Carbon Fixation Research Articles (Page 1)

Marine heatwaves affect the abundance and community structure of microbial plankton, with implications for food web and ecosystem processes, but their impact on microbially mediated elemental cycling remains poorly constrained. To determine the biogeochemical effects of increased temperature, we conducted an experiment in September 2023 in which a plankton community from a coastal, productive ecosystem (Ría de Vigo, NW Iberia) was exposed to a warming of + 2°C and + 4°C under unamended and nutrient-enriched conditions. The response of microbial plankton was characterized in terms of organic matter production, carbon fixation, nitrogen uptake, and oxygen net production. We found that warming caused increased nutrient consumption and biomass production, as well as faster bloom dynamics, both in unamended and nutrient-enriched treatments, indicating that the community was robust to thermal perturbation. Accelerated nutrient depletion under warming gave way to an earlier decrease in carbon fixation and nitrate uptake rates, together with a shift towards a negative or less positive metabolic balance. Carbon fixation was less sensitive than nitrate uptake to the different temperature and nutrient scenarios, leading to wide changes in the carbon-to-nitrogen uptake ratio, while respiration increased non-linearly with temperature. Overall, the investigated microbial fluxes were more responsive to nutrient availability than to temperature. Our results show that microbially driven ecosystem services in coastal waters have the potential to be enhanced during short-term warming events.

The mechanism of biochar and compost as soil amendments in urban green spaces remains unclear. Using Euonymus kiautschovicus as a model system, this study established eight treatment gradients, 0 (CK), single biochar applications: 4% (BC4), 8% (BC8), 12% (BC12), 7.5% compost (COM), and their combinations BCC4 (BC4 + 7.5% COM), BCC8 (BC8 + 7.5% COM), BCC12 (BC12 + 7.5% COM). Through metagenomic sequencing and metagenome-assembled genomes (MAGs) analysis, we investigated soil microbiome structure, carbon sequestration functional genes, and their interactions in response to amendments. The combined application of medium-low dose biochar (4–8%) with compost significantly optimized the physicochemical properties and microbial functions in soils. Compared to single amendments, hybrid treatments synergistically enhanced soil moisture content. Specifically, BCC8 increased by 27% compared to the CK, organic carbon levels reached 12.8 g/kg with BCC12, and available nutrients showed 45% higher available phosphorus with BCC4. Metagenomic analysis revealed that hybrid treatments reshaped microbial community structure, with BCC8 significantly enriching Acidobacteria (8.72%) and Nitrospira (1.42%), driving an increased abundance of carbon fixation genes. Among key carbon fixation pathways, the reductive tricarboxylic acid cycle (rTCA) exhibited the highest gene abundance (mean 15.03), dominated by MAG176. The Calvin-Benson-Bassham (CBB) cycle displayed broad adaptability, with MAG59 identified as a core carbon-fixing strain. This study has significant implications for the application of biochar-compost combinations in carbon management of urban green spaces.

The conversion of CO2 into quinazoline-2,4(1H,3H)-diones is a vital process in the pharmaceutical industry; however, developing efficient catalysts to realize ultrafast reaction rates remains challenging due to the complex reaction steps. Herein, the novel metal-organic framework {[(CH3)2NH2][Co3(μ3-OH)(BTB)2(BPT)]·4DMF·2H2O}n (Z-1) was synthesized, exhibiting high solvent and thermal stability, and featuring asymmetric [Co3]-clusters, abundant open metal sites, and nanocages. Remarkably, Z-1 catalyzed the reaction between CO2 and 2-amino-N-methylbenzamide at an ultrafast rate, achieving a 92% yield of 3-methylquinazoline-2,4(1H,3H)-diones within 2 min at room temperature. Its turnover frequency (613 h-1) is the highest value recorded in all catalytic systems for synthesizing quinazoline-2,4(1H,3H)-diones. Additionally, Z-1 accommodated 16 diverse substrates and maintained a high yield over ten catalytic cycles. Mechanistic studies revealed that the [Co3]-clusters effectively activated the amino group of substrates (the rate-determining step), while the thiadiazole moieties created alkaline microenvironments that enriched and activated CO2. Density functional theory calculations further confirmed that Z-1 effectively reduced the activation energy barrier of the rate-determining step, thereby accelerating the generation of the carbamate intermediate from CO2 and 2-aminobenzamide. This work presents the first heterogeneous catalyst capable of efficiently catalyzing the reaction between 2-aminobenzamide and CO2, providing new insights into the design of catalysts for the chemical fixation of CO2.

Strawberry (Fragaria × ananassa Duch.) is an important crop in the world. Environmental fluctuations have a significant impact on the growth of strawberries. Photoconversion films can change the environment of facility crops to increase production and improve quality. Therefore, this study investigated the effects of rare earth light conversion films (RPOs) on strawberry cultivation. The temperature, photosynthetic photon flux density, light transmittance and proportion of spectra beneficial to the crop production of RPO greenhouses were all greater than those of the control. Compared with those of the control, spongy tissues were sparser in RPO1 and RPO2 leaves. The cross-sectional surface area of the main vascular bundles of strawberry petioles treated with RPO1 and RPO2 increased slightly. Compared with those of the control, net CO2 assimilation, stomatal conductance, activity of Rubisco and gene expression levels of RPO1 and RPO2 were all increased, and the intercellular CO2 concentration was decreased. Compared with those of the control, yield, soluble solids, soluble sugar content, Vc content, and flavonoid contents of RPO1 and RPO2 increased, while the soluble protein content decreased. In conclusion, RPO promotes photosynthesis in strawberry plants by optimizing photosynthetic photon flux density, spectrum and temperature in greenhouses; adjusting the spectrum to change pigment content, spongy tissue structure, petiole vascular bundles, and Rubisco activity; and regulating the expression of the Rubisco gene, thereby increasing the quality and yield of strawberry plants. Compared with RPO1, RPO2 could be a more suitable film for strawberry production.

With the rapid industrial development, massive fossil fuel use has caused excessive carbon dioxide (CO2) emissions, triggering global warming and environmental issues. Thus, CO2 recovery and reuse have become a research focus, among which artificially designed in vitro biocatalytic pathways for converting CO2 into high-value chemicals show promise, with advantages like shorter routes, higher efficiency and lower energy consumption compared to natural pathways. However, challenges remain due to natural enzymes' issues in specificity, affinity, efficiency, stability and oxygen sensitivity. To tackle these problems, extensive research efforts have been undertaken. These include elucidating the mechanisms and catalytic efficiencies of carbon-fixing enzymes from diverse sources, as well as developing and refining novel in vitro carbon fixation pathways. Moreover, significant progress has been made in computer-aided investigations of enzyme structure, function, and engineering optimization, alongside advancements in enzyme immobilization strategies, cofactor regeneration systems, and the development of artificial cofactors. By summarizing the latest research progress in recent years, we can identify the current bottlenecks and challenges in in vitro enzymatic CO2 conversion, propose effective methods to enhance the efficiency of CO2 conversion, and thus promote the development of research in related fields.

Urban trees play a critical role in mitigating climate change by capturing atmospheric CO2 and providing multiple co-benefits, including cooling urban environments, reducing building energy demand, and enhancing citizens’ physical and psychological well-being. This study presents the Co Carbon Trees Measurement project, a citizen science initiative implemented in the city of Viladecans, Spain, involving 658 students, local administration, and academia, three components of the EU mission’s quadruple helix governance model. Over one year, 1274 urban trees were measured for trunk diameter and height to quantify annual CO2 sequestration using a direct measurement approach combining field data collection with a mobile application for a height assessment and a flexible measuring tape for diameter. Results indicate that carbon fixation increases with tree size, displaying a parabolic function with larger trees sequestering significantly more CO2. A range between 10 and 20 kg of CO2 is sequestered by the urban trees in the period 2024–2025. The study also highlights the broader benefits of urban trees, including shading, mitigation of the urban heat island effect, and positive impacts on mental health and social cohesion. While the total CO2 captured in Viladecans (≈810 tons/year) is small relative to city emissions (≈170,000 tons/year), the methodology demonstrates a scalable, replicable approach for monitoring progress toward climate neutrality and integrating urban trees into planning and climate action strategies. This approach positions green infrastructure as a central component of sustainable and resilient urban development.

Soil salinity poses a critical threat to global agricultural productivity, exacerbating food security challenges in arid and semi-arid regions. This review synthesizes current knowledge on the physiological and biochemical impacts of salinity stress in plants, with a focus on the role of gibberellic acid (GA3) in mitigating these effects. Salinity disrupts ion homeostasis, induces osmotic stress, and generates reactive oxygen species (ROS), leading to reduced chlorophyll content, impaired photosynthesis, and stunted growth across all developmental stages, i.e., from seed germination to flowering. Excess sodium (Na+) and chloride (Cl−) accumulation disrupts nutrient uptake, destabilizes membranes, and inhibits enzymes critical for carbon fixation, such as Rubisco. GA3 emerges as a key regulator of salinity resilience, enhancing stress tolerance through various mechanisms like scavenging ROS, stabilizing photosynthetic machinery, modulating stomatal conductance, and promoting osmotic adjustment via osmolyte accumulation (e.g., proline). Plant hormone’s interaction with DELLA proteins and cross-talk with abscisic acid, ethylene, and calcium signaling pathways further fine-tune stress responses. However, gaps persist in understanding GA3-mediated floral induction under salinity and its precise role in restoring photosynthetic efficiency. While exogenous GA3 application improves growth parameters, its efficacy depends on the concentration- and species-dependent, with lower doses often proving beneficial and optimum doses potentially inhibitory. Field validation of lab-based findings is critical, given variations in soil chemistry and irrigation practices. Future research must integrate biotechnological tools (CRISPR, transcriptomics) to unravel GA3 signaling networks, optimize delivery methods, and develop climate-resilient crops. This review underscores the urgency of interdisciplinary approaches to harness GA3’s potential in sustainable salinity management, ensuring food security and safety in the rapidly salinizing world.

The Danish subsurface ash series within the Eocene-aged Fur and Ølst Formations has a large theoretical CO2 storage capacity through carbon mineralisation, a potential that is the main motivation behind the C·ASH project initiated by researchers from the Department of Geoscience, Aarhus University. The potential carbon storage is achieved by injection of CO2 into the closely spaced volcanic ash beds in the Danish subsurface to accelerate silicate dissolution, leading to carbon fixation by mineralisation of CO2 as carbonate minerals. This provides a valuable alternative to conventional CO2 storage technologies that typically aim to store CO2 as a supercritical phase in deep porous aquifers. One of the essential requirements for the mineralisation technology is the identification of ash beds that contain enough reactive divalent cations (Ca2+, Fe2+, Mg2+) to sustain the silicate dissolution – carbonate precipitation reactions. This study aims to provide a geochemical proxy to identify and locate suitable ash beds with high CO2 sequestration potential. For this purpose, the shallow Harre borehole drilled in 1980 in northwestern Denmark is analysed using high-resolution XRF and SEM-EDS. In the Harre well the ash beds are most abundant within a five meters thick interval in the uppermost part of the Ølst Formation between 191 and 196 meters below surface. The XRF data show that titanium (Ti) is the most reliable elemental proxy for identifying the volcanic ash beds and that calcium (Ca), which is an important divalent cation for carbon mineralisation, is mostly enriched in the volcanic ash beds within the five meters interval. However, Ca may also be associated with gypsum (CaSO4·2H2O) and carbonates (CaCO3), suggesting that part of the Ca have already leached from silicates within the ash beds. This fraction is believed to be low and that the ash beds’ suitability for carbon mineralisation remain high.

Tree species differ in their ability to use light efficiently, affecting carbon gain, establishment and survival in highly heterogeneous environments. This efficiency relies on the maintenance of the photosynthetic induction state, regulated by structural, biochemical, photochemical and stomatal processes that vary along the leaf economics spectrum (LES). Slow return species, such as shade-tolerant species (often late successional), are thought to sustain higher photosynthetic induction state, while quick return species, like light-demanding species (often early successionals) would have lower shade acclimation and shade-tolerant species lower acclimation to high light. Yet, results often deviate from these predictions. Moreover, most LES traits reflect steady state performance, not dynamic responses. Here, we investigated photosynthetic induction responses in four widely distributed Brazilian tree species representing contrasting successional groups and LES positions, grown under 10% light, 50% light and Full sun. We quantified induction dynamics in terms of CO2 assimilation, stomatal conductance, electron transport rate, as well as chlorophyll content, and leaf mass per area (LMA). Acclimation to distinct light environments was assessed using a shade adjustment coefficient and a novel metric based on Principal Component Analysis (PCA), Relative Plasticity (RP). RP suggests an asymmetrical bell-shaped relationship with LES position: the slow return Hymenaea courbaril showed low plasticity and little change in resource allocation (LMA), photosynthetic rates or induction times; the fast-return Schinus terebinthifolia, displayed moderate plasticity but unexpectedly high shade acclimation showing high induction state and CO2 assimilation rates; and the intermediate strategists Cecropia pachystachya and Handroanthus impetiginosus exhibited the highest plasticity, with coordinated increases in LMA, CO2 assimilation, conductance and photosynthetic induction under increasing light conditions. These findings highlight the importance of integrating photosynthetic dynamics into ecophysiological frameworks for species selection in reforestation, particularly in heterogeneous light environments, where adaptive flexibility can play a critical role on the resilience of an ecosystem.

Cacti of the genera Opuntia and Nopalea exhibit morphophysiological and biochemical characteristics that favor their adaptation to semiarid environments, such as crassulacean acid metabolism (CAM) and cladode succulence. These strategies reduce water loss and allow the maintenance of photosynthesis under stress conditions. In this study, we evaluated the seasonal variation in the physiological and photochemical responses of forage cactus clones grown in semiarid environments, considering the rainy, dry, and transition seasons. The net photosynthetic rate (Pn) and chlorophyll fluorescence parameters varied significantly as a function of water availability and microclimatic conditions. We found higher CO2 assimilation rates during the rainy season, while the dry season resulted in a strong impairment of photosynthetic activity, with reductions of 65% in stomatal conductance, 37% in transpiration, 20% in maximum quantum efficiency of photosystem II, and 19% in the electron transport rate. Furthermore, during these periods, we observed an increase in initial fluorescence and non-photochemical dissipation, demonstrating the activation of photoprotective mechanisms against excess light energy. During the transition seasons, the cacti exhibited rapid adjustments in gas exchange and energy dissipation, indicating the adaptive plasticity of CAM pathway. The MIU (Nopalea cochenillifera (L.) Salm-Dyck), OEM (Opuntia stricta (Haw.) Haw.), and IPA (Nopalea cochenillifera (L.) Salm-Dyck) clones demonstrated greater resilience, maintaining greater stability in Pn, instantaneous water use efficiency, and photochemical parameters during the drought. In contrast, the OEA (Opuntia undulata Griffiths) clone showed high sensitivity to water and heat stress, with marked reductions in physiological and photochemical performance. In summary, the photosynthetic efficiency and chlorophyll fluorescence of CAM plants result from the interaction between water availability, air temperature, radiation, and genotypic traits. This study provides a new scientific basis for exploring the effects of environmental conditions on the carbon and biochemical metabolism of cacti grown in a semiarid environment.

Abstract. This paper describes a new version of the Real-time Air Quality Modeling System (RAQMS) which uses National Unified Operational Prediction Capability (NUOPC) coupling to combine the RAQMS chemical mechanism with the Global Ensemble Forecasting System with Aerosols (GEFS-Aerosols), the Goddard Chemistry Aerosol Radiation and Transport model (GOCART) aerosol mechanism, and NOAA's Unified Forecast System (UFS) version 9.1 Finite Volume Cubed Sphere (FV3) dynamical core. We also present an application of TROPOMI CO column data assimilation in UFS-RAQMS with the NOAA Grid Point Statistical Interpolation (GSI) three-dimensional variational (3D-Var) analysis system to constrain UFS-RAQMS CO. We validate UFS-RAQMS control and TROPOMI CO data assimilation CO analyses for the period 15 July–30 September 2019 against independent satellite, ground-based, and airborne observations. We show that the largest impacts of the TROPOMI CO data assimilation are in the lower troposphere over Siberia and Indonesia. We find that UFS-RAQMS biomass burning signatures in CO column are not consistent with those in aerosol optical depth (AOD) near the Siberian and Indonesian biomass burning source regions within our control experiment. Assimilation of TROPOMI CO improves the representation of the biomass burning AOD/CO relationship in UFS-RAQMS by increasing the CO column, which suggests that the biomass burning CO emissions from the Blended Global Biomass Burning Emissions Product (GBBEPx) used in UFS-RAQMS are too low for boreal wildfires.

Microalga Haematococcus lacustris is known for its ability to produce high-value product astaxanthin. The abrupt shift from weak-light in the vegetative phase to high-light in the astaxanthin induction phase triggers severe photodamage during the large-scale cultivation of H. lacustris for astaxanthin production in two phases, causing photobleaching with resultant biomass loss. Current mitigation relies primarily on physical shading. This study found that glutamate/glutamine supplementation before phase shift mitigated the photodamage caused by sudden high-light stress in H. lacustris. Glutamate rapidly enhanced CO2 fixation while simultaneously inducing various photoprotective pathways, including non-photochemical quenching, cyclic electron flow, chlororespiration and photorespiration. This maintained the balance between light absorption and energy utilization in H. lacustris during abrupt environmental shifts, thereby preventing damage on both the donor and acceptor sides in photosystem II. Pre-incubation with glutamate in the dark pre-activated these photoprotective pathways, thus enabling seamless acclimation to high-light stress following abrupt shifts. Meanwhile, glutamine exhibited equivalent efficacy in inducing multiple photoprotective pathways. These findings establish a novel strategy based on dark pretreatment for enhancing photosynthetic capacity under high light and protecting algal cells against photobleaching. The study provides fundamental insights into photoprotective acclimation mechanisms in microalgae and higher plants facing rapid environmental shifts.

Under global climate change, the rising frequency of extreme weather events profoundly affects ecosystem carbon cycles. However, in the ecologically fragile dry-hot valleys of Southwest China, the response of carbon source-sink dynamics to these extremes remains unclear, which hinders effective regional carbon management. This study investigates the Nu River dry-hot valley, using the Google Earth Engine platform to process multi-source remote sensing and meteorological data from 2001–2024. We established a framework of 15 extreme climate indices and applied Sen-Mann-Kendall trend analysis, Pearson correlation, and threshold regression models to explore the spatiotemporal evolution of carbon dynamics and their non-linear response to extreme climate. Our results show that: (1) The region’s carbon sink capacity displayed a fluctuating but overall increasing trend with significant spatial heterogeneity; areas of substantial increase were concentrated in the southern, low-altitude zones. (2) Extreme climate events triggered non-linear carbon cycle responses by altering hydrothermal conditions. The synergy of high temperatures and intense, short-duration precipitation weakened the carbon sink, whereas dispersed rainfall alleviated drought stress and enhanced carbon fixation. (3) Both extreme temperature and precipitation indices showed clear regulatory thresholds, above which their effects were significantly amplified; this reveals that the carbon cycle in the dry-hot valley is highly sensitive to extreme events and exhibits distinct threshold-driven responses. This research provides a theoretical basis for the mechanisms regulating carbon flux in dry-hot ecosystems under a variable climate and offers crucial scientific support for optimising regional pathways to carbon neutrality and implementing climate-adaptive management.

The effect of high temperature on plant performance and survival is a topic of great interest given the ongoing rise in global heatwave frequency, duration, and intensity. The temperature at which photosystem II (PSII) is disrupted is often used as a proxy for photosynthetic heat tolerance. Our current understanding of PSII heat tolerance is predominantly shaped by 'snapshot' measurements that capture heat tolerance at a single point in time. However, growing evidence of dynamic thermal acclimation of PSII raises questions about the accuracy of current estimates of photosynthetic heat tolerance based on snapshot measurements. We believe that failing to account for acclimation may result in the underestimation of PSII heat tolerance and that the extent of acclimation can be predicted from leaf economic traits, leaf habit, plant water use strategies, photosynthetic pathway, and habitat. We also explore efforts to use spectroscopy techniques to predict acclimation, and the biotic and abiotic factors that may influence these predictions. Finally, we provide recommendations for the future incorporation of PSII heat tolerance and acclimation into models of the thermal limits of plant performance.

Strategies for enhancing microalgal carbon sequestration: a review on strain development, culture system optimization, parameter control, and metabolic engineering.

The ethylene-insensitive tomato mutant Never ripe exhibits enhanced growth and phosphorus use efficiency under phosphorus stress.

Synchronous bio-oil upgrading and CO2 fixation: Pulsed electrolysis enhancement strategy

Insights into Fe(II) speciation influence on kinetics, microbial networks, and metabolism in Fe(II) oxidation coupled with carbon assimilation in paddy soil

A moderate diffuse PAR ratio improves the yield and quality of Panax notoginseng by enhancing photosynthesis and carbon fixation

Enrichment of Feammox microflora utilizing in-situ iron in excess activated sludge: substrate metabolism, gene variation, and microbial communities.