scholarly journals Organic matter exudation by <i>Emiliania huxleyi</i> under simulated future ocean conditions

2012 ◽  
Vol 9 (1) ◽  
pp. 1199-1236 ◽  
Author(s):  
C. Borchard ◽  
A. Engel
Keyword(s):  
Molecular Weight ◽  
Organic Carbon ◽  
Elevated Co2 ◽  
Emiliania Huxleyi ◽  
Greenhouse Condition ◽  
Pronounced Increase ◽  
Temperature Conditions ◽  
Extracellular Release ◽  
Aggregation Processes ◽  
Elevated Co2 And Temperature

Abstract. Emiliania huxleyi (strain B 92/11) was exposed to different growth, CO2 and temperature conditions in phosphorous controlled chemostats, to investigate effects on organic carbon exudation, and partitioning between the pools of particulate organic carbon (POC) and dissolved organic carbon (DOC). 14C incubation measurements for primary production (PP) and for extracellular release (ER) were performed. Chemical analysis included amount and composition of high molecular weight dissolved combined carbohydrates (>1 kDa, HMW-dCCHO), particulate combined carbohydrates (pCCHO) and the carbon content of transparent exopolymer particles (TEP-C). Applied CO2 and temperature conditions were 300, 550 and 900 μatm pCO2 at 14 °C, and additionally 900 μatm pCO2 at 18 °C simulating a greenhouse ocean scenario. A reduction in growth rate from μ =0.3 d−1 to μ =0.1 d−1 induced the most profound effect on the performance of E. huxleyi, relative to the effect of elevated CO2 and temperature. At μ =0.3 d−1, PP was significantly higher at elevated CO2 and temperature. DO14C production correlated to PO14C production in all cultures, resulting in similar percentages of extracellular release (DO14C/PP × 100; PER) of averaged 3.74 &amp;pm; 0.94%. At μ =0.1 d−1, PO14C decreased significantly, while exudation of DO14C increased, thus leading to a stronger partitioning from the particulate to the dissolved pool. Maximum PER of 16.3 &amp;pm; 2.3% were observed at μ =0.1 d−1 at greenhouse conditions. Concentrations of HMW-dCCHO and pCCHO were generally higher at μ =0.1 d−1 compared to μ =0.3 d−1. At μ =0.3 d−1, pCCHO concentration increased significantly along with elevated CO2 and temperature. Despite of high PER, the percentage of HMW-dCCHO was smallest at greenhouse conditions. However, highest TEP-formation was observed under greenhouse conditions, together with a pronounced increase in pCCHO concentration, suggesting a stronger partitioning of PP from DOC to POC by coagulation of exudates. Our results imply that greenhouse condition will enhance exudation processes in E. huxleyi and may affect organic carbon partitioning in the ocean due to an enhanced transfer of HMW-dCCHO to TEP by aggregation processes.

scholarly journals Organic matter exudation by <I>Emiliania huxleyi</I> under simulated future ocean conditions

2012 ◽  
Vol 9 (8) ◽  
pp. 3405-3423 ◽  
Author(s):  
C. Borchard ◽  
A. Engel
Keyword(s):  
Organic Carbon ◽  
Elevated Co2 ◽  
Nutrient Supply ◽  
Emiliania Huxleyi ◽  
Nutrient Stress ◽  
Temperature Conditions ◽  
Extracellular Release ◽  
Aggregation Processes ◽  
Cell Densities ◽  
Elevated Co2 And Temperature

Abstract. Emiliania huxleyi (strain B 92/11) was exposed to different nutrient supply, CO2 and temperature conditions in phosphorus controlled chemostats to investigate effects on organic carbon exudation and partitioning between the pools of particulate organic carbon (POC) and dissolved organic carbon (DOC). 14C incubation measurements for primary production (PP) and extracellular release (ER) were performed. Chemical analysis included the amount and composition of high molecular weight (>1 kDa) dissolved combined carbohydrates (HMW-dCCHO), particulate combined carbohydrates (pCCHO) and the carbon content of transparent exopolymer particles (TEP-C). Applied CO2 and temperature conditions were 300, 550 and 900 μatm pCO2 at 14 °C, and additionally 900 μatm pCO2 at 18 °C simulating a greenhouse ocean scenario. Enhanced nutrient stress by reducing the dilution rate (D) from D = 0.3 d−1 to D = 0.1 d−1 (D = μ) induced the strongest response in E. huxleyi. At μ = 0.3 d−1, PP was significantly higher at elevated CO2 and temperature and DO14C production correlated to PO14C production in all treatments, resulting in similar percentages of extracellular release (PER; (DO14C production/PP) × 100) averaging 3.74 ± 0.94%. At μ = 0.1 d−1, PO14C production decreased significantly, while exudation of DO14C increased. Thus, indicating a stronger partitioning from the particulate to the dissolved pool. Maximum PER of 16.3 ± 2.3% were observed at μ = 0.1 d−1 at elevated CO2 and temperature. While cell densities remained constant within each treatment and throughout the experiment, concentrations of HMW-dCCHO, pCCHO and TEP were generally higher under enhanced nutrient stress. At μ = 0.3 d−1, pCCHO concentration increased significantly with elevated CO2 and temperature. At μ = 0.1 d−1, the contribution (mol % C) of HMW-dCCHO to DOC was lower at elevated CO2 and temperature while pCCHO and TEP concentrations were higher. This was most pronounced under greenhouse conditions. Our findings suggest a stronger transformation of primary produced DOC into POC by coagulation of exudates under nutrient limitation. Our results further imply that elevated CO2 and temperature will increase exudation by E. huxleyi and may affect organic carbon partitioning in the ocean due to an enhanced transfer of HMW-dCCHO to TEP by aggregation processes.

scholarly journals Which are the most important parameters for modelling carbon assimilation in boreal Norway spruce under elevated [CO2] and temperature conditions?

2013 ◽  
Vol 33 (11) ◽  
pp. 1156-1176 ◽  
Author(s):  
M. Hall ◽  
B. E. Medlyn ◽  
G. Abramowitz ◽  
O. Franklin ◽  
M. Rantfors ◽  
...  
Keyword(s):  
Norway Spruce ◽  
Elevated Co2 ◽  
Carbon Assimilation ◽  
Temperature Conditions ◽  
Elevated Co2 And Temperature

scholarly journals Response of soybean genotypes to iron limiting stress in calcareous vertisol under ambient and elevated CO2 and temperature conditions

2021 ◽  
Vol 42 (2) ◽  
pp. 295-301
Author(s):  
Kiran Karthik Raj ◽  
◽  
R.N. Pandey ◽  
Bhupinder Singh ◽  
M.C. Meena ◽  
...  
Keyword(s):  
Climate Change ◽  
Iron Deficiency ◽  
Elevated Co2 ◽  
Ion Concentration ◽  
Night Temperature ◽  
Soybean Genotype ◽  
Temperature Conditions ◽  
Soybean Genotypes ◽  
Breeding Programmes ◽  
Elevated Co2 And Temperature

Aim: To compare the relative performance of two contrasting genotypes of soybean to iron limiting conditions under ambient and elevated CO2 and temperature conditions. Methodology: A pot culture experiment was performed using calcareous vertisol soil. The environmental factors viz. CO2 and temperature were combined and applied as a single factor with two levels: a-[CO2+T] (400±10 µmol mol-1, day/night temperature 30oC/22oC) and e-[CO2+T] (610±10 µmol mol-1, day/night temperature 34oC/26oC). Soybean genotype that differed in iron use efficiency was used as another factor and two contrasting genotypes were used as two levels viz. iron efficient and responsive (FeER) and iron inefficient and responsive (FeIR). Results: The higher partial pressure of CO2 under elevated carbon dioxide and temperature condition (Pco2 = 61.8 Pa) dissolved the native CaCO3 from calcareous vertisol soil and thereby resulted in higher HCO3- ion concentration. The antagonistic interaction between Fe2+ with HCO3- ion resulted in greater iron stress. As compared to ambient condition, seed yield was significantly reduced under more stressed e-[CO2+T] condition and resulted in ~1.4 and ~1.9 times drop in FeER and FeIR genotypes, respectively. Iron efficient and responsive (FeER) genotype recorded an impressive performance, as compared to the iron inefficient and responsive (FeIR) genotype, in counteracting iron deficiency stress, both under ambient and elevated conditions. Interpretation: The intra-specific variability between soybean genotypes and their response to elevated CO2 and temperature can be exploited to remediate the emerging iron deficiency stress in soybean plants and suggest ways to structure the future breeding programmes to adapt to the climate change. Key words: Calcareous vertisol, Chlorosis, Climate change, CO2, Soybean

Carbon partitioning in N2 fixing Medicago sativa plants exposed to different CO2 and temperature conditions

2008 ◽  
Vol 35 (4) ◽  
pp. 306 ◽  
Author(s):  
Iker Aranjuelo ◽  
Juan J. Irigoyen ◽  
Manuel Sánchez-Díaz ◽  
Salvador Nogués
Keyword(s):  
Elevated Temperature ◽  
Ambient Temperature ◽  
Medicago Sativa ◽  
Elevated Co2 ◽  
Growth Conditions ◽  
Photosynthetic Acclimation ◽  
Total Soluble Protein ◽  
Sink Strength ◽  
Temperature Conditions ◽  
Elevated Co2 And Temperature

Many of the studies analysing the CO2 effect on plant development have been conducted in optimal growth conditions. Furthermore, although some of those studies suggest that legumes might show a steady productivity increase with rising CO2, the role of nodule activity on the plant responsiveness to predicted atmospheric CO2 enhancement is not well understood. In this study, C (metabolism and allocation) and N (nodule activity) interaction between the plant and the bacterial symbiont during the photosynthetic acclimation of N2-fixing alfalfa (Medicago sativa L. cv. Aragón) plants exposed to elevated CO2 and temperature conditions was analysed. The plants were grown in temperature gradient greenhouses (TGG) where, in the case of elevated CO2 treatments, the isotopic 13C/12C composition (δ13C) inside the TGG was modified. Compared with the corresponding temperature treatment, exposure to 700 μmol mol–1 CO2 enhanced dry mass (DM) of plants in elevated temperature treatments (26%), whereas no significant effect was detected in ambient temperature treatments. The δ13C data revealed that although all the carbon corresponding to leaf total organic matter (TOM) came from newly assimilated C, plants exposed to elevated CO2 did not develop strong sink activity (especially in ambient temperature conditions). Leaf carbohydrate build-up induced reduction in the Rubisco (E.C. 4.1.1.39) carboxylation capacity of plants. Despite this reduction in Rubisco content, plants exposed to elevated CO2 conditions maintained (at ambient temperature) or increased (at elevated temperature) photosynthetic rates (measured at growth conditions) by increasing N use efficiency. The larger C sink strength of nodules in plants grown at elevated CO2 and temperature conditions did not contribute towards overcoming photosynthetic acclimation. Further, the inhibitory effect of CO2 on nodule total activity was caused by a large depletion in total soluble protein (TSP) of nodules. Depletion of leaf N demand, together with the reduction in nodule carbohydrate availability (as reflected by the nodule starch concentration), negatively affected the nodule TSP content and enzymatic activity.

scholarly journals Size-fractionated dissolved primary production and carbohydrate composition of the coccolithophore <i>Emiliania huxleyi</i>

2014 ◽  
Vol 11 (11) ◽  
pp. 15289-15325
Author(s):  
C. Borchard ◽  
A. Engel
Keyword(s):  
Steady State ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Production ◽  
Emiliania Huxleyi ◽  
Sugar Composition ◽  
Size Classes ◽  
Extracellular Release ◽  
State Growth ◽  
Acidic Sugars

Abstract. Extracellular release (ER) by phytoplankton is the major source of fresh dissolved organic carbon (DOC) in marine ecosystems and accompanies primary production during all growth phases. Little is known, so far, on size and composition of released molecules, and to which extent ER occurs passively, by leakage, or actively, by exudation. Here, we report on ER by the widespread and bloom-forming coccolithophore Emiliania huxleyi grown under steady state conditions in phosphorus controlled chemostats (N : P = 29, growth rate of μ = 0.2 d−1). 14C incubations were accomplished to determine primary production (PP), comprised by particulate (PO14C) and dissolved organic carbon (DO14C), and the concentration and composition of particulate combined carbohydrates (pCCHO), and of high molecular weight (>1 kDa, HMW) dissolved combined carbohydrates (dCCHO) as major components of ER. Information on size distribution of ER products was obtained by investigating distinct size classes (<0.40 μm, <1000 kDa, <100 kDa and <10 kDa) of DO14C and HMW-dCCHO. Our results revealed relatively low ER during steady state growth, corresponding to ∼4.5% of primary production, and similar ER rates for all size classes. Acidic sugars had a significant share on freshly produced pCCHO as well as on HMW-dCCHO. While pCCHO and the smallest size (<10 kDa) fraction of HMW-dCCHO exhibited a similar sugar composition, dominated by high percentages of glucose (74–80 Mol%), the composition of HMW-dCCHO size-classes >10 kDa was significantly different with higher Mol% of arabinose. Mol% of acidic sugars increased and Mol% glucose decreased with increasing size of HMW-dCCHO. We conclude that larger polysaccharides follow different production and release pathways than smaller molecules, potentially serving distinct ecological and biogeochemical functions.

scholarly journals Size-fractionated dissolved primary production and carbohydrate composition of the coccolithophore <i>Emiliania huxleyi</i>

2015 ◽  
Vol 12 (4) ◽  
pp. 1271-1284 ◽  
Author(s):  
C. Borchard ◽  
A. Engel
Keyword(s):  
Steady State ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Production ◽  
Size Fraction ◽  
Emiliania Huxleyi ◽  
Size Classes ◽  
Extracellular Release ◽  
State Growth ◽  
Acidic Sugars

Abstract. Extracellular release (ER) by phytoplankton is the major source of fresh dissolved organic carbon (DOC) in marine ecosystems and accompanies primary production during all growth phases. Little is known, so far, on size and composition of released molecules, and to which extent ER occurs passively, by leakage, or actively, by exudation. Here, we report on ER by the widespread and bloom-forming coccolithophore Emiliania huxleyi grown under steady-state conditions in phosphorus-controlled chemostats (N:P = 29, growth rate of μ = 0.2 d−1) at present-day and high-CO2 concentrations. 14C incubations were performed to determine primary production (PP), comprised of particulate (PO14C) and dissolved organic carbon (DO14C). Concentration and composition of particulate combined carbohydrates (pCCHO) and high-molecular-weight (>1 kDa, HMW) dissolved combined carbohydrates (dCCHO) were determined by ion chromatography. Information on size distribution of ER products was obtained by investigating distinct size classes (<0.4 μm (DO14C), <0.45 μm (HMW-dCCHO), <1000, <100 and <10 kDa) of DO14CC and HMW-dCCHO. Our results revealed relatively low ER during steady-state growth, corresponding to ~4.5% of primary production, and similar ER rates for all size classes. Acidic sugars had a significant share on freshly produced pCCHO as well as on HMW-dCCHO. While pCCHO and the smallest size fraction (<10 kDa) of HMW-dCCHO exhibited a similar sugar composition, dominated by high percentage of glucose (74–80 mol%), the composition of HMW-dCCHO size classes >10 kDa was significantly different, with a higher mol% of arabinose. The mol% of acidic sugars increased and that of glucose decreased with increasing size of HMW-dCCHO. We conclude that larger polysaccharides follow different production and release pathways than smaller molecules, potentially serving distinct ecological and biogeochemical functions.

HES 200/0.5 Is not HES 200/0.5

1995 ◽  
Vol 74 (06) ◽  
pp. 1452-1456 ◽  
Author(s):  
Johannes Treib ◽  
Anton Haass ◽  
Gerhard Pindur ◽  
Ulrich T Seyfert ◽  
Wolfgang Treib ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hydroxyethyl Starch ◽  
Clinical Relevance ◽  
Dilution Effect ◽  
Repeated Administration ◽  
Plasma Viscosity ◽  
Degree Of Substitution ◽  
Pronounced Increase ◽  
Large Molecules ◽  
Mean Molecular Weight

SummaryThe plasma clearance of hydroxyethyl starch (HES) depends on the initial molecular weight and the degree of substitution. So far, little attention has been paid to the clinical relevance of the C2/C6 substitution ratio of hydroxyethyl starch.10 patients with cerebrovascular circulatory disturbance received hemodilution therapy for 10 days, consisting of 10% HES 200/0.5 (mean molecular weight 200 kD, degree of substitution 0.5) with a C2/C6 ratio of 13.4. A second group of 10 patients received a starch solution with identical initial molecular weight and degree of substitution but with a C2/C6 ratio of 5.7.After the administration of a single dose, no significant differences between the two groups were observed. After repeated administration, significant differences could be detected in hemorheology, coagulation and elimination (p<0.01). The larger C2/C6 ratio led to a higher intravascular mean molecular weight (95 vs. 84 kD), which in turn led to a higher increase in serum concentration during the therapy (14.7 vs.8.6 mg/ml). Hematocrit was lowered more (-30,5 vs. -23,5%) and plasma viscosity was increased more. There was also a more pronounced increase in partial thromboplastin time (+30% vs. +13%) and a factor of 2 larger decrease of factor VIII/von Willebrand factor-complex (p <0.01), which exceeded the dilution effect.The higher C2/C6 ratio of HES 200/0.5/13.4 slows down enzymatic degradation. After repeated administration of this starch, large molecules accumulate which are inefficiently degraded. The same effect has been observed after therapy with highly-substituted HES. This accumulation of large molecules leads to a beneficial longer lasting volume effect. The disadvantages include an increase in plasma viscosity and coagulation disturbances, which cannot be explained with the respective dilution effect alone. For these reasons, the C2/C6 ratio is of clinical relevance and should be included in the product labeling in the future.

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