Elevated CO2 Partial Pressure Research Articles

Interactive effects of photoperiod and light intensity on blood physiological and biochemical reactions of broilers grown to heavy weights

The effects of photoperiod, light intensity, and their interaction on blood acid-base balance, metabolites, and electrolytes in broiler chickens under environmentally controlled conditions were examined in 2 trials. A 3 × 3 factorial experiment in a randomized complete block design was used in this study. In each trial, all treatment groups were provided 23L:1D with 20 lx of intensity from placement to 7 d, and then subjected to the treatments. The 9 treatments consisted of 3 photoperiods [long/continuous (23L:1D) from d 8 to 56, regular/intermittent (2L:2D), and short/nonintermittent (8L:16D) from d 8 to 48 and 23L:1D from d 49 to 56, respectively] and exposure to 3 light intensities (10, 5.0, and 0.5 lx) from d 8 through d 56 at 50% RH. Feed and water were provided ad libitum. Venous blood samples were collected on d 7, 14, 28, 42, and 56. Main effects indicated that short/nonintermittent photoperiod significantly (P < 0.05) reduced BW, pH, partial pressure of O2, saturated O2, Na(+), K(+), Ca(2+), Cl(-), osmolality, triiodothyronine (T3), and total protein along with significantly (P < 0.05) elevated partial pressure of CO2, hematocrit, hemoglobin, and lactate concentrations. In addition, there were no effects of photoperiod on HCO3(-), glucose, anion gap, and thyroxine (T4). Plasma corticosterone was not affected by photoperiod, light intensity, or their interaction. There was no effect of light intensity on most of the blood variables examined. Acid-base regulation during photoperiod and light intensity exposure did not deteriorate despite a lower pH and higher partial pressure of CO2 with normal HCO3(-). These results indicate that continuous exposure of broiler chickens to varying light intensities had a minor effect on blood physiological variables, whereas the short photoperiod markedly affected most blood physiological variables without inducing physiological stress in broilers.

Highly explosive 2010 Merapi eruption: Evidence for shallow-level crustal assimilation and hybrid fluid

The processes responsible for the highly explosive events at Merapi, Central Java, Indonesia have been investigated through a petrological, mineralogical and geochemical study of the first-stage tephra and pyroclastic flows sampled in October and November 2010, and second-stage ash sampled shortly after the 5–6th November 2010 paroxysmal subplinian eruption. Several chemical and physical parameters suggest that the magma assimilated calc-silicate xenoliths derived from the surrounding carbonate-bearing crust (Javanese limestone). The bulk volcanic samples have highly radiogenic 87Sr/86Sr (0.70571–0.70598) ratios that approach the compositional field of material similar to the calc-silicate xenoliths. The 2010 plagioclase phenocrysts from the pyroclastic flow and tephra reveal anorthite cores (up to An94–97) with low FeO contents (≤0.8wt.%), and 18O enrichment (6.5‰ δ18O). The major and trace elements of the silicic glasses and phenocrysts (plagioclase, low-Al augite and titanomagnetite), the Sr-isotopic compositions of the bulk samples and plagioclases erupted in 2010 can be explained by complete digestion of the 1998 and 2006 calc-silicate xenoliths. The bulk assimilation proceeded through binary mixing between a calcic melt (representing Crustal Assimilant, CaO up to 10.5wt.% and CaO/Al2O3 up to 1.2) and the deep source hydrous K-rich melt. Similarly to the 1998 and 2006 calc-silicate xenolith composition, the 2010 Crustal Assimilant is enriched in Mn (MnO up to 0.5wt.%), Zn, V, and Sc contents. In contrast, the hydrous K-rich melt is enriched in volatiles (Cl up to 0.37wt.% and bulk H2O+CO2 up to 5±1wt.%), Al2O3, TiO2 and REE contents, consistent with its derivation from deep source. This hydrous K-rich melt may have been saturated with an aqueous Cl-rich fluid at about 200MPa, a pressure consistent with the level of the crustal assimilation. We estimated that the pre-eruptive basaltic andesite magma assimilated from 15 to 40wt.% of the calc-silicate crustal material, corresponding to introduction of additional 0.19 to 2.1Mt of CO2 to the magma. Experimental leaching of the ash samples documents the release of an aqueous fluid enriched in Cl, Na, Ca, Cd, Sb and Zn during the paroxysmal subplinian eruption. The paroxysmal eruption may have been produced by saturation of the pre-eruptive basaltic andesite magma with hybrid aqueous carbonic NaCl–HCl-rich fluid due to bulk assimilation creating elevated partial pressure of CO2 at shallow crustal conditions of about 200MPa. In contrast, mildly explosive block-and-ash flows (typical Merapi-type) may result from selective assimilation of the carbonate-bearing xenoliths and lower CO2 partial pressure that may not lead to explosive degassing.

Accelerated Carbonation of Brucite in Mine Tailings for Carbon Sequestration

Atmospheric CO(2) is sequestered within ultramafic mine tailings via carbonation of Mg-bearing minerals. The rate of carbon sequestration at some mine sites appears to be limited by the rate of CO(2) supply. If carbonation of bulk tailings were accelerated, large mines may have the capacity to sequester millions of tonnes of CO(2) annually, offsetting mine emissions. The effect of supplying elevated partial pressures of CO(2) (pCO(2)) at 1 atm total pressure, on the carbonation rate of brucite [Mg(OH)(2)], a tailings mineral, was investigated experimentally with conditions emulating those at Mount Keith Nickel Mine (MKM), Western Australia. Brucite was carbonated to form nesquehonite [MgCO(3) · 3H(2)O] at a rate that increased linearly with pCO(2). Geochemical modeling indicated that HCO(3)(-) promoted dissolution accelerated brucite carbonation. Isotopic and aqueous chemistry data indicated that equilibrium between CO(2) in the gas and aqueous phases was not attained during carbonation, yet nesquehonite precipitation occurred at equilibrium. This implies CO(2) uptake into solution remains rate-limiting for brucite carbonation at elevated pCO(2), providing potential for further acceleration. Accelerated brucite carbonation at MKM offers the potential to offset annual mine emissions by ~22-57%. Recognition of mechanisms for brucite carbonation will guide ongoing work to accelerate Mg-silicate carbonation in tailings.

Impacts of seawater acidification on mantle gene expression patterns of the Baltic Sea blue mussel: implications for shell formation and energy metabolism

Marine organisms have to cope with increasing CO2 partial pressures and decreasing pH in the oceans. We elucidated the impacts of an 8-week acclimation period to four seawater pCO2 treatments (39, 113, 243 and 405 Pa/385, 1,120, 2,400 and 4,000 µatm) on mantle gene expression patterns in the blue mussel Mytilus edulis from the Baltic Sea. Based on the M. edulis mantle tissue transcriptome, the expression of several genes involved in metabolism, calcification and stress responses was assessed in the outer (marginal and pallial zone) and the inner mantle tissues (central zone) using quantitative real-time PCR. The expression of genes involved in energy and protein metabolism (F-ATPase, hexokinase and elongation factor alpha) was strongly affected by acclimation to moderately elevated CO2 partial pressures. Expression of a chitinase, potentially important for the calcification process, was strongly depressed (maximum ninefold), correlating with a linear decrease in shell growth observed in the experimental animals. Interestingly, shell matrix protein candidate genes were less affected by CO2 in both tissues. A compensatory process toward enhanced shell protection is indicated by a massive increase in the expression of tyrosinase, a gene involved in periostracum formation (maximum 220-fold). Using correlation matrices and a force-directed layout network graph, we were able to uncover possible underlying regulatory networks and the connections between different pathways, thereby providing a molecular basis of observed changes in animal physiology in response to ocean acidification.

Response of two marine bacterial isolates to high CO&lt;sub&gt;2 concentration

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 453:27-36 (2012) - DOI: https://doi.org/10.3354/meps09644 Response of two marine bacterial isolates to high CO2 concentration Eva Teira1,*, Ana Fernández1, Xosé Antón Álvarez-Salgado2, Enma Elena García-Martín1, Pablo Serret1, Cristina Sobrino1 1Departamento Ecoloxía e Bioloxía Animal, Universidade de Vigo, Campus Lagoas-Marcosende 36310 Vigo, Spain 2Consejo Superior de Investigaciones Científicas (CSIC), Instituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain *Email: teira@uvigo.es ABSTRACT: Experimental results related to the effects of ocean acidification on planktonic marine microbes are still rather inconsistent and occasionally contradictory. Moreover, laboratory or field experiments that address the effects of changes in CO2 concentrations on heterotrophic microbes are very scarce, despite the major role of these organisms in the marine carbon cycle. We tested the direct effect of an elevated CO2 concentration (1000 ppmv) on the biomass and metabolic rates (leucine incorporation, CO2 fixation and respiration) of 2 isolates belonging to 2 relevant marine bacterial families, Rhodobacteraceae (strain MED165) and Flavobacteriaceae (strain MED217). Our results demonstrate that, contrary to some expectations, high pCO2 did not negatively affect bacterial growth but increased growth efficiency in the case of MED217. The elevated partial pressure of CO2 ( pCO2) caused, in both cases, higher rates of CO2 fixation in the dissolved fraction and, in the case of MED217, lower respiration rates. Both responses would tend to increase the pH of seawater acting as a negative feedback between elevated atmospheric CO2 concentrations and ocean acidification. KEY WORDS: Bacterial metabolism · Flavobacteriaceae · Ocean acidification · Rhodobacteraceae Full text in pdf format PreviousNextCite this article as: Teira E, Fernández A, Álvarez-Salgado XA, García-Martín EE, Serret P, Sobrino C (2012) Response of two marine bacterial isolates to high CO2 concentration. Mar Ecol Prog Ser 453:27-36. https://doi.org/10.3354/meps09644 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 453. Online publication date: May 07, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Variable production of transparent exopolymeric particles by haploid and diploid life stages of coccolithophores grown under different CO2 concentrations

The production of transparent exopolymeric particles (TEP) by the coccolithophores, Emiliania huxleyi, Calcidiscus leptoporus and Syracosphaera pulchra was investigated in batch cultures. The abundance, size spectra and carbon content of TEP were examined during the exponential growth phase of both haploid and diploid life stages grown under ambient (400 atm) and elevated (760 atm) CO2 partial pressure (pCO(2)) conditions. Results showed species- and life stage-specific differences in TEP production rate (day(1)) derived from abundance and carbon content of TEP. At 400 atm, TEP production rate was the highest in the diploid stage of S. pulchra and E. huxleyi, while TEP carbon content per cell was the highest in the diploid stage of C. leptoporus. At 760 atm, TEP production rate increased in almost all species and was closely related to the cell growth rates (except in the diploid stage of C. leptoporus), while the slope values of the regression lines between TEP size distribution and concentration decreased. This means that the contribution of smaller size TEP was relatively more important than larger TEP in the high pCO(2) treatment. Elevated pCO(2) is potentially able to alter TEP size distribution. TEP-C content cell(1) generally decreased with increasing pCO(2). TEP-C accounted for 124 of the cell particulate organic carbon production and was inversely related to increasing pCO(2). TEP production by C. leptoporus and S. pulchra has not previously been documented. The amount of organic carbon released as TEP by these coccolithophores is comparable to and may even exceed TEP production by some diatoms.

Effects of CO2 and their modulation by light in the life‐cycle stages of the coccolithophore Emiliania huxleyi

The effects of ocean acidification on the life‐cycle stages of the coccolithophore Emiliania huxleyi and their modulation by light were examined. Calcifying diploid and noncalcifying haploid cells (Roscoff culture collection strains 1216 and 1217) were acclimated to present‐day and elevated CO2 partial pressures (PCO2; 38.5 vs. 101.3 Pa, i.e., 380 vs. 1000 µatm) under low and high light (50 vs. 300 µmol photons m−2 s−1). Growth rates as well as cellular quotas and production rates of C and N were measured. Sources of inorganic C for biomass buildup were determined using a 14C disequilibrium assay. Photosynthetic O2 evolution was measured as a function of dissolved inorganic C and light by means of membrane‐inlet mass spectrometry. The diploid stage responded to elevated PCO2 by shunting resources from the production of particulate inorganic C toward organic C yet keeping the production of total particulate C constant. As the effect of ocean acidification was stronger under low light, the diploid stage might be less affected by increased acidity when energy availability is high. The haploid stage maintained elemental composition and production rates under elevated PCO2. Although both life‐cycle stages involve different ways of dealing with elevated PCO2, the responses were generally modulated by energy availability, being typically most pronounced under low light. Additionally, PCO2 responses resembled those induced by high irradiances, indicating that ocean acidification affects the interplay between energy‐generating processes (photosynthetic light reactions) and processes competing for energy (biomass buildup and calcification). A conceptual model is put forward explaining why the magnitude of single responses is determined by energy availability.

Effects of elevated CO2 partial pressure and temperature on the coccolithophore Syracosphaera pulchra

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 64:221-232 (2011) - DOI: https://doi.org/10.3354/ame01520 Effects of elevated CO2 partial pressure and temperature on the coccolithophore Syracosphaera pulchra Sarah Fiorini1,2,3,*, Jack J. Middelburg3,4, Jean-Pierre Gattuso1,2 1INSU-CNRS, Laboratoire d’Océanographie de Villefranche, BP 28, 06234 Villefranche-sur-Mer Cedex, France 2UPMC University of Paris 06, Observatoire Océanologique de Villefranche-sur-Mer, 06230 Villefranche-sur-Mer, France 3Netherlands Institute of Ecology (NIOO-KNAW), PO Box 140, 4400 AC Yerseke, The Netherlands 4Faculty of Geosciences, Utrecht University, PO Box 80.021, 3508 TA Utrecht, The Netherlands *Email: fiorini.sarah@gmail.com ABSTRACT: The effects of elevated partial pressure of CO2 (pCO2) and temperature on the cocco­lithophore Syracosphaera pulchra were investigated in isolation and in combination. Both the diploid and the haploid life stages were studied. Batch cultures were grown under 4 conditions: 400 µatm and 19°C; 400 µatm and 22°C; 740 µatm and 19°C; and 740 µatm and 22°C. The growth rate (μ) ­significantly increased under elevated pCO2 only in the haploid stage and showed a different pattern with respect to temperature: it was higher at an elevated temperature in the haploid stage at 400 µatm whereas it decreased in the diploid stage at 740 µatm. Increasing both parameters together increased the growth rate by 11% in the haploid stage only. Elevated pCO2 had a negative impact on the content of particulate organic carbon (POC), production and cell size in both life stages at 19°C, while no significant effect was observed at 22°C. Increasing temperature significantly increased the content of POC and production in the diploid stage at 740 µatm, while at 400 µatm it significantly decreased both the content of POC and production in the haploid stage. A simultaneous increase in pCO2 and temperature had a negative effect on the content of POC and production in the haploid stage only. Neither the rate of calcification (production of particulate inorganic carbon, PIC) nor the PIC:POC ratio were significantly affected by elevated pCO2, temperature or their interaction. These results showed a strong interactive effect between pCO2 and temperature in affecting the physiology of S. pulchra, an effect that was often more pronounced in the haploid life stage. Elevated pCO2 had a stronger effect than temperature. KEY WORDS: Coccolithophores · Ocean acidification · Global warming · Carbon dioxide · Temperature · Calcification · Primary production · PIC:POC ratio Full text in pdf format PreviousNextCite this article as: Fiorini S, Middelburg JJ, Gattuso JP (2011) Effects of elevated CO2 partial pressure and temperature on the coccolithophore Syracosphaera pulchra. Aquat Microb Ecol 64:221-232. https://doi.org/10.3354/ame01520 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 64, No. 3. Online publication date: September 20, 2011 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2011 Inter-Research.

Proteomic response to elevated PCO2 level in eastern oysters, Crassostrea virginica: evidence for oxidative stress

Estuaries are characterized by extreme fluctuations in CO(2) levels due to bouts of CO(2) production by the resident biota that exceed its capacity of CO(2) consumption and/or the rates of gas exchange with the atmosphere and open ocean waters. Elevated partial pressures of CO(2) (P(CO(2)); i.e. environmental hypercapnia) decrease the pH of estuarine waters and, ultimately, extracellular and intracellular pH levels of estuarine organisms such as mollusks that have limited capacity for pH regulation. We analyzed proteomic changes associated with exposure to elevated P(CO(2)) in the mantle tissue of eastern oysters (Crassostrea virginica) after 2 weeks of exposure to control (∼39 Pa P(CO(2))) and hypercapnic (∼357 Pa P(CO(2))) conditions using two-dimensional gel electrophoresis and tandem mass spectrometry. Exposure to high P(CO(2)) resulted in a significant proteome shift in the mantle tissue, with 12% of proteins (54 out of 456) differentially expressed under the high P(CO(2)) compared with control conditions. Of the 54 differentially expressed proteins, we were able to identify 17. Among the identified proteins, two main functional categories were upregulated in response to hypercapnia: those associated with the cytoskeleton (e.g. several actin isoforms) and those associated with oxidative stress (e.g. superoxide dismutase and several peroxiredoxins as well as the thioredoxin-related nucleoredoxin). This indicates that exposure to high P(CO(2)) (∼357 Pa) induces oxidative stress and suggests that the cytoskeleton is a major target of oxidative stress. We discuss how elevated CO(2) levels may cause oxidative stress by increasing the production of reactive oxygen species (ROS) either indirectly by lowering organismal pH, which may enhance the Fenton reaction, and/or directly by CO(2) interacting with other ROS to form more free radicals. Although estuarine species are already exposed to higher and more variable levels of CO(2) than other marine species, climate change may further increase the extremes and thereby cause greater levels of oxidative stress.

Differential effects of ocean acidification on growth and photosynthesis among phylotypes of Symbiodinium (Dinophyceae)

We investigated the effect of elevated partial pressure of CO2 (pCO2) on the photosynthesis and growth of four phylotypes (ITS2 types A1, A13, A2, and B1) from the genus Symbiodinium, a diverse dinoflagellate group that is important, both free‐living and in symbiosis, for the viability of cnidarians and is thus a potentially important model dinoflagellate group. The response of Symbiodinium to an elevated pCO2 was phylotype‐specific. Phylotypes A1 and B1 were largely unaffected by a doubling in pCO2; in contrast, the growth rate of A13 and the photosynthetic capacity of A2 both increased by ~ 60%. In no case was there an effect of ocean acidification (OA) upon respiration (dark‐ or light‐dependent) for any of the phylotypes examined. Our observations suggest that OA might preferentially select among free‐living populations of Symbiodinium, with implications for future symbioses that rely on algal acquisition from the environment (i.e., horizontal transmission). Furthermore, the carbon environment within the host could differentially affect the physiology of different Symbiodinium phylotypes. The range of responses we observed also highlights that the choice of species is an important consideration in OA research and that further investigation across phylogenetic diversity, for both the direction of effect and the underlying mechanism(s) involved, is warranted.

New insight into photosynthetic acclimation to elevated CO2: The role of leaf nitrogen and ribulose-1,5-bisphosphate carboxylase/oxygenase content in rice leaves

We tested the hypothesis that photosynthetic (A) acclimation to elevated CO2 partial pressure (p[CO2]) is associated with the inhibition of protein synthesis, inhibition of nitrogen (N) partitioning into the leaf blade and/or accelerated leaf senescence in rice (Oryza sativa L. cv. Notohikari). Plants were grown for 70 days hydroponically in artificially illuminated growth chambers at a p[CO2] of either 39 or 100Pa at N 2mM. Leaf A, Vc.max, Jmax, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, E.C.4.1.1.39), mRNA for associated genes rbcS and rbcL, total N and carbohydrate concentrations in leaves at different positions in the canopy were measured. Spatial allocation of N and Rubisco synthesis of expanding leaf blade was also measured from the leaf ligule to tip of the leaf blade. Growth at elevated p[CO2] suppressed light saturated A, Vc.max and Jmax in leaf blades at all positions in the canopy. The suppression of A was 15% for the upper leaf blades compared to 37% in the lower leaf blades. Similar reductions in the amount of Rubisco, Chlorophyll, and total N were observed in the leaves of the plants grown in 100 p[CO2] compared to the 39 p[CO2]. Sucrose and starch concentration concentrations increased at elevated p[CO2] but we found no relationship between A, Rubisco or the amount of transcript abundance of rbcS and rbcL. Elevated p[CO2] substantially reduced N allocation into expanding leaf blades and this was well correlated with Rubisco synthesis. These results suggest that A acclimation to elevated p[CO2] occurs during all phases of the leaf development, is initiated during the cell maturation process and linked with spatial N allocation into the leaf blade. In addition, elevated p[CO2] accelerated lower leaf blade senescence which compounded the effect on A acclimation.

Enhanced Activity of SO2 Absorbent under High CO2 Partial Pressure in Pressurized Fluidized Bed Combustor

Emissions of SOX from a 4MWth twin-bed pressurized fluidized bed combustor (PFBC) system were measured during long-term (1187 hours) operation. The PFBC consisted of two bubbling beds, A-bed and B-bed. Though both reactors were operated at the same pressure and temperature, emissions of SO2 differed between two reactors. The limestone particles sampled from B-bed, which showed lower emission level, had more internal cracks and their particle size was smaller than those from A-bed. Basic studies of SO2 capture and calcination were also conducted using a pressurized fixed bed reactor for eight kinds of limestone. Calcination of limestone was found to increase reactivity with SO2 under elevated CO2 partial pressure conditions higher than equilibrium partial pressure. Limestones with more internal cracks were found to have higher reactivity towards SO2 absorption. The degree of crystallization measured by X-ray diffraction gave valuable information to predict reactivity and fragmentation. The difference in emission behavior between two fluidized beds is discussed in terms of crack formation and fragmentation.

Response of Mediterranean coralline algae to ocean acidification and elevated temperature

AbstractThe effects of elevated partial pressure of CO2(pCO2) and temperature, alone and in combination, on survival, calcification and dissolution were investigated in the crustose coralline algaLithophyllum cabiochae. Algae were maintained in aquaria during 1 year at near‐ambient conditions of irradiance, at ambient or elevated temperature (+3 °C) and at ambient [ca. 400 parts per million (ppm)] or elevatedpCO2(ca. 700 ppm). Algal necroses appeared at the end of summer under elevated temperature first at 700 ppm (60% of the thallus surface) and then at 400 ppm (30%). The death of algae was observed only under elevated temperature and was two‐ to threefold higher under elevatedpCO2. During the first month of the experiment, net calcification was significantly reduced under elevatedpCO2. At the end of the summer period, net calcification decreased by 50% when both temperature andpCO2were elevated while no effect was found under elevated temperature and elevatedpCO2alone. In autumn and winter, net calcification in healthy algae increased with increasing temperature, independently of thepCO2level, while necroses and death in the algal population caused a net dissolution at elevated temperature andpCO2. The dissolution of dead algal thalli was affected by elevatedpCO2, being two‐ to fourfold higher than under ambientpCO2. These results suggest that net dissolution is likely to exceed net calcification inL. cabiochaeby the end of this century. This could have major consequences in terms of biodiversity and biogeochemistry in coralligenous communities dominated by these algae.

Impacts of ocean acidification on marine fauna and ecosystem processes

AbstractFabry, V. J., Seibel, B. A., Feely, R. A., and Orr, J. C. 2008. Impacts of ocean acidification on marine fauna and ecosystem processes. – ICES Journal of Marine Science, 65: 414–432. Oceanic uptake of anthropogenic carbon dioxide (CO2) is altering the seawater chemistry of the world’s oceans with consequences for marine biota. Elevated partial pressure of CO2 (pCO2) is causing the calcium carbonate saturation horizon to shoal in many regions, particularly in high latitudes and regions that intersect with pronounced hypoxic zones. The ability of marine animals, most importantly pteropod molluscs, foraminifera, and some benthic invertebrates, to produce calcareous skeletal structures is directly affected by seawater CO2 chemistry. CO2 influences the physiology of marine organisms as well through acid-base imbalance and reduced oxygen transport capacity. The few studies at relevant pCO2 levels impede our ability to predict future impacts on foodweb dynamics and other ecosystem processes. Here we present new observations, review available data, and identify priorities for future research, based on regions, ecosystems, taxa, and physiological processes believed to be most vulnerable to ocean acidification. We conclude that ocean acidification and the synergistic impacts of other anthropogenic stressors provide great potential for widespread changes to marine ecosystems.

Physiological changes in marine picocyanobacterial Synechococcus strains exposed to elevated CO2 partial pressure

Unicellular marine cyanobacteria are abundant in both coastal and oligotrophic environments, where they contribute substantially to primary production. The physiological effect of future increases in atmospheric CO2 concentrations on the marine picocyanobacteria is still poorly known. We studied the physiological changes in marine phycocyanin (PC)-rich and phycoerythrin (PE)-rich Synechococcus strains under different CO2 partial pressures (350, 600 and 800 ppm). The PE strain showed no significant change in growth rate over the experimental CO2 range. A significant increase (25.4%) in carbohydrate was observed at 800 ppm CO2, but no significant change in protein and RNA/DNA ratio was observed in any CO2 treatment. The PC strain showed a significant increase (36.7%) in growth rate at 800 ppm CO2, but no significant change in carbohydrate or protein content was observed over the entire CO2 range. The RNA/DNA ratio increased with increasing CO2 concentration and was positively correlated with growth rate. Cellular red fluorescence and orange fluorescence of the PE strain tended to decline in all CO2 treatments. However, no such decline was observed at higher CO2 treatments in the PC strain. Our results suggest that the PC strain would probably benefit more than the PE strain from future increases in atmospheric CO2 concentrations.

Effects of elevated pCO2 on epilithic and endolithic metabolism of reef carbonates

AbstractWe investigated effects of elevated partial pressure of CO2 (pCO2) on the metabolism of epilithic and endolithic phototrophic communities that colonized experimental coral blocks. Blocks of the massive coral Porites lobata were exposed to colonization by epilithic and endolithic organisms at an oceanic site in Kaneohe Bay (Hawaii) for 6 months, and then were transported to laboratory tanks. A bubbling system was used to maintain two treatments for 3 months, one at ambient pCO2 (400 ppm) and the second at elevated pCO2 (750 ppm). Net photosynthetic rates of epilithic communities in the high pCO2 treatment, dominated by encrusting coralline algae, decreased by 35% while respiration rates remained constant. In contrast, metabolism of endolithic phototrophs, comprised of cyanobacteria and algae, was not significantly affected by the elevated pCO2 even though endoliths contributed about 63% to block production.

Mycorrhizas improve nitrogen nutrition of Trifolium repens after 8 yr of selection under elevated atmospheric CO2 partial pressure

Altered environmental conditions may change populations of arbuscular mycorrhizal fungi and thereby affect mycorrhizal functioning. We investigated whether 8 yr of free-air CO2 enrichment has selected fungi that differently influence the nutrition and growth of host plants. In a controlled pot experiment, two sets of seven randomly picked single spore isolates, originating from field plots of elevated (60 Pa) or ambient CO2 partial pressure (pCO2), were inoculated on nodulated Trifolium repens (white clover) plants. Fungal isolates belonged to the Glomus claroideum or Glomus intraradices species complex, and host plants were clonal micropropagates derived from nine genets. Total nitrogen (N) concentration was increased in leaves of plants inoculated with fungal isolates from elevated-pCO2 plots. These isolates took up nearly twice as much N from the soil as isolates from ambient-pCO2 plots and showed much greater stimulation of biological N2 fixation. The morpho-species identity of isolates had a more pronounced effect on N2 fixation and on root length colonized than isolate identity. We conclude that rising atmospheric pCO2 may select for fungal strains that will help their host plants to meet increased N demands.

Effect of nutrient enrichment and elevated CO2 partial pressure on growth rate of Atlantic scleractinian coral Acropora cervicornis

The growth rate of Acropora cervicornis branch tips maintained in the laboratory was measured before, during, and after exposure to elevated nitrate (5 and 10 pM NO 3 - ), phosphate (2 and 4 pM P-PO 4 3 ) and/or pCO 2 (CO 2 ∼700 to 800 patm). The effect of increased pCO 2 was greater than that of nutrient enrichment alone. High concentrations of nitrate or phosphate resulted in significant decreases in growth rate, in both the presence and absence of increased pCO 2 . The effect of nitrate and phosphate enrichment combined was additive or antagonistic relative to nutrient concentration and pCO 2 level. Growth rate recovery was greater after exposure to increased nutrients or CO 2 compared to increased nutrients and CO 2 . If these results accurately predict coral response in the natural environment, it is reasonable to speculate that the survival and reef-building potential of this species will be significantly negatively impacted by continued coastal nutrification and projected pCO 2 increases.

Biological Impact of Elevated Ocean CO2 Concentrations: Lessons from Animal Physiology and Earth History

CO2 currently accumulating in the atmosphere permeates into ocean surface layers, where it may impact on marine animals in addition to effects caused by global warming. At the same time, several countries are developing scenarios for the disposal of anthropogenic CO2 in the worlds' oceans, especially the deep sea. Elevated CO2 partial pressures (hypercapnia) will affect the physiology of water breathing animals, a phenomenon also considered in recent discussions of a role for CO2 in mass extinction events in earth history. Our current knowledge of CO2 effects ranges from effects of hypercapnia on acid-base regulation, calcification and growth to influences on respiration, energy turnover and mode of metabolism. The present paper attempts to evaluate critical processes and the thresholds beyond which these effects may become detrimental. CO2 elicits acidosis not only in the water, but also in tissues and body fluids. Despite compensatory accumulation of bicarbonate, acid-base parameters (pH, bicarbonate and CO2 levels) and ion levels reach new steady-state values, with specific, long-term effects on metabolic functions. Even though such processes may not be detrimental, they are expected to affect long-term growth and reproduction and may thus be harmful at population and species levels. Sensitivity is maximal in ommastrephid squid, which are characterized by a high metabolic rate and extremely pH-sensitive blood oxygen transport. Acute sensitivity is interpreted to be less in fish with intracellular blood pigments and higher capacities to compensate for CO2 induced acid-base disturbances than invertebrates. Virtually nothing is known about the degree to which deep-sea fishes are affected by short or long term hypercapnia. Sensitivity to CO2 is hypothesized to be related to the organizational level of an animal, its energy requirements and mode of life. Long-term effects expected at population and species levels are in line with recent considerations of a detrimental role of CO2 during mass extinctions in the earth's history. Future research is needed in this area to evaluate critical effects of the various CO2 disposal scenarios.

Variations in dark respiration and mitochondrial numbers within needles of Pinus radiata grown in ambient or elevated CO2 partial pressure.

Within-leaf variations in cell size, mitochondrial numbers and dark respiration rates were compared in the most recently expanded tip, the mid-section and base of needles of Pinus radiata D. Don trees grown for 4 years in open-top chambers at ambient (36 Pa) or elevated (65 Pa) carbon dioxide partial pressure (p(CO2)a). Mitochondrial numbers and respiratory activity varied along the length of the needle, with the highest number of mitochondria per unit cytoplasm and the highest rate of respiration per unit leaf area at the base of the needle. Regardless of the location of the cells (tip, middle or basal sections), needles collected from trees grown in elevated p(CO2)a had nearly twice the number of mitochondria per unit cytoplasm as those grown in ambient p(CO2)a. This stimulation of mitochondrial density by growth at elevated p(CO2)a was greater at the tip of the needle (2.7 times more mitochondria than in needles grown in ambient CO2) than at the base of the needle (1.7 times). The mean size of individual mitochondria was unaffected either by growth at elevated p(CO2)a or by position along the needle. Tree growth at elevated p(CO2)a had a variable effect on respiration per unit leaf area, significantly increasing respiration in the tip of the needles (+25%) and decreasing respiration at the mid-section and base of the needles (-14% and -25%, respectively). Although a simple relationship between respiration per unit leaf area and mitochondrial number per unit cytoplasm was found within each CO2 treatment, the variable effect of growth at elevated p(CO2)a on respiration along the length of the needles indicates that a more complex relationship must determine the association between structure and function in these needles.