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  1. Thesis ; Online: Interactive effects of ocean acidification and warming on marine phytoplankton - from physiology to biogeochemical cycling

    Sett, Scarlett

    2014  

    Abstract: Climate change driven by anthropogenic utilization of fossil fuels and deforestation over the past 250 years is leading to ongoing changes in sea surface temperature (i.e. ocean warming) and seawater carbonate chemistry speciation (i.e. ocean ... ...

    Abstract Climate change driven by anthropogenic utilization of fossil fuels and deforestation over the past 250 years is leading to ongoing changes in sea surface temperature (i.e. ocean warming) and seawater carbonate chemistry speciation (i.e. ocean acidification, OA) at an unprecedented pace. Both of these environmental stressors are expected to impact marine ecosystem functioning in the near future with consequences for marine biogeochemical cycling. In the context of this doctoral thesis, phytoplankton physiology and biogeochemical dynamics were investigated under the individual and combined effects of OA and warming through experimental work. Chapter I of this thesis presents data on the individual and synergistic effects of OA and warming on coccolithophore physiology. In order to test for possible synergistic effects, two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, were exposed to a broad range in CO2 concentrations at three different temperatures. The results from this study showed that both species displayed optimum-curve responses for key metabolic processes (i.e. growth, photosynthesis and calcification) at all temperatures, with species-specific sensitivities. Most importantly, increasing temperature modulated the optimum CO2 concentration and sensitivity of metabolic processes. Our results enabled us to propose a conceptual model showing that the temperature sensitivity of metabolic processes in these organisms could help explain the discrepancies found in the literature on coccolithophore physiology in response to OA. Interested by the results from experiments in Chapter I with single species, mesocosm experiments were carried out in Chapters II and III with natural plankton communities. Since most of the literature with natural communities has focused on effects of individual environmental factors, experiments in Chapters II and III investigated the combined effects of OA and warming during a natural spring bloom (Kiel Bight) and a nutrient-induced summer bloom (Thau lagoon, ...
    Subject code 551
    Language English
    Publishing country de
    Document type Thesis ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Book ; Online ; Thesis: Interactive effects of ocean acidification and warming on marine phytoplankton - from physiology to biogeochemical cycling

    Sett, Scarlett [Verfasser]

    2014  

    Author's details Scarlett Sett
    Keywords Geowissenschaften ; Earth Sciences
    Subject code sg550
    Language English
    Publisher Universitätsbibliothek Kiel
    Publishing place Kiel
    Document type Book ; Online ; Thesis
    Database Digital theses on the web

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  3. Article ; Online: Access and benefit-sharing by the European Virus Archive in response to COVID-19.

    Sett, Scarlett / Dos Santos Ribeiro, Carolina / Prat, Christine / Haringhuizen, George / Scholz, Amber Hartman

    The Lancet. Microbe

    2021  Volume 3, Issue 4, Page(s) e316–e323

    Abstract: Biobanking infrastructures, which are crucial for responding early to new viral outbreaks, share pathogen genetic resources in an affordable, safe, and impartial manner and can provide expertise to address access and benefit-sharing issues. The European ... ...

    Abstract Biobanking infrastructures, which are crucial for responding early to new viral outbreaks, share pathogen genetic resources in an affordable, safe, and impartial manner and can provide expertise to address access and benefit-sharing issues. The European Virus Archive has had a crucial role in the global response to the COVID-19 pandemic by distributing EU-subsidised (free of charge) viral resources to users worldwide, providing non-monetary benefit sharing, implementing access and benefit-sharing compliance, and raising access and benefit-sharing awareness among members and users. All currently available SARS-CoV-2 material in the European Virus Archive catalogue, including variants of concern, are not access and benefit-sharing cases per se, but multilateral benefit-sharing has nevertheless occurred. We propose and discuss how a multilateral system enabling access and benefit-sharing from pathogen genetic resources, based on the European Virus Archive operational model, could help bridge the discrepancies between the current bilateral legal framework for pathogen genetic resources and actual pandemic response practices.
    MeSH term(s) Biological Specimen Banks ; COVID-19/epidemiology ; DNA Viruses ; Humans ; Pandemics ; SARS-CoV-2 ; Viruses ; Viruses, Unclassified
    Language English
    Publishing date 2021-11-16
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ISSN 2666-5247
    ISSN (online) 2666-5247
    DOI 10.1016/S2666-5247(21)00211-1
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Conference proceedings ; Online: The combined effect of global warming and ocean acidification on the coccolithophore Geophyrocapsa oceanica carbon production and physiology

    Sett, Scarlett

    2010  

    Publishing country de
    Document type Conference proceedings ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article: Shift towards larger diatoms in a natural phytoplankton assemblage under combined high-CO

    Sett, Scarlett / Schulz, Kai G / Bach, Lennart T / Riebesell, Ulf

    Journal of plankton research

    2018  Volume 40, Issue 4, Page(s) 391–406

    Abstract: An indoor mesocosm experiment was carried out to investigate the combined effects of ocean acidification and warming on the species composition and biogeochemical element cycling during a winter/spring bloom with a natural phytoplankton assemblage from ... ...

    Abstract An indoor mesocosm experiment was carried out to investigate the combined effects of ocean acidification and warming on the species composition and biogeochemical element cycling during a winter/spring bloom with a natural phytoplankton assemblage from the Kiel fjord, Germany. The experimental setup consisted of a "Control" (ambient temperature of ~4.8 °C and ~535 ± 25 μatm
    Language English
    Publishing date 2018-05-29
    Publishing country England
    Document type Journal Article
    ZDB-ID 756271-8
    ISSN 0142-7873
    ISSN 0142-7873
    DOI 10.1093/plankt/fby018
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Thesis ; Online: The combined effect of global warming and ocean acidification on the coccolithophore Gephyrocapsa oceanica carbon production and physiology

    Sett, Scarlett

    2010  

    Abstract: Climate change is expected to impact oceanic ecosystem functioning in the upcoming decades, ocean acidification and global warming being the most important factors which will shape the future ocean dynamics (Jackson 2008). In the experiments presented ... ...

    Abstract Climate change is expected to impact oceanic ecosystem functioning in the upcoming decades, ocean acidification and global warming being the most important factors which will shape the future ocean dynamics (Jackson 2008). In the experiments presented here we used an innovative approach that consisted of extending the number of treatments across a wide range of carbon dioxide partial pressure (pC02) levels and two temperatures which allowed to test lower and upper thresholds of biological production. Growth, calcification and POC production rates showed an optimum curve response to increasing pC02, with an almost doubling in production rates at 20CC and opt imum rates for pC02 levels of ~290-599 μatm at 15CC and ~488-1052 μatm pC02 at 20CC. PIC and POC cellular quotas showed changes to increasing pC02 but no effect from increasing temperature. Results obtained from the combined effect of global warming and increasing pC02 from these experiments might contribute to shape biogeochemical modeling formulations in the near future.
    Keywords Course of study: MSc Biological Oceanography
    Subject code 551
    Language English
    Publishing country de
    Document type Thesis ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  7. Article ; Online: Shift towards larger diatoms in a natural phytoplankton assemblage under combined high-CO2 and warming conditions

    Sett, Scarlett / Schulz, Kai G. / Bach, Lennart T. / Riebesell, Ulf

    2018  

    Abstract: An indoor mesocosm experiment was carried out to investigate the combined effects of ocean acidification and warming on the species composition and biogeochemical element cycling during a winter/spring bloom with a natural phytoplankton assemblage from ... ...

    Abstract An indoor mesocosm experiment was carried out to investigate the combined effects of ocean acidification and warming on the species composition and biogeochemical element cycling during a winter/spring bloom with a natural phytoplankton assemblage from the Kiel fjord, Germany. The experimental setup consisted of a "Control" (ambient temperature of similar to 4.8 degrees C and similar to 535 +/- 25 mu atm pCO(2)), a "High-CO2" treatment (ambient temperature and initially 1020 +/- 45 mu atm pCO(2)) and a "Greenhouse" treatment (similar to 8.5 degrees C and initially 990 +/- 60 mu atm pCO(2)). Nutrient replete conditions prevailed at the beginning of the experiment and light was provided at in situ levels upon reaching pCO(2) target levels. A diatom-dominated bloom developed in all treatments with Skeletonema costatum as the dominant species but with an increased abundance and biomass contribution of larger diatom species in the Greenhouse treatment. Conditions in the Greenhouse treatment accelerated bloom development with faster utilization of inorganic nutrients and an earlier peak in phytoplankton biomass compared to the Control and High CO2 but no difference in maximum concentration of particulate organic matter (POM) between treatments. Loss of POM in the Greenhouse treatment, however, was twice as high as in the Control and High CO2 treatment at the end of the experiment, most likely due to an increased proportion of larger diatom species in that treatment. We hypothesize that the combination of warming and acidification can induce shifts in diatom species composition with potential feedbacks on biogeochemical element cycling.
    Subject code 580
    Language English
    Publishing date 2018-05-29
    Publisher Oxford Univ. Press
    Publishing country de
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article ; Online: Temperature modulates coccolithophorid sensitivity of growth, photosynthesis and calcification to increasing seawater pCO₂.

    Sett, Scarlett / Bach, Lennart T / Schulz, Kai G / Koch-Klavsen, Signe / Lebrato, Mario / Riebesell, Ulf

    PloS one

    2014  Volume 9, Issue 2, Page(s) e88308

    Abstract: Increasing atmospheric CO₂ concentrations are expected to impact pelagic ecosystem functioning in the near future by driving ocean warming and acidification. While numerous studies have investigated impacts of rising temperature and seawater ... ...

    Abstract Increasing atmospheric CO₂ concentrations are expected to impact pelagic ecosystem functioning in the near future by driving ocean warming and acidification. While numerous studies have investigated impacts of rising temperature and seawater acidification on planktonic organisms separately, little is presently known on their combined effects. To test for possible synergistic effects we exposed two coccolithophore species, Emiliania huxleyi and Gephyrocapsa oceanica, to a CO₂ gradient ranging from ∼0.5-250 µmol kg⁻¹ (i.e. ∼20-6000 µatm pCO₂) at three different temperatures (i.e. 10, 15, 20°C for E. huxleyi and 15, 20, 25°C for G. oceanica). Both species showed CO₂-dependent optimum-curve responses for growth, photosynthesis and calcification rates at all temperatures. Increased temperature generally enhanced growth and production rates and modified sensitivities of metabolic processes to increasing CO₂. CO₂ optimum concentrations for growth, calcification, and organic carbon fixation rates were only marginally influenced from low to intermediate temperatures. However, there was a clear optimum shift towards higher CO₂ concentrations from intermediate to high temperatures in both species. Our results demonstrate that the CO₂ concentration where optimum growth, calcification and carbon fixation rates occur is modulated by temperature. Thus, the response of a coccolithophore strain to ocean acidification at a given temperature can be negative, neutral or positive depending on that strain's temperature optimum. This emphasizes that the cellular responses of coccolithophores to ocean acidification can only be judged accurately when interpreted in the proper eco-physiological context of a given strain or species. Addressing the synergistic effects of changing carbonate chemistry and temperature is an essential step when assessing the success of coccolithophores in the future ocean.
    MeSH term(s) Calcification, Physiologic ; Carbon Dioxide/analysis ; Carbon Dioxide/metabolism ; Haptophyta/physiology ; Photosynthesis ; Seawater/analysis ; Seawater/chemistry ; Temperature
    Chemical Substances Carbon Dioxide (142M471B3J)
    Language English
    Publishing date 2014-02-05
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1932-6203
    ISSN (online) 1932-6203
    DOI 10.1371/journal.pone.0088308
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  9. Article ; Online: Effects of increasing seawater carbon dioxide concentrations on chain formation of the diatom Asterionellopsis glacialis.

    Barcelos e Ramos, Joana / Schulz, Kai Georg / Brownlee, Colin / Sett, Scarlett / Azevedo, Eduardo Brito

    PloS one

    2014  Volume 9, Issue 3, Page(s) e90749

    Abstract: Diatoms can occur as single cells or as chain-forming aggregates. These two strategies affect buoyancy, predator evasion, light absorption and nutrient uptake. Adjacent cells in chains establish connections through various processes that determine ... ...

    Abstract Diatoms can occur as single cells or as chain-forming aggregates. These two strategies affect buoyancy, predator evasion, light absorption and nutrient uptake. Adjacent cells in chains establish connections through various processes that determine strength and flexibility of the bonds, and at distinct cellular locations defining colony structure. Chain length has been found to vary with temperature and nutrient availability as well as being positively correlated with growth rate. However, the potential effect of enhanced carbon dioxide (CO2) concentrations and consequent changes in seawater carbonate chemistry on chain formation is virtually unknown. Here we report on experiments with semi-continuous cultures of the freshly isolated diatom Asterionellopsis glacialis grown under increasing CO2 levels ranging from 320 to 3400 µatm. We show that the number of cells comprising a chain, and therefore chain length, increases with rising CO2 concentrations. We also demonstrate that while cell division rate changes with CO2 concentrations, carbon, nitrogen and phosphorus cellular quotas vary proportionally, evident by unchanged organic matter ratios. Finally, beyond the optimum CO2 concentration for growth, carbon allocation changes from cellular storage to increased exudation of dissolved organic carbon. The observed structural adjustment in colony size could enable growth at high CO2 levels, since longer, spiral-shaped chains are likely to create microclimates with higher pH during the light period. Moreover increased chain length of Asterionellopsis glacialis may influence buoyancy and, consequently, affect competitive fitness as well as sinking rates. This would potentially impact the delicate balance between the microbial loop and export of organic matter, with consequences for atmospheric carbon dioxide.
    MeSH term(s) Carbon Dioxide/chemistry ; Carbon Dioxide/pharmacology ; Carbonates/chemistry ; Carbonates/metabolism ; Cell Division ; Diatoms/drug effects ; Diatoms/growth & development ; Diatoms/metabolism ; Seawater/chemistry
    Chemical Substances Carbonates ; Carbon Dioxide (142M471B3J)
    Language English
    Publishing date 2014-03-11
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2267670-3
    ISSN 1932-6203 ; 1932-6203
    ISSN (online) 1932-6203
    ISSN 1932-6203
    DOI 10.1371/journal.pone.0090749
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article: An approach for particle sinking velocity measurements in the 3-400 μm size range and considerations on the effect of temperature on sinking rates.

    Bach, Lennart Thomas / Riebesell, Ulf / Sett, Scarlett / Febiri, Sarah / Rzepka, Paul / Schulz, Kai Georg

    Marine biology

    2012  Volume 159, Issue 8, Page(s) 1853–1864

    Abstract: The flux of organic particles below the mixed layer is one major pathway of carbon from the surface into the deep ocean. The magnitude of this export flux depends on two major processes-remineralization rates and sinking velocities. Here, we present an ... ...

    Abstract The flux of organic particles below the mixed layer is one major pathway of carbon from the surface into the deep ocean. The magnitude of this export flux depends on two major processes-remineralization rates and sinking velocities. Here, we present an efficient method to measure sinking velocities of particles in the size range from approximately 3-400 μm by means of video microscopy (FlowCAM
    Language English
    Publishing date 2012-05-22
    Publishing country Germany
    Document type Review
    ZDB-ID 1117-4
    ISSN 1432-1793 ; 0025-3162
    ISSN (online) 1432-1793
    ISSN 0025-3162
    DOI 10.1007/s00227-012-1945-2
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