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  • 2015-2019  (13)
  • 2000-2004  (45)
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  • 1
    Keywords: Hochschulschrift ; Aufsatzsammlung
    Type of Medium: Online Resource
    Pages: 1 Online-Ressource (288 Seiten = 17 MB) , Illustrationen, Graphen
    Edition: Online-Ausgabe
    Language: English
    Note: Zusammenfassung in deutscher und englischer Sprache
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 46 (2003), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Observations that the majority of silica dissolution occurs within the upper 200 m of the ocean, and that sedimentation rates of diatom frustules generally do not decrease significantly with depth, suggested reduced dissolution rates of diatoms embedded within sinking aggregates. To investigate this hypothesis, silica dissolution rates of aggregated diatom cells were compared to those of dispersed cells during conditions mimicking sedimentation below the euphotic zone. Changes in the concentrations of biogenic silica, silicic acid, cell numbers, chlorophyll a and transparent exopolymer particles (TEP) were monitored within aggregates and in the surrounding seawater (SSW) during two 42-day experiments. Whereas the concentration of dispersed diatoms decreased over the course of the experiment, the amount of aggregated cells remained roughly constant after an initial increase. Initially only 6% of cells were aggregated and at the end of the experiment more than 60% of cells were enclosed within aggregates. These data imply lower dissolution rates for aggregated cells. However, fluxes of silica between the different pools could not be constrained reliably enough to unequivocally prove reduced dissolution for aggregated cells.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2023-03-03
    Keywords: CTD; Date/Time of event; DEPTH, water; Elevation of event; Event label; Latitude of event; Littorina; Longitude of event; MSN; Multiple opening/closing net; PEX86; PEX86_10; PEX86_11; PEX86_12; PEX86_13; PEX86_14; PEX86_15; PEX86_16; PEX86_17; PEX86_18; PEX86_19; PEX86_20; PEX86_21; PEX86_22; PEX86_23; PEX86_24; PEX86_25; PEX86_26; PEX86_27; PEX86_28; PEX86_29; PEX86_3; PEX86_30; PEX86_31; PEX86_32; PEX86_33; PEX86_4; PEX86_5; PEX86_6; PEX86_7; PEX86_8; PEX86_9; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 390 data points
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  • 4
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    PANGAEA
    In:  Supplement to: Taucher, Jan; Jones, Jacob; James, A; Brzezinski, Mark A; Carlson, C A; Riebesell, Ulf; Passow, Uta (2015): Combined effects of CO2 and temperature on carbon uptake and partitioning by the marine diatoms Thalassiosira weissflogii and Dactyliosolen fragilissimus. Limnology and Oceanography, 60(3), 901-919, https://doi.org/10.1002/lno.10063
    Publication Date: 2024-03-15
    Description: Carbon uptake and partitioning of two globally abundant diatom species, Thalassiosira weissflogii and Dactyliosolen fragilissimus, was investigated in batch culture experiments under four conditions: ambient (15°C, 400 µatm), high CO2 (15°C, 1000 µatm), high temperature (20°C, 400 µatm), and combined (20°C, 1000 µatm). The experiments were run from exponential growth into the stationary phase (six days after nitrogen depletion), allowing us to track biogeochemical dynamics analogous to bloom situations in the ocean. Elevated CO2 had a fertilizing effect and enhanced uptake of dissolved inorganic carbon (DIC) by about 8% for T. weissflogii and by up to 39% for D. fragilissimus. This was also reflected in higher cell numbers, build-up of particulate and dissolved organic matter, and transparent exopolymer particles. The CO2 effects were most prominent in the stationary phase when nitrogen was depleted and CO2(aq) concentrations were low. This indicates that diatoms in the high CO2 treatments could take up more DIC until CO2 concentrations in seawater became so low that carbon limitation occurs. These results suggest that, contrary to common assumptions, diatoms could be highly sensitive to ongoing changes in oceanic carbonate chemistry, particularly under nutrient limitation. Warming from 15 to 20 °C had a stimulating effect on one species but acted as a stressor on the other species, highlighting the importance of species-specific physiological optima and temperature ranges in the response to ocean warming. Overall, these sensitivities to CO2 and temperature could have profound impacts on diatoms blooms and the biological pump.
    Keywords: Alkalinity, total; Aragonite saturation state; Bacterial production; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, organic, dissolved; Carbon, organic, particulate; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Dactyliosolen fragilissimus; Duration, number of days; Fluorescence; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Laboratory experiment; Laboratory strains; Nitrate; Nitrogen, organic, dissolved; Nitrogen, organic, particulate; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Other metabolic rates; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phosphate; Phytoplankton; Replicate; Salinity; Silicate; Single species; Species; Spectrophotometric; Temperature; Temperature, water; Thalassiosira weissflogii; Transparent exopolymer particles as Gum Xanthan equivalents per volume
    Type: Dataset
    Format: text/tab-separated-values, 4976 data points
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  • 5
    Publication Date: 2024-03-15
    Description: Shifts in phytoplankton composition and productivity are anticipated in the future, because phytoplankton are frequently bottom-up controlled, and environmental conditions, like temperature, partial pressure of CO2 (pCO2), and light climate continue to change. Culture experiments revealed that whereas future (elevated) pCO2 had no effect on T. weissflogii in the absence of environmental stressors, growth rate was drastically decreased under future pCO2 if cells grew under light and temperature stress. The reduction in growth rates and a smaller decline in cellular photosynthesis under high pCO2 were associated with 2- to 3-fold increases in the production of transparent exopolymer particles (TEP), in the cell quotas of organic carbon, and the chl a:C ratios. Results suggest that under light- and temperature-stressed growth, elevated pCO2 led to increased energy requirements, which were fulfilled by increased light harvesting capabilities that permitted photosynthesis of acclimatized cells to remain relatively high. This was combined with the inability of these cells to acclimatize their growth rate to sub-optimal temperatures. As a consequence, growth rate was low and decoupled from photosynthesis. This decoupling led to large cell sizes and high excretion rates in future pCO2 treatments compared to ambient treatments if growth temperature and light were sub-optimal. Under optimal growth conditions the increased energy demands required to re-equilibrate the disturbed acid-base balance in future pCO2 treatments were likely mediated by a variety of physiological acclimatization mechanisms, individually too small to show a statistically detectable response in terms of growth rate, photosynthesis, pigment concentration, or excretion.
    Keywords: Alkalinity, total; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, organic, particulate, per cell; Carbon/Nitrogen ratio; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a/carbon ratio; Chlorophyll a per cell; Chromista; Colorimetric; Dry mass per cell; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Identification; Irradiance; Laboratory experiment; Laboratory strains; Light; Nitrogen, organic, particulate, per cell; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phytoplankton; Potentiometric titration; Registration number of species; Salinity; Single species; Species; Spectrophotometric; Temperature; Temperature, water; Thalassiosira weissflogii; Transparent exopolymer particles as Gum Xanthan equivalents per cell; Treatment; Type; Uniform resource locator/link to reference
    Type: Dataset
    Format: text/tab-separated-values, 3762 data points
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  • 6
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    PANGAEA
    In:  Supplement to: Diner, Rachel E; Benner, Ina; Passow, Uta; Komada, Tomoko; Carpenter, E J; Stillman, Jonathon H (2015): Negative effects of ocean acidification on calcification vary within the coccolithophore genus Calcidiscus. Marine Biology, 162(6), 1287-1305, https://doi.org/10.1007/s00227-015-2669-x
    Publication Date: 2024-05-27
    Description: A large percentage of CO2 emitted into the atmosphere is absorbed by the oceans, causing chemical changes in surface waters known as ocean acidification (OA). Despite the high interest and increased pace of OA research to understand the effects of OA on marine organisms, many ecologically important organisms remain unstudied. Calcidiscus is a heavily calcified coccolithophore genus that is widespread and genetically and morphologically diverse. It contributes substantially to global calcium carbonate production, organic carbon production, oceanic carbon burial, and ocean-atmosphere CO2 exchange. Despite the importance of this genus, relatively little work has examined its responses to OA. We examined changes in growth, morphology, and carbon allocation in multiple strains of Calcidiscus leptoporus in response to ocean acidification. We also, for the first time, examined the OA response of Calcidiscus quadriperforatus, a larger and more heavily calcified Calcidiscus congener. All Calcidiscus coccolithophores responded negatively to OA with impaired coccolith morphology and a decreased ratio of particulate inorganic to organic carbon (PIC:POC). However, strains responded variably; C. quadriperforatus showed the most sensitivity, while the most lightly calcified strain of C. leptoporus showed little response to OA. Our findings suggest that calcium carbonate production relative to organic carbon production by Calcidiscus coccolithophores may decrease in future oceans and that Calcidiscus distributions may shift if more resilient strains and species become dominant in assemblages. This study demonstrates that variable responses to OA may be strain or species specific in a way that is closely linked to physiological traits, such as cellular calcite quota.
    Keywords: Alkalinity, total; Alkalinity, total, standard error; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcidiscus leptoporus; Calcidiscus quadriperforatus; Calcification/Dissolution; Calcite saturation state; Calculated; Calculated using CO2calc; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Carbon, inorganic, particulate, per cell; Carbon, inorganic, particulate, production per cell; Carbon, organic, particulate, per cell; Carbon, organic, particulate, production per cell; Carbon, total, particulate, per cell; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Change; Change, standard error; Chromista; Coccoliths; Coulometric titration; Figure; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Haptophyta; Laboratory experiment; Laboratory strains; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air), standard error; Particulate alcian blue-stainable material, per cell; Particulate inorganic carbon/particulate organic carbon ratio; Pelagos; Percentage; Percentage, standard deviation; pH; pH, standard error; Phytoplankton; Potentiometric titration; Primary production/Photosynthesis; Replicate; Salinity; Salinity, standard error; Single species; Species; Strain; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 4298 data points
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  • 7
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    PANGAEA
    In:  Supplement to: Diner, Rachel E; Benner, Ina; Passow, Uta; Komada, Tomoko; Carpenter, E J; Stillman, Jonathon H (2015): Negative effects of ocean acidification on calcification vary within the coccolithophore genus Calcidiscus. Marine Biology, 162(6), 1287-1305, https://doi.org/10.1007/s00227-015-2669-x
    Publication Date: 2024-05-27
    Description: A large percentage of CO2 emitted into the atmosphere is absorbed by the oceans, causing chemical changes in surface waters known as ocean acidification (OA). Despite the high interest and increased pace of OA research to understand the effects of OA on marine organisms, many ecologically important organisms remain unstudied. Calcidiscus is a heavily calcified coccolithophore genus that is widespread and genetically and morphologically diverse. It contributes substantially to global calcium carbonate production, organic carbon production, oceanic carbon burial, and ocean-atmosphere CO2 exchange. Despite the importance of this genus, relatively little work has examined its responses to OA. We examined changes in growth, morphology, and carbon allocation in multiple strains of Calcidiscus leptoporus in response to ocean acidification. We also, for the first time, examined the OA response of Calcidiscus quadriperforatus, a larger and more heavily calcified Calcidiscus congener. All Calcidiscus coccolithophores responded negatively to OA with impaired coccolith morphology and a decreased ratio of particulate inorganic to organic carbon (PIC:POC). However, strains responded variably; C. quadriperforatus showed the most sensitivity, while the most lightly calcified strain of C. leptoporus showed little response to OA. Our findings suggest that calcium carbonate production relative to organic carbon production by Calcidiscus coccolithophores may decrease in future oceans and that Calcidiscus distributions may shift if more resilient strains and species become dominant in assemblages. This study demonstrates that variable responses to OA may be strain or species specific in a way that is closely linked to physiological traits, such as cellular calcite quota.
    Keywords: Alkalinity, total; Alkalinity, total, standard error; Aragonite saturation state; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcidiscus leptoporus; Calcidiscus quadriperforatus; Calcification/Dissolution; Calcite saturation state; Calculated; Calculated using CO2calc; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Carbon, inorganic, particulate, per cell; Carbon, inorganic, particulate, production per cell; Carbon, organic, particulate, per cell; Carbon, organic, particulate, production per cell; Carbon, total, particulate, per cell; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Change; Change, standard error; Chromista; Coccoliths; Coulometric titration; Figure; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Haptophyta; Laboratory experiment; Laboratory strains; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Partial pressure of carbon dioxide (water) at sea surface temperature (wet air), standard error; Particulate alcian blue-stainable material, per cell; Particulate inorganic carbon/particulate organic carbon ratio; Pelagos; Percentage; Percentage, standard deviation; pH; pH, standard error; Phytoplankton; Potentiometric titration; Primary production/Photosynthesis; Replicate; Salinity; Salinity, standard error; Single species; Species; Strain; Temperature, water
    Type: Dataset
    Format: text/tab-separated-values, 4298 data points
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  • 8
    Publication Date: 2021-02-08
    Description: Marine life is controlled by multiple physical and chemical drivers and by diverse ecological processes. Many of these oceanic properties are being altered by climate change and other anthropogenic pressures. Hence, identifying the influences of multifaceted ocean change, from local to global scales, is a complex task. To guide policy-making and make projections of the future of the marine biosphere, it is essential to understand biological responses at physiological, evolutionary and ecological levels. Here, we contrast and compare different approaches to multiple driver experiments that aim to elucidate biological responses to a complex matrix of ocean global change. We present the benefits and the challenges of each approach with a focus on marine research, and guidelines to navigate through these different categories to help identify strategies that might best address research questions in fundamental physiology, experimental evolutionary biology and community ecology. Our review reveals that the field of multiple driver research is being pulled in complementary directions: the need for reductionist approaches to obtain process-oriented, mechanistic understanding and a requirement to quantify responses to projected future scenarios of ocean change. We conclude the review with recommendations on how best to align different experimental approaches to contribute fundamental information needed for science-based policy formulation.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    Format: text
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  • 9
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    Inter Research
    In:  Marine Ecology Progress Series, 219 . pp. 1-10.
    Publication Date: 2018-05-28
    Description: The carbon and nitrogen content of transparent exopolymer particles (TEP) was determined and related to the concentration of TEP as quantified by a colorimetrical method. TEP were produced in the laboratory from dissolved precursors by laminar or turbulent shear. Dissolved precursors were obtained by 0.2 µm filtration from diatom cultures, with or without nutrient reduction, and from natural diatom populations. The relationship between carbon and TEP was significant, linear and species-specific. Carbon concentration of TEP derived from this relationship concurred with previous findings. Shortage of silicic acid or nitrate in the culture media had no effect on the carbon content of TEP. Molar C:N ratios of TEP were above the Redfield ratio, with a mean value of 26. It is suggested that the nitrogen fraction of TEP can be explained by adsorption of dissolved organic nitrogen (DON) onto TEP. Based on the newly established relationship, concentrations of TEP-derived carbon (TEP-C) were calculated for the Baltic Sea, the coastal Pacific, the North East Atlantic and the Northern Adriatic Sea.
    Type: Article , PeerReviewed
    Format: text
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  • 10
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    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 47 (3). pp. 753-761.
    Publication Date: 2014-01-30
    Description: Flows of the major biogeochemical elements (C, N, P, Si) and of transparent exopolymer particles (TEP) were traced during a bloom of a natural assemblage of marine diatoms in a mesocosm (l m(3)) to determine whether the exudation and subsequent gelation of carbon-rich phytoplankton exopolymers can account for the formation and potential export of carbon in excess of that predicted by Redfield ratios. Exponential growth of the phytoplankton community in the mesocosm extended for 10 d until nitrate concentration fell below detection and concentrations of dissolved inorganic and particulate organic nitrogen and phosphorus remained stable. Tight covariation of particulate organic elements occurred as long as nutrients were replete. But, after nitrate depletion, decoupling of carbon dynamics from that of nitrogen and phosphorus was observed, with a large flow of carbon into TEP An uptake of 72% more dissolved inorganic carbon (DIC) than inferred from nitrate supply and Redfield stoichiometry (referred to as carbon overconsumption) occurred during the study, largely during the postbloom phase, and was almost entirely traced to the particulate organic matter (POM) pool. Marine snow (aggregates 〉0.5 mm) appeared at the onset of nitrate depletion and coincided with rapid increase in TEP concentrations. Elemental composition of marine snow differed from the Redfield ratio by an enrichment in carbon and a depletion in phosphorus relative to nitrogen. It is suggested that sinking of TEP-rich marine snow could be a possible mechanism for export of carbon above calculations that are based on the Redfield stoichiometry.
    Type: Article , PeerReviewed
    Format: text
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