CO2 World Research Articles

Roles for redox processes in adaptation to a high CO2 world

Roles for redox processes in adaptation to a high CO2 world

Eccentricity-paced monsoon variability on the northeastern Tibetan Plateau in the Late Oligocene high CO2 world.

Constraining monsoon variability and dynamics in the warm unipolar icehouse world of the Late Oligocene can provide important clues to future climate responses to global warming. Here, we present a ~4-thousand year (ka) resolution rubidium-to-strontium ratio and magnetic susceptibility records between 28.1 and 24.1 million years ago from a distal alluvial sedimentary sequence in the Lanzhou Basin (China) on the northeastern Tibetan Plateau margin. These Asian monsoon precipitation records exhibit prominent short (~110-ka) and long (405-ka) eccentricity cycles throughout the Late Oligocene, with a weak expression of obliquity (41-ka) and precession (19-ka and 23-ka) cycles. We conclude that a combination of eccentricity-modulated low-latitude summer insolation and glacial-interglacial Antarctic Ice Sheet fluctuations drove the eccentricity-paced precipitation variability on the northeastern Tibetan Plateau in the Late Oligocene high CO2 world by governing regional temperatures, water vapor loading in the western Pacific and Indian Oceans, and the Asian monsoon intensity and displacement.

The effect of elevated CO2 on aboveground and belowground carbon allocation and eco-physiology of four species of angiosperm and gymnosperm forest trees

Although atmospheric CO2 concentration ([CO2]) continues to rise, the question of how tree carbon (C) allocation is affected by this change remains. Studies show that C assimilation increases under elevated CO2 (eCO2). Yet, no detailed study has determined the fate of the surplus C, i.e., its compartment and physiological process allocation, nor in multiple species together. In this project, we grew 2-year-old saplings of four key Mediterranean tree species (the conifers Cupressus sempervirens L. and Pinus halepensis Mill., and the broadleaf Quercus calliprinos Webb. and Ceratonia siliqua L.) to [CO2] levels of 400 or 700p.p.m. for 6months. We measured the allocation of C to below and aboveground growth, respiration, root exudation, storage and leaf litter. In addition, we monitored intrinsic water-use efficiency (WUE), soil moisture, soil chemistry and nutrient uptake. Net assimilation, WUE and soil nitrogen uptake significantly increased at eCO2 across the four species. Broadleaf species showed soil water savings, which were absent in conifers. All other effects were species-specific: Cupressus had higher leaf respiration, Pinus had lower starch in branches and transiently higher exudation rate and Quercus had higher root respiration. Elevated CO2 did not affect growth or litter production. Our results are pivotal to understanding the sensitivity of tree C allocation to the change in [CO2] when water is abundant. Species-specific responses should be regarded cautiously when predicting future changes in forest function in a higher CO2 world.

Carbon Isotopic Fractionation of Alkenones and Gephyrocapsa Coccoliths Over the Late Quaternary (Marine Isotope Stages 12–9) Glacial‐Interglacial Cycles at the Western Tropical Atlantic

AbstractThe sensitivity of coccolithophores to changing CO2 and its role modulating cellular photosynthetic carbon isotopic fractionation (εp) is crucial to understand the future adaptation of these organisms to higher CO2 world and to assess the reliability of εp for past CO2 estimation. Here, we present εp measured on natural fossil samples across the glacial‐interglacial (G‐I) CO2 variations of marine isotope stages 12 to 9 interval (454–334 ka) at the western tropical Atlantic Ocean Drilling Program Site 925 together with a set of organic and inorganic geochemical, micropaleontological and morphometrical data from Gephyrocapsa coccoliths in the same samples. The ∼2‰ variation in εp is significantly correlated with the CO2[aq] concentrations calculated from assumption of air‐sea equilibrium with measured ice core pCO2 concentrations. The sensitivity of εp to CO2[aq] is similar to that derived from a multiple regression model of culture observations and is not well simulated with the classical purely diffusive model of algal CO2 acquisition. The measured range of Gephyrocapsa cell sizes is insufficient to explain the non‐CO2 effects on εp at this location, via either direct size effect or growth rate correlated to cell size. Primary productivity, potentially triggered by shifting growth rates and light levels, may also affect εp. Proposed productivity proxies % Florisphaera profunda and the ratio between the C37 to C38.et alkenone (C37/C38.et ratio) both correlates modestly with the non‐CO2 effects on εp. When the observed G‐I εp to CO2 sensitivity at this site is used to estimate pCO2 from εp since the Miocene, the inferred pCO2 declines are larger in amplitude compared to that calculated from a theoretical εp diffusive model. We find that oxygen and carbon stable isotope vital effects in the near monogeneric‐separated Gephyrocapsa coccoliths (respectively Δδ18OGephyrocapsa–Trilobatus sacculifer and εcoccolith) are coupled through the time series, but the origins of these vital effects are not readily explained by existing models.

Nutritional quality of crops in a high CO2 world: an agenda for research and technology development

Essential nutrients, including carbohydrates, proteins, fats, vitamins, and minerals, are required for human health and development. Inadequate intake can negatively affect development and result in a wide range of adverse health outcomes. Rice, maize, and wheat provide over 60% of the world’s food energy intake. Atmospheric carbon dioxide (CO2), water, nitrogen, and soil micronutrients are the basis of this plant material. Since 1850–1900, CO2 concentrations have increased about 50%, with most of that increase since 1950. Higher CO2 concentrations increase photosynthesis, which then increases plant biomass, but also alters the nutritional quality of wheat, rice, and other C3 plants. We review the possible impacts of rising CO2 concentrations on human health, highlight uncertainties, and propose a research agenda to maintain the nutritional quality of C3 plants. We also synthesize options for addressing this critical challenge to nutritional safety and security. A complete research agenda requires addressing data and knowledge gaps surrounding plant biology and policy responses. Data on key nutrients are lacking, leading to a limited mechanistic understanding of the response of the plant ionome to elevated CO2 concentrations. Regular data are largely missing on nutritional status and food safety in low- and middle-income countries, limiting assessments of the magnitude of the risks. Research opportunities to fill gaps in data and understanding include herbaria studies, field-based natural and manipulative studies, leveraging natural plant variability, and innovations in seed quality. Improved models of cereal crop nutritional quality can project the magnitude and direction of possible future challenges; incorporating the effects of climate change into those models can further improve their robustness. Transdisciplinary research involving at least ecologists, plant physiologists, economists, and experts in human nutrition is essential for developing a systems-based understanding of the potential impacts of rising CO2 concentrations for human nutrition and the attendant consequences for achieving the sustainable development goal on food security.

Anthropogenic CO2 of High Emission Scenario Compensated After 3500 Years of Ocean Alkalinization With an Annually Constant Dissolution of 5 Pg of Olivine

The CO2 removal model inter-comparison (CDRMIP) has been established to approximate the usefulness of climate mitigation by some well-defined negative emission technologies. I here analyze ocean alkalinization in a high CO2 world (emission scenario SSP5-85-EXT++ and CDR-ocean-alk within CDRMIP) for the next millennia using a revised version of the carbon cycle model BICYCLE, whose long-term feedbacks are calculated for the next 1 million years. The applied model version not only captures atmosphere, ocean, and a constant marine and terrestrial biosphere, but also represents solid Earth processes, such as deep ocean CaCO3 accumulation and dissolution, volcanic CO2 outgassing, and continental weathering. In the applied negative emission experiment, 0.14 Pmol/yr of alkalinity—comparable to the dissolution of 5 Pg of olivine per year—is entering the surface ocean starting in year 2020 for either 50 or 5000 years. I find that the cumulative emissions of 6,740 PgC emitted until year 2350 lead to a peak atmospheric CO2 concentration of nearly 2,400 ppm in year 2326, which is reduced by only 200 ppm by the alkalinization experiment. Atmospheric CO2 is brought down to 400 or 300 ppm after 2730 or 3480 years of alkalinization, respectively. Such low CO2 concentrations are reached without ocean alkalinization only after several hundreds of thousands of years, when the feedbacks from weathering and sediments bring the part of the anthropogenic emissions that stays in the atmosphere (the so-called airborne fraction) below 4%. The efficiency of carbon sequestration by this alkalinization approach peaks at 9.7 PgC per Pmol of alkalinity added during times of maximum anthropogenic CO2 emissions and slowly declines to half this value 2000 years later due to the non-linear marine chemistry response and ocean-sediment processes. In other words, ocean alkalinization sequesters carbon only as long as the added alkalinity stays in the ocean. To understand the basic model behavior, I analytically explain why in the simulation results a linear relationship in the transient climate response (TCR) to cumulative emissions is found for low emissions (similarly as for more complex climate models), which evolves for high emissions to a non-linear relation.

The methylome is altered for plants in a high CO2 world: Insights into the response of a wild plant population to multigenerational exposure to elevated atmospheric [CO2

Unravelling plant responses to rising atmospheric CO2 concentration ([CO2 ]) has largely focussed on plastic functional attributes to single generation [CO2 ] exposure. Quantifying the consequences of long-term, decadal multigenerational exposure to elevated [CO2 ] and the genetic changes that may underpin evolutionary mechanisms with [CO2 ] as a driver remain largely unexplored. Here, we investigated both plastic and evolutionary plant responses to elevated [CO2 ] by applying multi-omic technologies using populations of Plantago lanceolata L., grown in naturally high [CO2 ] for many generations in a CO2 spring. Seed from populations at the CO2 spring and an adjacent control site (ambient [CO2 ]) were grown in a common environment for one generation, and then offspring were grown in ambient or elevated [CO2 ] growth chambers. Low overall genetic differentiation between the CO2 spring and control site populations was found, with evidence of weak selection in exons. We identified evolutionary divergence in the DNA methylation profiles of populations derived from the spring relative to the control population, providing the first evidence that plant methylomes may respond to elevated [CO2 ] over multiple generations. In contrast, growth at elevated [CO2 ] for a single generation induced limited methylome remodelling (an order of magnitude fewer differential methylation events than observed between populations), although some of this appeared to be stably transgenerationally inherited. In all, 59 regions of the genome were identified where transcripts exhibiting differential expression (associated with single generation or long-term natural exposure to elevated [CO2 ]) co-located with sites of differential methylation or with single nucleotide polymorphisms exhibiting significant inter-population divergence. This included genes in pathways known to respond to elevated [CO2 ], such as nitrogen use efficiency and stomatal patterning. This study provides the first indication that DNA methylation may contribute to plant adaptation to future atmospheric [CO2 ] and identifies several areas of the genome that are targets for future study.

Acidification slows algal movement

Ocean acidification is changing the productivity and composition of phytoplankton communities at the base of the aquatic food web. Now a study shows that acidification impairs the swimming ability of flagellated microalgae, suggesting that their capacity to survive is threatened in a high CO2 world.

To what extent can cirrus cloud seeding counteract global warming?

The idea of modifying cirrus clouds to directly counteract greenhouse gas warming has gained momentum in recent years, despite disputes over its physical feasibility. Previous studies that analyzed modifications of cirrus clouds by seeding of ice nucleating particles showed large uncertainties in both cloud and surface climate responses, ranging from no effect or even a small warming to a globally averaged cooling of about 2.5 °C. We use two general circulation models that showed very different responses in previous studies, ECHAM6-HAM and CESM-CAM5, to determine which radiative and climatic responses to cirrus cloud seeding in a 1.5 × CO2 world are common and which are not. Seeding reduces the net cirrus radiative effect for −1.8 W m−2 in CESM compared with only −0.8 W m−2 in ECHAM. Accordingly, the surface temperature decrease is larger in CESM, counteracting about 70% of the global mean temperature increase due to CO2 and only 30% in ECHAM. While seeding impacts on mean precipitation were addressed in past studies, we are the first to analyze extreme precipitation responses to cirrus seeding. Seeding decreases the frequency of the most extreme precipitation globally. However, the extreme precipitation events occur more frequently in the Sahel and Central America, following the mean precipitation increase due to a northward shift of the Intertropical Convergence Zone. In addition, we use a quadratic climate damage metric to evaluate the amount of CO2-induced damage cirrus seeding can counteract. Seeding decreases the damage by about 50% in ECHAM, and by 85% in CESM over the 21 selected land regions. Climate damage due to CO2 increase is significantly reduced as a result of seeding in all of the considered land regions.

The allocation of CO2 emissions as a claims problem

In the context of multilateral negotiations on climate change, this paper proposes to use the claims approach as a reasonable and practicable alternative in order to allocate the admissible CO2 emissions per region. The proposed methodology entails analyze the application of a broad group of theoretical solutions through the establishment of equity and stability criteria. To this regard, the empirical analyzing combines several CO2 world endowments from Meinshausen et al. (2009) together with claims forecasts associated with the RCP (Representative Concentration Pathways) scenarios. The results obtained indicate that the constrained equal awards and α-minimal solutions are clearly equity-sensitive. Given that the CO2 emission reduction imposed by the constrained equal awards solution on Asia and the OECD are very important, and considering the better balance between equity and proportionality associated with the α-min solution, it could be that this latter solution would be the most practicable and acceptable.

Could ocean acidification influence epiphytism? A comparison of carbon-use strategies between Fucus vesiculosus and its epiphytes in the Baltic Sea

Reduced seawater pH due to elevated carbon dioxide (CO2), a process known as ocean acidification (OA), is a globally significant environmental issue. OA is predicted to influence a range of ecosystem processes, but little is known about how changing seawater carbon chemistry could influence the extent and impacts of epiphytism. In the brackish Baltic Sea, increased epiphytism is associated with coastal eutrophication and the potential for OA to interact with this relationship remains unclear. This study focuses on slow-growing perennial algae Fucus vesiculosus—which is one of the most important habitat-forming species in the Baltic Sea—and two of its most common and abundant filamentous epiphytes Ceramium tenuicorne and Pylaiella littoralis. Material for this study was collected from Estonian coastal waters. The aim of the research was to determine which carbon acquisition strategies these species possess, which could indicate how they respond to predicted changes in seawater chemistry due to elevated CO2. Carbon-use strategies in macroalgae were determined by analyzing natural carbon isotope signatures (δ13C), pH drift experiments, and photosynthesis vs. dissolved inorganic carbon (P vs. DIC) curves. Our results showed that although F. vesiculosus and its filamentous epiphytes all possess a carbon concentrating mechanism (CCM), the potential species-specific variation in the CCMs operation will favor C. tenuicorne over F. vesiculosus and P. littoralis in a future high CO2 world.

Aerobic performance of two tropical cephalopod species unaltered by prolonged exposure to projected future carbon dioxide levels.

Squid and many other cephalopods live continuously on the threshold of their environmental oxygen limitations. If the abilities of squid to effectively take up oxygen are negatively affected by projected future carbon dioxide (CO2) levels in ways similar to those demonstrated in some fish and invertebrates, it could affect the success of squid in future oceans. While there is evidence that acute exposure to elevated CO2 has adverse effects on cephalopod respiratory performance, no studies have investigated this in an adult cephalopod after relatively prolonged exposure to elevated CO2 or determined any effects on aerobic scope. Here, we tested the effects of prolonged exposure (≥20% of lifespan) to elevated CO2 levels (~1000μatm) on the routine and maximal oxygen uptake rates, aerobic scope and recovery time of two tropical cephalopod species, the two-toned pygmy squid, Idiosepius pygmaeus and the bigfin reef squid, Sepioteuthis lessoniana. Neither species exhibited evidence of altered aerobic performance after exposure to elevated CO2 when compared to individuals held at control conditions. The recovery time of I. pygmaeus under both control and elevated CO2 conditions was less than 1hour, whereas S. lessoniana required approximately 8hours to recover fully following maximal aerobic performance. This difference in recovery time may be due to the more sedentary behaviours of I. pygmaeus. The ability of these two cephalopod species to cope with prolonged exposure to elevated CO2 without detriment to their aerobic performance suggests some resilience to an increasingly high CO2 world.

THE FUTURE OF PASSENGER AIR TRANSPORT – VERY LARGE AIRCRAFT AND OUT KEY HUMAN FACTORS AFFECTING THE OPERATION AND SAFETY OF PASSENGER AIR TRANSPORT

The article outlines some human factors affecting the operation and safety of passenger air transport given the massive increase in the use of the VLA. Decrease of the impact of the CO2 world emissions is one of the key goals for the new aircraft design. The main wave is going to reduce the burned fuel. Therefore, the eco-efficiency engines combined with reasonable economic operation of the aircraft are very important from an aviation perspective. The prediction for the year 2030 says that about 90% of people, which will use long-haul flights to fly between big cities. So, the A380 was designed exactly for this time period, with a focus on the right capacity, right operating cost and right fuel burn per seat. There is no aircraft today with better fuel burn combined with eco-efficiency per seat, than the A380. The very large aircrafts (VLAs) are the future of the commercial passenger aviation. Operating cost versus safety or CO2 emissions versus increasing automation inside the new generation aircraft. Almost 80% of the world aircraft accidents are caused by human error based on wrong action, reaction or final decision of pilots, the catastrophic failures of aircraft systems, or air traffic control errors are not so frequent. So, we are at the beginning of a new age in passenger aviation and the role of the human factor is more important than ever.

Integrating Plant Science and Crop Modeling: Assessment of the Impact of Climate Change on Soybean and Maize Production.

Increasing global CO2 emissions have profound consequences for plant biology, not least because of direct influences on carbon gain. However, much remains uncertain regarding how our major crops will respond to a future high CO2 world. Crop model inter-comparison studies have identified large uncertainties and biases associated with climate change. The need to quantify uncertainty has drawn the fields of plant molecular physiology, crop breeding and biology, and climate change modeling closer together. Comparing data from different models that have been used to assess the potential climate change impacts on soybean and maize production, future yield losses have been predicted for both major crops. When CO2 fertilization effects are taken into account significant yield gains are predicted for soybean, together with a shift in global production from the Southern to the Northern hemisphere. Maize production is also forecast to shift northwards. However, unless plant breeders are able to produce new hybrids with improved traits, the forecasted yield losses for maize will only be mitigated by agro-management adaptations. In addition, the increasing demands of a growing world population will require larger areas of marginal land to be used for maize and soybean production. We summarize the outputs of crop models, together with mitigation options for decreasing the negative impacts of climate on the global maize and soybean production, providing an overview of projected land-use change as a major determining factor for future global crop production.

Ocean warming and acidification prevent compensatory response in a predator to reduced prey quality

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 563:111-122 (2017) - DOI: https://doi.org/10.3354/meps11956 Ocean warming and acidification prevent compensatory response in a predator to reduced prey quality Ben P. Harvey1,3,*, Pippa J. Moore1,2 1Institute of Biological, Environmental, and Rural Sciences, Aberystwyth University, Aberystwyth SY23 3DA, UK 2Centre for Marine Ecosystems Research, Edith Cowan University, Perth 6027, Australia 3Present address: Shimoda Marine Research Center, University of Tsukuba, 5-10-1 Shimoda, Shizuoka 415-0025, Japan *Corresponding author: harvey.benjaminpaul@gmail.com ABSTRACT: While there is increasing evidence for the impacts of climate change at the individual level, much less is known about how species’ likely idiosyncratic responses may alter ecological interactions. Here, we demonstrate that ocean acidification and warming not only directly alter species’ (individual) physiological performance, but also their predator-prey dynamics. Our results demonstrate that tissue production (used as a proxy for prey quality) in the barnacle Semibalanus balanoides was reduced under scenarios of future climate change, and hence their ability to support energy acquisition for dogwhelk Nucella lapillus through food provision was diminished. However, rather than increasing their feeding rates as a compensatory mechanism, consumption rates of N. lapillus were reduced to the point that they exhibited starvation (a loss of somatic tissue), despite prey resources remaining abundant. The resilience of any marine organism to stressors is fundamentally linked to their ability to obtain and assimilate energy. Therefore, our findings suggest that the cost of living under future climate change may surpass the energy intake from consumption rates, which is likely exacerbated through the bottom-up effects of reduced prey quality. If, as our results suggest, changes in trophic transfer of energy are more common in a warmer, high CO2 world, such alterations to the predator-prey dynamic may have negative consequences for the acquisition of energy in the predator and result in energetic trade-offs. Given the importance of predator-prey interactions in structuring marine communities, future climate change is likely to have major consequences for community composition and the structure and function of ecosystems. KEY WORDS: Predator-prey · Climate change · Ocean warming · Ocean acidification · Trophic interactions · Ecological interactions · Compensatory Full text in pdf format Supplementary material PreviousNextCite this article as: Harvey BP, Moore PJ (2017) Ocean warming and acidification prevent compensatory response in a predator to reduced prey quality. Mar Ecol Prog Ser 563:111-122. https://doi.org/10.3354/meps11956 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 563. Online publication date: January 20, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

The Influence of CO2 Enrichment on Net Photosynthesis of Seagrass Zostera marina in a Brackish Water Environment

Seagrasses are distributed across the globe and their communities may play key roles in the coastal ecosystems. Seagrass meadows are expected to benefit from the increased carbon availability which might be used in photosynthesis in a future high CO2 world. The main aim of this study was to examine the effect of elevated pCO2 on the net photosynthesis of seagrass Zostera marina in a brackish water environment. The short-term mesocosm experiments were conducted in Kõiguste Bay (northern part of Gulf of Riga, the Baltic Sea) in June-July 2013 and 2014. As the levels of pCO2 naturally range from ca. 150 μatm to well above 1000 μatm under summer conditions in Kõiguste Bay we chose to operate in mesocosms with the pCO2 levels of ca. 2000, ca. 1000 and ca. 200 μatm. Additionally, in 2014 the photosynthesis of Z. marina was measured outside of the mesocosm in the natural conditions. In the shallow coastal Baltic Sea seagrass Z. marina lives in a highly variable environment due to seasonality and rapid changes in meteorological conditions. This was demonstrated by the remarkable differences in water temperatures between experimental years of ca. 8°C. Thus, the current study also investigated the effect of elevated pCO2 in combination with short-term natural fluctuations of environmental factors, i.e. temperature and PAR on the photosynthesis of Z. marina. Our results show that elevated pCO2 alone did not enhance the photosynthesis of the seagrass. The photosynthetic response of Z. marina to CO2 enrichment was affected by changes in water temperature and light availability.

Coral Reefs and People in a High-CO2 World: Where Can Science Make a Difference to People?

Reefs and People at RiskIncreasing levels of carbon dioxide in the atmosphere put shallow, warm-water coral reef ecosystems, and the people who depend upon them at risk from two key global environmental stresses: 1) elevated sea surface temperature (that can cause coral bleaching and related mortality), and 2) ocean acidification. These global stressors: cannot be avoided by local management, compound local stressors, and hasten the loss of ecosystem services. Impacts to people will be most grave where a) human dependence on coral reef ecosystems is high, b) sea surface temperature reaches critical levels soonest, and c) ocean acidification levels are most severe. Where these elements align, swift action will be needed to protect people’s lives and livelihoods, but such action must be informed by data and science.An Indicator ApproachDesigning policies to offset potential harm to coral reef ecosystems and people requires a better understanding of where CO2-related global environmental stresses could cause the most severe impacts. Mapping indicators has been proposed as a way of combining natural and social science data to identify policy actions even when the needed science is relatively nascent. To identify where people are at risk and where more science is needed, we map indicators of biological, physical and social science factors to understand how human dependence on coral reef ecosystems will be affected by globally-driven threats to corals expected in a high-CO2 world. Western Mexico, Micronesia, Indonesia and parts of Australia have high human dependence and will likely face severe combined threats. As a region, Southeast Asia is particularly at risk. Many of the countries most dependent upon coral reef ecosystems are places for which we have the least robust data on ocean acidification. These areas require new data and interdisciplinary scientific research to help coral reef-dependent human communities better prepare for a high CO2 world.

Does Size Matter? Atmospheric CO2 May Be a Stronger Driver of Stomatal Closing Rate Than Stomatal Size in Taxa That Diversified under Low CO2.

One strategy for plants to optimize stomatal function is to open and close their stomata quickly in response to environmental signals. It is generally assumed that small stomata can alter aperture faster than large stomata. We tested the hypothesis that species with small stomata close faster than species with larger stomata in response to darkness by comparing rate of stomatal closure across an evolutionary range of species including ferns, cycads, conifers, and angiosperms under controlled ambient conditions (380 ppm CO2; 20.9% O2). The two species with fastest half-closure time and the two species with slowest half-closure time had large stomata while the remaining three species had small stomata, implying that closing rate was not correlated with stomatal size in these species. Neither was response time correlated with stomatal density, phylogeny, functional group, or life strategy. Our results suggest that past atmospheric CO2 concentration during time of taxa diversification may influence stomatal response time. We show that species which last diversified under low or declining atmospheric CO2 concentration close stomata faster than species that last diversified in a high CO2 world. Low atmospheric [CO2] during taxa diversification may have placed a selection pressure on plants to accelerate stomatal closing to maintain adequate internal CO2 and optimize water use efficiency.

Environmental carbonate chemistry selects for phenotype of recently isolated strains of Emiliania huxleyi

Coccolithophorid algae, particularly Emiliania huxleyi, are prolific biomineralisers that, under many conditions, dominate communities of marine eukaryotic plankton. Their ability to photosynthesise and form calcified scales (coccoliths) has placed them in a unique position in the global carbon cycle. Contrasting reports have been made with regards to the response of E. huxleyi to ocean acidification. Therefore, there is a pressing need to further determine the fate of this key organism in a rising CO2 world. In this paper, we investigate the phenotype of newly isolated, genetically diverse, strains of E. huxleyi from UK Ocean Acidification Research Programme (UKOA) cruises around the British Isles, the Arctic, and the Southern Ocean. We find a continuum of diversity amongst the physiological and photosynthetic parameters of different strains of E. huxleyi morphotype A under uniform, ambient conditions imposed in the laboratory. This physiology is best explained by adaptation to carbonate chemistry in the former habitat rather than being prescribed by genetic fingerprints such as the coccolithophore morphology motif (CMM). To a first order, the photosynthetic capacity of each strain is a function of both aqueous CO2 availability, and calcification rate, suggestive of a link between carbon concentrating ability and calcification. The calcification rate of each strain is related linearly to the natural environmental [CO32−] at the site of isolation, but a few exceptional strains display low calcification rates at the highest [CO32−] when calcification is limited by low CO2 availability and/or a lack of a carbon concentrating mechanism. We present O2-electrode measurements alongside coccolith oxygen isotopic composition and the uronic acid content (UAC) of the coccolith associated polysaccharide (CAP), that act as indirect tools to show the differing carbon concentrating ability of the strains. The environmental selection revealed amongst our recently isolated strain collection points to the future outcompetition of the slow growing morphotypes B/C and R (which also lack a carbon concentrating mechanism) by more rapidly photosynthesising, and lightly calcified strains of morphotype A but with their rate of calcification highly dependent on the surface ocean saturation state. The mechanism of E. huxleyi response to carbonate chemistry in the modern ocean appears to be selection from a continuum of phenotype.

Seasonal climatology of CO2 across North America from aircraft measurements in the NOAA/ESRL Global Greenhouse Gas Reference Network

AbstractSeasonal spatial and temporal gradients for the CO2 mole fraction over North America are examined by creating a climatology from data collected 2004–2013 by the NOAA/ESRL Global Greenhouse Gas Reference Network Aircraft Program relative to trends observed for CO2 at the Mauna Loa Observatory. The data analyzed are from measurements of air samples collected in specially fabricated flask packages at frequencies of days to months at 22 sites over continental North America and shipped back to Boulder, Colorado, for analysis. These measurements are calibrated relative to the CO2 World Meteorological Organization mole fraction scale. The climatologies of CO2 are compared to climatologies of CO, CH4, SF6, N2O (which are also measured from this sampling program), and winds to understand the dominant transport and chemical and biological processes driving changes in the spatial and temporal mole fractions of CO2 as air passes over continental North America. The measurements show that air masses coming off the Pacific on the west coast of North America are relatively homogeneous with altitude. As air masses flow eastward, the lower section from the surface to 4000 m above sea level (masl) becomes distinctly different from the 4000–8000 masl section of the column. This is due in part to the extent of the planetary boundary layer, which is directly impacted by continental sources and sinks, and to the vertical gradient in west‐to‐east wind speeds. The slowdown and southerly shift in winds at most sites during summer months amplify the summertime drawdown relative to what might be expected from local fluxes. This influence counteracts the dilution of summer time CO2 drawdown (known as the “rectifier effect”) as well as changes the surface influence “footprint” for each site. An early start to the summertime drawdown, a pronounced seasonal cycle in the column mean (500 to 8000 masl), and small vertical gradients in CO2, CO, CH4, SF6, and N2O at high‐latitude western sites such as Poker Flat, Alaska, suggest recent influence of transport from southern latitudes and not local processes. This transport pathway provides a significant contribution to the large seasonal cycle observed in the high latitudes at all altitudes sampled. A sampling analysis of the NOAA/ESRL CarbonTracker model suggests that the average sampling resolution of 22 days is sufficient to get a robust estimate of mean seasonal cycle of CO2 during this 10 year period but insufficient to detect interannual variability in emissions over North America.