Increasing CO2 Levels Research Articles

Effect of Elevated Air Temperature and Carbon Dioxide Levels on Dry Season Irrigated Rice Productivity in Bangladesh

Agricultural productivity is affected by air temperature and CO2 concentration. The relationships among grain yields of dry season irrigated rice (Boro) varieties (BRRI dhan28, BRRI dhan29 and BRRI dhan58) with increased temperatures and CO2 concentrations were investigated for futuristic crop management in six regions of Bangladesh using CERES-Rice model (DSSATv4.6). Maximum and minimum temperature increase rates considered were 0°C, +1°C, +2°C, +3°C and +4°C and CO2 concentrations were ambient (380), 421, 538, 670 and 936 ppm. At ambient temperature and CO2 concentration, attainable grain yields varied from 6506 to 8076 kg·ha-1 depending on rice varieties. In general, grain yield reduction would be the highest (13% - 23%) if temperature rises by 4°C and growth duration reduction would be 23 - 33 days. Grain yield reductions with 1°C, 2°C and 3°C rise in temperature are likely to be compensated by increased CO2 levels of 421, 538 and 670 ppm, respectively. In future, the highest reduction in grain yield and growth duration would be in cooler region and the least in warmer saline region of the country. Appropriate adaptive techniques like shifting in planting dates, water and nitrogen fertilizer management would be needed to overcome climate change impacts on rice production.

Effects of -12° head-down tilt with and without elevated levels of CO2 on cognitive performance: the SPACECOT study.

Microgravity and elevated levels of CO2 are two common environmental stressors in spaceflight that may affect cognitive performance of astronauts. In this randomized, double-blind, crossover trial (SPACECOT), 6 healthy males (mean ± SD age: 41 ± 5 yr) were exposed to 0.04% (ambient air) and 0.5% CO2 concentrations during 26.5-h periods of -12° head-down tilt (HDT) bed rest with a 1-wk washout period between exposures. Subjects performed the 10 tests of the Cognition Test Battery before and on average 0.1, 5.2, and 21.0 h after the initiation of HDT bed rest. HDT in ambient air induced a change in response strategy, with increased response speed (+0.19 SD; P = 0.0254) at the expense of accuracy (-0.19 SD; P = 0.2867), resulting in comparable cognitive efficiency. The observed effects were small and statistically significant for cognitive speed only. However, even small declines in accuracy can potentially cause errors during mission-critical tasks in spaceflight. Unexpectedly, exposure to 0.5% CO2 reversed the response strategy changes observed under HDT in ambient air. This was possibly related to hypercapnia-induced cerebrovascular reactivity that favors cortical regions in general and the frontal cortex in particular, or to the CNS arousing properties of mildly to moderately increased CO2 levels. There were no statistically significant time-in-CO2 effects for any cognitive outcome. The small sample size and the small effect sizes are major limitations of this study and its findings. The results should not be generalized beyond the group of investigated subjects until they are confirmed by adequately powered follow-up studies. NEW & NOTEWORTHY Simulating microgravity with exposure to 21 h of -12° head-down tilt bed rest caused a change in response strategy on a range of cognitive tests, with a statistically significant increase in response speed at the expense of accuracy. Cognitive efficiency was not affected. The observed speed-accuracy tradeoff was small but may nevertheless be important for mission-critical tasks in spaceflight. Importantly, the change in response strategy was reversed by increasing CO2 concentrations to 0.5%.

Projected impact of future climate on water-stress patterns across the Australian wheatbelt.

Drought frequently limits Australian wheat production, and the expected future increase in temperatures and rainfall variability will further challenge productivity. A modelling approach captured plant×environment×management interactions to simulate water-stress patterns experienced by wheat crops at representative locations across the Australian wheatbelt for 33 climate model projections, considering the 'business as usual' emission scenario RCP8.5. The results indicate that projections of future water-stress patterns are region specific. Significant variations in projected impacts were found across climate models, providing local ranges of uncertainty to consider in planning efforts. Most climate models projected an increase in the frequency of severe water-stress conditions in the Western area, the largest producing region, and fewer severe water stresses in other regions. Where found, reductions in water-stress conditions were largely due to shorter crop cycles (a result of warmer temperatures), increased water use efficiency (resulting from increased CO2 levels), and, in some cases, increased local rainfall. Overall, simulations indicate that all areas of the Australian wheatbelt will continue to experience severe water-stress conditions (43.9, 42.6, and 40.2% for 2030, 2050, and 2070 compared with 42.8% for 1990). Given projected frequencies of severe water stress and warmer conditions, efforts towards maintaining or improving yields are essential.

Modeling the respiration rate of Golden papayas stored under different atmosphere conditions at room temperature

The present study aimed to measure the respiration rate of papayas (cv. Golden) stored under controlled atmosphere at room temperature, with decreasing O2 and increasing CO2 levels, in order to identify mathematical models capable of predicting respiration rate throughout storage. A model was proposed based on the Michaelis–Menten equation with uncompetitive inhibition and kinetic parameters that change during storage time. A second-order nonlinear regression model was used as reference for the mathematical approach. Nine experiments with three replicates were conducted under different controlled atmospheres to generate respiration data. A closed system method was used to measure the respiration rate at 2d intervals over 13d of storage at ambient temperature (23°C). Peel color measurements indicated total ripening of fruit stored in high O2 atmospheres, whereas ripening was minimal in atmospheres containing low O2 and high CO2 levels. The respiration rate remained at the lowest value, but gradually increased during storage at the lowest O2 level associated with the highest CO2 concentration. The nonlinear regression model obtained the lowest AICc value with VarPow variance, indicating a better fit than the Michaelis–Menten model. However, the latter, whose kinetic parameters change according to a polynomial second-order equation (MMQ), displayed a better fit than the nonlinear regression model evaluated by homoscedastic variance. Additionally, MMQ was more sensitive than nonlinear regression in detecting the real change in respiration rate in a biological system as a function of different gas compositions during storage.

Responses of photosynthesis and CO2 concentrating mechanisms of marine crop Pyropia haitanensis thalli to large pH variations at different time scales

Wild and cultivated populations of Pyropia haitanensis have frequently experienced extremely low pH conditions in the last few decades. This could potentially threaten the development of the aquaculture of this economically important marine crop. To gain a broader perspective, we investigated the short- (4h) and long- (7days) term responses of CO2 concentrating mechanisms (CCMs) of P. haitanensis thalli to large variations in pH. Our study found that a pH of 4 and 5, which mimicked the decreased pH caused by acid rain, resulted in decreased photosynthesis and respiration while leading to the death of P. haitanensis thalli. Thus, acid rain would result in a decline in P. haitanensis production and threaten wild seaweed sources. However, a pH of 6 and 7 enhanced the growth of P. haitanensis thalli by >30%, mainly because increased CO2 levels favored photosynthesis, while the algae need to effectively maintain intracellular pH homeostasis to support rapid growth rates. The contributions of extracellular carbonic anhydrases (eCAs) to photosynthetic rates remained at >77% when pH≥7, regardless of the treatment time. However, at pH6, the contribution of eCAs to photosynthesis increased from 25% for a short-term treatment to 66% for a long-term treatment. Thus, except for work on carbon assimilation, this study proposes that the CCMs component involved in the movement and metabolism of inorganic carbon may play an important role in pH homeostasis. In addition, pH9 also led to the death of P. haitanensis thalli, which is consistent with observations of the natural distribution of this algae and hints that P. haitanensis thalli prefer to use inorganic carbon via eCAs when pH≥7. The present study suggested that the actual variation in pH experienced by marine organisms needs to be considered in the experimental design of related studies.

Effect of carbon dioxide (CO2) and oxygen (O2) levels on quality of 'Palmer' mangoes under controlled atmosphere storage.

With the objective to evaluate the modifications in the fruit quality, 'Palmer' mangoes were stored at 12.8°C for 30days in controlled atmosphere storage that contained a low level of oxygen (5kPa) which was associated with increasing levels of carbon dioxide CO2 (0, 1, 5, 10, 15 and 20kPa CO2). Controlled atmosphere storage did not effect mango respiration. However, transfer mangoes, that were previously stored at high levels of CO2 (5kPa O2+15kPa CO2 and 5kPa O2+20kPa CO2) to ambient temperature presented higher respiratory rates. No significant effects of increasing CO2 levels on color (L*, chromaticity, and hue angle), firmness, physical-chemical parameter and carbohydrate metabolism (total and reducing sugars, soluble pectin) were observed. After transfer to ambient temperature the mangoes ripened normally without any signs of CO2 injury. Therefore, the increment levels of CO2 neither improved the quality of the 'Palmer' mangoes nor presented a synergistic effect with low-oxygen when compared to 5kPa O2-control.

Effects of increased CO2 and temperature on the growth and photosynthesis in the marine macroalga Gracilaria lemaneiformis from the coastal waters of South China

The marine red macroalga Gracilaria lemaneiformis (Gracilariales, Rhodophyta) is one of the most important species for seaweed cultivation along the coastal waters of South China. In this study, G. lemaneiformis was incubated under present-day (390 ppm) or predicted-year CO2 levels (700 ppm), and under normal (20 °C) versus elevated temperatures (24 °C), to investigate possible effects of climate change conditions on the growth and photosynthesis. The chlorophyll a (Chl a), carotenoid (Car), and phycobiliprotein (PB) contents responded significantly to increased temperature under normal CO2 and high CO2 concentrations. However, CO2 enrichment in the culture had no significant impact on Chl a and Car but decreased the PB contents in G. lemaneiformis. The growth rates of G. lemaneiformis were significantly improved by increasing temperature, especially under concurrent increasing CO2 levels. Additionally, short-term exposure to high temperature stimulated the irradiance-saturated maximum photosynthetic rate (P max), and this stimulation was preserved with exposure to the high temperature in long-term incubations, with such stimulation being much more pronounced under normal CO2 concentrations than high CO2 concentrations. Results suggest that increased temperature exerted more pronounced effects on the growth and photosynthesis of G. lemaneiformis than increased CO2 concentrations did. We proposed that the sea cultivation of G. lemaneiformis would benefit from the ongoing climate change (increasing atmospheric CO2 concentrations and sea surface temperatures) through enhanced growth and carbon sequestration.

Reaction of Bentgrass Cultivars to a Resistance Activator and Elevated CO2 Levels When Challenged with Microdochium nivale, the Cause of Microdochium Patch

Climate change prediction models forecast increased CO2 levels and temperature changes. Microdochium nivale is a common pathogen of turfgrasses in temperate climates, and these changes may increase Microdochium patch disease severity. This research involved experiments on cultivars of Agrostis spp. and Poa annua inoculated with M. nivale and incubated under two CO2 concentrations. The efficacy of a resistance activator, Civitas + Harmonizer, was tested on eight cultivars that were grown under 400 or 800 ppm of CO2 during a 15°C/10°C (day/night), 16‐h photoperiod. The grasses were treated with water or Civitas + Harmonizer and inoculated 1 wk later with M. nivale. Disease severity was lower at 800 ppm than at 400 ppm of CO2, and the application of Civitas + Harmonizer decreased disease symptoms. This research will be useful for recommendations on turfgrass cultivars for northern temperate zone golf courses and on sustainable management practices to face the challenges of climate change.

The effect of carbon dioxide on growth and energy metabolism in pikeperch (Sander lucioperca)

Pikeperch (Sander lucioperca) is a popular fish for human consumption and decreasing wild catches increase the demand for aquaculture production. Limited knowledge of the species' requirements under intense recirculating aquaculture system (RAS) culture conditions has motivated this study to focus on the effect of elevated carbon dioxide (CO2) levels on pikeperch metabolism. The trial was conducted in a recirculating aquaculture respirometer system with pikeperch (average body weight 251.9g) and three hypercapnia regimes over 58 feeding days. Food grade CO2 gas was gradually added to the medium (15mgL−1) and high (30mgL−1) treatments while no gas was added to the low treatment (hence 4mgL−1). Fish were fed daily for 10min with a commercial diet (ALLER Metabolica). O2, T, pH, CO2 were measured individually for each tank and logged every 2h to calculate oxygen consumption rates of each treatment. Total Ammonia-Nitrogen was measured monthly for individual tanks and used to calculate TAN excretion. Results showed a linear decrease of 6% in final body weight with increasing CO2 levels between the low and the high CO2 treatment. Feed intake was linearly increased after four weeks of the experiment from 0.97±0.07% in the low CO2 treatment to 0.86±0.03% in the high CO2 treatment but the effect faded after eight weeks, indicating a habituation to the hypercapnia conditions. High levels of CO2 were associated with reductions in haematocrit and metabolic oxygen consumption. The results suggest that adult pikeperch can survive carbon dioxide concentrations of up to 30mgL−1 when other water quality parameters are in acceptable levels but will be affected in metabolism already at moderate CO2 levels of 15mgL−1.

The impact of door opening on CO2 levels: A case study from the Balcarka Cave (Moravian Karst, Czech Republic)

The impact of door opening on cave carbon dioxide (CO2) levels was studied in the Entrance Chamber and the Gallery Chamber of the Balcarka Cave (Moravian Karst, Czech Republic). The effect of door opening differed with cave ventilation modes. Under upward airflow mode, the cave door opening led to the increase of output advective CO2 fluxes from the cave and to the decrease of CO2 levels. This effect was evident especially in the Entrance Chamber near the cave entrance and then suppressed in the Gallery Chamber situated deeper in the cave. Under the downward airflow mode, the cave door opening changed airflow paths and main CO2 sources/fluxes. This resulted in the increase of CO2 level in the Entrance Chamber while the levels in the Gallery Chamber decrease. Modeling indicates that the increase could be result of input advective CO2 fluxes from epikarst (up to 5.9 × 10-2 mol s-1). To reduce the impact on cave microclimate, a careful control of the visiting regime without overlapping of individual doors’ openings is recommended.

Impact of heat stress and hypercapnia on physiological, hematological, and behavioral profile of Tharparkar and Karan Fries heifers.

Aim:The present investigation was undertaken to study the impact of heat stress and hypercapnia on physiological, hematological, and behavioral profile of Tharparkar and Karan Fries (KF) heifers.Materials and Methods:The animals of both the breeds of Tharparkar and KF were exposed at different temperatures and CO2 levels. Exposure conditions of 25°C, 400 ppm CO2 level, and 60% relative humidity (RH) were taken as a control condition. The exposure conditions 40°C with two levels of CO2 500 ppm and 600 ppm with RH 55±5% and exposure conditions 42°C with two levels of CO2 500 ppm and 600 ppm with RH 55±5% were taken as treatments. The exposure period in each condition was 4 h daily for 5 consecutive days.Results:Physiological responses (respiration rate [RR], pulse rate [PR], and rectal temperature [RT]) were significantly (p<0.01) higher and different during all exposure conditions compared to control condition in both the breeds of cattle. KF heifers had higher RR, PR, and RT than Tharparkar heifers. Hematological parameters, namely, red blood cell, hemoglobin, and packed cell volume were significantly higher and different during all exposure condition than control in both the breeds, whereas no significant changes were observed in total leukocyte count and differential leukocyte count. Blood pH increased with increase in temperature and CO2 levels and was significantly higher than control conditions. PCO2 and base excess were significantly (p<0.05) lower, and PO2 was higher during different exposure conditions than control in both breeds. Restlessness and excitement signs were observed in all the exposure conditions as compared to control condition in both the breeds.Conclusion:Changes in physiological responses, behavioral pattern, and hematological parameters reflect the current functional status of the body system, and it can be used as an index for assessing the adaptation capacity of cattle to predict changes occurring in climate variables due to increasing CO2 levels and environmental temperature.

Carbon and nitrogen allocation strategy in Posidonia oceanica is altered by seawater acidification

Rising atmospheric CO2 causes ocean acidification that represents one of the major ecological threats for marine biota. We tested the hypothesis that long-term exposure to increased CO2 level and acidification in a natural CO2 vent system alters carbon (C) and nitrogen (N) metabolism in Posidonia oceanica L. (Delile), affecting its resilience, or capability to restore the physiological homeostasis, and the nutritional quality of organic matter available for grazers. Seawater acidification decreased the C to N ratio in P. oceanica tissues and increased grazing rate, shoot density, leaf proteins and asparagine accumulation in rhizomes, while the maximum photochemical efficiency of photosystem II was unaffected. The 13C-dilution in both structural and non-structural C metabolites in the acidified site indicated quali-quantitative changes of C source and/or increased isotopic fractionation during C uptake and carboxylation associated with the higher CO2 level. The decreased C:N ratio in the acidified site suggests an increased N availability, leading to a greater storage of 15N–enriched compounds in rhizomes. The amount of the more dynamic C storage form, sucrose, decreased in rhizomes of the acidified site in response to the enhanced energy demand due to higher shoot recruitment and N compound synthesis, without affecting starch reserves. The ability to modulate the balance between stable and dynamic C reserves could represent a key ecophysiological mechanism for P. oceanica resilience under environmental perturbation. Finally, alteration in C and N dynamics promoted a positive contribution of this seagrass to the local food web.

Increased CO2 availability promotes growth of a tropical coastal diatom assemblage (Goa coast, Arabian Sea, India)

Responses of tropical coastal phytoplankton assemblages to increasing CO2 levels are poorly known. The Arabian Sea (AS), the western part of the north Indian Ocean, is an upwelling-induced, highly productive region, but there are virtually no studies from this area documenting the responses of the natural phytoplankton communities to increasing CO2 concentrations. CO2-induced growth responses of a diatom-dominated phytoplankton community from the coastal water of Arabian Sea (Dona Paula, Goa) were investigated in a set of three experiments (one long-term and two short-term) in nutrient-replete, semi-continuous batches. Significant increases in photosynthetic rate, growth rate, carbohydrate content and carbohydrate to protein ratio were observed in the cells grown under elevated CO2. Trace amounts of zinc (Zn) addition to low CO2 grown cells also resulted in a marked increase in growth rate, carbohydrate content and carbohydrate to protein ratio. Zn addition at elevated CO2 only induced increased cell division. These results show that the experimental diatom-dominated phytoplankton community, (1) responded positively to CO2 enrichment, (2) probably possesses a carbon-concentration mechanism (CCM) and (3) uses a Zn-carbonic anhydrase in carbon acquisition. It is likely that the experimental diatom communities downregulated CCM activity with increased CO2 but grew faster. Future increases in coastal water CO2 concentrations may significantly impact phytoplankton primary production and biochemical composition and thus have large biogeochemical consequences.

Phytoplankton community responses to iron and CO2 enrichment in different biogeochemical regions of the Southern Ocean

The ongoing rise in atmospheric CO2 concentration is causing rapid increases in seawater pCO2 levels. However, little is known about the potential impacts of elevated CO2 availability on the phytoplankton assemblages in the Southern Ocean’s oceanic regions. Therefore, we conducted four incubation experiments using surface seawater collected from the subantarctic zone (SAZ) and the subpolar zone (SPZ) in the Australian sector of the Southern Ocean during the austral summer of 2011–2012. For incubations, FeCl3 solutions were added to reduce iron (Fe) limitation for phytoplankton growth. Ambient and high (~750 µatm) CO2 treatments were then prepared with and without addition of CO2-saturated seawater, respectively. Non-Fe-added (control) treatments were also prepared to assess the effects of Fe enrichment (overall, control, Fe-added, and Fe-and-CO2-added treatments). In the initial samples, the dominant phytoplankton taxa shifted with latitude from haptophytes to diatoms, likely reflecting silicate availability in the water. Under Fe-enriched conditions, increased CO2 level significantly reduced the accumulation of biomarker pigments in haptophytes in the SAZ and AZ, whereas a significant decrease in diatom markers was only detected in the SAZ. The CO2-related changes in phytoplankton community composition were greater in the SAZ, most likely due to the decrease in coccolithophore biomass. Our results suggest that an increase in CO2, if it coincides with Fe enrichment, could differentially affect the phytoplankton community composition in different geographical regions of the Southern Ocean, depending on the locally dominant taxa and environmental conditions.

Atmospheric CO2 Alters Resistance of Arabidopsis to Pseudomonas syringae by Affecting Abscisic Acid Accumulation and Stomatal Responsiveness to Coronatine.

Atmospheric CO2 influences plant growth and stomatal aperture. Effects of high or low CO2 levels on plant disease resistance are less well understood. Here, resistance of Arabidopsis thaliana against the foliar pathogen Pseudomonas syringae pv. tomato DC3000 (Pst) was investigated at three different CO2 levels: high (800 ppm), ambient (450 ppm), and low (150 ppm). Under all conditions tested, infection by Pst resulted in stomatal closure within 1 h after inoculation. However, subsequent stomatal reopening at 4 h, triggered by the virulence factor coronatine (COR), occurred only at ambient and high CO2, but not at low CO2. Moreover, infection by Pst was reduced at low CO2 to the same extent as infection by mutant Pst cor-. Under all CO2 conditions, the ABA mutants aba2-1 and abi1-1 were as resistant to Pst as wild-type plants under low CO2, which contained less ABA. Moreover, stomatal reopening mediated by COR was dependent on ABA. Our results suggest that reduced ABA levels at low CO2 contribute to the observed enhanced resistance to Pst by deregulation of virulence responses. This implies that enhanced ABA levels at increasing CO2 levels may have a role in weakening plant defense.

Simultaneously reducing CO2 and particulate exposures via fractional recirculation of vehicle cabin air

Prior studies demonstrate that air recirculation can reduce exposure to nanoparticles in vehicle cabins. However when people occupy confined spaces, air recirculation can lead to carbon dioxide (CO2) accumulation which can potentially lead to deleterious effects on cognitive function. This study proposes a fractional air recirculation system for reducing nanoparticle concentration while simultaneously suppressing CO2 levels in the cabin. Several recirculation scenarios were tested using a custom-programmed HVAC (heat, ventilation, air conditioning) unit that varied the recirculation door angle in the test vehicle. Operating the recirculation system with a standard cabin filter reduced particle concentrations to 1000 particles/cm3, although CO2 levels rose to 3000 ppm. When as little as 25% fresh air was introduced (75% recirculation), CO2 levels dropped to 1000 ppm, while particle concentrations remained below 5000 particles/cm3. We found that nanoparticles were removed selectively during recirculation and demonstrated the trade-off between cabin CO2 concentration and cabin particle concentration using fractional air recirculation. Data showed significant increases in CO2 levels during 100% recirculation. For various fan speeds, recirculation fractions of 50–75% maintained lower CO2 levels in the cabin, while still reducing particulate levels. We recommend fractional recirculation as a simple method to reduce occupants’ exposures to particulate matter and CO2 in vehicles. A design with several fractional recirculation settings could allow air exchange adequate for reducing both particulate and CO2 exposures. Developing this technology could lead to reductions in airborne nanoparticle exposure, while also mitigating safety risks from CO2 accumulation.

Ecophysiological responses to elevated CO2 and temperature in Cystoseira tamariscifolia (Phaeophyceae)

Ocean acidification increases the amount of dissolved inorganic carbon (DIC) available in seawater which can benefit photosynthesis in those algae that are currently carbon limited, leading to shifts in the structure and function of seaweed communities. Recent studies have shown that ocean acidification-driven shifts in seaweed community dominance will depend on interactions with other factors such as light and nutrients. The study of interactive effects of ocean acidification and warming can help elucidate the likely effects of climate change on marine primary producers. In this study, we investigated the ecophysiological responses of Cystoseira tamariscifolia (Hudson) Papenfuss. This large brown macroalga plays an important structural role in coastal Mediterranean communities. Algae were collected from both oligotrophic and ultraoligotrophic waters in southern Spain. They were then incubated in tanks at ambient (ca. 400–500 ppm) and high CO2 (ca. 1200–1300 ppm), and at 20 °C (ambient temperature) and 24 °C (ambient temperature +4 °C). Increased CO2 levels benefited the algae from both origins. Biomass increased in elevated CO2 treatments and was similar in algae from both origins. The maximal electron transport rate (ETRmax), used to estimate photosynthetic capacity, increased in ambient temperature/high CO2 treatments. The highest polyphenol content and antioxidant activity were observed in ambient temperature/high CO2 conditions in algae from both origins; phenol content was higher in algae from ultraoligotrophic waters (1.5–3.0%) than that from oligotrophic waters (1.0–2.2%). Our study shows that ongoing ocean acidification can be expected to increase algal productivity (ETRmax), boost antioxidant activity (EC 50 ), and increase production of photoprotective phenols. Cystoseira tamariscifolia collected from oligotrophic and ultraoligotrophic waters were able to benefit from increases in DIC at ambient temperatures. Warming, not acidification, may be the key stressor for this habitat as CO2 levels continue to rise.

Elevated field atmospheric CO2 concentrations affect the characteristics of winter wheat (cv. Bologna) grains

The aim of this study was to investigate the impact of elevated concentration of carbon dioxide (CO2), as expected over coming decades, on yield and quality of winter bread wheat (Triticum aestivum L.). Plants (cv. Bologna) were grown by using the free-air CO2 enrichment (FACE) system at Fiorenzuola d’Arda under ambient (control) and elevated (570 ppm, e[CO2]) CO2 concentrations for two growing seasons. We addressed whether there would be a response of wheat grains to elevated CO2 concentration in terms of the contents of nitrogen (N), micro- and macronutrients, proteins and free amino acids. Under e[CO2], total wheat biomass and grain yield increased in both years of the study. Grain N percentage was reduced under e[CO2], but grain N yield (kg ha–1) was increased. Among macro- and micronutrients, a decrease in zinc concentration was observed. The proteome pattern was significantly different in grains grown at the two different CO2 levels, but the observed changes were highly dependent on interactions with prevailing environmental conditions. Finally, a negative trend was observed in the early germination rates of seeds from plants grown under e[CO2] compared with the controls. The results suggest that the expected increase in CO2 levels and their interactive effects with environmental variables may influence agronomic performance by increasing yield and negatively affecting quality.

Responses of the diatom Asterionellopsis glacialis to increasing sea water CO2 concentrations and turbulence

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 589:33-44 (2018) - DOI: https://doi.org/10.3354/meps12450 Responses of the diatom Asterionellopsis glacialis to increasing sea water CO2 concentrations and turbulence Francesca Gallo1,*, Kai G. Schulz2, Eduardo B. Azevedo1, João Madruga1, Joana Barcelos e Ramos1 1Institute for Agricultural and Environmental Research and Technology of the Azores, University of Azores, Rua do Capitão d’Ávila, Pico da Urze 970-0042 Angra do Heroísmo, Açores, Portugal 2Centre for Coastal Biogeochemistry, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia *Corresponding author: effegal@gmail.com ABSTRACT: Greenhouse gas emissions, such as carbon dioxide (CO2), lead to enhanced atmospheric and surface ocean temperatures. At the same time, CO2 equilibrates between the atmosphere and the surface ocean, resulting in lower seawater pH. The changes in physical and chemical properties of the ocean potentially affect marine primary producers in various ways. A number of researches have addressed the effects of ocean acidification on marine phytoplankton. However, phytoplankton responses to combined effects are still poorly understood. Here, we chose the cosmopolitan chain-forming diatom Asterionellopsis glacialis to assess the combined effect of ocean acidification and carbonation (~420 to 2800 µatm) and water motion on its physiological rates. At current CO2 levels, we observed an increase in growth rates of A. glacialis accompanied by a prevalence of longer chains (>6 cells) under enhanced water motion. However, at increasing CO2 levels (up to ~2800 µatm) and decreasing pH values, enhanced water motion significantly decreased growth rates, chain length and organic matter production of A. glacialis. Thus, our study suggests that even though A. glacialis benefited from enhanced water motion at present CO2 concentration, at higher CO2 levels, the more unstable environment magnified the stress caused by acidification. If in the future the ocean surface layer will be more frequently exposed to storm and wind events, then phytoplankton communities might be more sensitive to lower pH, with potential consequences for community composition and productivity. KEY WORDS: Phytoplankton · Climate change · Growth rate · Ocean acidification · CO2 · Water motion Full text in pdf format PreviousNextCite this article as: Gallo F, Schulz KG, Azevedo EB, Madruga J, Barcelos e Ramos J (2018) Responses of the diatom Asterionellopsis glacialis to increasing sea water CO2 concentrations and turbulence. Mar Ecol Prog Ser 589:33-44. https://doi.org/10.3354/meps12450 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 589. Online publication date: February 23, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Effect of ocean acidification on the structure and fatty acid composition of a natural plankton community in the Baltic Sea

Abstract. Increasing atmospheric carbon dioxide (CO2) is changing seawater chemistry towards reduced pH, which affects various properties of marine organisms. Coastal and brackish water communities are expected to be less affected by ocean acidification (OA) as these communities are typically adapted to high fluctuations in CO2 and pH. Here we investigate the response of a coastal brackish water plankton community to increasing CO2 levels as projected for the coming decades and the end of this century in terms of community and biochemical fatty acid (FA) composition. A Baltic Sea plankton community was enclosed in a set of offshore mesocosms and subjected to a CO2 gradient ranging from natural concentrations ( ∼ 347 µatm fCO2) up to values projected for the year 2100 ( ∼ 1333 µatm fCO2). We show that the phytoplankton community composition was resilient to CO2 and did not diverge between the treatments. Seston FA composition was influenced by community composition, which in turn was driven by silicate and phosphate limitation in the mesocosms and showed no difference between the CO2 treatments. These results suggest that CO2 effects are dampened in coastal communities that already experience high natural fluctuations in pCO2. Although this coastal plankton community was tolerant of high pCO2 levels, hypoxia and CO2 uptake by the sea can aggravate acidification and may lead to pH changes outside the currently experienced range for coastal organisms.