primär- und Sekundärproduzenten im marinen Nahrungsnetz eine zentrale Rolle in diesem Prozess. Die Erwärmung der oberflächennahen Schichten in Ozeanen und Randmeeren hat ökologische Veränderungen in Form von Verschiebungen in den biogeographischen und zeitlichen Verteilungsmustern von planktischen Organismen zur Folge. Indirekte Temperatureffekte können u.a. aus einer verstärkten Stratifizierung, welche den vertikalen Austausch von Nährstoffen und damit ihre Verfügbarkeit für das Phytoplankton in der euphotischen Zone reduziert, resultieren. Unterschiede in der phänologischen Reaktion von Phyto- und Zooplanktern hinsichtlich gestiegener Wassertemperaturen können zur innerjährlichen Entkopplung funktionaler Verbindungen zwischen beiden Gruppen führen, mit Folgen auch für die Nahrungsverfügbarkeit und -qualität von Fischen. Der Anstieg der atmosphärischen Kohlendioxid-Konzentration (CO2) führt zu einer Versauerung der Meere und dadurch zu Veränderungen der chemischen Zusammensetzung des Meerwassers. Eine Abnahme des pH-Wertes hat u.a. potentiell negative Implikationen für kalzifizierende, planktische Organismen. Klimatische Effekte auf marine Ökosysteme können sich lokal und regional unterschiedlich manifestieren und, etwa in Küstenregionen, durch anthropogene Einflüsse (z.B. Nährstoffeinträge) überlagert werden. Biologisch-physikalische gekoppelte Modelle können einen Beitrag liefern, die Auswirkungen klimatischer Änderungen auf marine Ökosysteme besser zu verstehen und potentielle, zukünftige Entwicklungen abzuschätzen.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Inbook , peerRev
    Format: application/pdf
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  • 7
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    German Bight residual current variability on a daily basis: principal components of multi-decadal barotropic simulations. (2017)
    SPRINGER
    In:  EPIC3Geo-Marine Letters, SPRINGER, 37(2), pp. 151-162, ISSN: 0276-0460
    Details
    Publication Date: 2018-02-16
    Description: Time variability of Eulerian residual currents in the German Bight (North Sea) is studied drawing on existing multi-decadal 2D barotropic simulations (1.6 km resolution) for the period Jan. 1958–Aug. 2015. Residual currents are calculated as 25 h means of velocity fields stored every hour. Principal component analysis (PCA) reveals that daily variations of these residual currents can be reasonably well represented in terms of only 2–3 degrees of freedom, partly linked to wind directions. The daily data refine monthly data already used in the past. Unlike existing classifications based on subjective assessment, numerical principal components (PCs) provide measures of strength and can directly be incorporated into more comprehensive statistical data analyses. Daily resolution in particular fits the time schedule of data sampled at the German Bight long-term monitoring station at Helgoland Roads. An example demonstrates the use of PCs and corresponding empirical orthogonal functions (EOFs) for the interpretation of short-term variations of these local observations. On the other hand, monthly averaging of the daily PCs enables to link up with previous studies on longer timescales.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    Phytoplankton phenology on the decadal scale: lessons from Helgoland Roads (German Bight / North Sea) (2016)
    In:  EPIC3ICES Annual Science Conference, Riga, Latvia, 2016-09-19-2016-09-23
    Details
    Publication Date: 2017-02-02
    Description: The annual and periodical recurrence of events and processes in marine plankton populations plays a central role in pelagic food webs. Annual cycles of light and temperature trigger the seasonality of marine plankton populations. Here we analyse phenological variability of 26 phytoplankton species (diatoms and dinoflagellates) monitored at Helgoland Roads during the period 1962-2014. We derive temporal indices based on the cumulative percentage of annual abundance to approximate timing and length of annual growth periods. Differences in species-specific preferences in combination with seasonally varying trends in environmental parameters led to a non-homogeneous phenological response on the decadal scale. The median phenological response of spring species (diatoms) is reflected by a shift towards earlier timing due to warming and improved light conditions, but single species show a remarkable constancy in timing over the entire period. During early summer several diatoms and dinoflagellates exhibit a trend towards earlier timing, responding to the temporal expansion of the warm water phase around the annual maximum. Related to this during late summer and early autumn several species show prolonged growing periods. These displacements are characterized by shifts in the centre or the end of the growing period. Cross-comparisons with the total abundances associated with the individual timing points show that phenological trends are not necessarily related to shifts of relevant proportions in phytoplankton abundance. We outline the uncertainty of drawing conclusions about ecological consequences in the light of the debate about the response of coastal ecosystems to climatic fluctuations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 9
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    Helgoland data cookbook: Ein Handbuch für die Daten und Metadaten des Helgoland Langzeitobservaotoriums (Helgoland Reede, Schnittfahrten und Ferrybox) (2016)
    AWI
    In:  EPIC3AWI, 42 p.
    Details
    Publication Date: 2017-02-02
    Repository Name: EPIC Alfred Wegener Institut
    Type: Miscellaneous , notRev
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  • 10
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    Extreme Flood Impact on Estuarine and Coastal Biogeochemistry: the 2013 Elbe Flood (2017)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Biogeosciences, COPERNICUS GESELLSCHAFT MBH, 14(3), pp. 541-557, ISSN: 1726-4170
    Details
    Publication Date: 2017-06-06
    Description: Within the context of predicted and observed increase in droughts and floods with climate change, large summer floods are likely to become more frequent. These extreme events can alter typical biogeochemical patterns in coastal systems. The extreme Elbe River flood in June, 2013 not only caused major damages in several European countries, but also generated large scale biogeochemical changes in the Elbe Estuary and the adjacent German Bight. Due to a number of well documented and unusual atmospheric conditions, the early summer of 2013 in Central and Eastern Europe was colder and wetter than usual, with saturated soils, and higher than average cumulative precipitation. Additional precipitation at the end of May, and beginning of June, 2013, caused widespread floods within the Danube and Elbe Rivers, as well as billions of euros in damages. The floods generated the largest summer discharge on record within the last 140 years. The high-frequency monitoring network in the German Bight available within the Coastal Observing System for Northern and Arctic Seas (COSYNA) captured the flood influence on the German Bight. Monitoring data from a FerryBox station in the Elbe Estuary (Cuxhaven) and from a FerryBox platform aboard the M/V Funny Girl Ferry (traveling between Büsum and Helgoland) documented the salinity changes on the German Bight, which persisted for about 2 months after the peak discharge. The flood generated a large influx of nutrients, dissolved and particulate organic carbon on the coast. These conditions subsequently led to the onset of a chlorophyll bloom within the German Bight, observed by dissolved oxygen supersaturation, and higher than usual pH in surface coastal waters. The prolonged stratification also led to widespread bottom water dissolved oxygen depletion, unusual for the south eastern German Bight in the summer.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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