Elevated Carbon Dioxide Levels Research Articles

Selective low concentration ammonia sensing in a microfluidic lab-on-a-chip

In the medical community, there is a considerable interest in a diagnostic breath analyzer for ammonia that is selectively enough to measure in exhaled air and small enough for the small volumes available in such an application. An indirect measurement system for low gaseous ammonia concentrations has been miniaturized and integrated on a chip in order to reach this goal. The detection limit of the system was calculated to be 1.1 parts per billion (ppb). The response time was determined to be 1.6 min with a gas How of 50 ml/min. The required gas volume for one measurement is therefore sufficiently small, although sampling assistance is required for breath analysis. The selectivity of the system is sufficient to measure ammonia concentrations in the low-ppb range. The system is even sufficiently selective to be used in environments that contain elevated carbon dioxide levels, like exhaled air. The lower ammonia concentration expected in diagnostic breath analysis applications, 50 ppb, was demonstrated to be detectable.

Long-term facilitation of ventilation and genioglossus muscle activity is evident in the presence of elevated levels of carbon dioxide in awake humans

We hypothesized that long-term facilitation (LTF) of minute ventilation and peak genioglossus muscle activity manifests itself in awake healthy humans when carbon dioxide is sustained at elevated levels. Eleven subjects completed two trials. During trial 1, baseline carbon dioxide levels were maintained during and after exposure to eight 4-min episodes of hypoxia. During trial 2, carbon dioxide was sustained 5 mmHg above baseline levels during exposure to episodic hypoxia. Seven subjects were exposed to sustained elevated levels of carbon dioxide in the absence of episodic hypoxia, which served as a control experiment. Minute ventilation was measured during trial 1, trial 2, and the control experiment. Peak genioglossus muscle activity was measured during trial 2. Minute ventilation during the recovery period of trial 1 was similar to baseline (9.3 +/- 0.5 vs. 9.2 +/- 0.7 l/min). Likewise, minute ventilation remained unchanged during the control experiment (beginning vs. end of control experiment, 14.4 +/- 1.7 vs. 14.7 +/- 1.4 l/min). In contrast, minute ventilation and peak genioglossus muscle activity during the recovery period of trial 2 was greater than baseline (minute ventilation: 28.4 +/- 1.7 vs. 19.6 +/- 1.0 l/min, P < 0.001; peak genioglossus activity: 1.6 +/- 0.3 vs. 1.0 fraction of baseline, P < 0.001). We conclude that exposure to episodic hypoxia is necessary to induce LTF of minute ventilation and peak genioglossus muscle activity and that LTF is only evident in awake humans in the presence of sustained elevated levels of carbon dioxide.

Atmospheric carbon dioxide enrichment reduces carbohydrate and nitrogen reserves in overwintering Picea mariana

Elevated levels of atmospheric carbon dioxide (CO2) can directly affect the cold hardening process in evergreens through their effect on the accumulation of carbon and nitrogen reserves. This study investigated the biochemical responses of black spruce [Picea mariana (Mill.) B.S.P.] seedlings to CO2 enrichment during growth, cold hardening and dehardening. Seedlings were grown under 350 (ambient) or 710 (elevated) ppm of CO2 for 12 months in eight mini-greenhouses. Photoperiod and temperature were gradually lowered in autumn to induce cold hardening, and the conditions were reversed in spring to promote dehardening. At regular intervals, cold tolerance was assessed and sugars, starch and amino acid concentrations were measured. The freezing tolerance differed between the two treatments only in early autumn, with seedlings growing under high CO2 being more tolerant. The northern ecotype was more cold tolerant with concomitant higher concentrations of sucrose, fructose, pinitol, glucose and total soluble sugars. The concentration of soluble sugars increased in needles and roots of black spruce along with cold hardening, and the concentrations of the cryoprotective sugars sucrose and raffinose were lower under elevated CO2. Amino acid concentrations were also lower under elevated than under ambient CO2. The lower level of reserve did not translate into a lower level of freezing tolerance.

Effect of nitric oxide, reduced oxygen and elevated carbon dioxide levels on the postharvest life of strawberries and lettuce

Strawberries and iceberg lettuce were fumigated with nitric oxide gas in air containing 2 and 5% oxygen, followed by storage at 5 and 10°C, respectively, in the same atmosphere. The postharvest life of strawberries and lettuce was significantly increased by fumigation with nitric oxide or storage in low oxygen, respectively. When both treatments were applied there was no additional increase in the postharvest life of lettuce arising from the NO and in that of strawberries from the low oxygen. However, fumigation with NO and storage in elevated carbon dioxide and reduced oxygen resulted in the greatest extension in postharvest life for both produce with the increase over air storage being about 250% for strawberries and 100% for lettuce.

SOLUBILITY OF CARBON DIOXIDE IN FAT AND MUSCLE TISSUE

ABSTRACT When meat is packed in atmospheres containing elevated carbon dioxide (CO 2 ) levels, substantial amounts of CO 2 are absorbed into the meat. Knowledge of CO 2 absorption into the meat is important to ensure optimal microbial protection of the meat and package design, preventing package collapse when the headspace is reduced because of CO 2 absorption. However, knowledge on fatty products is lacking. This study shows that there is a significant difference between the amounts of CO 2 that can be absorbed in meat with different fat content. The CO 2 absorption in fats has a rather complex temperature dependence that varies with fatty acid composition. The CO 2 absorption increases along with the increasing content of unsaturated fat, the effect growing larger as the temperature rises. In conclusion, the CO 2 solubility in meat samples varies with fat content, fatty acid composition as well as temperature. In this study CO 2 absorptions between 0.55 and 0.85 L CO 2 /kg meat were observed when varying these factors.

The Effect of Elevated Levels of Carbon Dioxide on Potato Crops

SUMMARY Experiments, which have investigated the effect of elevated concentrations of atmospheric CO2 on the physiology, growth and yield of potato (Solanum tuberosum L.), are reviewed. These studies were conducted in controlled environment chambers, in glasshouses, in open top field chambers as well as using free air carbon dioxide (FACE) exposure systems. In general, photosynthesis is stimulated by elevated CO2 initially although long-term exposure leads to acclimation. The stomata of potato leaves partially close in response to elevated CO2 and starch granules build up in the chloroplasts. Although above- and below-ground biomass production is stimulated, accelerated senescence limits growth towards the end of the growing season exposure to elevated CO2 stimulates tuber yield, the magnitude of which depends on agronomic practise, cultivar choice and growing conditions. The beneficial effects of elevated CO2 may be reduced by interaction with other components of climate change, such as drought stress. Modelling of the effects of climate change on potato yield has predicted an increase in yields in northern Europe with little change in central and southern Europe. It is suggested that further research is needed to understand the reasons for photosynthetic acclimation, field trials are also needed to understand and quantify the interaction between elevated CO2 and drought stress.

Early Jurassic schizosphaerellid crisis in Cantabria, Spain: Implications for calcification rates and phytoplankton evolution across the Toarcian oceanic anoxic event

The Toarcian oceanic anoxic event (∼183 Myr ago) represents a global perturbation marked by increasing organic carbon burial and a general decrease in calcium carbonate production likely triggered by elevated carbon dioxide levels in the atmosphere. Here we present quantitative analyses of calcareous nannofossil diversity and abundance from the Castillo de Pedroso section in Cantabria, northern Spain. We compare these data with geochemical data (C and O isotopes) obtained from biogenic and bulk carbonate records in order to highlight the response of calcareous phytoplankton to major climatic and paleoceanographic changes. The Pliensbachian/Toarcian boundary is characterized by an abrupt decrease in abundance of Schizosphaerella punctulata, the most important lithogenic contributor to (hemi) pelagic carbonates in the Early Jurassic. The early Toarcian nannofloral assemblages show an increase in abundance of Mitrolithus jansae and small‐sized r‐selected taxa and a progressive decrease in S. punctulata percentages. The deep dwellers M. jansae and S. punctulata experienced a major crisis slightly prior to the deposition of the Toarcian black shales that are characterized by high abundances of eutrophic taxa such as Lotharingius spp. and Biscutum spp. The return of S. punctulata associated with lower percentages of eutrophic taxa was observed just above the Toarcian black shales. The Toarcian episode reveals that high CO2 levels and increasing primary productivity probably triggered a shift in abundance from highly calcified nannoliths such as S. punctulata and M. jansae to small‐sized r‐selected coccoliths that overall record a biocalcification crisis at the onset and during the Toarcian episode.

Climate simulation of the latest Permian: Implications for mass extinction

Life at the Permian-Triassic boundary (ca. 251 Ma) underwent the largest disruption in Earth's history. Paleoclimatic data indicate that Earth was significantly warmer than present and that much of the ocean was anoxic or euxinic for an extended period of time. We present results from the first fully coupled comprehensive climate model using paleo- geography for this time period. The coupled climate system model simulates warm high- latitude surface air temperatures related to elevated carbon dioxide levels and a stagnate global ocean circulation in concert with paleodata indicating low oxygen levels at ocean depth. This is the first climate simulation that captures these observed features of this time period.

Performance and endocrine responses of group housed weaner pigs exposed to the air quality of a commercial environment

The growth performance and endocrine responses of male weaner pigs (3 to 8 weeks of age) was evaluated in two different environments (clean and dirty) and housing (single or groups of 10 pigs/pen) conditions. The dirty environment contained significantly elevated ammonia, carbon dioxide and dust levels compared with the clean environment. Pigs grew faster and consumed more feed in the clean environment and this was associated with reduced plasma cortisol concentrations compared with pigs in the dirty environment. Pigs housed in groups in the dirty environment had increased β-endorphin and decreased IGF-I concentrations compared to group housed pigs in the clean environment. Feed conversion efficiency did not differ due to environment or group housing. Plasma concentration of cortisol, β-endorphin, IGF-I and IGF-II did not differ between single and group housed pigs. Activity of the hypothalamic–pituitary–adrenal (HPA) axis was greater in response to environmental conditions than group housing, and this was associated with reduced growth in weaner pigs.

A Drosophila fearomone response proceeds through a single glomerulus

Relating a particular odorant to a specific behavior has proven difficult. A recent study in Nature uses clever technology to show that fruit flies possess a specialized olfactory pathway that allows them to sense, and react to, elevated levels of carbon dioxide.

Soil C Accumulation in a White Oak CO2-Enrichment Experiment via Enhanced Root Production

Abstract After four growing seasons, soil below white oak trees exposed to elevated atmospheric carbon dioxide levels (ambient + 300 ppm) had an average of 14% more soil carbon than soil below trees exposed to ambient levels of carbon dioxide. The soil carbon inventories in five soil cores collected from ambient chambers and six soil cores collected from elevated chambers at the Global Change Field Research Site, Oak Ridge, Tennessee, were measured. The authors conclude that the increase in soil carbon was due to an increase in belowground soil carbon input, because aboveground litter inputs were excluded by experimental design. These findings are consistent with the hypothesis that elevated carbon dioxide levels are increasing the amount of carbon stored in soil.

Antioxidant Levels Decrease in Primary Leaves of Barley during Growth at Ambient and Elevated Carbon Dioxide Levels

Previous studies revealed that the primary leaves of barley (Hordeum vulgare L. cv. Brant) that were grown in high‐light growth chambers in elevated CO2 (100 Pa) developed symptoms of senescence earlier than primary leaves of barley plants concurrently grown in ambient CO2 (36 Pa). The onset of senescence in these leaves was hypothesized to be associated with a decline in antioxidant capacity that resulted in higher levels of active oxygen species, which caused oxidative stress. In this new study, barley was grown from planting in high‐light growth chambers supplied with either ambient CO2 (36 Pa) or elevated CO2 (100 Pa). From 9 to 17 d after planting (DAP), primary leaf chlorophyll level as well as photosynthetic oxygen evolution per unit fresh mass decreased in plants in elevated CO2 to a greater extent than in plants in ambient CO2. Exposure of plants to elevated CO2 resulted in higher levels of primary leaf–free glucose, sucrose, and starch than in plants concurrently exposed to ambient CO2; this was most evident during 9–13 DAP. However, between 13 and 17 DAP, levels of foliar carbohydrates decreased to a greater extent in elevated CO2 than in ambient CO2, indicating that photosynthetic carbon metabolism was more repressed in this period in elevated CO2 treatments. In ambient CO2 over the period of 9–17 DAP, primary leaf total ascorbic acid (ASCtot) and total glutathione (GSHtot) levels decreased 38% and 51%, respectively. In elevated CO2 over this same time period, ASCtot and GSHtot decreased 45% and 63%, respectively. Since ASCtot and GSHtot are antioxidants involved in protecting the chloroplast from damage by active oxygen species such as hydrogen peroxide, we conclude that the decrease in ASCtot and GSHtot were factors in elevated CO2‐induced photosynthetic decline in barley primary leaves. Further, we interpret the greater decrease in ASCtot in elevated CO2 to be caused by a greater decrease in photosynthate partitioning and photosynthate availability, which supports ASC synthesis. We also suggest that decrease in glutathione in elevated CO2 may be related to an inhibition by elevated CO2 of photorespiratory carbon metabolism.

Soil CO2 efflux of two silver birch clones exposed to elevated CO2 and O3 levels during three growing seasons

AbstractIn the present open‐top chamber experiment, two silver birch clones (Betula pendula Roth, clone 4 and clone 80) were exposed to elevated levels of carbon dioxide (CO2) and ozone (O3), singly and in combination, and soil CO2 efflux was measured 14 times during three consecutive growing seasons (1999–2001). In the beginning of the experiment, all experimental trees were 7 years old and during the experiment the trees were growing in sandy field soil and fertilized regularly. In general, elevated O3 caused soil CO2 efflux stimulation during most measurement days and this stimulation enhanced towards the end of the experiment. The overall soil respiration response to CO2 was dependent on the genotype, as the soil CO2 efflux below clone 80 trees was enhanced and below clone 4 trees was decreased under elevated CO2 treatments. Like the O3 impact, this clonal difference in soil respiration response to CO2 increased as the experiment progressed. Although the O3 impact did not differ significantly between clones, a significant time × clone × CO2× O3 interaction revealed that the O3‐induced stimulation of soil respiration was counteracted by elevated CO2 in clone 4 on most measurement days, whereas in clone 80, the effect of elevated CO2 and O3 in combination was almost constantly additive during the 3‐year experiment. Altogether, the root or above‐ground biomass results were only partly parallel with the observed soil CO2 efflux responses. In conclusion, our data show that O3 impacts may appear first in the below‐ground processes and that relatively long‐term O3 exposure had a cumulative effect on soil CO2 efflux. Although the soil respiration response to elevated CO2 depended on the tree genotype as a result of which the O3 stress response might vary considerably within a single tree species under elevated CO2, the present experiment nonetheless indicates that O3 stress is a significant factor affecting the carbon cycling in northern forest ecosystems.

Nitrate assimilation in plant shoots depends on photorespiration.

Photorespiration, a process that diminishes net photosynthesis by approximately 25% in most plants, has been viewed as the unfavorable consequence of plants having evolved when the atmosphere contained much higher levels of carbon dioxide than it does today. Here we used two independent methods to show that exposure of Arabidopsis and wheat shoots to conditions that inhibited photorespiration also strongly inhibited nitrate assimilation. Thus, nitrate assimilation in both dicotyledonous and monocotyledonous species depends on photorespiration. This previously undescribed role for photorespiration (i) explains several responses of plants to rising carbon dioxide concentrations, including the inability of many plants to sustain rapid growth under elevated levels of carbon dioxide; and (ii) raises concerns about genetic manipulations to diminish photorespiration in crops.

Export of dissolved organic carbon from peatlands under elevated carbon dioxide levels.

Peatlands represent a vast store of global carbon. Observations of rapidly rising dissolved organic carbon concentrations in rivers draining peatlands have created concerns that those stores are beginning to destabilize. Three main factors have been put forward as potential causal mechanisms, but it appears that two alternatives--warming and increased river discharge--cannot offer satisfactory explanations. Here we show that the third proposed mechanism, namely shifting trends in the proportion of annual rainfall arriving in summer, is similarly unable to account for the trend. Instead we infer that a previously unrecognized mechanism--carbon dioxide mediated stimulation of primary productivity--is responsible. Under elevated carbon dioxide levels, the proportion of dissolved organic carbon derived from recently assimilated carbon dioxide was ten times higher than that of the control cases. Concentrations of dissolved organic carbon appear far more sensitive to environmental drivers that affect net primary productivity than those affecting decomposition alone.

High levels of atmospheric carbon dioxide necessary for the termination of global glaciation.

The possibility that the Earth suffered episodes of global glaciation as recently as the Neoproterozoic period, between about 900 and 543 million years ago, has been widely discussed. Termination of such 'hard snowball Earth' climate states has been proposed to proceed from accumulation of carbon dioxide in the atmosphere. Many salient aspects of the snowball scenario depend critically on the threshold of atmospheric carbon dioxide concentrations needed to trigger deglaciation. Here I present simulations with a general circulation model, using elevated carbon dioxide levels to estimate this deglaciation threshold. The model simulates several phenomena that are expected to be significant in a 'snowball Earth' scenario, but which have not been considered in previous studies with less sophisticated models, such as a reduction of vertical temperature gradients in winter, a reduction in summer tropopause height, the effect of snow cover and a reduction in cloud greenhouse effects. In my simulations, the system remains far short of deglaciation even at atmospheric carbon dioxide concentrations of 550 times the present levels (0.2 bar of CO2). I find that at much higher carbon dioxide levels, deglaciation is unlikely unless unknown feedback cycles that are not captured in the model come into effect.

Soil carbon CO2fertilization factor: The measure of an ecosystem's capacity to increase soil carbon storage in response to elevated CO2levels

This research introduces the concept of a “CO2fertilization factor for soil carbon” (σCF). The σCFis a measure of an ecosystem's capacity to increase soil carbon storage in response to elevated carbon dioxide levels. This paper describes the mathematical derivation of σCFand illustrates how σCFcan be determined experimentally, using data from a white oak study. I have developed this concept to compare the results of carbon dioxide enrichment experiments having different soil carbon turnover times, different levels of CO2enrichment, and different lengths of exposure to elevated carbon dioxide levels. The σCFcan also be used to estimate increases in soil carbon uptake due to observed contemporary increases in atmospheric carbon dioxide levels. Although the approach used here may seem oversimplified, I present it as a simple way of estimating the extent to which elevated levels of CO2could increase soil carbon storage. I have determined a σCFof 1.18 for a white oak ecosystem using soil carbon and radiocarbon measurements. If major terrestrial ecosystems have similar σCFvalues, CO2fertilization may be transferring enough carbon from the atmosphere to soil to balance the global carbon budget.

Ocean science. Global warming and the next ice age.

There is a popular notion in the media that human-induced global warming will result in the onset of a new ice age. In their Perspective, Weaver and Hillaire-Marcel refute this view, explaining that global warming is unlikely to dramatically alter the North Atlantic ocean circulation. They also emphasize that elevated levels of atmospheric carbon dioxide lead to summer temperatures that do not allow glacier formation and growth.

Commentary

HIGHLIGHTED TOPICSOxygen Sensing in Health and DiseaseCommentaryGary C. SieckGary C. SieckPublished Online:01 Mar 2004https://doi.org/10.1152/japplphysiol.01327.2003MoreSectionsPDF (9 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations Understanding the critical role of oxygen sensing in the physiological states of health and disease is important to our understanding of disease processes. This issue of the Journal concludes the Highlighted Topics series on “Oxygen Sensing in Health and Disease” and includes two articles that warrant comment, as they represent significant contributions to our general understanding of the mechanisms underlying oxygen sensing.In the first featured article, “Peripheral chemoreflex responsiveness is increased at elevated levels of carbon dioxide after episodic hypoxia in awake humans,” Dr. J. Mateika and colleagues (2) discuss the influence of episodic hypoxia on ventilatory response. After exposing awake humans to episodic hypoxia, these investigators evaluated the acute ventilatory response to hypoxia in the presence of progressively increasing levels of carbon dioxide. Their study showed that the ventilatory response to hypercapnia/hypoxia, but not hypocapnia/hypoxia, was increased after exposure to episodic hypoxia. This response was evident even though elevated ventilation levels (i.e., long-term facilitation) were not observed immediately after exposure to episodic hypoxia. These findings may have important implications for the control of breathing in individuals who suffer from sleep apnea. Disproportionate increases in the ventilatory response to hypercapnia/hypoxia after exposure to episodic hypoxia could subsequently drive carbon dioxide levels below the apneic threshold. Consequently, a reduction in central respiratory drive to chest wall and upper airway muscles might occur, and activation of this phenomenon might thus promote apnea during sleep.The second featured article, “Facilitation of dopamine and acetylcholine release by intermittent hypoxia in PC12 cells: involvement of calcium and reactive oxygen species” by Dr. D.-K. Kim and colleagues (1), reports, for the first time, the effect of intermittent hypoxia on transmitter release during hypoxia and examines the underlying cellular mechanisms that are activated and lead to altered transmitter release. These investigators simultaneously monitored the release of dopamine and acetylcholine from both naive and intermittent hypoxia-conditioned PC12 cells by using two dedicated and highly sensitive HPLC systems combined with an electrochemical detection method. From these measurements, the authors made an intriguing observation, wherein hypoxia selectively facilitates the release of dopamine, but not acetylcholine, in naive cells. By contrast, hypoxia increased the release of both dopamine and acetylcholine in intermittent hypoxia-conditioned cells. Notably, the mechanisms that are activated by intermittent hypoxia and coupled to intermittent hypoxia-evoked transmitter release seem to be different from those activated during acute hypoxia. In naive cells, the entry of extracellular calcium appears to be critical for hypoxia-evoked dopamine release. On the contrary, intermittent hypoxia-induced transmitter release during hypoxia depends on the mobilization of calcium from intracellular stores through activation of inositol 1,4,5-trisphosphate receptors, as well as generation of reactive oxygen species. References 1 Kim DK, Natarajan N, Prabhakar NR, and Kumar GK. Facilitation of dopamine and acetylcholine release by intermittent hypoxia in PC12 cells: involvement of calcium and reactive oxygen species. J Appl Physiol 96: 1206-1215, 2004.Link | ISI | Google Scholar2 Mateika JH, Mendello C, Obeid D, and Badr MS. Peripheral chemoreflex responsiveness is increased at elevated levels of carbon dioxide after episodic hypoxia in awake humans. J Appl Physiol 96: 1197-1205, 2004.Link | ISI | Google Scholar Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 96Issue 3March 2004Pages 1196-1196 Copyright & PermissionsCopyright © 2004 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.01327.2003History Published online 1 March 2004 Published in print 1 March 2004 Metrics

Mycelial production, spread and root colonisation by the ectomycorrhizal fungi Hebeloma crustuliniforme and Paxillus involutus under elevated atmospheric CO2.

Effects of elevated atmospheric carbon dioxide (CO2) levels on the production and spread of ectomycorrhizal fungal mycelium from colonised Scots pine roots were investigated. Pinus sylvestris (L.) Karst. seedlings inoculated with either Hebeloma crustuliniforme (Bull:Fr.) Quel. or Paxillus involutus (Fr.) Fr. were grown at either ambient (350 ppm) or elevated (700 ppm) levels of CO2. Mycelial production was measured after 6 weeks in pots, and mycelial spread from inoculated seedlings was studied after 4 months growth in perlite in shallow boxes containing uncolonised bait seedlings. Plant and fungal biomass were analysed, as well as carbon and nitrogen content of seedling shoots. Mycelial biomass production by H. crustuliniforme was significantly greater under elevated CO2 (up to a 3-fold increase was observed). Significantly lower concentrations and total amounts of N were found in plants exposed to elevated CO2.