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  • 1
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    Ocean Acidification Reduces Growth and Calcification in a Marine Dinoflagellate (2013)
    Public Library of Science
    In:  PLoS ONE, 8 (6). e65987.
    Details
    Publication Date: 2014-04-22
    Description: Ocean acidification is considered a major threat to marine ecosystems and may particularly affect calcifying organisms such as corals, foraminifera and coccolithophores. Here we investigate the impact of elevated pCO2 and lowered pH on growth and calcification in the common calcareous dinoflagellate Thoracosphaera heimii. We observe a substantial reduction in growth rate, calcification and cyst stability of T. heimii under elevated pCO2. Furthermore, transcriptomic analyses reveal CO2 sensitive regulation of many genes, particularly those being associated to inorganic carbon acquisition and calcification. Stable carbon isotope fractionation for organic carbon production increased with increasing pCO2 whereas it decreased for calcification, which suggests interdependence between both processes. We also found a strong effect of pCO2 on the stable oxygen isotopic composition of calcite, in line with earlier observations concerning another T. heimii strain. The observed changes in stable oxygen and carbon isotope composition of T. heimii cysts may provide an ideal tool for reconstructing past seawater carbonate chemistry, and ultimately past pCO2. Although the function of calcification in T. heimii remains unresolved, this trait likely plays an important role in the ecological and evolutionary success of this species. Acting on calcification as well as growth, ocean acidification may therefore impose a great threat for T. heimii.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1371/journal.pone.0065987
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Effects of ocean acidification on primary production in a coastal North Sea phytoplankton community (2017)
    Public Library of Science
    In:  PLoS ONE, 12 (3). e0172594.
    Details
    Publication Date: 2020-02-06
    Description: We studied the effect of ocean acidification (OA) on a coastal North Sea plankton community in a long-term mesocosm CO2-enrichment experiment (BIOACID II long-term mesocosm study). From March to July 2013, 10 mesocosms of 19 m length with a volume of 47.5 to 55.9 m3 were deployed in the Gullmar Fjord, Sweden. CO2 concentrations were enriched in five mesocosms to reach average CO2 partial pressures (pCO2) of 760 μatm. The remaining five mesocosms were used as control at ambient pCO2 of 380 μatm. Our paper is part of a PLOS collection on this long-term mesocosm experiment. Here, we here tested the effect of OA on total primary production (PPT) by performing 14C-based bottle incubations for 24 h. Furthermore, photoacclimation was assessed by conducting 14C-based photosynthesis-irradiance response (P/I) curves. Changes in chlorophyll a concentrations over time were reflected in the development of PPT, and showed higher phytoplankton biomass build-up under OA. We observed two subsequent phytoplankton blooms in all mesocosms, with peaks in PPT around day 33 and day 56. OA had no significant effect on PPT, except for a marginal increase during the second phytoplankton bloom when inorganic nutrients were already depleted. Maximum light use efficiencies and light saturation indices calculated from the P/I curves changed simultaneously in all mesocosms, and suggest that OA did not alter phytoplankton photoacclimation. Despite large variability in time-integrated productivity estimates among replicates, our overall results indicate that coastal phytoplankton communities can be affected by OA at certain times of the seasonal succession with potential consequences for ecosystem functioning.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.1371/journal.pone.0172594
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Cellular inorganic carbon fluxes in Trichodesmium: a combined approach using measurements and modelling (2015)
    OXFORD UNIV PRESS
    In:  EPIC3Journal of Experimental Botany, OXFORD UNIV PRESS, 66(3), pp. 749-759, ISSN: 0022-0957
    Details
    Publication Date: 2015-02-10
    Description: To predict effects of climate change on phytoplankton, it is crucial to understand how their mechanisms for carbon acquisition respond to environmental conditions. Aiming to shed light on the responses of extra- and intracellular inorganic C (Ci) fluxes, the cyanobacterium Trichodesmium erythraeum IMS101 was grown with different nitrogen sources (N2 vs NO3 –) and pCO2 levels (380 vs 1400 µatm). Cellular Ci fluxes were assessed by combining membrane inlet mass spectrometry (MIMS), 13C fractionation measurements, and modelling. Aside from a significant decrease in Ci affinity at elevated pCO2 and changes in CO2 efflux with different N sources, extracellular Ci fluxes estimated by MIMS were largely unaffected by the treatments. 13C fractionation during biomass production, however, increased with pCO2, irrespective of the N source. Strong discrepancies were observed in CO2 leakage estimates obtained by MIMS and a 13C-based approach, which further increased under elevated pCO2. These offsets could be explained by applying a model that comprises extracellular CO2 and HCO3 – fluxes as well as internal Ci cycling around the carboxysome via the CO2 uptake facilitator NDH-14. Assuming unidirectional, kinetic fractionation between CO2 and HCO3 – in the cytosol or enzymatic fractionation by NDH-14, both significantly improved the comparability of leakage estimates. Our results highlight the importance of internal Ci cycling for 13C composition as well as cellular energy budgets of Trichodesmium, which ought to be considered in process studies on climate change effects.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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    PAPER (OA)
  • 4
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    Shake it easy: a gently mixed continuous culture system for dinoflagellates (2014)
    OXFORD UNIV PRESS
    In:  EPIC3Journal of Plankton Research, OXFORD UNIV PRESS, 36(3), pp. 889-894, ISSN: 0142-7873
    Details
    Publication Date: 2014-11-06
    Description: An important requirement for continuous cultures is a homogeneous distribution of resources and microorganisms, often achieved by rigorous mixing. Many dinoflagellate species are known to be vulnerable to turbulence. Here, we present a newly developed continuous culture system based on gentle mixing in which the two dinoflagellate species Scrippsiella trochoidea and Alexandrium tamarense, with different turbulence sensitivities, grew well under steady state conditions. We also show that the continuous culture system can be applied at low nutrient conditions and low population densities.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
    Format: application/pdf
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    PAPER (OA)
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