Methodologies for simulating impacts of climate change on crop production

Ecophysiological models are widely used to forecast potential impacts of climate change on future agricultural productivity and to examine options for adaptation by local stakeholders and policy makers. However, protocols followed in such assessments vary to such an extent that they constrain cross-study syntheses and increase the potential for bias in projected impacts. We reviewed 221 peer-reviewed papers that used crop simulation models to examine diverse aspects of how climate change might affect agricultural systems. Six subject areas were examined: target crops and regions; the crop model(s) used and their characteristics; sources and application of data on [CO₂] and climate; impact parameters evaluated; assessment of variability or risk; and adaptation strategies. Wheat, maize, soybean and rice were considered in approximately 170 papers. The USA (55 papers) and Europe (64 papers) were the dominant regions studied. The most frequent approach used to simulate response to CO₂ involved adjusting daily radiation use efficiency (RUE) and transpiration, precluding consideration of the interacting effects of CO₂, stomatal conductance and canopy temperature, which are expected to exacerbate effects of global warming. The assumed baseline [CO₂] typically corresponded to conditions 10-30 years earlier than the date the paper was accepted, exaggerating the relative impacts of increased [CO₂]. Due in part to the diverse scenarios for increases in greenhouse gas emissions, assumed future [CO₂] also varied greatly, further complicating comparisons among studies. Papers considering adaptation predominantly examined changes in planting dates and cultivars; only 20 papers tested different tillage practices or crop rotations. Risk was quantified in over half the papers, mainly in relation to variability in yield or effects of water deficits, but the limited consideration of other factors affecting risk beside climate change per se suggests that impacts of climate change were overestimated relative to background variability. A coordinated crop, climate and soil data resource would allow researchers to focus on underlying science. More extensive model intercomparison, facilitated by modular software, should strengthen the biological realism of predictions and clarify the limits of our ability to forecast agricultural impacts of climate change on crop production and associated food security as well as to evaluate potential for adaptation.     

Impacts of elevated atmospheric CO2 and temperature on plant community structure of a temperate grassland are modulated by cutting frequency

To determine the impacts of climate change and defoliation on the community structure and plant diversity of a semi‐natural temperate grassland, monoliths of a permanent grassland were exposed to ambient or elevated atmospheric CO₂ concentrations (ambient + 235 ppmv) and temperature (ambient + 3°C) from October 1998 to December 2000. The monoliths were subjected to two different cutting frequencies, either two or six cuts per year. The grassland community structure changed during the course of the experiment and was more responsive to changes in management than to changes in climate. Increased cutting frequency stimulated plant diversity by enhancing the number of forb species, but plant diversity was not significantly affected by climate change. The contribution of individual plant species to the vegetation cover revealed species‐specific responses to climate change and cutting frequency, but for most species significant interactions between climate change and cutting frequency were present. There were no clear‐cut effects of treatments on the total annual yield and the proportion of forbs present, as significant interactions between climate change and cutting frequency occurred. It is concluded that differential grassland management will modify plant species‐specific responses to climate change and resulting changes in the botanical composition of mixed‐species, temperate grasslands.     

Perspective on the relative insignificance of increasing atmospheric CO2 concentration to crop yield

Average yield of most crops in many countries increased significantly during the past 50 to 100 years. Although atmospheric CO₂ concentration, [CO₂]_a, also increased during that time period, and although crop growth and yield can respond positively to [CO₂]_a increase, yield increases were due mainly to factors other than increasing [CO₂]_a. Similarly, some yield increases prior to 1900 were also associated primarily with factors other than changes in [CO₂]_a. In particular, past national average yield increases were the result chiefly of technological advances such as nitrogen fertilization; selection of genotypes with increased harvest index and disease resistance; mechanization of planting, cultivation, and harvesting; and chemical weed and pest control. If technology continues to increase average yields at recent rates, near-future increases in [CO₂]_a will have only small impacts on yield in comparison to technology in many countries. Conversely, if future increases in [CO₂]_a are the main drivers of future yield increases, those yield increases will be small. These points are demonstrated through a comparison of (i) long-term records of yield, (ii) data from key controlled-[CO₂] experiments, and (iii) records of past [CO₂]_a. Finally, it is noted that continued [CO₂]_a increase may bring with it climatic changes that could have negative or positive impacts on future yield.     

Variability in grass forage quality and quantity in response to elevated CO2 and water limitation

Global climate change is expected to alter carbon dioxide concentration ([CO₂]) and water availability, with uncertain impacts on agriculture. Forage quality and quantity in grazing systems are of particular concern because C₃ and C₄ plants respond differently to altered environmental conditions. In a growth chamber, we compared crude protein content, biomass recovery and total crude protein across a set of perennial C₃ and C₄ grasses from the northern U.S. Great Plains under elevated [CO₂] and simulated drought. Simulated 95% confidence intervals indicate both C₃ and C₄ grasses increased forage quality and quantity under elevated [CO₂]. C₄ grasses were generally resistant to water limitation while forage quality and quantity of C₃ grasses declined under simulated drought. Our results are consistent with literature on forage quantity responses to elevated [CO₂] and drought, but forage quality responses contradict expectations. We suggest measuring plant functional traits might better elucidate response mechanisms and ameliorate methodological differences even if traits are not directly applicable to grazing management.     

The Effect of Elevated Levels of Carbon Dioxide on Potato Crops

SUMMARY

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

Elevated atmospheric CO2 effects on N fertilization in grain sorghum and soybean

Increasing atmospheric CO₂ concentration has led to concerns about global changes to the environment. One area of global change that has not been fully addressed is the effect of elevated atmospheric CO₂ on agriculture production inputs. Elevated CO₂ concentration alterations of plant growth and C:N ratios may modify C and N cycling in soil and N fertility. This study was conducted to examine the effects of legume, soybean (Glycine max (L.) Merr.), and non-legume, grain sorghum (Sorghum bicolor (L.) Moench.) carbon dioxide-enriched agro-ecosystems on N soil fertility in a Blanton loamy sand (loamy siliceous, thermic, Grossarenic Paleudults). The study was a split-plot design replicated three times with crop species (soybean and grain sorghum) as the main plots and CO₂ concentration (ambient and twice ambient) as subplots using open top field chambers. Fertilizer application was made with ${}^{15}\text{N}$-depleted NH₄NO₃ to act as a fertilizer tracer. Elevated CO₂ increased total biomass production in all 3 years of both grain sorghum (average 30%) and soybean (average 40%). With soybean, while no impact on the plant C:N ratio was observed, the total N content was greatly increased (average 29%) due to increased atmospheric N₂ fixation with elevated CO₂ concentration. With grain sorghum, the total N uptake was not affected, but the C:N ratio was markedly increased (average 31%) by elevated CO₂. No impact of elevated CO₂ level was observed for fertilizer N in grain sorghum. The results from this study indicated that while elevated CO₂ may enhance crop production and change N status in plant tissue, changes to soil N fertilizer application practices may not be needed.     

Impact of climate change on paddy field irrigation in southern Taiwan

Climate change can have a serious impact on water resources. The main agricultural product in southern Taiwan is rice, the planting of which consumes far more water than other crops. This makes agriculture in Taiwan especially vulnerable to climate change. In this study, we used the generalized watershed loading functions (GWLF) hydrological model to simulate the discharge of the Kaoping River under climate change scenarios A2 and B2 as released by the Intergovernmental Panel on Climate Change. We discussed the potential impact of climate change on water resources based on the results of GWLF simulations carried out using rainfall and temperature data from five general circulation models (GCMs). The simulation results indicate that river discharge in the wet season increases significantly, and decreases in the dry season. The discharge variations from using the various GCMs as inputs fall within the range of ?26 to +15 % for the dry season and ?10 to +82 % for the wet season. The variation in available water will seriously impact the first period rice farming (the period between the beginning of January and the end of May) in southern Taiwan. Consequently, effective reduction in conveyance loss in the irrigation canal systems and proper fallowing of paddy fields will be the main challenges to Taiwan’s agricultural sector for alleviating the impact of climate change. For further decision making, we show the effects of adapting to climate change by various degrees of the following two methods: fallowing paddy fields to various degrees and reducing conveyance loss in irrigation canal systems.     

Panicum maximum cv. Tanzânia: climate trends and regional pasture production in Brazil

Projected change in forage production under a range of climate scenarios is important for the evaluation of the impacts of global climate change on pasture‐based livestock production systems in Brazil. We evaluated the effects of regional climate trends on Panicum maximum cv. Tanzânia production, predicted by an agro‐meteorological model considering the sum of degree days and corrected by a water availability index. Data from Brazilian weather stations (1963–2009) were considered as the current climate (baseline), and future scenarios, based on contrasting scenarios in terms of increased temperature and atmospheric CO₂ concentrations (high and low increases), were determined for 2013–2040 (2025 scenario) and for 2043–2070 (2055 scenario). Predicted baseline scenarios indicated that there are regional and seasonal variations in P. maximum production related to variation in temperature and water availability during the year. Production was lower in the Northeast region and higher in the rainforest area. Total annual production under future climate scenarios was predicted to increase by up to 20% for most of the Brazilian area, mainly due to temperature increase, according to each climate model and scenario evaluated. The highest increase in forage production is expected to be in the South, Southeast and Central‐west areas of Brazil. In these regions, future climate scenarios will not lead to changes in the seasonal production, with larger increases in productivity during the summer. Climate risk is expected to decrease, as the probability of occurrence of low forage productions will be lower. Due to the predicted increase in temperature and decrease in rainfall in the Northeast area, P. maximum production is expected to decrease, mainly when considering scenarios based on the PRECIS model for the 2055 scenario.     

Effect of water management on soil respiration and <Emphasis Type="Italic">NEE</Emphasis> of paddy fields in Southeast China

Water management is an important factor in regulating soil respiration and the net ecosystem exchange of CO₂ (NEE) between croplands and atmosphere. However, how water management affects soil respiration and the NEE of paddy fields remains unexplored. Thus, a 2-year field experiment was carried out to study the effects of controlled irrigation (CI) during the rice season on the variation of soil respiration and NEE, with flooding irrigation (FI) as the control. A decrease of irrigation water input by 46.39% did not significantly affect rice yield but significantly increased irrigation water use efficiency by 0.99 kg m^?3. The soil respiration rate of CI paddy fields was larger than that of FI paddy fields except during the ripening stage. Natural drying management during the ripening stage resulted in a significant increase of the soil respiration rate of the FI paddy fields. Variations of NEE with different water managements were opposite to soil respiration rates during the whole rice growth stages. Total CO₂ emission of CI paddy fields through soil respiration (total R _soil) increased by 11.66% compared with FI paddy fields. The increase of total R _soil resulted in the significant decrease of total net CO₂ absorption of CI paddy fields by 11.57% compared with FI paddy fields (p < 0.05). There were inter-annual differences of soil respiration and the NEE of paddy fields. Frequent alternate wetting and drying processes in the CI paddy fields were the main factors influencing soil respiration and NEE. CI management slightly enhanced the rice dry matter amount but accelerated the consumption and decomposition of soil organic carbon and significantly increased soil respiration, which led to the decrease of net CO₂ absorption. CI management and organic carbon input technologies should be combined in applications to achieve sustainable use of water and soil resources in paddy fields.     

Interactions between elevated atmospheric CO2 and defoliation on North American rangeland plant species at low and high N availability

Although common disturbances of grazing lands like plant defoliation are expected to affect their sensitivity to increasing atmospheric CO₂ concentration, almost no research has been conducted to evaluate how important such effects might be on the direct responses of rangelands to CO₂. This growth chamber experiment subjected intact plant–soil cylinders from a Wyoming, USA, prairie to a 3‐way factorial of CO₂ (370 vs. 720 μL L^?1), defoliation (non‐clipped vs. clipped) and soil nitrogen (control vs. 10 g m^?2 added N) under simulated natural climatic conditions. Above‐ and below‐ground biomass and N dynamics of the functional groups C₃ grasses, C₄ grasses and forbs were investigated. CO₂ and defoliation had independent influences on biomass and N parameters of these rangeland plants. Growth under CO₂‐enriched conditions enhanced above‐ground biomass 50% in C₃ grasses alone, while shoot N concentration declined 16% in both C₃ and C₄ grasses. Plant‐soil ¹⁵N uptake was unaffected by CO₂ treatment. In contrast, defoliation had no effect on biomass, but increased tissue N concentration 29% across all functional groups. Without additional N, forage quality, which is in direct relation to N concentration, will decline under increasing atmospheric CO₂. Increased dominance of C₃ grasses plus reduced forage quality may necessitate changes in grazing management practices in mixed‐species rangelands.     

Water uptake of soybean (Glycine max L. Merr.) during exposure to O2 deficiency and field level CO2 concentration in the root zone

This study determined whether the field level concentration of root zone CO₂ affects transpiration rate and root water transport in soybean (Glycine max L. Merr.). In an upland field converted from a paddy field, topsoil CO₂ during the cropping season rose to 8 kPa of partial pressure after rainfall, whereas O₂ dropped only to a minimum of 7 kPa. An elevated root zone CO₂ pressure of 6 kPa significantly reduced transpiration rate. Although the transpiration rate of soybean plants exposed to hypoxia of 1.5 kPa O₂ alone was reduced by 52% of the aerated plant, the rate was more decreased by 33 by adding CO₂ gas to low root zone O₂. Similarly, the elevated root zone CO₂ significantly reduced hydraulic conductance of roots. The low transpiration rate with a high leaf water potential and low leaf greenness in the elevated root zone CO₂ indicated that stomatal closure in high root zone CO₂ may also occur irrespective of leaf water status and be involved in depressed nitrogen supply to a shoot. The results indicate that root zone CO₂ at the field level is a growth inhibitor of waterlogged soybean through decreasing water uptake and/or stomatal aperture.     

High-temperature-tolerant mungbean (Vigna radiata L.) lines produce better yields when exposed to higher CO2 levels

Increasing global air temperatures, along with rising CO₂ levels, are causing concerns about reducing available freshwater resources and altering cropping patterns. They may influence overall growth and production pattern of crop plants. These likely changes would become major limiting factors for future sustainable food production largely in the tropics and subtropics. Thus, understanding physiological responses hold the key to determining the functional relationship between the environment and crop performance. We explore here the impact of rising CO₂ on the growth and yield traits of a few selected high-temperature (HT)-tolerant mungbean lines, which we earlier screened for HT tolerance using a physiological assay under managed growth conditions. The HT-tolerant lines grown under elevated CO₂ levels (550 and 700 μL L^?1) showed a considerable improvement in growth rates (13.5%, 67.8%, and 46.5% in plant height, leaf area, and total dry matter, respectively) and pod and seed yield (48.7% and 31.7%, respectively), compared to local checks under the same environments. Interestingly, the symptoms of accelerated pod maturity were also observed in most of these lines. The outcome of the study would undoubtedly open up opportunities for increased yield potentials of legumes under the conditions of the warming climate and elevated levels of carbon dioxide.     

Impact of Global Change on Biological Processes in Soil

SUMMARY

The Earth is undergoing rapid environmental changes due to human activities. Three components of the ongoing global change, elevated atmospheric CO₂, N deposition, and global warming, may significantly impact soil biota directly through modifying the physical and chemical environment, and indirectly through altering aboveground plant growth and community composition. The biomass, community structure, and activities of microbes and animals in soil as well as their interactions will likely be affected, leading to changes in ecological processes and functions. Biological processes that may be modified by global change include organic matter decomposition, N mineralization, food web interaction, and biotic N fixation. Lack of the complexity in agroecosystems may amplify the effects of global change on many biological processes in agricultural soils. However, minimizing human disturbance and thus increasing the complexity of agroecosystems may enhance the potential of C sequestration in agricultural soils and the stability of belowground systems, thereby contributing to ecological sustainability.     

The Potential Effect of Climate Change and Elevated Air Carbon Dioxide on Agricultural Crop Production in Central and Southeastern Europe

SUMMARY

The vulnerability and adaptation of major agricultural crops to different soils in Austria and Bulgaria under a changing climate and elevated air CO₂ were investigated. Several incremental and transient GCM climate change scenarios were created and applied. Warming will decrease the crop-growing duration of the selected crops in the regions of interest. All GCM scenarios, including the climate change effect only, projected reductions in grain yield of winter wheat and spring barley, caused by a shorter crop-growing period. However, when the direct effect of an increased CO₂ level was assumed, most GCM climate change scenarios projected an increase in wheat and barley yield and especially in soybean yield. An increased level of CO₂ alone had no significant impact on the simulated maize yield reductions under climate change.     

Effects of elevated atmospheric CO2 on grain quality of wheat

Wheat (Triticum aestivum L.) is one of the most important agricultural crops worldwide. Due to its high content of starch and unique gluten proteins, wheat grain is used for many food and non-food applications. Although grain quality is an important topic for food and feed as well as industrial processing, the consequences of future increases in atmospheric carbon dioxide (CO₂) concentrations on quality parameters such as nutritional and bread-making rheological properties are still unclear. Wheat productivity increases under CO₂ enrichment. Concomitantly, the chemical composition of vegetative plant parts is often changed and grain quality is altered. In particular, the decrease in grain protein concentration and changes in protein composition may have serious economic and health implications. Additionally, CO₂ enrichment affects amino acid composition and the concentrations of macro- and micro-elements. However, experimental results are often inconsistent. The present review summarises the results from numerous CO₂ enrichment experiments using different exposure techniques in order to quantify the potential impacts of projected atmospheric CO₂ levels on wheat grain yield and on aspects of grain composition relevant to processing and human nutrition.     

Seasonal changes in the effects of free-air CO2 enrichment (FACE) on dry matter production and distribution of rice (Oryza sativa L.)

It is reported that stimulating effect of elevated atmospheric [CO₂] on photosynthesis of rice (Oryza sativa L.) is likely to be reduced during the plant growth period. However, there is little information on seasonal changes in dry matter (DM) production and distribution of rice under elevated atmospheric [CO₂]. A free-air CO₂ enrichment (FACE) experiment was conducted at Wuxi, Jiangsu, China, in 2001–2003, using Wuxiangging 14, a japonica cultivar. The rice was grown at ambient or elevated (ca. 200 μmol mol⁻¹ above ambient) [CO₂] and supplied with 25 g N m², which is the normal N application rate for local farmers. DM accumulation of rice in FACE plots was significantly increased by 40, 30, 22, 26 and 16% on average at tillering, panicle initiation (PI), heading, mid-ripening and grain maturity, respectively. Rice DM production under FACE was significantly enhanced by 41, 27, 15 and 38% on average during the growth periods from transplanting to tillering (Period 1), tillering to PI (Period 2), PI to heading (Period 3) and heading to mid-ripening (Period 4), respectively, but significantly decreased by 25% in the period from mid-ripening to grain maturity (Period 5). In general, seasonal changes in crop response to FACE in both green leaf area index (GLAI) and net assimilation rate (NAR) followed a similar pattern to that of the DM production. Under FACE the leaves decreased significantly in proportion to the total above-ground DM over the season, the stems showed an opposite trend, while the spikes depended on crop development stage: showing no change at heading, significant increase (+4%) at mid-ripening and significant decrease (−3%) at grain maturity. Grain yield was stimulated by an average of 13% by FACE, due to increased total DM production rather than any changes in partitioning to the grain. We conclude that the gradual acclimation of rice growth to elevated [CO₂] do not occur inevitably, and it could also be altered by environmental conditions (e.g., cultivation technique).     

Cadmium transport and tolerance in rice: perspectives for reducing grain cadmium accumulation

In recent decades, numerous studies have attempted to project the impact of hypothesised anthropogenic climate change on rice production. In this study, we offer a comprehensive review of our current understanding related to temperature, CO₂, and water-demand parameters in rice growth models. As to future rice yield, night time temperature should be focused in the models as well as day time temperature owing to the contribution of temperature on the night time respiration. Furthermore, although CO₂-enhanced photosynthesis is critical for the accurate prediction of rice production in a higher CO₂ atmosphere, we found that recent well-developed photosynthesis-stomatal model cannot realize the variation of CO₂ stomatal sensitivity with humidity conditions. To estimate water stress under projected climate-change conditions, rice growth model should be required to link with water resource model, which includes natural processes and anthropogenic regulations. The understanding of abilities and limitations in the models is important not only to improve the schemes that models employ, but to also critically review the simulated results.     

Effects of elevated atmospheric CO2 on grain quality of wheat

Wheat (Triticum aestivum L.) is one of the most important agricultural crops worldwide. Due to its high content of starch and unique gluten proteins, wheat grain is used for many food and non-food applications. Although grain quality is an important topic for food and feed as well as industrial processing, the consequences of future increases in atmospheric carbon dioxide (CO₂) concentrations on quality parameters such as nutritional and bread-making rheological properties are still unclear. Wheat productivity increases under CO₂ enrichment. Concomitantly, the chemical composition of vegetative plant parts is often changed and grain quality is altered. In particular, the decrease in grain protein concentration and changes in protein composition may have serious economic and health implications. Additionally, CO₂ enrichment affects amino acid composition and the concentrations of macro- and micro-elements. However, experimental results are often inconsistent. The present review summarises the results from numerous CO₂ enrichment experiments using different exposure techniques in order to quantify the potential impacts of projected atmospheric CO₂ levels on wheat grain yield and on aspects of grain composition relevant to processing and human nutrition.     

Production Ecophysiology of Hungarian Green Pepper Under Elevated Air CO2 Concentration

SUMMARY

Production, dry matter (including reproductive) allocation, photosynthesis, transpiration, water use efficiency and carbon and nitrogen responses of a Hungarian sweet pepper (Capsicum annum L.) under continuous elevated CO₂ concentrations are reported. Plants were grown in open top chambers under a temperate-continental climate in Hungary from plantation at ambient (350 μmol mol^?1) and elevated (700 μmol mol^?1) CO₂ concentrations. The CO₂ assimilation responses of the green pepper plants grown in high CO₂ from plantation until final harvest reflected down-regulation of their photosynthesis. The integrated and combined effect of the increased net CO₂ assimilation rate and the unchanged rate of transpiration resulted in higher WUE at elevated CO₂ concentrations in the high CO₂ plants than in the control ones grown at ambientCO₂. However, the improved water use efficiency in the high CO₂ plants was not followed by an acclimation in C-trans-location and C-allocation to the reproductive organs in the required degree. This was reflected in a slightly increased overall plant production and higher reproductive allocation, but was not accompanied by an increased fresh or dry berry mass production. The acclimation discussed may be of advantage for plant growth in a high CO₂ environment with restricted water availability. We did not find worthy statistical difference between the yield mass of the control and elevated CO₂, although the dry matter production parameters of the high CO₂ plants had statistically not significantly higher values.     

Impact of ocean acidification on energy metabolism of oyster, Crassostrea gigas--changes in metabolic pathways and thermal response

Climate change with increasing temperature and ocean acidification (OA) poses risks for marine ecosystems. According to Pörtner and Farrell [1], synergistic effects of elevated temperature and CO₂-induced OA on energy metabolism will narrow the thermal tolerance window of marine ectothermal animals. To test this hypothesis, we investigated the effect of an acute temperature rise on energy metabolism of the oyster, Crassostrea gigas chronically exposed to elevated CO₂ levels (partial pressure of CO₂ in the seawater ~0.15 kPa, seawater pH ~ 7.7). Within one month of incubation at elevated Pco₂ and 15 °C hemolymph pH fell (pH_e = 7.1 ± 0.2 (CO₂-group) vs. 7.6 ± 0.1 (control)) and P_eco₂ values in hemolymph increased (0.5 ± 0.2 kPa (CO₂-group) vs. 0.2 ± 0.04 kPa (control)). Slightly but significantly elevated bicarbonate concentrations in the hemolymph of CO₂-incubated oysters ([HCO⁻ ₃]_e = 1.8 ± 0.3 mM (CO₂-group) vs. 1.3 ± 0.1 mM (control)) indicate only minimal regulation of extracellular acid-base status. At the acclimation temperature of 15 °C the OA-induced decrease in pH_e did not lead to metabolic depression in oysters as standard metabolism rates (SMR) of CO₂-exposed oysters were similar to controls. Upon acute warming SMR rose in both groups, but displayed a stronger increase in the CO₂-incubated group. Investigation in isolated gill cells revealed a similar temperaturedependence of respiration between groups. Furthermore, the fraction of cellular energy demand for ion regulation via Na⁺/K⁺-ATPase was not affected by chronic hypercapnia or temperature. Metabolic profiling using ¹H-NMR spectroscopy revealed substantial changes in some tissues following OA exposure at 15 °C. In mantle tissue alanine and ATP levels decreased significantly whereas an increase in succinate levels was observed in gill tissue. These findings suggest shifts in metabolic pathways following OA-exposure. Our study confirms that OA affects energy metabolism in oysters and suggests that climate change may affect populations of sessile coastal invertebrates such as mollusks.