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  • Wiley  (8)
  • Kiel : Universitätsbibliothek Kiel
  • 2010-2014  (7)
  • 1990-1994  (1)
  • 1
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    Functional Genetic Divergence in High CO2 adapted E. huxleyi populations (2013)
    Wiley
    In:  Evolution, 67 . pp. 1892-1900.
    Details
    Publication Date: 2019-09-23
    Description: Predicting the impacts of environmental change on marine organisms, food webs, and biogeochemical cycles presently relies almost exclusively on short-term physiological studies, while the possibility of adaptive evolution is often ignored. Here, we assess adaptive evolution in the coccolithophore Emiliania huxleyi, a well-established model species in biological oceanography, in response to ocean acidification. We previously demonstrated that this globally important marine phytoplankton species adapts within 500 generations to elevated CO2. After 750 and 1000 generations, no further fitness increase occurred, and we observed phenotypic convergence between replicate populations. We then exposed adapted populations to two novel environments to investigate whether or not the underlying basis for high CO2-adaptation involves functional genetic divergence, assuming that different novel mutations become apparent via divergent pleiotropic effects. The novel environment “high light” did not reveal such genetic divergence whereas growth in a low-salinity environment revealed strong pleiotropic effects in high CO2 adapted populations, indicating divergent genetic bases for adaptation to high CO2. This suggests that pleiotropy plays an important role in adaptation of natural E. huxleyi populations to ocean acidification. Our study highlights the potential mutual benefits for oceanography and evolutionary biology of using ecologically important marine phytoplankton for microbial evolution experiments.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1558-5646.2012.01812.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    The viscosity effect on marine particle flux: A climate relevant feedback mechanism (2014)
    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 28 (4). pp. 415-422.
    Details
    Publication Date: 2018-03-19
    Description: Oceanic uptake and long-term storage of atmospheric carbon dioxide (CO2) are strongly driven by the marine “biological pump,” i.e., sinking of biotically fixed inorganic carbon and nutrients from the surface into the deep ocean (Sarmiento and Bender, 1994; Volk and Hoffert, 1985). Sinking velocity of marine particles depends on seawater viscosity, which is strongly controlled by temperature (Sharqawy et al., 2010). Consequently, marine particle flux is accelerated as ocean temperatures increase under global warming (Bach et al., 2012). Here we show that this previously overlooked “viscosity effect” could have profound impacts on marine biogeochemical cycling and carbon uptake over the next centuries to millennia. In our global warming simulation, the viscosity effect accelerates particle sinking by up to 25%, thereby effectively reducing the portion of organic matter that is respired in the surface ocean. Accordingly, the biological carbon pump's efficiency increases, enhancing the sequestration of atmospheric CO2 into the ocean. This effect becomes particularly important on longer time scales when warming reaches the ocean interior. At the end of our simulation (4000 A.D.), oceanic carbon uptake is 17% higher, atmospheric CO2 concentration is 180 ppm lower, and the increase in global average surface temperature is 8% weaker when considering the viscosity effect. Consequently, the viscosity effect could act as a long-term negative feedback mechanism in the global climate system.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/2013GB004728
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Dissecting the impact of CO2and pH on the mechanisms of photosynthesis and calcification in the coccolithophoreEmiliania huxleyi (2013)
    Wiley
    In:  New Phytologist, 199 (1). pp. 121-134.
    Details
    Publication Date: 2019-01-23
    Description: Coccolithophores are important calcifying phytoplankton predicted to be impacted by changes in ocean carbonate chemistry caused by the absorption of anthropogenic CO2. However, it is difficult to disentangle the effects of the simultaneously changing carbonate system parameters (CO2, bicarbonate, carbonate and protons) on the physiological responses to elevated CO2. Here, we adopted a multifactorial approach at constant pH or CO2 whilst varying dissolved inorganic carbon (DIC) to determine physiological and transcriptional responses to individual carbonate system parameters. We show that Emiliania huxleyi is sensitive to low CO2 (growth and photosynthesis) and low bicarbonate (calcification) as well as low pH beyond a limited tolerance range, but is much less sensitive to elevated CO2 and bicarbonate. Multiple up-regulated genes at low DIC bear the hallmarks of a carbon-concentrating mechanism (CCM) that is responsive to CO2 and bicarbonate but not to pH. Emiliania huxleyi appears to have evolved mechanisms to respond to limiting rather than elevated CO2. Calcification does not function as a CCM, but is inhibited at low DIC to allow the redistribution of DIC from calcification to photosynthesis. The presented data provides a significant step in understanding how E. huxleyi will respond to changing carbonate chemistry at a cellular level.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1111/nph.12225
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Synergistic effects of ocean acidification and warming on overwintering pteropods in the Arctic (2012)
    Wiley
    In:  Global Change Biology, 18 (12). pp. 3517-3528.
    Details
    Publication Date: 2018-05-17
    Description: Ocean acidification and warming will be most pronounced in the Arctic Ocean. Aragonite shell-bearing pteropods in the Arctic are expected to be among the first species to suffer from ocean acidification. Carbonate undersaturation in the Arctic will first occur in winter and because this period is also characterized by low food availability, the overwintering stages of polar pteropods may develop into a bottleneck in their life cycle. The impacts of ocean acidification and warming on growth, shell degradation (dissolution), and mortality of two thecosome pteropods, the polar Limacina helicina and the boreal L. retroversa, were studied for the first time during the Arctic winter in the Kongsfjord (Svalbard). The abundance of L. helicina and L. retroversa varied from 23.5 to 120 ind m−2 and 12 to 38 ind m−2, and the mean shell size ranged from 920 to 981 μm and 810 to 823 μm, respectively. Seawater was aragonite-undersaturated at the overwintering depths of pteropods on two out of ten days of our observations. A 7-day experiment [temperature levels: 2 and 7 °C, pCO2 levels: 350, 650 (only for L. helicina) and 880 μatm] revealed a significant pCO2 effect on shell degradation in both species, and synergistic effects between temperature and pCO2 for L. helicina. A comparison of live and dead specimens kept under the same experimental conditions indicated that both species were capable of actively reducing the impacts of acidification on shell dissolution. A higher vulnerability to increasing pCO2 and temperature during the winter season is indicated compared with a similar study from fall 2009. Considering the species winter phenology and the seasonal changes in carbonate chemistry in Arctic waters, negative climate change effects on Arctic thecosomes are likely to show up first during winter, possibly well before ocean acidification effects become detectable during the summer season.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1111/gcb.12020
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Das Kohlenstoffrätsel (1993)
    Wiley
    In:  Biologie in unserer Zeit, 23 (2). pp. 97-101.
    Details
    Publication Date: 2016-06-17
    Description: Etwa ein Drittel des von Menschen freigesetzten Treibhausgases Kohlendioxid (CO2) reichert sich in der Atmosphäre an und verstärkt dort den Treibhauseffekt. Zwei Drittel dieses Eintrags werden der Atmosphäre wieder entzogen und an anderer Stelle deponiert. Doch nur für etwa die Hälfte des wieder gebundenen Kohlendioxids kennen wir bisher die Senken. Wo bleibt der Rest? Um Aussagen über den Verbleib weiterer CO2-Emissionen und damit über die zukünftige Entwicklung des Treibhauseffektes machen zu können, bedarf es der Lösung des Kohlenstoffrätsels.
    Type: Article , NonPeerReviewed
    Format: text
    DOI: 10.1002/biuz.19930230208
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    OceanRep: Article in a Scientific Journal - without review
  • 6
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    Acclimation to ocean acidification during long-term CO2 exposure in the cold-water coral Lophelia pertusa (2012)
    Wiley
    In:  Global Change Biology, 18 (3). pp. 843-853.
    Details
    Publication Date: 2018-05-17
    Description: Ocean acidity has increased by 30% since preindustrial times due to the uptake of anthropogenic CO2 and is projected to rise by another 120% before 2100 if CO2 emissions continue at current rates. Ocean acidification is expected to have wide-ranging impacts on marine life, including reduced growth and net erosion of coral reefs. Our present understanding of the impacts of ocean acidification on marine life, however, relies heavily on results from short-term CO2 perturbation studies. Here, we present results from the first long-term CO2 perturbation study on the dominant reef-building cold-water coral Lophelia pertusa and relate them to results from a short-term study to compare the effect of exposure time on the coral's responses. Short-term (1 week) high CO2 exposure resulted in a decline of calcification by 26–29% for a pH decrease of 0.1 units and net dissolution of calcium carbonate. In contrast, L. pertusa was capable to acclimate to acidified conditions in long-term (6 months) incubations, leading to even slightly enhanced rates of calcification. Net growth is sustained even in waters sub-saturated with respect to aragonite. Acclimation to seawater acidification did not cause a measurable increase in metabolic rates. This is the first evidence of successful acclimation in a coral species to ocean acidification, emphasizing the general need for long-term incubations in ocean acidification research. To conclude on the sensitivity of cold-water coral reefs to future ocean acidification further ecophysiological studies are necessary which should also encompass the role of food availability and rising temperatures.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1111/j.1365-2486.2011.02583.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Expression of biomineralization-related ion transport genes in Emiliania huxleyi (2011)
    Wiley
    In:  Environmental Microbiology, 13 (12). pp. 3250-3265.
    Details
    Publication Date: 2018-09-12
    Description: Biomineralization in the marine phytoplankton Emiliania huxleyi is a stringently controlled intracellular process. The molecular basis of coccolith production is still relatively unknown although its importance in global biogeochemical cycles and varying sensitivity to increased pCO2 levels has been well documented. This study looks into the role of several candidate Ca2+, H+ and inorganic carbon transport genes in E. huxleyi, using quantitative reverse transcriptase PCR. Differential gene expression analysis was investigated in two isogenic pairs of calcifying and non-calcifying strains of E. huxleyi and cultures grown at various Ca2+ concentrations to alter calcite production. We show that calcification correlated to the consistent upregulation of a putative HCO3- transporter belonging to the solute carrier 4 (SLC4) family, a Ca2+/H+ exchanger belonging to the CAX family of exchangers and a vacuolar H+-ATPase. We also show that the coccolith-associated protein, GPA is downregulated in calcifying cells. The data provide strong evidence that these genes play key roles in E. huxleyi biomineralization. Based on the gene expression data and the current literature a working model for biomineralization-related ion transport in coccolithophores is presented.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1111/j.1462-2920.2011.02561.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Cellular pH measurements in Emiliania huxleyi reveal pronounced membrane proton permeability (2011)
    Wiley
    In:  New Phytologist, 190 (3). pp. 595-608.
    Details
    Publication Date: 2019-09-23
    Description: To understand the influence of changing surface ocean pH and carbonate chemistry on the coccolithophore Emiliania huxleyi, it is necessary to characterize mechanisms involved in pH homeostasis and ion transport. Here, we measured effects of changes in seawater carbonate chemistry on the fluorescence emission ratio of BCECF (2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein) as a measure of intracellular pH (pH(i)). Out of equilibrium solutions were used to differentiate between membrane permeation pathways for H+, CO(2) and HCO(3)-. Changes in fluorescence ratio were calibrated in single cells, resulting in a ratio change of 0.78 per pH(i) unit. pH(i) acutely followed the pH of seawater (pH(e)) in a linear fashion between pH(e) values of 6.5 and 9 with a slope of 0.44 per pH(e) unit. pH(i) was nearly insensitive to changes in seawater CO(2) at constant pH(e) and HCO(3)-. An increase in extracellular HCO(3)- resulted in a slight intracellular acidification. In the presence of DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid), a broad-spectrum inhibitor of anion exchangers, E. huxleyi acidified irreversibly. DIDS slightly reduced the effect of pH(e) on pH(i). The data for the first time show the occurrence of a proton permeation pathway in E. huxleyi plasma membrane. pH(i) homeostasis involves a DIDS-sensitive mechanism.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1469-8137.2010.03633.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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