Significant CO2 Effects Research Articles

The impact of different batter mixing atmospheres on the quality of reduced sucrose sponge and cream cakes

Cakes are chemically-leavened sugar-rich bakery products. Depending on the cake type, air is incorporated differently during mixing. Sponge cake batter is a gas bubble rich foam, while cream cake batter is an emulsion containing less gas cells. Given the consumer interest in reduced sucrose food systems, we here examined the potential of using altered mixing atmospheres [pure nitrogen (N2) or carbon dioxide (CO2)] to improve reduced sucrose cake quality. The use of poorly soluble N2 resulted in voluminous, stable batter. This was especially the case for foam-type sponge cake batters. During baking of sponge and cream cake batters, leavening was similar for batters prepared either under air or N2, resulting in similar cake qualities. Use of the highly soluble CO2 as mixing atmosphere negatively affected batter density, but positively leavening during baking due to temperature-induced release of previously solubilized CO2. In foam-type sponge cake making, the significant negative effect of CO2 on batter density was not overruled by the positive effect of CO2 release during leavening/baking. In contrast, the CO2 mixing atmosphere during batter-type cream cake making had only a limited negative effect on batter density while greatly affecting leavening, and resulting in high-quality, voluminous (reduced sucrose) cakes.

Temperature and elevated CO2 alter soybean seed yield and quality, exhibiting transgenerational effects on seedling emergence and vigor.

Environmental conditions play a prime role in the growth and development of plant species, exerting a significant influence on their reproductive capacity. Soybean is sensitive to high temperatures during flowering and seed developmental stages. Little is known about the combined environmental effect of temperature and CO2 on seed yield and quality and its future generation. A study was conducted to examine the effect of temperature (22/14°C (low), 30/22°C (optimum), and 38/30°C (high)), and CO2 (420 ppm (ambient; aCO2) and 720 ppm (elevated; eCO2)) on seed yield, quality, and transgenerational seedling vigor traits of soybean cultivars (DS25-1 and DS31-243) using Soil-Plant-Atmospheric-Research facility. A significant temperature effect was recorded among yield and quality attributes. At high-temperature, the 100-seed weights of DS25-1 and DS31-243 declined by 40% and 24%, respectively, over the optimum temperature at aCO2. The harvest index of varieties reduced by 70% when exposed to high temperature under both aCO2 and eCO2, compared to the optimum temperature at aCO2. The seed oil (- 2%) and protein (8%) content altered when developed under high temperature under aCO2. Maximum sucrose (7.5%) and stachyose (3.8%) accumulation in seeds were observed when developed under low temperatures and eCO2. When the growing temperature increased from optimum to high, the seed oleic acids increased (63%), while linoleic and linolenic acids decreased (- 28% and - 43%, respectively). Significant temperature and CO2 effects were observed in progenies with the highest maximum seedling emergence (80%), lesser time to 50% emergence (5.5 days), and higher seedling vigor from parents grown at low-temperature treatment under eCO2. Exposure of plants to 38/30°C was detrimental to soybean seed yield, and eCO2 levels did not compensate for this yield loss. The high temperature during seed developmental stages altered the chemical composition of the seed, leading to an increased content of monounsaturated fatty acids. The findings suggest that parental stress can significantly impact the development of offspring, indicating that epigenetic regulation or memory repose may be at play.

Mutual inhibition effects of elevated CO2 and climate change on global forest GPP

The impact of CO2 fertilization on enhancing global forest gross primary productivity (GPP) is acknowledged, but its interaction with climate factors—air temperature (Tem), precipitation (Pre), vapor pressure deficit (VPD), and radiation (Rad)—remains unclear. In this study, global forest GPP trends from 1982 to 2018 were examined using BEPS, NIRv, FLUXCOM, and revised EC-LUE datasets, with interannual trends of 5.618 (p < 0.01), 5.831 (p < 0.01), 0.227, and 6.566 g C m−2 yr−1 (p < 0.01), respectively. Elevated CO2 was identified as the primary driver of GPP trends, with the dominant area ranging from 51.11% to 90.37% across different GPP datasets. In the NIRv and revised EC-LUE datasets, the positive impact of CO2 on GPP showed a decrease of 0.222 g C m−2 yr−1, while the negative impact of Rad increased by 0.007 g C m−2 yr−1. An inhibitory relationship was found between the actual effects of elevated CO2 and climate change on GPP in most forest types. At lower latitudes, Tem primarily constrained CO2 fertilization, while at higher latitudes, VPD emerged as the key limiting factor. This was mainly attributed to the potential trade-off or competition between elevated CO2 and climate change in influencing GPP, with strategic resource allocation varying across different forest ecosystems. This study highlights the significant inhibitory effects of elevated CO2 and climate change on global forest GPP, providing insights into the dynamic responses of forest ecosystems to changing environments.

In-situ co-precipitation of Bi-MOF derivatives for highly sensitive electrochemical glucose sensing

Bimetallic organic frameworks (Bi-MOFs) have been recognized as one of the hotpots for electrochemical sensing due to their high surface area, abundant active sites, tunable structures and porosity. However, inadequate conductivity and hidden active site of MOFs remain as great challenges, hindered its further development. Here, an in-situ co-precipitation strategy was proposed for preparing sophisticated hierarchical Bi-MOF derivatives with excellent glucose sensing. Firstly, uniform CuO nanorods as the precursor are synthesized in situ on a Carbon Cloth (CC). Subsequently, Cu-BTC and Co-BTC were co-precipitated on the precursor, while the significant effect of incremental Co2+ doping concentration was investigated. Finally, Cu/Co-MOF derivatives are successfully obtained by controlled thermal structural transformation. Due to the synergistic effect of bimetallic oxides and the exposed active sites, the prepared sensing electrode exhibits high sensitivity (4.93 mA mM−1 cm−2), fast response time (2.9 s), and outstanding long-term stability (30 days). This study proposes a practical method for in-situ synthesizing hierarchical Bi-MOF derivatives, which provides wide-ranging prospects in the field of electrochemical sensing.

Homogeneous oxidation of SO2 in the tail gas incinerator of sulfur recovery unit

The formation and emission of sulfur trioxide (SO3) in sulfur recovery unit has received increasing attention due to its adverse effects on the operation of plant and environment. Due to the excess oxygen, high concentration of SO2 and high temperature, SO3 formation in the sulfur recovery unit tail gas incinerator may significantly increase. A small horizontal tube reactor was employed to simulate the homogeneous oxidation of SO2 in the tail gas incinerator. The SO3 concentration was measured with a controlled condensation method at the outlet of the reactor. The present work focuses on the gas-phase chemistry and examines the impact of different combustion parameters and atmospheres on the formation of SO3 in the tail gas incinerator. Experiment results show that the increased O2 and SO2 concentrations along with increasing temperature are favorable for enhancing SO3 formation over the range of tested parameters. The presence of water vapor has an enhancing effect of SO2 oxidation in the experiments conducted. No significant effect of CO2 was found to the oxidation of SO2.

Juvenile Atlantic sea scallop, Placopecten magellanicus, energetic response to increased carbon dioxide and temperature changes

This study assessed the energy budget for juvenile Atlantic Sea Scallop,Placopecten magellanicus, during a natural drop in temperature (15.6°C to 5.8°C) over an 8-week time period during the fall at three different enrichment levels of carbon dioxide (CO2). Every 2 weeks, individuals were sampled for ecophysiological measurements of feeding activity, respiration rate (RR) and excretion rate (ER) to enable the calculation of scope for growth (SFG) and atomic oxygen:nitrogen ratios (O:N). In addition, 36 individuals per treatment were removed for shell height, dry tissue weight (DTW) and dry shell weight (DSW). We found a significant decrease in feeding rates as CO2increased. Those rates also were significantly affected by temperature, with highest feeding at 9.4°C. No significant CO2effect was observed for catabolic energy processes (RR and ER); however, these rates did increase significantly with temperature. The O:N ratio was not significantly affected by CO2, but was significantly affected by temperature. There was a significant interaction between CO2and temperature for ER and the O:N ratio, with low CO2levels resulting in a U-shaped response that was not sustained as CO2levels increased. This suggests that the independent effects of CO2and temperature observed at low levels are different once a CO2threshold is reached. Additionally, there were significant differences in growth estimators (shell height and DSW), with the best growth occurring at the lowest CO2level. In contrast to temperature variations that induced a trade-off response in energy acquisition and expenditure, results from this research support the hypothesis that sea scallops have a limited ability to alter physiological processes to compensate for increasing CO2.

Physicochemical Properties of Egg-Box-Mediated Hydrogels with Transiently Decreased pH Employing Carbonated Water.

Anionic polysaccharides, including low-methoxy (LM) pectin, are extensively used in biomaterial applications owing to their safety, biocompatibility, and feasibility in constructing supramolecular assemblies by forming egg-box structures with divalent cations. Mixing an LM pectin solution with CaCO3 spontaneously forms a hydrogel. The gelation behavior can be controlled by adding an acidic compound to change the solubility of CaCO3. CO2 is used as the acidic agent and can be easily removed after gelation, thereby reducing the acidity of the final hydrogel. However, CO2 addition has been controlled under varied thermodynamical conditions; therefore, specific CO2 effects on gelation are not necessarily visualized. To evaluate the CO2 impact on the final hydrogel, which would be extended to control hydrogel properties further, we utilized carbonated water to supply CO2 into the gelation mixture without changing its thermodynamic conditions. The addition of the carbonated water accelerated gelation and significantly increased the mechanical strength, promoting cross-linking. However, the CO2 volatilized into the atmosphere, and the final hydrogel became more alkaline than that without the carbonated water, probably because a considerable amount of the carboxy group was consumed for cross-linking. Moreover, when aerogels were prepared from the hydrogels with carbonated water, they exhibited highly ordered networks of elongated porosity in scanning electron microscopy, proposing an intrinsic structural change by CO2 in the carbonated water. We also controlled the pH and strength of the final hydrogels by changing the CO2 amounts in the carbonated water added, thereby validating the significant effect of CO2 on hydrogel properties and the feasibility of using carbonated water.

Carbon dioxide enrichment effects on concentration, partitioning and uptake of metallic micronutrient elements in soybean under varied nitrogen application rates

Information on the fate of micronutrients in plant tissue and total uptake from soil upon exposure to elevated carbon dioxide (CO2) is meager. Hence, this field study was conducted in open top field chambers to investigate the effects of elevated CO2 and applied nitrogen (N) on partitioning and uptake of zinc (Zn), copper (Cu), iron (Fe), and manganese (Mn) in soybean crop under two CO2 and four N levels during 2016 and 2018 crop seasons. The two CO2 concentrations were ambient and elevated (∼550 µmol mol−1). Nitrogen treatments included application at 0, 50, 100, and 150% of the recommended dose. Significant effects of CO2 and N were observed on grain yield, biomass and uptake of the four micronutrients. Seed Fe concentration was significantly increased by 12% under CO2 enrichment. Tukey’s post-hoc test revealed significantly higher grain yield, biomass and uptake of micronutrients in seed and straw under CO2 elevation and at higher N application. Uptake of Fe, Zn, Cu, and Mn increased by 53, 42, 36, and 41%, respectively, in seed and by 25, 26, 31, and 18% in straw under elevated CO2. Total uptake of Fe, Zn, Cu, and Mn increased by 39, 38, 34, and 29%, respectively. Nitrogen at 100% level enhanced uptake of Fe, Zn, Cu, and Mn by 25, 20, 32, and 28%. The study bears implications in micronutrient management for sustaining soil health under changing climate.

Short- and long-term responses of leaf day respiration to elevated atmospheric CO2.

Evaluating leaf day respiration rate (RL), which is believed to differ from that in the dark (RDk), is essential for predicting global carbon cycles under climate change. Several studies have suggested that atmospheric CO2 impacts RL. However, the magnitude of such an impact and associated mechanisms remain uncertain. To explore the CO2 effect on RL, wheat (Triticum aestivum) and sunflower (Helianthus annuus) plants were grown under ambient (410 ppm) and elevated (820 ppm) CO2 mole fraction ([CO2]). RL was estimated from combined gas exchange and chlorophyll fluorescence measurements using the Kok method, the Kok-Phi method, and a revised Kok method (Kok-Cc method). We found that elevated growth [CO2] led to an 8.4% reduction in RL and a 16.2% reduction in RDk in both species, in parallel to decreased leaf N and chlorophyll contents at elevated growth [CO2]. We also looked at short-term CO2 effects during gas exchange experiments. Increased RL or RL/RDk at elevated measurement [CO2] were found using the Kok and Kok-Phi methods, but not with the Kok-Cc method. This discrepancy was attributed to the unaccounted changes in Cc in the former methods. We found that the Kok and Kok-Phi methods underestimate RL and overestimate the inhibition of respiration under low irradiance conditions of the Kok curve, and the inhibition of RL was only 6%, representing 26% of the apparent Kok effect. We found no significant long-term CO2 effect on RL/RDk, originating from a concurrent reduction in RL and RDk at elevated growth [CO2], and likely mediated by acclimation of nitrogen metabolism.

The effect of long-term CO2 enrichment on carbon and nitrogen content of roots and soil of natural pastureland

Abstract Increasing levels of atmospheric CO2 may change C and N dynamics in pasture ecosystems. The present study was conducted to examine the impact of four years of CO2 enrichment on soil and root composition and soil N transformation in natural pastureland. Plots of open-top growth chambers were continuously injected with ambient CO2 (350 µL L–1) and elevated CO2 (625 µL L–1). Soil cores exposed to ambient and elevated CO2 treatment were incubated and collected each year. Net N-mineralization rates in soil (NH4 +-N plus NO3ˉ–-N), in addition to total C and N content (%) of soil and root tissues were measured. Results revealed that elevated CO2 caused a significant reduction in soil NO3 (P &lt; 0.05), however, no significant CO2 effect was found on total soil C and N content (%). Roots of plants grown under elevated CO2 treatment had higher C/N ratios. Changes in root C/N ratios were driven by changes in root N concentrations as total root N content (%) was significantly reduced by 30% (P &lt; 0.05). Overall, findings suggest that the effects of CO2 enrichment was more noticeable on N content (%) than C content (%) of soil and roots; elevated CO2 significantly affected soil N-mineralization and total N content (%) in roots, however, no substantial change was found in C inputs in CO2-enriched soil.

Consecutive 4-year Elevated Atmospheric CO2 on Shaped Microbial Communities in the Rhizosphere Soil of Robinia pseudoacacia L. Seedlings Grown in Pb-contaminated Soils

Elevated atmospheric CO2 could affect the speciation of heavy metals in rhizosphere soils by changing root exudates, thereby influencing soil microecosystem in the rhizosphere. Therefore, understanding the function of heavy metals in soils on rhizospheric ecology under elevated atmospheric CO2 scenarios is highly important. Here, we investigated the combined effects of a four-year period of elevated air CO2 concentrations[(700±27) μmol·L-1] and Pb-contamination (15.6 mg·kg-1 and 515.6 mg·kg-1) on the soil rhizopheric microbial community of Robinia pseudoacacia L. seedlings. Significant (P<0.05) effects of CO2, Pb, and their interaction on bacterial richness and fungal diversity were observed. Relative to Pb exposure alone, elevated CO2 significantly increased pH, total C, total N, and water-soluble organic carbon, and the C/N ratio under Pb exposure (P<0.05) and significantly decreased total and soluble Pb content (P<0.05). The richness and diversity of bacteria increased (P<0.05), fungal richness decreased (P<0.05), and microbial diversity increased (P<0.05) under the combined treatments relative to Pb contamination alone. The changes in the relative abundance of the top two dominant bacterial and fungal genera were not significant; however, differences in the relative abundances of other groups, such as Anaerolineaceae, Solirubrobacterales, Eurotiomycetes, Aspergillus, and Trichocomaceae, were significant between the different treatments. According to a redundancy analysis, total C and soluble Pb had a significant influence (P<0.05) on the dominant bacterial genera, and total C affected (P<0.05) the dominant genera in the fungal community. These results suggest that the responses of soil environmental factors to the combination of elevated atmospheric CO2 and Pb could shape soil microbial community structure in the rhizosphere of R. pseudoacacia seedlings.

Effects of long-term CO2 enrichment on forage quality of extensively managed temperate grassland

Different studies revealed an increased biomass production in grasslands due to elevated CO2 (eCO2). Thus, the question arises whether forage quality of grassland biomass is also influenced.In the present study, we assessed the long-term effects of eCO2 in context of the accompanied site conditions soil moisture, air temperature and precipitation on different forage quality and energy parameters of grassland biomass in an extensively managed temperate grassland. The study took place at the Free-Air Carbon dioxide Enrichment site near Giessen [GiFACE], which was set up in 1998. Our main objective was to assess the differences in the quality and energy content of grassland forage, exposed to elevated CO2 [+ 20%; eCO2] and ambient CO2 (aCO2) concentrations. Crude protein, C/N-ratio, crude fat, total non-structural carbohydrates, ash, crude fibre, metabolisable energy [ME] and net energy for lactation [NEL] were determined to assess the forage quality and energy content of grassland biomass separated in grasses and forbs, which was harvested twice per year (end of May, beginning of September), over the period of 2006–2015.Forbs showed a significant decrease for most tested parameters under eCO2 at both harvests, except for crude fibre, which showed a significant increase at the second harvest of the year under eCO2. Grasses showed a significant negative CO2 effect for ash content at the first harvest of the year. In addition to eCO2, site and climatic conditions, e.g. soil moisture, affected the investigated parameters.Based on the last 10 observation years (2006–2015) within the 18 year long experiment, eCO2 is likely to cause a decline in forage quality, especially of forbs caused by reduced crude protein and fat contents and increased crude fibre content, in extensively managed grassland ecosystems. However, site and climatic conditions should also be considered showing the importance of long-term observations that contain the full range of climatic conditions. Periods of heat, drought and precipitation, which are expected to increase in the future, lead to a decrease of the CO2 fertilization effect on grassland biomass and also to a negative impact on forage quality.

Reduced host plant growth and increased tyrosine-derived secondary metabolites under climate change and negative consequences on its specialist herbivore

Compositive changes in climatic factors, e.g., carbon dioxide (CO2) and precipitation frequency and intensity, affect the strength of species interactions via responses in plants. Therefore, understanding the effects of climate change on plant-herbivore interactions is important to maintain biodiversity as about 70% of insects are herbivorous. However, the interactive effects of CO2 and precipitation on plants and consequences for herbivores are poorly understood. Here, we examined how elevated CO2 and increased watering frequency affect the growth and resistance responses of Aristolochia contorta and the growth performance of its specialist herbivore, Sericinus montela. Elevated CO2 suppressed growth with decreased photosynthesis ability, and increased resistance in plants. In contrast, increased watering frequency partly ameliorated the negative effects of high CO2. Growth performance of specialist herbivores decreased under elevated CO2 condition as a consequence of increased resistance in plants. Due to the significant effects of CO2, we suggest that both the quantity and the quality of host plants as a food would decline, and the growth performance of its specialist herbivore might be threatened as climate change progresses.

Analyzing the Impacts of Elevated-CO2 Levels on the Development of a Subtropical Zooplankton Community During Oligotrophic Conditions and Simulated Upwelling

Ocean acidification (OA) is affecting marine ecosystems through changes in carbonate chemistry that may influence consumers of phytoplankton, often via trophic pathways. Using a mesocosm approach, we investigated OA effects on a subtropical zooplankton community during oligotrophic, bloom, and post-bloom phases under a range of different pCO2 levels (from ∼400 to ∼1480 μatm). Furthermore, we simulated an upwelling event by adding 650 m-depth nutrient-rich water to the mesocosms, which initiated a phytoplankton bloom. No effects of pCO2 on the zooplankton community were visible in the oligotrophic conditions before the bloom. The zooplankton community responded to phytoplankton bloom by increased abundances in all treatments, although the response was delayed under high-pCO2 conditions. Microzooplankton was dominated by small dinoflagellates and aloricate ciliates, which were more abundant under medium- to high-pCO2 conditions. The most abundant mesozooplankters were calanoid copepods, which did not respond to CO2 treatments during the oligotrophic phase of the experiment but were found in higher abundance under medium- and high-pCO2 conditions toward the end of the experiment, most likely as a response to increased phyto- and microzooplankton standing stocks. The second most abundant mesozooplankton taxon were appendicularians, which did not show a response to the different pCO2 treatments. Overall, CO2 effects on zooplankton seemed to be primarily transmitted through significant CO2 effects on phytoplankton and therefore indirect pathways. We conclude that elevated pCO2 can change trophic cascades with significant effects on zooplankton, what might ultimately affect higher trophic levels in the future.

Simulated global increases in atmospheric CO2 alter the tissue composition, but not the growth of some submerged aquatic plant bicarbonate users growing in DIC rich waters

Current global change scenarios predict an increase in atmospheric CO2 from the current 380 ppm to a value ranging from 540 ppm to 960 ppm by the year 2100. The effects of three air CO2 levels (400, 600 and 800 ppm) on five submerged aquatic plants that utilize HCO3− were studied, using the elevated CO2 Open Top Chamber facility at Rhodes University (Grahamstown, South Africa). Plants grew in water with two different initial dissolved inorganic carbon (DIC) concentrations of 1.5 and 3.0 mM. Overall, the growth rates and biomass allocation to roots were not affected by the initial DIC and air CO2, even though differences between the species were found. Furthermore, no overall effects were found on net photosynthesis, chlorophyll and starch content, even though significant effects of CO2 and DIC were observed in some species. In contrast, with increasing DIC and air CO2 a significant global decline in leaf nitrogen content linked with an increased C:N molar ratio was observed. The results indicate that submerged aquatic HCO3− users will be less affected by atmospheric CO2 increases when growing in DIC rich waters, in comparison to obligate CO2 users growing under CO2 limiting conditions as documented in previous studies. However, the changes found in plant nitrogen illustrate that atmospheric CO2 increases will affect nitrogen absorption by submerged plants, with subsequent ecosystem level effects.

You Better Repeat It: Complex CO2 × Temperature Effects in Atlantic Silverside Offspring Revealed by Serial Experimentation

Concurrent ocean warming and acidification demand experimental approaches that assess biological sensitivities to combined effects of these potential stressors. Here, we summarize five CO2 × temperature experiments on wild Atlantic silverside, Menidia menidia, offspring that were reared under factorial combinations of CO2 (nominal: 400, 2200, 4000, and 6000 µatm) and temperature (17, 20, 24, and 28 °C) to quantify the temperature-dependence of CO2 effects in early life growth and survival. Across experiments and temperature treatments, we found few significant CO2 effects on response traits. Survival effects were limited to a single experiment, where elevated CO2 exposure reduced embryo survival at 17 and 24 °C. Hatch length displayed CO2 × temperature interactions due largely to reduced hatch size at 24 °C in one experiment but increased length at 28 °C in another. We found no overall influence of CO2 on larval growth or survival to 9, 10, 15 and 13–22 days post-hatch, at 28, 24, 20, and 17 °C, respectively. Importantly, exposure to cooler (17 °C) and warmer (28 °C) than optimal rearing temperatures (24 °C) in this species did not appear to increase CO2 sensitivity. Repeated experimentation documented substantial inter- and intra-experiment variability, highlighting the need for experimental replication to more robustly constrain inherently variable responses. Taken together, these results demonstrate that the early life stages of this ecologically important forage fish appear largely tolerate to even extreme levels of CO2 across a broad thermal regime.

Interactive effect of nitrogen source and high CO2 concentration on the growth of the dinoflagellate Alexandrium tamarense and its toxicity to zebrafish (Danio rerio) embryos

The effects and interactive effects of different nitrogen (N) sources (ammonium, nitrate, and urea) and carbon dioxide (CO2) concentrations were investigated on Alexandrium tamarense, a harmful marine dinoflagellate, by measuring its growth (μ), extracellular carbonic anhydrase (CA), and its toxicity to zebrafish (Danio rerio) embryo. The μ and CA were influenced more strongly by CO2 concentrations rather than by N sources; significant effects of CO2 on μ and CA were observed under low CO2 concentration (LC) conditions compared to high CO2 concentration (HC) conditions. The ammonium and nitrate media under LC conditions had the maximum μ and CA, which was inhibited under HC conditions. The embryotoxic effects were influenced more strongly by the N sources than by CO2 concentrations, thus excluding the lower deformation in urea under HC conditions. Moreover, the antioxidant enzymes superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione S-transferase (GST), and catalase (CAT) were detected in normal (untreated) zebrafish embryos, and among them, the level of SOD was the highest. In summary, this study provides a clear insight for understanding the effects and interactive effects of N sources and CO2 concentrations on the growth and toxicity of harmful dinoflagellates.

Acidification increases abundances of Vibrionales and Planctomycetia associated to a seaweed-grazer system: potential consequences for disease and prey digestion efficiency.

Ocean acidification significantly affects marine organisms in several ways, with complex interactions. Seaweeds might benefit from rising CO2 through increased photosynthesis and carbon acquisition, with subsequent higher growth rates. However, changes in seaweed chemistry due to increased CO2 may change the nutritional quality of tissue for grazers. In addition, organisms live in close association with a diverse microbiota, which can also be influenced by environmental changes, with feedback effects. As gut microbiomes are often linked to diet, changes in seaweed characteristics and associated microbiome can affect the gut microbiome of the grazer, with possible fitness consequences. In this study, we experimentally investigated the effects of acidification on the microbiome of the invasive brown seaweed Sargassum muticum and a native isopod consumer Synisoma nadejda. Both were exposed to ambient CO2 conditions (380 ppm, pH 8.16) and an acidification treatment (1,000 ppm, pH 7.86) for three weeks. Microbiome diversity and composition were determined using high-throughput sequencing of the variable regions V5-7 of 16S rRNA. We anticipated that as a result of acidification, the seaweed-associated bacterial community would change, leading to further changes in the gut microbiome of grazers. However, no significant effects of elevated CO2 on the overall bacterial community structure and composition were revealed in the seaweed. In contrast, significant changes were observed in the bacterial community of the grazer gut. Although the bacterial community of S. muticum as whole did not change, Oceanospirillales and Vibrionales (mainly Pseudoalteromonas) significantly increased their abundance in acidified conditions. The former, which uses organic matter compounds as its main source, may have opportunistically taken advantage of the possible increase of the C/N ratio in the seaweed under acidified conditions. Pseudoalteromonas, commonly associated to diseased seaweeds, suggesting that acidification may facilitate opportunistic/pathogenic bacteria. In the gut of S. nadejda, the bacterial genus Planctomycetia increased abundance under elevated CO2. This shift might be associated to changes in food (S. muticum) quality under acidification. Planctomycetia are slow-acting decomposers of algal polymers that could be providing the isopod with an elevated algal digestion and availability of inorganic compounds to compensate the shifted C/N ratio under acidification in their food.In conclusion, our results indicate that even after only three weeks of acidified conditions, bacterial communities associated to ungrazed seaweed and to an isopod grazer show specific, differential shifts in associated bacterial community. These have potential consequences for seaweed health (as shown in corals) and isopod food digestion. The observed changes in the gut microbiome of the grazer seem to reflect changes in the seaweed chemistry rather than its microbial composition.

Flowering in grassland predicted by CO2 and resource effects on species aboveground biomass.

Continuing enrichment of atmospheric CO2 may change plant community composition, in part by altering the availability of other limiting resources including soil water, nutrients, or light. The combined effects of CO2 enrichment and altered resource availability on species flowering remain poorly understood. We quantified flowering culm and ramet production and biomass allocation to flowering culms/ramets for 10years in C4 -dominated grassland communities on contrasting soils along a CO2 concentration gradient spanning pre-industrial to expected mid-21st century levels (250-500μl/L). CO2 enrichment explained up to 77% of the variation in flowering culm count across soils for three of the five species, and was correlated with flowering culm count on at least one soil for four of five species. In contrast, allocation to flowering culms was only weakly correlated with CO2 enrichment for two species. Flowering culm counts were strongly correlated with species aboveground biomass (AGB; R2 =.34-.74), a measure of species abundance. CO2 enrichment also increased soil moisture and decreased light levels within the canopy but did not affect soil inorganic nitrogen availability. Structural equationmodels fit across the soils suggested species-specific controls on flowering in two general forms: (1) CO2 effects on flowering culm count mediated by canopy light level and relative species AGB (species AGB/total AGB) or by soil moisture effects on flowering culm count; (2) effects of canopy light level or soil inorganic nitrogen on flowering and/or relative species AGB, but with no significant CO2 effect. Understanding the heterogeneity in species responses to CO2 enrichment in plant communities across soils in edaphically variable landscapes is critical to predict CO2 effects on flowering and other plant fitness components, and species potential to adapt to future environmental changes.

Quantifying the effects of air pollution control policies: A case of Shanxi province in China

With a rapid growth rate of economic development in China, air pollution has attained to an extremely high level. Consequently, air pollution has become a pressing challenge facing Chinese authorities. To control air pollution, a variety of economic instruments (such as Pigou tax and Coase means) as well as command and control means (such as environmental regulation, etc.) have been adopted. As one of China's important energy resources bases, Shanxi Province is also one of the most polluted regions. Therefore, the adapted air pollution control policies and its influence in Shanxi Province is representative for China. With this regard, a dynamic computable general equilibrium (CGE) model is constructed to evaluate the effects of air pollution control tools including SO2 taxation, clean technical progress (CTP) and energy efficient (EE) improvement, etc. and their socioeconomic impacts on Shanxi province. The results indicate that, in a variety of scenarios, SO2 taxation combining with technical progress can effectively control air pollution, improve energy consumption structure, and do not exert remarkable negative impact on economic performance. Additionally, significant synergistic effects of CO2 and PM2.5 emission reduction and energy rebound effect are found as well.