scholarly journals Carbon fixation prediction during a bloom of <i>Emiliania huxleyi</i> is highly sensitive to the assumed regulation mechanism

2009 ◽  
Vol 6 (3) ◽  
pp. 5339-5372 ◽  
Author(s):  
O. Bernard ◽  
A. Sciandra ◽  
S. Rabouille
Keyword(s):  
Large Scale ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Carbon Fluxes ◽  
Emiliania Huxleyi ◽  
Regulation Mechanism ◽  
Fixation Rate ◽  
Saturation State ◽  
Calcite Saturation ◽  
Order Of Magnitude

Abstract. Large scale precipitation of calcium carbonate in the oceans by coccolithophorids plays an important role in carbon sequestration. However, there is a controversy on the effect of an increase in atmospheric CO2 concentration on both calcification and photosynthesis of coccolithophorids. Indeed recent experiments, performed under nitrogen limitation, revealed that the associated fluxes may be slowed down, while other authors claim the reverse. We designed models to account for various scenarii of calcification and photosynthesis regulation in chemostat cultures of Emiliania huxleyi, based on different hypotheses on the regulation mechanism. These models consider that either carbon dioxide, bicarbonate, carbonate or calcite saturation state (Ω) is the regulating factor. All were calibrated to predict the same carbon fixation rate in nowadays pCO2, but they turn out to respond differently to an increase in CO2 concentration. Thus, using the four possible models, we simulated a large bloom of Emiliania huxleyi. It results that models assuming a regulation by CO32− or Ω predicted much higher carbon fluxes. The response when considering a doubled pCO2 was different and models controlled by CO2 or HCO3 − led to increased carbon fluxes. In addition, the variability between the various scenarii proved to be in the same order of magnitude than the response to pCO2 increase. These sharp discrepancies reveal the consequences of model assumptions on the simulation outcome.

scholarly journals Morphology of <i>Emiliania huxleyi</i> coccoliths on the North West European shelf – is there an influence of carbonate chemistry?

2014 ◽  
Vol 11 (3) ◽  
pp. 4531-4561 ◽  
Author(s):  
J. R. Young ◽  
A. J. Poulton ◽  
T. Tyrrell
Keyword(s):  
Environmental Samples ◽  
Significant Variation ◽  
Emiliania Huxleyi ◽  
Morphometric Study ◽  
Saturation State ◽  
North West ◽  
The North ◽  
Microscope Images ◽  
Calcite Saturation ◽  
The Uk

Abstract. Within the context of the UK Ocean Acidification project, Emiliania huxleyi (type A) coccolith morphology was examined from samples collected during cruise D366. In particular, a morphometric study of coccolith size and degree of calcification was made on scanning electron microscope images of samples from shipboard CO2 perturbation experiments and from a set of environmental samples with significant variation in calcite saturation state (Ωcalcite). One bioassay in particular (E4 from the southern North Sea) yielded unambiguous results – in this bioassay exponential growth from a low level occurred with no artificial stimulation and coccosphere numbers increased ten-fold during the experiment. The samples with elevated CO2 saw significantly reduced coccolithophore growth. However, coccolithophore morphology was not significantly affected by the changing CO2 conditions even under the highest levels of perturbation (1000 μatm). Environmental samples similarly showed no correlation of coccolithophore morphology with calcite saturation state. Some variation in coccolith size and degree of calcification does occur but this seems to be predominantly due to genotypic differentiation between populations on the shelf and in the open ocean.

scholarly journals Generic analysis of the response of calcifying microalgae to an elevation of pCO2 : qualitative vs quantitative analysis

2008 ◽  
Vol Volume 9, 2007 Conference in... ◽  
Author(s):  
Olivier Bernard ◽  
Antoine Sciandre
Keyword(s):  
Large Scale ◽  
Co2 Concentration ◽  
Emiliania Huxleyi ◽  
Atmospheric Co2 ◽  
Quantitative Prediction ◽  
General Level ◽  
Sont Encore ◽  
Chemostat Cultures ◽  
International Audience ◽  
Parameter Values

International audience Calcifying microalgae can play a key role in atmospheric CO2 trapping through large scale precipitation of calcium carbonate in the oceans. However, recent experiments revealed that the associated fluxes may be slow down by an increase in atmospheric CO2 concentration. In this paper we design models to account for the decrease in calcification and photosynthesis rates observed after an increase of pCO2 in Emiliania huxleyi chemostat cultures. Since the involved mechanisms are still not completely understood, we consider various models, each of them being based on a different hypothesis. These models are kept at a very general level, by maintaining the growth and calcification functions in a generic form, i.e. independent on the exact shape of these functions and on parameter values. The analysis is thus performed using these generic functions where the only hypothesis is an increase of these rates with respect to the regulating carbon species. As a result, each model responds differently to a pCO2 elevation. Surprisingly, the only models whose behaviour are in agreement with the experimental results correspond to carbonate as the regulating species for photosynthesis. Finally we show that the models whose qualitative behaviour are wrong could be considered as acceptable on the basis of a quantitative prediction error criterion. Les microalgues calcifiantes jouent un rôle clé dans le piégeage du CO2 atmosphérique d’origine anthropique en précipitant du carbonate de calcium qui sédimente au fond des océans. Toutefois, des expériences en laboratoire ont suggéré que cette activité biologique pourrait être diminuée par l’augmentation de la pression partielle de CO2 (pCO2) dans les océans qui a tendance à s’ équilibrer avec celle de l’atmosphère. Dans ce papier, nous concevons des modèles dynamiques pour essayer de simuler la diminution des taux de calcification et de photosynthèse observés chez Emiliania huxleyi après une hausse de la pCO2 reproduite en chémostat. Comme les mécanismes physiologiques impliqués sont encore loin d’ être complètement élucidés, nous considérons différents modèles, chacun d’eux étant basé sur une hypothèse biologique différente. Ces modèles, construits en utilisant des fonctions génériques pour caractériser les processus de croissance et de calcification, peuvent être analysés indépendamment de la forme exacte de ces fonctions et de la valeur des paramètres. L’ étude s’appuie donc sur ces fonctions génériques où la seule hypothèse est une régulation de ces taux par une des trois formes qui composent la totalité du carbone inorganique dissous : le CO2, les carbonates et les bicarbonates. Il s’en suit que chaque modèle réagit différemment à une élévation de la pCO2. Contrairement aux hypothèses classiquement admises, notre étude montre que les seuls modèles dont le comportement est en accord avec les résultats expérimentaux sont ceux pour lesquels une régulation de la photosynthèse par les carbonates a été supposée, ce qui corrobore les conclusions de travaux récents. Enfin, nous montrons que les modèles dont le comportement qualitatif est mauvais ne seraient pas rejetés sur la base d’un critère quantitatif d’erreur de prédiction.

SECULAR VARIATIONS IN THE 14C CONCENTRATION OF DOUGLAS FIR TREE RINGS

1966 ◽  
Vol 3 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Willy Dyck
Keyword(s):  
Large Scale ◽  
Carbon Fixation ◽  
Douglas Fir ◽  
Sunspot Activity ◽  
Short Term ◽  
Fixation Rate ◽  
Pumping Rate ◽  
Counting Error ◽  
Annual Growth Rings

Measurements of the 14C concentration in a Douglas fir from Vancouver Island indicate a maximum variation of 44‰, during the past 1 100 years. The magnitude and trend of these variations are similar to those observed by de Vries (1958) in oak from Germany and by Willis et al. (1960) in sequoias from California, confirming earlier observations that atmospheric mixing of CO2 takes place rapidly on a large scale.14C measurements of successive annual growth rings from the piths of two firs (346 years and 1 142 years old) show no variations beyond those attributable to the statistical counting error of ± 6‰. Thus, cyclic variations in sunspot activity and (or) climate, if present during these intervals, did not affect the 14C concentration in the biosphere appreciably.A mechanism, based on a climate-sensitive carbon pumping rate of the biosphere coupled with the temperature-dependent oceanic CO2 content is postulated to explain, qualitatively, the observed short-term (150 years or less) and long-term (1 000 years or more) 14C variations in the land biosphere. Short-term fluctuations are directly proportional to temperature because variations in the carbon fixation rate lead to a pulsating CO2 content of the atmosphere. Long-term changes are inversely proportional to temperature because large quantities of carbon, normally stored in deeper regions of the ocean, are exchanged between biosphere and hydrosphere.

scholarly journals An improved estimate of microbially mediated carbon fluxes from the Greenland ice sheet

2012 ◽  
Vol 58 (212) ◽  
pp. 1098-1108 ◽  
Author(s):  
J.M. Cook ◽  
A.J. Hodson ◽  
A.M. Anesio ◽  
E. Hanna ◽  
M. Yallop ◽  
...  
Keyword(s):  
Carbon Fixation ◽  
Ice Sheet ◽  
Stable State ◽  
Greenland Ice Sheet ◽  
Carbon Fluxes ◽  
Total Carbon ◽  
Biological Production ◽  
Spatial Uniformity ◽  
Annual Carbon ◽  
Order Of Magnitude

AbstractMicrobially mediated carbon fluxes on the surface of the Greenland ice sheet (GrIS) were recently quantified by Hodson and others (2010) using measurements of the surface coverage of debris (cryoconite) and rates of biological production associated with debris near the ice-sheet margin. We present updated models that do not assume the same spatial uniformity in key parameters employed by Hodson and others (2010) because they make use of biomass distribution and biological production data from a 79 km transect of the GrIS. Further, the models presented here also include for the first time biomass associated with both cryoconite holes and surficial algae. The predicted annual carbon flux for a small (1600 km2) section of ice surrounding the field transect is about four times that estimated using spatially uniform biomass and production in this area. When surficial algae are included, the model predicts about 11 times more carbon fixation via photosynthesis per year than the cryoconite-only models. We therefore suggest that supraglacial carbon fluxes from the GrIS have previously been underestimated by more than an order of magnitude and that the hitherto overlooked surficial algal ecosystem can be the most crucial contributor. The GrIS is shown to be in a relatively stable state of net autotrophy according to our model and so a strong link between bare-ice area and total carbon fluxes is evident. The implication is a biomass feedback to surface albedo and enhanced ablation as a result. Climate predictions for the year 2100 show that greater carbon fixation could also result from climate warming.

scholarly journals Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation

2017 ◽  
Author(s):  
Shanying Tong ◽  
David A. Hutchins ◽  
Kunshan Gao
Keyword(s):  
Ocean Acidification ◽  
Uv Radiation ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Emiliania Huxleyi ◽  
Marine Phytoplankton ◽  
Negative Effects ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon ◽  
Increasing Temperature

Abstract. Marine phytoplankton such as bloom-forming, calcite-producing coccolithophores, are naturally exposed to solar UV radiation (UVR, 280–400 nm) in the ocean's upper mixed layers. Nevertheless, effects of increasing CO2-induced ocean acidification and warming have rarely been investigated in the presence of UVR. We examined calcification and photosynthetic carbon fixation performance in the most cosmopolitan coccolithophorid, Emiliania huxleyi, grown under high (1000 μatm, HC; pHT: 7.70) and low (400 μatm, LC; pHT: 8.02) CO2 levels, at 15 °C (LT), 20 °C (MT) and 24 °C (HT) with or without UVR. The HC treatment didn't affect photosynthetic carbon fixation at 15 °C, but significantly enhanced it with increasing temperature. Exposure to UVR inhibited photosynthesis, with higher inhibition by UVA (320–395 nm) than UVB (295–320 nm), except in the HC and 24 °C-grown cells, in which UVB caused more inhibition than UVA. Reduced thickness of the coccolith layer in the HC-grown cells appeared to be responsible for the UV-induced inhibition, and an increased repair rate of UVA-derived damage in the HCHT-grown cells could be responsible for lowered UVA-induced inhibition. While calcification was reduced with the elevated CO2 concentration, exposure to UVB or UVA affected it differentially, with the former inhibiting and the latter enhancing it. UVA-induced stimulation of calcification was higher in the HC-grown cells at 15 and 20 °C, whereas at 24 °C, observed enhancement was not significant. The calcification to photosynthesis ratio (Cal / Pho ratio) was lower in the HC treatment, and increasing temperature also lowered the value. However, at 20 and 24 °C, exposures to UVR significantly increased the Cal / Pho ratio, especially in HC-grown cells, by up to 100 %. This implies that UVR can counteract the negative effects of the greenhouse treatment on the Cal / Pho ratio, and so may be a key stressor when considering the impacts of future greenhouse conditions on E. huxleyi.

scholarly journals Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation

2019 ◽  
Vol 16 (2) ◽  
pp. 561-572 ◽  
Author(s):  
Shanying Tong ◽  
David A. Hutchins ◽  
Kunshan Gao
Keyword(s):  
Ocean Acidification ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Emiliania Huxleyi ◽  
Marine Phytoplankton ◽  
Negative Effects ◽  
Solar Ultraviolet Radiation ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon ◽  
Increasing Temperature

Abstract. Marine phytoplankton such as bloom-forming, calcite-producing coccolithophores, are naturally exposed to solar ultraviolet radiation (UVR, 280–400 nm) in the ocean's upper mixed layers. Nevertheless, the effects of increasing carbon dioxide (CO2)-induced ocean acidification and warming have rarely been investigated in the presence of UVR. We examined calcification and photosynthetic carbon fixation performance in the most cosmopolitan coccolithophorid, Emiliania huxleyi, grown under high (1000 µatm, HC; pHT: 7.70) and low (400 µatm, LC; pHT: 8.02) CO2 levels, at 15 ∘C, 20 ∘C and 24 ∘C with or without UVR. The HC treatment did not affect photosynthetic carbon fixation at 15 ∘C, but significantly enhanced it with increasing temperature. Exposure to UVR inhibited photosynthesis, with higher inhibition by UVA (320–395 nm) than UVB (295–320 nm), except in the HC and 24 ∘C-grown cells, in which UVB caused more inhibition than UVA. A reduced thickness of the coccolith layer in the HC-grown cells appeared to be responsible for the UV-induced inhibition, and an increased repair rate of UVA-derived damage in the HC–high-temperature grown cells could be responsible for lowered UVA-induced inhibition. While calcification was reduced with elevated CO2 concentration, exposure to UVB or UVA affected the process differentially, with the former inhibiting it and the latter enhancing it. UVA-induced stimulation of calcification was higher in the HC-grown cells at 15 and 20 ∘C, whereas at 24 ∘C observed enhancement was not significant. The calcification to photosynthesis ratio (Cal ∕ Pho ratio) was lower in the HC treatment, and increasing temperature also lowered the value. However, at 20 and 24 ∘C, exposure to UVR significantly increased the Cal ∕ Pho ratio, especially in HC-grown cells, by up to 100 %. This implies that UVR can counteract the negative effects of the “greenhouse” treatment on the Cal ∕ Pho ratio; hence, UVR may be a key stressor when considering the impacts of future greenhouse conditions on E. huxleyi.

scholarly journals Morphology of <i>Emiliania huxleyi</i> coccoliths on the northwestern European shelf – is there an influence of carbonate chemistry?

2014 ◽  
Vol 11 (17) ◽  
pp. 4771-4782 ◽  
Author(s):  
J. R. Young ◽  
A. J. Poulton ◽  
T. Tyrrell
Keyword(s):  
Environmental Samples ◽  
Significant Variation ◽  
Emiliania Huxleyi ◽  
Morphometric Study ◽  
Carbonate Chemistry ◽  
Saturation State ◽  
Initial Cell ◽  
Microscope Images ◽  
Calcite Saturation ◽  
The Uk

Abstract. Within the context of the UK Ocean Acidification project, Emiliania huxleyi (type A) coccolith morphology was examined from samples collected during cruise D366. In particular, a morphometric study of coccolith size and degree of calcification was made on scanning electron microscope images of samples from shipboard CO2 perturbation experiments and from a set of environmental samples with significant variation in calcite saturation state (Ωcalcite). One bioassay in particular (E4 from the southern North Sea) yielded unambiguous results – in this bioassay exponential growth from a low initial cell density occurred with no nutrient enrichment and coccosphere numbers increased tenfold during the experiment. The samples with elevated CO2 saw significantly reduced coccolithophore growth. However, coccolithophore morphology was not significantly affected by the changing CO2 conditions even under the highest levels of perturbation (1000 μatm CO2). Environmental samples similarly showed no correlation of coccolithophore morphology with calcite saturation state. Some variation in coccolith size and degree of calcification does occur but this seems to be predominantly due to genotypic differentiation between populations on the shelf and in the open ocean.

scholarly journals Abundances and morphotypes of the coccolithophore <i>Emiliania huxleyi</i> in southern Patagonia compared to neighboring oceans and northern-hemisphere fjords

2021 ◽  
Author(s):  
Francisco Díaz-Rosas ◽  
Catharina Alves-de-Souza ◽  
Emilio Alarcón ◽  
Eduardo Menschel ◽  
Humberto E. González ◽  
...  
Keyword(s):  
Niche Breadth ◽  
Minor Component ◽  
Emiliania Huxleyi ◽  
Early Spring ◽  
Saturation State ◽  
Southern Patagonia ◽  
Calcite Saturation ◽  
Chemical Conditions ◽  
Freshwater Inputs ◽  
Patagonian Fjords

Abstract. Coccolithophores are potentially affected by ongoing ocean acidification, where rising CO2 lowers seawater pH and calcite saturation state (Ωcal). Southern Patagonian fjords and channels provide natural laboratories for studying these issues due to high variability in physical and chemical conditions. We surveyed coccolithophore assemblages in Patagonian fjords during late-spring 2015 and early-spring 2017. Surface Ωcal exhibited large variations driven mostly by freshwater inputs. High Ωcal conditions (max. 3.6) occurred in the Archipelago Madre de Dios. Ωcal ranged from 2.0–2.6 in the western Strait of Magellan, 1.5–2.2 in the Inner Channel, and was sub-saturating (0.5) in Skyring Sound. Emiliania huxleyi was the only coccolithophore widely distributed in Patagonian fjords (> 96 % of total coccolitophores), only disappearing in the Skyring Sound, a semi-closed mesohaline system. Correspondence analysis associated higher E. huxleyi biomasses with lower diatom biomasses. The highest E. huxleyi abundances in Patagonia were in the lower range of those reported in Norwegian fjords. Predominant morphotypes were distinct from those previously documented in nearby oceans but similar to those of Norwegian fjords. Moderate-calcified forms of E. huxleyi A morphotype were uniformly distributed throughout Patagonia fjords. The exceptional R/hyper-calcified coccoliths, associated with low Ωcal values in Chilean and Peruvian coastal upwellings, were a minor component associated with high Ωcal levels in Patagonia. Outlying mean index (OMI) niche analysis suggested that pH/Ωcal conditions explained most variation in the realized niches of E. huxleyi morphotypes. The moderate-calcified A morphotype exhibited the widest niche-breadth (generalist), while the R/hyper-calcified morphotype exhibited a more restricted realized niche (specialist). Nevertheless, when considering an expanded sampling domain, including nearby Southeast Pacific coastal and offshore waters, even the R/hyper-calcified morphotype exhibited a higher niche breadth than other closely phylogenetically-related coccolithophore species. The occurrence of E. huxleyi in naturally low pH/Ωcal environments indicates that its ecological response is plastic and capable of adaptation.

scholarly journals Effect of CO2 concentration of growth and carbon fixation rate of pleurochrysis carterae.

1995 ◽  
Vol 28 (4) ◽  
pp. 474-476 ◽  
Author(s):  
Minoru Seki ◽  
Takahiko Hirokawa ◽  
Hajime Hasegawa ◽  
Shintaro Furusaki
Keyword(s):  
Carbon Fixation ◽  
Co2 Concentration ◽  
Fixation Rate ◽  
Pleurochrysis Carterae

scholarly journals Ocean acidification mediates photosynthetic response to UV radiation and temperature increase in the diatom <i>Phaeodactylum tricornutum</i>

2012 ◽  
Vol 9 (10) ◽  
pp. 3931-3942 ◽  
Author(s):  
Y. Li ◽  
K. Gao ◽  
V. E. Villafañe ◽  
E. W. Helbling
Keyword(s):  
Ocean Acidification ◽  
Elevated Co2 ◽  
Uv Radiation ◽  
Phaeodactylum Tricornutum ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Photochemical Quenching ◽  
Fixation Rate ◽  
Ps Ii ◽  
Temperature Levels

Abstract. Increasing atmospheric CO2 concentration is responsible for progressive ocean acidification, ocean warming as well as decreased thickness of upper mixing layer (UML), thus exposing phytoplankton cells not only to lower pH and higher temperatures but also to higher levels of solar UV radiation. In order to evaluate the combined effects of ocean acidification, UV radiation and temperature, we used the diatom Phaeodactylum tricornutum as a model organism and examined its physiological performance after grown under two CO2 concentrations (390 and 1000 μatm) for more than 20 generations. Compared to the ambient CO2 level (390 μatm), growth at the elevated CO2 concentration increased non-photochemical quenching (NPQ) of cells and partially counteracted the harm to PS II (photosystem II) caused by UV-A and UV-B. Such an effect was less pronounced under increased temperature levels. The ratio of repair to UV-B induced damage decreased with increased NPQ, reflecting induction of NPQ when repair dropped behind the damage, and it was higher under the ocean acidification condition, showing that the increased pCO2 and lowered pH counteracted UV-B induced harm. As for photosynthetic carbon fixation rate which increased with increasing temperature from 15 to 25 °C, the elevated CO2 and temperature levels synergistically interacted to reduce the inhibition caused by UV-B and thus increase the carbon fixation.

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