Björn Rost

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

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Clara J. M. Hoppe

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Scarlett Trimborn

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Sebastian Rokitta

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Ulf Riebesell

GEOMAR Helmholtz Centre for Ocean Research Kiel

Sven A. Kranz

Rice University

Klaus‐Uwe Richter

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

Philippe D. Tortell

University of British Columbia

Dedmer B. Van de Waal

University of Amsterdam

Uwe John

Helmholtz Institute for Functional Marine Biodiversity

Gerald Langer

Universitat Autònoma de Barcelona

Cooperative Institutions

Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung

141

University of Bremen

Centre National de la Recherche Scientifique

GEOMAR Helmholtz Centre for Ocean Research Kiel

Rutgers, The State University of New Jersey

University of Plymouth

Sorbonne Université

Kiel University

University of British Columbia

Max Planck Society

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Adaptive mechanisms of phytoplankton in a changing Arctic: The hidden dynamics of intraspecific selection

Klara K. E. Wolf Clara J. M. Hoppe Florian Leese Björn Rost Uwe John

Dynamics

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Isotope disequilibrium and mass spectrometric studies of inorganic carbon acquisition by phytoplankton

Limnology and Oceanography Methods (2007)

Björn Rost Sven A. Kranz Klaus‐Uwe Richter Philippe D. Tortell

Given the need to assess potential effects of rising atmospheric CO 2 on aquatic primary productivity, many studies have investigated the physiological mechanisms of inorganic carbon acquisition by a variety of phytoplankton species. Membrane inlet mass spectrometry (MIMS) has become the preferred methodological approach for laboratory experiments, whereas the 14 C disequilibrium method has proven to be particularly useful for field studies. In the present investigation, we explicitly compare results of carbon acquisition measurements obtained with both of these approaches. Testing a range of phytoplankton species from different taxa, we show that both methods provide nearly identical results on the contribution of HCO 3 − and CO 2 relative to net carbon fixation. In contrast, although both approaches yielded highly reproducible estimates for extracellular carbonic anhydrase activity, the results differed significantly between the two methods. By directly comparing these two leading methods, we provide experimental confirmation of key assumptions used for data interpretation and discuss possible effects of assay conditions. Our analysis highlights the individual strengths and weaknesses of different approaches.

Total inorganic carbon

Carbon fibers

Disequilibrium

Emiliania huxleyi

Primary productivity

10.4319/lom.2007.5.328

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Citations (51)

CO2 sensitivities: DOC production and acidification, Modelling the response of marine ecosystems to increasing levels of CO2

Markus Schartau Anja Engel Judith Piontek Björn Rost

Ocean Acidification

Marine ecosystem

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Effects of CO₂ and their modulation by light in the life‐cycle stages of the coccolithophore Emiliania huxleyi

Limnology and Oceanography (2012)

Sebastian Rokitta Björn Rost

The effects of ocean acidification on the life‐cycle stages of the coccolithophore Emiliania huxleyi and their modulation by light were examined. Calcifying diploid and noncalcifying haploid cells (Roscoff culture collection strains 1216 and 1217) were acclimated to present‐day and elevated CO 2 partial pressures (P CO 2 ; 38.5 vs. 101.3 Pa, i.e., 380 vs. 1000 µatm) under low and high light (50 vs. 300 µmol photons m −2 s −1 ). Growth rates as well as cellular quotas and production rates of C and N were measured. Sources of inorganic C for biomass buildup were determined using a 14 C disequilibrium assay. Photosynthetic O 2 evolution was measured as a function of dissolved inorganic C and light by means of membrane‐inlet mass spectrometry. The diploid stage responded to elevated P CO 2 by shunting resources from the production of particulate inorganic C toward organic C yet keeping the production of total particulate C constant. As the effect of ocean acidification was stronger under low light, the diploid stage might be less affected by increased acidity when energy availability is high. The haploid stage maintained elemental composition and production rates under elevated P CO 2 . Although both life‐cycle stages involve different ways of dealing with elevated P CO 2 , the responses were generally modulated by energy availability, being typically most pronounced under low light. Additionally, P CO 2 responses resembled those induced by high irradiances, indicating that ocean acidification affects the interplay between energy‐generating processes (photosynthetic light reactions) and processes competing for energy (biomass buildup and calcification). A conceptual model is put forward explaining why the magnitude of single responses is determined by energy availability.

Emiliania huxleyi

Coccolithophore

Coccolith

Haptophyte

Ocean Acidification

10.4319/lo.2012.57.2.0607

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Citations (140)

Controls of primary production in two phytoplankton blooms in the Antarctic Circumpolar Current

Deep Sea Research Part II Topical Studies in Oceanography (2015)

Clara J. M. Hoppe Christine Klaas Sharyn Ossebaar Mariana Altenburg Soppa Wee Cheah

The Antarctic Circumpolar Current has a high potential for primary production and carbon sequestration through the biological pump. In the current study, two large-scale blooms observed in 2012 during a cruise with R.V. Polarstern were investigated with respect to phytoplankton standing stocks, primary productivity and nutrient budgets. While net primary productivity was similar in both blooms, chlorophyll a –specific photosynthesis was more efficient in the bloom closer to the island of South Georgia (39 °W, 50 °S) compared to the open ocean bloom further east (12 °W, 51 °S). We did not find evidence for light being the driver of bloom dynamics as chlorophyll standing stocks up to 165 mg m−2 developed despite mixed layers as deep as 90 m. Since the two bloom regions differ in their distance to shelf areas, potential sources of iron vary. Nutrient (nitrate, phosphate, silicate) deficits were similar in both areas despite different bloom ages, but their ratios indicated more pronounced iron limitation at 12 °W compared to 39 °W. While primarily the supply of iron and not the availability of light seemed to control onset and duration of the blooms, higher grazing pressure could have exerted a stronger control toward the declining phase of the blooms.

Bloom

Iron fertilization

Circumpolar star

Grazing pressure

New production

10.1016/j.dsr2.2015.10.005

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Citations (61)

Effects of ocean acidification on the calcification of coccolithophores - Evidence from experimental studies

Gerald Langer Ian Probert Björn Rost Patrizia Ziveri

Ocean Acidification

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Haptophyta

Springer eBooks (2016)

Wenche Eikrem Linda Medlin Jorijntje Henderiks Sebastian Rokitta Björn Rost

Haptophyte

10.1007/978-3-319-32669-6_38-1

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Citations (16)

Combined Effects of CO₂ and Light on the N₂-Fixing Cyanobacterium Trichodesmium IMS101: Physiological Responses

PLANT PHYSIOLOGY (2010)

Sven A. Kranz Orly Levitan Klaus‐Uwe Richter Ondřej Prášil Ilana Berman‐Frank

Recent studies on the diazotrophic cyanobacterium Trichodesmium erythraeum (IMS101) showed that increasing CO2 partial pressure (pCO2) enhances N2 fixation and growth. Significant uncertainties remain as to the degree of the sensitivity to pCO2, its modification by other environmental factors, and underlying processes causing these responses. To address these questions, we examined the responses of Trichodesmium IMS101 grown under a matrix of low and high levels of pCO2 (150 and 900 μatm) and irradiance (50 and 200 μmol photons m−2 s−1). Growth rates as well as cellular carbon and nitrogen contents increased with increasing pCO2 and light levels in the cultures. The pCO2-dependent stimulation in organic carbon and nitrogen production was highest under low light. High pCO2 stimulated rates of N2 fixation and prolonged the duration, while high light affected maximum rates only. Gross photosynthesis increased with light but did not change with pCO2. HCO3− was identified as the predominant carbon source taken up in all treatments. Inorganic carbon uptake increased with light, but only gross CO2 uptake was enhanced under high pCO2. A comparison between carbon fluxes in vivo and those derived from 13C fractionation indicates high internal carbon cycling, especially in the low-pCO2 treatment under high light. Light-dependent oxygen uptake was only detected under low pCO2 combined with high light or when low-light-acclimated cells were exposed to high light, indicating that the Mehler reaction functions also as a photoprotective mechanism in Trichodesmium. Our data confirm the pronounced pCO2 effect on N2 fixation and growth in Trichodesmium and further show a strong modulation of these effects by light intensity. We attribute these responses to changes in the allocation of photosynthetic energy between carbon acquisition and the assimilation of carbon and nitrogen under elevated pCO2. These findings are supported by a complementary study looking at photosynthetic fluorescence parameters of photosystem II, photosynthetic unit stoichiometry (photosystem I:photosystem II), and pool sizes of key proteins in carbon and nitrogen acquisition.

Trichodesmium

Carbon fixation

Light intensity

Carbon fibers

Total inorganic carbon

10.1104/pp.110.159145

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Citations (137)

Supplementary material to "The Arctic picoeukaryote <i>Micromonas pusilla</i> benefits from Ocean Acidification under constant and dynamic light"

Emily White Clara J. M. Hoppe Björn Rost

Constant (computer programming)

10.5194/bg-2019-343-supplement