The brain is energetically expensive. Energy availability may, therefore, determine whether costly cognitive processes such as long-term memory can be expressed. However, there is a limited understanding of the metabolic costs associated with long-term memory formation. Here, we explored the potential induced costs of long-term memory formation using honeybees (Apis mellifera) as a model species. We monitored the sucrose intake of bees over the 20-hour period following a classical spaced olfactory conditioning protocol that induced long-term memory formation, relative to a control group that experienced the same reward schedule but no odour pairing. Bees in the experimental treatment drank significantly more sucrose than controls. We then tested whether the increased energy demands of long-term memory formation showed parallel increases in metabolic rate, by measuring carbon dioxide production in groups of bees at four timepoints following conditioning (1-hour, 4-hours, 24-hours and 72-hours). We found no change in metabolic rate between learning and control groups across all time points, suggesting that long-term memory formation does not impact metabolic rate to an extent that is detectable by our group metabolic rate protocol. While our findings point to dietary costs associated with long-term memory formation, any metabolic consequences may operate at a resolution below that detectable in group-level analyses and may be more effectively examined using individual or cellular-level energy flux approaches.

Energy and nutrient composition and origin of common feed substrates for black soldier fly larvae determine their efficiency and life-stage-specific carbon dioxide and ammonia production.

Background: Patients being weaned from mechanical ventilation are evaluated using portable metabolic carts to measure oxygen consumption (V̇O2) and carbon dioxide production (V̇CO2) to determine resting energy expenditure (REE) and oxygen cost of breathing (OCOB). The purpose of this study was to investigate the cutoff threshold and the predictive values of OCOB and REE variation in such patients at a surgical critical care unit. Methods: A cross-sectional study was conducted from March 2023 to February 2024. A total of 58 patients who were at least 18 years old and receiving orotracheal ventilation for more than 48 hours met the criteria for weaning. The relationship among OCOB, variation in resting energy expenditure (∆REE) index, and weaning results was examined. Calculations were performed to determine the receiver operating characteristic (ROC) curve, area under the curve (AUC), sensitivity, specificity, and positive and negative predictive values (PPV and NPV). Results: The overall weaning success rate was 72.4% (42/58). Compared to the failure group, the successful weaning group had significantly lower median values of ∆REE and OCOB (6.3% and 6.93% vs. 15.64% and 16.21%, P=0.002, respectively). According to ROC analysis, weaning success was predicted when ∆REE ≤8.28% (AUC, 0.768) or OCOB ≤9.1% (AUC, 0.762). Conclusions: Both OCOB and ∆REE can be used to predict a successful outcome of ventilator weaning, with a criterion of OCOB ≤9.1% or ∆REE ≤8.28% in surgical critical care patients.

Cardiopulmonary exercise testing (CPET) provides a comprehensive assessment of functional capacity by measuring key physiological variables including oxygen consumption ([Formula: see text]), carbon dioxide production ([Formula: see text]), and pulmonary ventilation (VE) during exercise. Previous research has identified peak [Formula: see text] and [Formula: see text] ratio as robust predictors of mortality risk in chronic heart failure (CHF) patients as well as in congenital heart disease (CHD). This study utilises CPET variables as surrogate mortality endpoints for patients with CHD. To our knowledge, this represents the first successful implementation of an advanced machine learning approach that predicts CPET outcomes by integrating electrocardiograms (ECGs) with information derived from clinical letters. Our methodology began with extracting unstructured patient information from clinical letters using natural language processing techniques, organising this data into a structured database. We then digitised ECGs to obtain quantifiable waveforms and established comprehensive data linkages. The core innovation of our approach lies in exploiting the Riemannian geometric properties of covariance matrices derived from both 12-lead ECGs and clinical text data to develop robust regression and classification models. Through extensive ablation studies, we demonstrated that the integration of ECG signals with clinical documentation, enhanced by covariance augmentation techniques in Riemannian space, consistently produced superior predictive performance compared to conventional approaches.

Hyperlactatemia during cardiopulmonary bypass (CPB) is a marker of inadequate oxygen delivery and correlates with postoperative morbidity and mortality. Although lactate is measured directly via enzymatic sensors, its rise can be anticipated through perfusion, hemodynamic, and metabolic indicators. We reviewed the literature and synthesized a Lactate Risk Score (LRS) weighted by published population data, focusing on adult cardiac surgery procedures performed under mild hypothermia (34-36°C). A Evidence-based Conceptual Review (PubMed, Embase, Scopus, up to September 2025) was conducted using keywords lactate, oxygen delivery, DO2, carbon dioxide production, vasoactive drugs, arterial pressure, glucose, microemboli, cardiopulmonary bypass duration, cardiac surgery. Studies reporting perfusion thresholds linked with lactate levels in adult cardiac surgery were prioritized. Weighting of score components reflected both the strength of association and the population size of published cohorts. Across the literature, indexed oxygen delivery (DO2i) below 260-280mL/min/m2 emerged as the strongest predictor of lactate increase and was assigned +2 points in the score. Similarly, indexed carbon dioxide production greater than 60mL/min/m2 (+2) and a DO2i/VCO2i ratio lower than 5 (+2) were strongly correlated with anaerobic metabolism. An oxygen extraction ratio ≥ 0.35 (+1) and a venous-to-arterial CO2 gap ≥ 6mmHg or a Pv-PaCO2/Ca-CvO2 ratio ≥ 1.8 (+1) added further risk information. The cumulative oxygen debt, quantified as the area under the curve of DO2 below the critical threshold, was weighted with +2 points, while prolonged CPB duration increased the score according to time: >90min (+1), >120min (+2), and >180min (+3). Hemodynamic instability with mean arterial pressure or arterial line pressure persistently <50mmHg was considered highly relevant and attributed +2 points, and the requirement for noradrenaline infusion >0.05µg/kg/min was weighted with +1. Among preoperative factors, advanced age, coronary artery disease, and baseline hemoglobin <8g/dL were each scored +1. Metabolic stress, reflected by intraoperative glucose increase >180mg/dL, added +1, and significant gaseous microembolic activity in the arterial line, defined as more than 500 bubbles per hour or emboli >40µm diameter, contributed +1. Based on this integration, the Lactate Risk Score ranges from 0 to 18 points, with risk stratification defined as low (0-3), intermediate (4-7), and high (≥8) for the development of clinically significant hyperlactatemia (≥4mmol/L). The Lactate Risk Score integrates preoperative vulnerability (age, coronary artery disease, anemia), perfusion adequacy, cumulative oxygen debt, CPB duration, hemodynamic stability, vasoactive use, metabolic stress, and gaseous microembolic load. Derived from published cardiac surgery cohorts at 34-36°C, the score provides a structured, evidence-weighted framework to anticipate lactate elevation during CPB. Prospective validation is warranted before clinical adoption.

The refining and petrochemical industries play an extremely important role in meeting society’s needs by providing products essential for various economic activities. Due to their dependence on fossil fuels (coal, crude oil, and natural gas), used both as an energy source and as raw materials, they are a significant source of greenhouse gas emissions. The aim of this review article is to present the potential for decarbonization in the refining and petrochemical industries. Hydrogen is used in large quantities in the refining processes and in the production of key products and intermediates in the petrochemical industry. This article examines the dependence of the refining and petrochemical sectors on hydrogen. To achieve this, key platforms/databases collecting information on publications, such as Web of Science and Scopus, were used. Studies by the International Energy Agency and the European Commission on developing policies for the hydrogen, emission reduction and industrial sectors guided the selection of papers. This article focuses on technologies related to the production of petrochemical products. A strong emphasis is placed on the fact that the primary cause of emissions in this industry is the use of large quantities of hydrogen, meaning that one of the main ways to reduce CO2 emissions is to replace traditionally produced hydrogen with green hydrogen, which is obtained using technologies that do not produce carbon dioxide emissions throughout the entire process. The emission intensity of hydrogen production is therefore a key issue that determines the decarbonization of these industries. Achieving carbon neutrality by 2050 will not be possible without global cooperation from all stakeholders, including financial support for this sector. Decarbonization goals set at the national and global levels should reflect this fact.

Tannin extracts (TE) of isolated condensed or hydrolyzable tannins have been evaluated for their methane (CH4) mitigation potential in beef cattle. Despite the potential for a combination of tannin types to yield synergistic effects, the dose-response pattern and optimal supplementation rate of a TE blend remain unclear. Our objectives were to investigate changes in nutrient utilization and gas emission patterns in response to supplementation with a TE blend (Silvafeed ByPro; SILVATEAM, San Michele Mondovi, Italy), and to determine the optimal dose to minimize emissions in growing steers (308 ± 9.4 kg BW). Supplementation rates were 0.0, 0.3, 0.6, and 0.9% of DM (TE0.0, TE0.3, TE0.6, and TE0.9, respectively) within a total mixed ration fed at 1.62% of BW (DM basis). Whole-animal gas exchange and total fecal and urine production were measured over 48 h using two open-circuit, indirect calorimetry respiration chambers in a 4 × 8 Latin rectangle design with four periods and eight animals. Blood and ruminal parameters were evaluated from samples collected from steers upon removal from chambers. Nutrient and water intake were not influenced (P ≥ 0.42) by TE rate. Fecal excretion of acid detergent fiber (ADF) displayed a dose-response pattern (quadratic P < 0.01, cubic P = 0.01) with increasing TE rate. Apparent digestibility of ADF decreased at an increasing rate (quadratic P < 0.01, cubic P = 0.01) with TE. There was a quadratic effect (P = 0.01) on ruminal propionate concentration, but no other ruminal parameters were influenced by TE rate (P ≥ 0.13). There was a quadratic pattern (P = 0.04) in fecal N excretion and N digestibility. The rate of TE did not affect urinary N excretion (P ≥ 0.58), but N retention tended to linearly decrease (P = 0.06) with increased TE and blood urea N tended (P = 0.06) to follow a cubic pattern. There was a quadratic (P ≤ 0.05) dose-response relationship for gaseous energy loss. Although oxygen consumption and carbon dioxide production were not influenced by TE rate (P ≥ 0.64), the respiratory quotient increased linearly (P = 0.02) with TE inclusion. However, no other energy partitioning was influenced by TE supplementation rate (P ≥ 0.18). Regardless of how it was expressed, CH4 production displayed a quadratic pattern (P ≤ 0.04) in relation to increased TE rate, with equations suggesting an optimal TE dose between 0.20 and 0.22% of DM for CH4 mitigation without compromising nutrient utilization or energy efficiency.

ABSTRACT This study aims to critically investigate the development of self-compacting ultra-high-performance geopolymer concrete (SCUHPGC), with a particular focus on the influence of the type of alkaline activator and curing regime on mechanical performance, embodied CO2 emissions, and cost efficiency. A detailed comparative analysis was conducted between ambient-cured mixtures activated by a sodium hydroxide (SH)-sodium silicate (SS) mixture versus combined-cured mixtures (a 90°C hot water followed by 250°C dry-air curing) activated by calcium carbide residue (CCR). The ambient-cured SH-SS-activated mixtures were designed using a ternary binder, achieving a slump flow diameter of 740 mm and a compressive strength of 132.7 MPa. The CCR-activated mixtures reported in the literature consisted of a binary binder. It was reported that under combined curing conditions, the plain CCR-activated mixture achieved a slump flow diameter of 700 mm and a compressive strength of 130.4 MPa. The total carbon dioxide equivalent (CO2-e) emissions and production cost of the ambient-cured SH-SS-activated SCUHPGC were lower than the corresponding total CO2-e emissions and production cost of the combined-cured CCR-activated SCUHPGC by approximately 15.9% and 13.5%, respectively. The ambient-cured SH – SS-activated SCUHPGC demonstrates superior efficiency, combining ultra-high mechanical performance with a lower environmental impact.

Greenhouse gas emissions from beaver ponds exceed emissions from shallow lakes in subantarctic ecosystems.

Abstract Objective: Energy metabolism and immune function have beneficial effects on health. In this study, we demonstrated that early intervention with Jingfang granules (JFGs) promoted energy metabolism and immune function by using an eight-channel energy metabolism detection system and metabolomics techniques combined with physiological and biochemical indicators. Materials and Methods: Male Sprague-Dawley rats were randomly divided into Control, LPS-induced lung injury model, and Jingfang Granules (JFG) intervention groups. Energy metabolism was monitored in freely moving rats using an eight-channel metabolic system), measuring oxygen consumption, carbon dioxide production, and respiratory exchange ratio. Metabolomic profiling was performed using UPLC-Q-TOF/MS chromatography. Physiological and biochemical parameters including inflammatory cytokine levels (TNF-α, IL-6, IL-1β) were assessed by ELISA. Lung histopathology was evaluated through H&amp;E staining following LPS challenge. Results: JFG pretreatment significantly enhanced systemic energy metabolism. Metabolomic analysis revealed JFG-mediated normalization of disrupted metabolic pathways, particularly in amino acid metabolism (valine, leucine, isoleucine degradation) and tricarboxylic acid cycle intermediates. These metabolic improvements correlated with attenuated inflammatory responses, showing significantly reduced pro-inflammatory cytokine levels (TNF-α, IL-6, IL-1β) in JFG-treated animals. Histopathological examination confirmed the protective efficacy of JFG intervention, demonstrating substantially alleviated lung tissue damage, diminished inflammatory cell infiltration, and preserved alveolar architecture following LPS exposure. Conclusions: The experimental results indicated that intervention with JFGs for 1 week could alleviate lung injury in male rats when exposed to lipopolysaccharides.

ABSTRACT Plums are an important fruit that is widely grown in temperate climates in Europe, such as the Czech Republic. Currently, stone fruits, including plums, are more susceptible to ongoing climate changes, which leads to a lower production. One possible solution is to cultivate Asian species, which show greater resistance in that regard. The fruit of Asian plum trees feature a higher variability of fruit – size, aroma and color. To support more significant distribution of such species in the European temperate zone, it is necessary to monitor their resistance as well as the potential of storing the fruits. The low storage temperature of 1°C vs. 20°C (shelf-life) had a more significant effect on carbon dioxide and ethylene production than the composition of the ultra low oxygen (ULO) atmosphere vs. random atmosphere (RA). Based on the physiological response observed, the “Sorriso Di Primavera” fruit can be classified as having a suppressed climacteric phase.

ObjectiveTo compare the muscular activity and metabolic response between a novel handle-based wheelchair drive (KURT) and conventional push rim propulsion in a simulated daily mobility circuit.DesignSingle-group comparative study between 3 wheelchair configurations.Participants22 healthy individuals without prior wheelchair experience.MethodsParticipants completed a multi-movement circuit including ramps, obstacle avoidance, and directional changes using KURT and 2 push-rim wheelchairs with different wheel sizes (small wheels, SW; large wheels, LW). Electromyographic data were collected bilaterally from 7 upper body muscles, and cardiopulmonary variables were continuously monitored.ResultsBiceps brachii activity was significantly higher with KURT than with SW and LW for both arms (all p< 0.001), while triceps brachii and pectoralis major activity were significantly lower (all p < 0.001). Other monitored muscles showed smaller relative differences between configurations, often resulting in limited or no statistically significant effects. Metabolic demand was lower with KURT: heart rate, oxygen consumption, and carbon dioxide production were reduced compared with LW (all p < 0.05), while respiratory exchange ratio was unchanged and respiratory frequency was higher than with SW (p < 0.05).ConclusionKURT appears to be a promising, more energy-efficient alternative to push-rim wheelchairs, reducing upper limb muscle demand and metabolic cost. These findings motivate studies in regular wheelchair users and longer-term use in daily living scenarios.

Passive range of motion (PROM) is a common early mobilization technique in intensive care, especially for sedated, mechanically ventilated patients. This study aimed to evaluate the effect of early PROM on oxygen consumption (VO₂) and carbon dioxide production (VCO₂) in mechanically ventilated critically ill adults. A prospective observational cohort study was conducted in the tertiary ICU of a university hospital between May and September 2023. PROM was initiated within 24-48 hours of admission in hemodynamically stable, sedated patients (RASS: -2 to -4). A physiotherapist performed a standardized 10-minute PROM protocol. VO₂ and VCO₂ were measured via indirect calorimetry before, during, and after the intervention. Statistical analyses were conducted using a repeated-measures ANOVA, with the average level before and after the measurement, as well as the peak level of VCO₂ during the intervention. Cardiovascular parameters were also recorded. Twenty-three patients were included. PROM exercises showed a significant quadratic trend in VCO₂; F = 6.686, p = 0.017 and a borderline quadratic trend in VO₂ (F = 4.320, p = 0.050). Heart rate decreased significantly compared to baseline (P = 0.043). No significant change in blood pressure levels was observed. Early PROM exercises in sedated, mechanically ventilated ICU patients induced a quadratic trend in VCO₂ and VO₂, indicating a temporary and reversible metabolic response. PROM does not cause any hemodynamic instability. It accelerates the elimination of metabolic waste and can be used as part of early rehabilitation protocols.

Basic aim is to draw attention to most of the known influences that have as effect global warming. Why? The physical phenomenon called global warming has become a political issue that uses or rather abuses for example, the issue of increased production of carbon dioxide and greenhouse gases for economic pressures. For each of the thematic areas described further in the text, there are many publications printed and placed on www sites. To tell the htrouth each part would require the co-authorship of an expert, a narow specialist, and a more intensive analysis. Given the number of influences, this is not practically possible, and only basic key quotes are given. However, author hopes that the basic main an ONE goal stated here –i.e to show the quantity of influences and parallel influence of this factors on global warming – will be fulfilled. The large number of effects that have a real or probable significant influence on global warming and and vice versa the fact, how few of these effects are actually evaluated in scientific texts is surprising. It seeems also, that in case of climate change, cause and effect are often confused by authors. Quote:Greenhouse warming theory is probably rapidly becoming the most expensive mistake ever made in the history of science, economically, politically, and environmentally.

ABSTRACTThe validity and between‐day reliability of cardiopulmonary exercise testing (CPET) systems remain largely unexplored. We therefore evaluate the validity and between‐day technological and biological reliability of five popular CPET systems for assessing respiratory variables, substrate use, and energy expenditure during simulated and real human exercise. The following systems were assessed: Vyntus CPX, Oxycon Pro, VO2 Master, KORR, and Calibre. A metabolic simulator was used to simulate breath‐by‐breath gas exchange. The values measured by each system (minute ventilation (V̇E), breathing frequency (BF), oxygen uptake (V̇O2), carbon dioxide production (V̇CO2), respiratory exchange ratio (RER), energy from carbohydrates and fats, and total energy expenditure) were compared to the simulated values to assess the validity. Six well‐trained participants cycled 5% below their first ventilatory threshold on 2 days to verify the validity in human exercise. Between‐session reliability was assessed in both the simulation and human experiments to determine technological and biological variability. Absolute percentage errors during the simulations ranged from 0.69% to 5.56% for V̇E, 0.92% to 1.44% for BF, 3.12% to 7.86% for V̇O2, 4.07% to 12.1% for V̇CO2, 1.21% to 6.94% for RER, 2.83% to 48.8% for Kcal from carbohydrates, 14.1% to 50.3% for Kcal from fats, and 4.21% to 6.98% for total energy expenditure. Between‐session variability during simulation (i.e., technological variability) ranged from 0.46% to 3.15% for V̇O2 and 0.71% to 4.99% for V̇CO2. The error and between‐day variability of the error for respiratory gas variables, substrate, and energy use differed substantially between systems. Biological and technological V̇O2 and V̇CO2 variability, respectively, accounted for ~60%–70% and 40%–30% of the variability in repeated human testing.

Blood flow restriction (BFR) implemented during aerobic exercise has been shown to alter cardiopulmonary responses under intensity-matched conditions, but its effects relative to maximal running speed and the gas exchange threshold (GET) remain unclear. The purpose of this investigation was to examine cardiopulmonary (oxygen consumption [V̇O<inf>2</inf>] and carbon dioxide production [V̇CO<inf>2</inf>]) responses during submaximal running with BFR relative to maximal running without BFR and the GET. Fifteen aerobically trained females completed a custom ramp protocol to determine peak running speed and GET. Participants randomly completed four, three-minute running bouts at 70%<inf>BFR</inf>, 80%<inf>BFR</inf>, and 90%<inf>BFR</inf> of their top speed with BFR and 100%<inf>NOBFR</inf> of their top speed without BFR. Separate Bayesian repeated-measure models were performed to examine differences in V̇O<inf>2</inf> and V̇CO<inf>2</inf> during the final minute of the bouts. V̇O<inf>2</inf> largely increased across bouts but was similar between the 80%<inf>BFR</inf> and 90%<inf>BFR</inf> (Mean<inf>diff</inf>=-2.26±-0.44 mL·kg-1·min-1) bouts as well as the 90%<inf>BFR</inf> and 100%<inf>NOBFR</inf> (Mean<inf>diff</inf>=-2.54±0.03 mL·kg-1·min-1) bouts. V̇CO<inf>2</inf> also increased across bouts and was similar between the 90%<inf>BFR</inf> and 100%<inf>NOBFR</inf> (Mean<inf>diff</inf>=-0.25±-0.02 L·min-1) bouts. Relative to GET, V̇O<inf>2</inf> and V̇CO<inf>2</inf> was greater during each bout (GET < 70%<inf>BFR</inf>, 80%<inf>BFR</inf>, 90%<inf>BFR</inf>, and 100%<inf>NOBFR</inf>). Pulmonary gas exchange during submaximal running with BFR was comparable to maximal running without BFR (i.e., 90%<inf>BFR</inf> and 100%<inf>NOBFR</inf>) and greater than speed-matched running (i.e., relative to GET). Thus, BFR may serve as a training adjunct to lower the intensity (i.e., ≤10%) relative to the GET.

Accurate metabolic exercise testing is essential for assessing cardiometabolic health in both athletes and clinical populations with prediabetes and diabetes. This study investigated whether and how fat, carbohydrates and lactate diagnostics are influenced by ergometry testing pedaling frequency. This randomized cross-over repeated-measures trial, examined human participants for cardiorespiratory oxygen uptake ( ) and carbon dioxide production ( ), and blood lactate concentration (BLC), using two separate incremental load ergometry exercise tests until exhaustion, at higher versus lower cycling pedaling frequencies of 100 and 50 revolution per minute (RPM). Metabolic diagnostics of fatty acid oxidation (FAO), carbohydrates oxidation (CHO), maximal FAO (MFO) and associated MFO intensity (Fatmax) were estimated by stoichiometric equations and compared at 100 versus 50 RPM. Higher , , BLC and CHO and lower FAO were found for all submaximal intensities at 100 RPM than at 50 RPM (all p < 0.01). Fatmax power output was significantly lower (83.7 ± 20.3 vs. 99.8 ± 25.8 W, p < 0.05, effect size d = 0.70) at 100 than at 50 RPM. However, pedaling frequency-dependent effects reflected nonsignificant changes in MFO (0.58 ± 0.16 vs. 0.52 ± 0.15 g.min-1, p = 0.12, d = 0.39), and also in the corresponding BLC at MFO (1.70 ± 0.45 vs. 1.30 ± 0.39 mmol.L-1, p = 0.06, d = 0.9). Metabolic assessments should prioritize absolute MFO and BLC dynamical changes over Fatmax intensities, when interpreting fat-oxidation capacity, particularly under varying pedaling frequencies. By jointly characterizing blood-based and respiratory-based diagnostics under different exercise assessment conditions, this study helps improve the reliability of diagnosing the metabolic status in both healthy individuals and patients with metabolic disease.

Mitochondrial Acyl-Coenzyme Synthetase Short Chain Family Member-1 (ACSS1) converts free acetate into acetyl-coenzyme A (acetyl-CoA), regulated, in part, by acetylation at lysine 635 (ACSS1-K635). We challenged our ACSS1 constitutive acetylation mimic knock-in (K635Q) mice by injecting a β3-adrenergic receptor agonist, CL-316243 (CL), to induce a thermogenic response. Strikingly, we show that Acss1K635Q/K635Q mice exhibit hypothermia and acute metabolic crisis following CL stimulus, as shown by significantly reduced oxygen consumption, carbon dioxide production, respiratory exchange ratio, and heat production. We also observed histological differences in both brown adipose tissue (BAT) and subcutaneous white adipose tissue (WAT), accompanied by altered expression and regulation of lipogenic enzymes and Uncoupling Protein 1 (UCP1) in Acss1K635Q/K635Q. In contrast to wild-type adipose tissues, Acss1K635Q/K635Q did not show changes in acetyl-CoA and acetate levels in response to CL, and mitochondria isolated from BAT displayed impaired respiration on palmitate. Lastly, beige adipocytes differentiated ex vivo from Acss1K635Q/K635Q mice showed altered response to the adenylate cyclase stimulator, forskolin, with unresponsive mitochondria and lipogenic lipid droplets, and lower fatty acid oxidation activity. These results suggest that non-acetylated ACSS1 plays an essential role in thermoregulation and the ability to metabolize free fatty acids.

Abstract Rivers transform and transport much of the organic input they receive from terrestrial ecosystems. This carbon sustains stream food webs and fuels the production and release of carbon dioxide and methane to the atmosphere. Warming water temperatures and intensification of the hydrologic cycle due to climate change are likely to affect these carbon transformations and downstream transport in streams. Here, we examine the natural variability and long‐term shifts in the metabolism of New Hope Creek, North Carolina, USA, site of the earliest published estimates of a stream's annual metabolic regime in 1969. We estimated annual ecosystem metabolism over 3 yr (2017–2020) and used the variability observed in the modern dataset to provide context for interpreting long‐term change in response to climate drivers. We found that New Hope Creek was heterotrophic in all years, with highly seasonal carbon cycling. Much of the modern variability can be explained by water temperature and flow conditions. Warmer temperatures and longer periods of low flow conditions led to faster carbon cycling and increased heterotrophy, while autumn floods suppressed annual ecosystem respiration by reducing river carbon stocks. Comparing modern estimates to those from 50 yr ago, we find that New Hope Creek is now substantially warmer and has higher metabolic fluxes. Despite the limitations of inferring trends between two distant time points, we use modern data to hindcast metabolism and show how climate change has likely accelerated carbon cycling and shortened carbon residence time in New Hope Creek.

Graduate Student Literature Review: The development of the Brouwer equation to estimate heat production-Past, present, and future perspectives.