High pCO2 Research Articles

Effects of the glacial meltwater supply on carbonate chemistry in Bowdoin Fjord, Northwestern Greenland

To understand the effects of the glacial meltwater supply on carbonate chemistry and the air–sea CO2 flux within the fjord, water samples were collected in Bowdoin Fjord in northwestern Greenland for dissolved inorganic carbon (DIC) concentration, total alkalinity (TA), oxygen isotopic ratio (δ18O), and chlorophyll a concentration analyses in the summers of 2016 and 2017. The partial pressure of CO2 (pCO2) in surface water, calculated from DIC and TA, was less than 200 µatm, and was significantly lower than that in the atmosphere (399 ± 3 µatm). Therefore, surface water of the fjord acts as sink for CO2 in the atmosphere (–4.9 ± 0.7 mmol m–2 d–1). To evaluate the effects of freshwater and land-derived substances by glacial meltwater on pCO2 in the fjord, we calculated the changes of pCO2 in salinity and carbonate chemistry that would result from the inflow of glacial meltwater into the fjord. The calculated pCO2 was high near the calving front, where the contribution of glacier meltwater was significant. Examination of the relationship between salinity-normalized DIC and TA, which was considered DIC and TA input from the land, suggested that the land-derived high pCO2 freshwater affected mainly by the remineralization of the organic matter by bacterial activity was supplied to the Bowdoin Fjord.

Capturing the short-term variability of carbon dioxide emissions from sedimentary rock weathering in a remote mountainous catchment, New Zealand

Weathering of organic carbon contained in sedimentary rocks (petrogenic OC, OCpetro) is an important control on the concentrations of carbon dioxide (CO2) and oxygen in the atmosphere. Of particular significance are steep mountainous catchments, where high rates of physical erosion introduce OCpetro to the surface, where oxygen in air and water can help drive oxidative weathering reactions, yet measurements of CO2 emissions from OCpetro oxidation are still scarce. Here, we use in situ gas accumulation chambers and show that CO2 fluxes, and their environmental controls, can be determined during a stand-alone, short-term (8 days) field campaign, applied to a remote setting. In the rapidly eroding Waiapu River catchment, New Zealand, dominated by mudstones, we measured high rates of CO2 release (222–1590 mgC m−2 d−1) in five accumulation chambers in the near-surface of naturally fractured and bedded rock outcrops. The corresponding CO2 concentrations are very high (pCO2 ~4700–27,100 ppmv), and such values could influence acid-hydrolysis reactions during chemical weathering of co-occurring silicate minerals. The CO2 is radiocarbon depleted (fraction modern, F14C = 0.0122–0.0547), confirming it is petrogenic in origin. Stable carbon isotopes suggest a source from OCpetro, but δ13C values of the CO2 are lower by ~3.5–3.7 ± 0.1 ‰ from those of OCpetro (−25.9 ± 0.1 ‰), consistent with isotope fractionation associated with microbial respiration of OCpetro. Over 6 days of measurement, we find that CO2 fluxes respond quickly to changes in temperature and humidity, indicating an environmental regulation that is captured by our short-term installation. The approaches applied here mean that future research can now seek to constrain the climatic, lithological and biological controls on OCpetro oxidation across regional to global scales.

Greenhouse gases concentrations and emissions from a small subtropical cascaded river-reservoir system

The damming of rivers can significantly intercept carbon transportation and regulate dynamic biogeochemistry, which then greatly influence carbon gases (CO2 and CH4) metabolism and emissions. However, little is known about the spatial–temporal pattern and controls of carbon emissions from a cascaded river-reservoir system. In this study, we investigated the spatial and seasonal partial pressure of CO2 and CH4 (i.e. pCO2 and pCH4) dynamics along a subtropical cascaded dammed river (Wubu River) located in Southwest China. The pCO2 and pCH4 in the Wubu River basin showed significantly spatial–temporal and were generally supersaturated with gas fluxes of 89.5 ± 89.7 mmol CO2 m−2 d-1 and 1.19 ± 1.18 mmol CH4 m−2 d-1. The pCO2 and pCH4 were all increasing from upstream to downstream. And, most of river sections had significantly higher pCO2 and CO2 than their downstream reservoir sections, while the pCH4 and CH4 flux were the opposite. Meanwhile, released waters had invariably high pCO2 and pCH4 and were carbon gas emission hotspots in the river-reservoir system. The intercepts of carbon and nutrients by cascade damming, created a series of eutrophic hotspots and enhanced primary productivity, could inhibit riverine CO2 emissions but promote CH4 production. Thus, the spatial patterns of riverine pCO2, pCH4 and the “pCO2/pCH4” in cascade hydroelectric river were importantly altered. It was evaluated that cascade damming would reduce about 17.9 % of the total CO2 evasion amount but increase approximately 16.3 % of CH4. The global warming potential of rivers would be enhanced when organic carbon was captured and mineralized to CH4 rather than to CO2 in cascade damming river system. pH, dissolved oxygen and chlorophyll a (chl-a) were indicated as natural controls of pCO2 in such a cascade river-reservoir system, while dissolved organic carbon, dissolved organic carbon and chl-a were significantly correlated with pCH4 and acted as good predictors of CH4 emissions. The temperature and autotrophic production were responsible for the different seasonal patterns of carbon gas concentrations observed between river sections and reservoir sections. Our study highlighted that cascaded damming decreased CO2 emissions and created CH4 hotspots in river systems and may have significantly increased the complexity of the spatial–temporal pattern and construction of riverine carbon gases emissions. Given the increasing damming of rivers worldwide for energy demand, researches are needed to quantify the role of cascaded damming in the riverine C budget.

Consequences of Warming and Acidification for the Temperate Articulated Coralline Alga, Calliarthron Tuberculosum (Florideophyceae, Rhodophyta).

Global climate changes, such as warming and ocean acidification (OA), are likely to negatively impact calcifying marine taxa. Abundant and ecologically important coralline algae may be particularly susceptible to OA; however, multi‐stressor studies and those on articulated morphotypes are lacking. Here, we use field observations and laboratory experiments to elucidate the impacts of warming and acidification on growth, calcification, mineralogy, and photophysiology of the temperate articulated coralline alga, Calliarthron tuberculosum. We conducted a 4‐week fully factorial mesocosm experiment exposing individuals from a southern CA kelp forest to current and future temperature and pH/pCO2 conditions (+2°C, −0.5 pH units). Calcification was reduced under warming (70%) and further reduced by high pCO2 or high pCO2 x warming (~150%). Growth (change in linear extension and surface area) was reduced by warming (40% and 50%, respectively), high pCO2 (20% and 40%, respectively), and high pCO2 x warming (50% and 75%, respectively). The maximum photosynthetic rate (Pmax) increased by 100% under high pCO2 conditions, but we did not detect an effect of pCO2 or warming on photosynthetic efficiency (α). We also did not detect the effect of warming or pCO2 on mineralogy. However, variation in Mg incorporation in cell walls of different cell types (i.e., higher mol % Mg in cortical vs. medullary) was documented for the first time in this species. These results support findings from a growing body of literature suggesting that coralline algae are often more negatively impacted by warming than OA, with the potential for antagonistic effects when factors are combined.

Ocean acidification elicits differential bleaching and gene expression patterns in larval reef coral Pocillopora damicornis under heat stress

The successful dispersal of coral larvae is vital to the population replenishment and reef recovery and resilience. Despite that this critical early stage is susceptible to ocean warming and acidification, little is known about the responses of coral larvae to warming and acidification across different biological scales. This study explored the influences of elevated temperature (29 °C versus 33 °C) and pCO2 (500 μatm versus 1000 μatm) on brooded larvae of Pocillopora damicornis at the organismal, cellular and gene expression levels. Heat stress caused bleaching, depressed light-enhanced dark respiration, photosynthesis and autotrophy, whereas high pCO2 stimulated photosynthesis. Although survival was unaffected, larvae at 33 °C were ten-times more likely to settle than those at 29 °C, suggesting reduced capacity to disperse and differentiate suitable substrate. Remarkably, heat stress induced greater symbiont loss at ambient pCO2 than at high pCO2, while cell-specific pigment concentrations of symbionts at 33 °C increased twofold under ambient pCO2 relative to high pCO2, suggesting pCO2-dependent bleaching patterns. Considerable increases in activities of host antioxidants superoxide dismutase (SOD) and catalase (CAT) at 33 °C indicated oxidative stress, whereas lipid peroxidation and caspase activities were contained, thereby restraining larval mortality at 33 °C. Furthermore, the coral host mounted stronger transcriptional responses than symbionts. High pCO2 stimulated host metabolic pathways, possibly because of the boosted algal productivity. In contrast, host metabolic processes and symbiont photosystem genes were downregulated at 33 °C. Interestingly, the upregulation of extracellular matrix genes and glycosaminoglycan degradation pathway at 33 °C was more evident under ambient pCO2 than high pCO2, suggesting compromised host tissue integrity that could have facilitated symbiont expulsion and bleaching. Our results provide insights into how coral larvae respond to warming and acidification at different levels of biological organization, and demonstrate that ocean acidification can mediate thermal bleaching and gene expression in coral larvae under heat stress.

Effects of controlled atmosphere and storage temperature on the quality of shelled ‘Barton’ pecan nuts during long-term storage

This study aimed to evaluate the effects of controlled atmosphere (CA) storage at a low oxygen partial pressure (pO2; 2 kPa of O2) and low pO2 associated with high pCO2 (2 kPa O2 + 15 kPa CO2) in relation to ambient atmospheric conditions (control), at different temperatures, on shelled ‘Barton’ pecan nuts quality after storage. Color, respiration rates, moisture content (MC), and oxidation markers, such as peroxide value (PV), acidity value (AV), and volatile compounds (VC), were evaluated. During six months of storage, the MC decreased in all CA treatments, and treatments at 10 °C had the lowest AVs and PVs. However, the treatment with high pCO2 levels also guaranteed lower AVs at 20 °C. The color parameter b* (yellow), which is related to the golden appearance of pecans and is a highly desirable visual attribute in the commercialization of nuts, was maintained high in treatments at 10 °C with CA treatments until six months of storage. The VCs, characteristic of lipid oxidation (aldehydes, acids, alcohols, and ketones), increase in all treatments with prolonging storage. When pCO2 was associated to 10 °C at six month of storage, it showed a larger area in the acids and unsaturated aldehyde classes, while it was relevant for alcohols, lactones, and esters at 20 °C, with sweet characteristics, including ethyl ethanoate, ethyl hexanoate, and butyrolactone. Thus, this study shows another advance in the storage techniques of shelled pecans, pointing to alternatives for reducing energy costs in the cooling chain.

Impact of Elevated Levels of Dissolved CO2 on Performance and Proteome Response of an Industrial 2'-Fucosyllactose Producing Escherichia coli Strain.

Large-scale microbial industrial fermentations have significantly higher absolute pressure and dissolved CO2 concentrations than otherwise comparable laboratory-scale processes. Yet the effect of increased dissolved CO2 (dCO2) levels is rarely addressed in the literature. In the current work, we have investigated the impact of industrial levels of dCO2 (measured as the partial pressure of CO2, pCO2) in an Escherichia coli-based fed-batch process producing the human milk oligosaccharide 2′-fucosyllactose (2′-FL). The study evaluated the effect of high pCO2 levels in both carbon-limited (C-limited) and carbon/nitrogen-limited (C/N-limited) fed-batch processes. High-cell density cultures were sparged with 10%, 15%, 20%, or 30% CO2 in the inlet air to cover and exceed the levels observed in the industrial scale process. While the 10% enrichment was estimated to achieve similar or higher pCO2 levels as the large-scale fermentation it did not impact the performance of the process. The product and biomass yields started being affected above 15% CO2 enrichment, while 30% impaired the cultures completely. Quantitative proteomics analysis of the C-limited process showed that 15% CO2 enrichment affected the culture on the protein level, but to a much smaller degree than expected. A more significant impact was seen in the dual C/N limited process, which likely stemmed from the effect pCO2 had on nitrogen availability. The results demonstrated that microbial cultures can be seriously affected by elevated CO2 levels, albeit at higher levels than expected.

High-CO2 Levels Rather than Acidification Restrict Emiliania huxleyi Growth and Performance

The coccolithophore Emiliania huxleyi shows a variety of responses to ocean acidification (OA) and to high-CO2 concentrations, but there is still controversy on differentiating between these two factors when using different strains and culture methods. A heavily calcified type A strain isolated from the Norwegian Sea was selected and batch cultured in order to understand whether acclimation to OA was mediated mainly by CO2 or H+, and how it impacted cell growth performance, calcification, and physiological stress management. Emiliania huxleyi responded differently to each acidification method. CO2-enriched aeration (1200 µatm, pH 7.62) induced a negative effect on the cells when compared to acidification caused by decreasing pH alone (pH 7.60). The growth rates of the coccolithophore were more negatively affected by high pCO2 than by low pH without CO2 enrichment with respect to the control (400 µatm, pH 8.1). High CO2 also affected cell viability and promoted the accumulation of reactive oxygen species (ROS), which was not observed under low pH. This suggests a possible metabolic imbalance induced by high CO2 alone. In contrast, the affinity for carbon uptake was negatively affected by both low pH and high CO2. Photochemistry was only marginally affected by either acidification method when analysed by PAM fluorometry. The POC and PIC cellular quotas and the PIC:POC ratio shifted along the different phases of the cultures; consequently, calcification did not follow the same pattern observed in cell stress and growth performance. Specifically, acidification by HCl addition caused a higher proportion of severely deformed coccoliths, than CO2 enrichment. These results highlight the capacity of CO2 rather than acidification itself to generate metabolic stress, not reducing calcification.

Utility of D-dimers in COVID-19 Patients Requiring Extracorporeal Membrane Oxygenation.

A retrospective study was performed examining the trend of inflammatory markers, including D-dimers, in 29 COVID-19 patients requiring veno-venous (VV) extracorporeal membrane oxygenation (ECMO) support. We observed that COVID-19 patients with pre-cannulation D-dimer levels >3,000 ng/mL had a significantly shorter time from admission to cannulation (4.78 vs. 8.44 days, p = 0.049) compared to those with D-dimer <3,000 ng/mL. Furthermore, patients with D-dimer >3,000 ng/mL had a trend of lower pH (7.24 vs. 7.33), higher pCO2 (61.33 vs. 50.69), and higher vasoactive inotropic score (7.23 vs. 3.97) at time of cannulation, however, these were not statistically significant. This cohort of patients also required a longer duration of ECMO support (51.44 vs. 31.25 days). However, 13 patients required at least one ECMO-circuit exchange and 16 patients did not require any exchanges. There was a consistent drop in D-dimer values after every circuit exchange, which was not observed in any of the other examined inflammatory markers, including ferritin, lactate dehydrogenase, or C-reactive protein. We propose that elevated D-dimer levels (>3,000 ng/mL) reflect increased disease severity in COVID-19, and predict a longer ECMO course. Once on ECMO, however, the D-Dimer level consistently decreased with every circuit exchange, which may reflect thrombus within the oxygenator rather than just disease severity.

Ocean Acidification Alters the Predator – Prey Relationship Between Hydrozoa and Fish Larvae

Anthropogenic CO2 emissions cause a drop in seawater pH and shift the inorganic carbon speciation. Collectively, the term ocean acidification (OA) summarizes these changes. Few studies have examined OA effects on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities. Because Hydrozoa can seriously compete with and prey on other higher-level predators such as fish, changes in their abundances may have significant consequences for marine food webs and ecosystem services. To investigate the interaction between Hydrozoa and fish larvae influenced by OA, we enclosed a natural plankton community in Raunefjord, Norway, for 53 days in eight ≈ 58 m³ pelagic mesocosms. CO2 levels in four mesocosms were increased to ≈ 2000 µatm pCO2, whereas the other four served as untreated controls. We studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study. These results indicate that a decrease in predation pressure shortly after hatch likely shaped higher herring larvae survival, when hydromedusae abundance was lower in the OA treatment compared to control conditions. We conclude that indirect food-web mediated OA effects drove the observed changes in the Hydrozoa – fish relationship, based on significant changes in the phyto-, micro-, and mesoplankton community under high pCO2. Ultimately, the observed immediate consequences of these changes for fish larvae survival and the balance of the Hydrozoa – fish larvae predator – prey relationship has important implications for the functioning of oceanic food webs.

Effects of seawater pCO2 on the skeletal morphology of massive Porites spp. corals

Ocean acidification alters the dissolved inorganic carbon chemistry of seawater and can reduce the calcification rates of tropical corals. Here we explore the effect of altering seawater pCO2 on the skeletal morphology of 4 genotypes of massive Porites spp. which display widely different calcification rates. Increasing seawater pCO2 causes significant changes in in the skeletal morphology of all Porites spp. studied regardless of whether or not calcification was significantly affected by seawater pCO2. Both the median calyx size and the proportion of skeletal surface occupied by the calices decreased significantly at 750 µatm compared to 400 µatm indicating that polyp size shrinks in this genus in response to ocean acidification. The coenosteum, connecting calices, expands to occupy a larger proportion of the coral surface to compensate for this decrease in calyx area. At high seawater pCO2 the spines deposited at the skeletal surface became more numerous and the trabeculae (vertical skeletal pillars) became significantly thinner in 2 of the 4 genotypes. The effect of high seawater pCO2 is most pronounced in the fastest growing coral and the regular placement of trabeculae and synapticulae is disturbed in this genotype resulting in a skeleton that is more randomly organised. The study demonstrates that ocean acidification decreases the polyp size and fundamentally alters the architecture of the skeleton in this major reef building species from the Indo-Pacific Ocean.

The spatial distribution of surface ocean primary productivity in the wake of Marinoan global glaciation

Termination of the Marinoan global glaciation (~650–635 Ma) was followed by the diversification of eukaryotes (e.g., early animals) and oxygenation of deep oceans in the early Ediacaran Period. Previous studies indicate the recovery of marine primary productivity immediately before the cap carbonate precipitation but after melting of the Marinoan global glaciation. Pyrite concretions from the topmost Nantuo Formation in the Yangtze Block, South China, decrease in abundance from shelf to basin facies, while their high positive sulfur (S) isotope values argue the development of oceanic euxinia, which require ample supply of organic matter, presumably reflecting the recovery of marine productivity. However, pyrite contents and pyrite S isotopes alone cannot uniquely constrain the extent and spatial distribution of surface ocean organic matter production. In this study, we conducted in situ analyses of pyrite iron (Fe) (δ56Fepy) and S isotopes (δ34Spy) of pyrite concretions collected from four sections of the Nantuo Formation, spanning from shelf to basin environments. Pyrite from different facies has distinct δ34Spy and δ56Fepy values. In general, δ34Spy values display an increasing trend from shelf to basin, whereas δ56Fepy values demonstrate an opposite trend with the lowest value in the basin sections. The opposite δ34Spy and δ56Fepy shelf-basin gradients strongly argue against the hydrothermal origin, yet verify the diagenetic precipitation of Nantuo pyrite in sediment porewater. Numerical models were developed to quantify the microbial sulfate reduction (MSR), microbial iron reduction (MIR) and pyrite precipitation processes. The modeling results provide an explanation for the shelf-basin decrease of δ56Fepy values, indicating that both the fraction of MIR (fMIR) and the fraction of Fe2+ consumed by pyrite precipitation (fpy) increase from shelf to basin sections. In addition, high δ34Spy values and pyrite contents in the basin sections also imply more intense MSR and higher supplies of H2S from sulfidic seawater. Both MSR and MIR were fueled by organic matter, thus suggesting that the surface ocean primary productivity displayed an unusual increasing trend toward the open ocean, which was different from the higher productivity in modern near-shore regions. We speculate that the reversed shelf-basin gradient of surface ocean primary productivity might be attributed to high P concentration in the post-glacial ocean. Terrestrial riverine P supply, on the contrary, might have diluted seawater P concentration in the near-shore regions. Therefore, our result indicates that the recovery of marine productivity in the aftermath of the Marinoan global glaciation may be not controlled by the availability of nutrients, instead, the immediate recovery of productivity might have been prohibited by, e.g., low seawater pH at a high atmospheric pCO2 level in the initial melting of the Marinoan global glaciation. The marine primary productivity did not recover until a substantive rise of seawater pH, during which deglacial intense continental weathering delivered abundant P into the ocean and accordingly elevated the seawater P concentration.

Comprehending the role of different mechanisms and drivers affecting the sea-surface pCO2 and the air-sea CO2 fluxes in the Bay of Bengal: A modeling study

We apply a coupled physical and biogeochemical (ROMS+PISCES) to understand the influence of distinct drivers and mechanisms on the sea-surface pCO2 and the air-sea CO2 flux of the Bay of Bengal (BoB). The model evaluation suggests that the model simulated sea-surface pCO2 is in accord with the observations. The north of BoB is found to be a sink for the atmospheric CO2, whereas the rest of the region acts as a source. The effect of dissolved inorganic carbon (DIC) and the total alkalinity (TALK) is found to be predominant but is contrasting in nature. Mixing-induced changes in DIC and TALK results in high pCO2 (+570μatm) and, consequently, the positive CO2 flux. The biological activity does draw down the surface pCO2 (−120μatm) but is insufficient in completely opposing the effect of mixing. The uptake of CO2 in the north is due to the CO2 solubility, which is a function of salinity and temperature. The northern rivers, having a high discharge rate, reduce the salinity and temperatures in the north, which possibly aids in this region to be a sink. In the northeast monsoon season, the impact of temperature and DIC is high and opposing. The TALK reduces the pCO2 in the northeast monsoon, but the magnitude is low. The pCO2 in the southwest monsoon is influenced primarily by temperature, whereas in the postmonsoon monsoon, the freshwater dominates. The pre-monsoon season experiences the TALK, temperature, and freshwater increase the pCO2 anomalies, and only the DIC reduces pCO2 anomalies.

The combined effects of ocean acidification and copper on the physiological responses of the tropical coral Stylophora pistillata

A decrease in ocean pH of 0.3 units will likely double the proportion of dissolved copper (Cu) present as the free metal ion, Cu2+, the most bioavailable form of Cu, and one of the most common marine pollutants. We assess the impact of ocean acidification and Cu, separately and in combination, on calcification, photosynthesis and respiration of sub-colonies of a single tropical Stylophora pistillata colony. After 15 days of treatment, total calcification rates were significantly decreased in corals exposed to high seawater pCO2 (∼1000-μatm, 2100 scenario) and at both ambient (1.6–1.9 nmols) and high (2.5–3.6 nmols) dissolved Cu concentrations compared to controls. The effect was increased when both stressors were combined. Coral respiration rates were significantly reduced by the combined stressors after 2 weeks of exposure, indicating the importance of experiment duration. It is therefore likely rising atmospheric CO2 will exacerbate the negative effects of Cu pollution to S. pistillata.

How Important Are Arterial Blood Gas Parameters for Severe Head Trauma in Children?

Aim: Our aim in this study is to consider the relationship between arterial blood gas (ABG) parameters and prognosis in severe head trauma in children.&#x0D; Material and Methods: Patients younger than 17 years of age with a Glasgow Coma Scale (GCS) of 8 and below with a history of head trauma were retrospectively analyzed. The relation of ABG parameters taken at the time of admission with mortality was examined. Independent sample T-test was used for pH, PCO2 and base extract (BE) parameters in ABG, and Mann Whitney U test was used for PO2 and lactate parameters.&#x0D; Results: 48 patients were included in the study. Gender, age, admission blood pressure arterial values, GCS and Abbreviated Injury Scale (AIS) scores, length of stay in intensive care, and the surgical application did not differ statistically between the patient groups who died and survived (p&gt; 0.05). Ph and PO2 values were lower, PCO2, lactate and BE values were found to be higher in the deceased patient group compared to the living patient group (p˂0.05). The presence of acidosis, hypercapnia, or hyperlactatemia according to ABG values in the patient group who died was statistically significantly higher (p˂0.05).&#x0D; Conclusion: In our study, we found that the presence of acidosis, hypercapnia, and hyperlactatemia in patients according to ABG values increased mortality. In addition, according to the results of ROC analysis, we found that high PCO2 and lactate values could be specific indicators indicating poor prognosis. We think that PCO2 and lactate measured in arterial blood may be biomarkers that can determine the prognosis.

Comparison between pulse oximetry and venous blood gas analyses to assess lamb asphyxia at parturition

Early detection of fetal distress at lambing is essential to reduce mortality. Practicality and accuracy of pulse oximetry to assess oxygenation status in newborn lambs under field conditions was evaluated. Oximetry was compared with blood gas analyses and included assessment of vitality (Apgar test) and vigour (attempt to and successful standing and suckling) of 135 Finnish by Polwarth lambs. Sampling of data was obtained immediately after fetal expulsion; percentage of oxygen saturation (satO2) was measured using a pulse oximeter clamped to an ear, and was compared with gas analyses variables measured from a jugular vein sample (Gas Analyser: Siemens-Rapidlab 248®). Correlations between satO2 measured by pulse oximetry and venous blood gas parameters either directly (partial pressure of carbon dioxide (pCO2), partial pressure of oxygen (pO2) and pH) or estimated (bicarbonate concentration, extracellular fluid base excess, and oxygen saturation) were studied. Considering pH as a good indicator of hypoxia at parturition, data was grouped as: G1 = pH < 7.1; G2 = 7.1 ≤ pH < 7.2; G3 = 7.2 ≤ pH < 7.3 and G4 = pH ≥ 7.3. Saturation of oxygen measured by pulse oximetry correlated significantly with pCO2 (r = −0.50; P < 0.001), pH (r = 0.36; P < 0.001) and pO2 (r = 0.2, P = 0.04) measured by blood gas analyses. Lambs with low pH values (G1 = pH ≤ 7.1, acidosis) showed the lowest percentage to attempt and success to stand and suck, lowest Apgar score (G1 = 6.7, G2 = 8.6, G3 = 8.6, G4 = 8.5, P = 0.025), lowest percentage of satO2 measured by oximetry (G1 = 78.8%, G2 = 87.5%, G3 = 87.7%, G4 = 92.1%, P = 0.011) and highest pCO2 (G1 = 78.5, G2 = 73.8, G3 = 65.8, G4 = 53.8 mmHg, P < 0.001). Pulse oximetry appears an accurate method to evaluate lamb birth asphyxia, helping to identify oxygenation constraints during labour, facilitating priority of perinatal handling, and thus improving lamb survival.

Association of Arterial Metabolic Content with Cerebral Blood Flow Regulation and Cerebral Energy Metabolism-A Multimodality Analysis in Aneurysmal Subarachnoid Hemorrhage.

BackgroundIn this study, the association of the arterial content of oxygen, carbon dioxide, glucose, and lactate with cerebral pressure reactivity, energy metabolism and clinical outcome after aneurysmal subarachnoid hemorrhage (aSAH) was investigated.MethodsIn this retrospective study, 60 patients with aSAH, treated at the neurointensive care (NIC), Uppsala University Hospital, Sweden, between 2016 and 2021 with arterial blood gas (ABG), intracranial pressure, and cerebral microdialysis (MD) monitoring were included. The first 10 days were divided into an early phase (day 1 to 3) and a vasospasm phase (day 4 to 10).ResultsHigher arterial lactate was independently associated with higher/worse pressure reactivity index (PRx) in the early phase (β = 0.32, P = .02), whereas higher pO2 had the opposite association in the vasospasm phase (β = −0.30, P = .04). Arterial glucose and pCO2 were not associated with PRx. Higher arterial lactate (β = 0.29, P = .05) was independently associated with higher MD-glucose in the vasospasm phase, whereas higher pO2 had the opposite association in the vasospasm phase (β = −0.33, P = .03). Arterial glucose and pCO2 were not associated with MD-glucose. Higher pCO2 in the early phase, lower arterial glucose in both phases, and lower arterial lactate in the vasospasm phase were associated (P < .05) with better clinical outcome.ConclusionsArterial variables associated with more vasoconstriction (higher pO2 and lower arterial lactate) were associated with better cerebral pressure reactivity, but worse energy metabolism. In severe aSAH, when cerebral large-vessel vasospasm with exhausted distal vasodilation is common, more vasoconstriction could increase distal vasodilatory reserve and pressure reactivity, but also reduce cerebral blood flow and metabolic supply. The MD may be useful to monitor the net effects on cerebral metabolism in PRx-targeted NIC.

High PCO2does not alter the thermal plasticity of developing Pacific herring embryos during a marine heatwave.

ABSTRACTForage fish tend to respond strongly to environmental variability and therefore may be particularly sensitive to marine climate stressors. We used controlled laboratory experiments to assess the vulnerability of Pacific herring (Clupea pallasii) embryos to the combined effects of high partial pressure of carbon dioxide (PCO2) and a simulated marine heatwave. The two PCO2 treatments reflected current conditions (∼550 µatm) and a future extreme level (∼2300 µatm). The dynamics of the heatwave (i.e. rate of onset: ∼0.85°C day−1; maximum intensity: +4.4°C) were modeled from the most extreme events detected by a long-term regional temperature dataset. Simultaneous exposure to these potential stressors did not affect embryo survival. However, the heatwave did elicit significant metabolic effects that included higher rates of routine metabolism (Q10=1.15–1.72), growth (Q10=1.87), rate of development to hatch (Q10=3.01) and yolk consumption (Q10=3.21), as well as a significant reduction in production efficiency (−10.8%) and a three-fold increase in the rate of developmental anomalies. By contrast, high PCO2 conditions produced comparatively small effects on vital rates, including a significant increase in time to hatch (+0.88 days) and a reduction in routine metabolic rate (−6.3%) under the ambient temperature regime only. We found no evidence that high PCO2 increased routine metabolic rate at either temperature. These results indicate that Pacific herring embryos possess sufficient physiological plasticity to cope with extreme seawater acidification under optimal and heatwave temperature conditions, although lingering metabolic inefficiencies induced by the heatwave may lead to important carryover effects in later life stages.

Mechanical power in pediatric acute respiratory distress syndrome: a PARDIE study

BackgroundMechanical power is a composite variable for energy transmitted to the respiratory system over time that may better capture risk for ventilator-induced lung injury than individual ventilator management components. We sought to evaluate if mechanical ventilation management with a high mechanical power is associated with fewer ventilator-free days (VFD) in children with pediatric acute respiratory distress syndrome (PARDS).MethodsRetrospective analysis of a prospective observational international cohort study.ResultsThere were 306 children from 55 pediatric intensive care units included. High mechanical power was associated with younger age, higher oxygenation index, a comorbid condition of bronchopulmonary dysplasia, higher tidal volume, higher delta pressure (peak inspiratory pressure—positive end-expiratory pressure), and higher respiratory rate. Higher mechanical power was associated with fewer 28-day VFD after controlling for confounding variables (per 0.1 J·min−1·Kg−1 Subdistribution Hazard Ratio (SHR) 0.93 (0.87, 0.98), p = 0.013). Higher mechanical power was not associated with higher intensive care unit mortality in multivariable analysis in the entire cohort (per 0.1 J·min−1·Kg−1 OR 1.12 [0.94, 1.32], p = 0.20). But was associated with higher mortality when excluding children who died due to neurologic reasons (per 0.1 J·min−1·Kg−1 OR 1.22 [1.01, 1.46], p = 0.036). In subgroup analyses by age, the association between higher mechanical power and fewer 28-day VFD remained only in children < 2-years-old (per 0.1 J·min−1·Kg−1 SHR 0.89 (0.82, 0.96), p = 0.005). Younger children were managed with lower tidal volume, higher delta pressure, higher respiratory rate, lower positive end-expiratory pressure, and higher PCO2 than older children. No individual ventilator management component mediated the effect of mechanical power on 28-day VFD.ConclusionsHigher mechanical power is associated with fewer 28-day VFDs in children with PARDS. This association is strongest in children < 2-years-old in whom there are notable differences in mechanical ventilation management. While further validation is needed, these data highlight that ventilator management is associated with outcome in children with PARDS, and there may be subgroups of children with higher potential benefit from strategies to improve lung-protective ventilation.Take Home Message: Higher mechanical power is associated with fewer 28-day ventilator-free days in children with pediatric acute respiratory distress syndrome. This association is strongest in children <2-years-old in whom there are notable differences in mechanical ventilation management.

Emiliania huxleyi biometry and calcification response to the Indian sector of the Southern Ocean environmental gradients

An increase in the atmospheric pCO2 and temperature is expected to reduce ocean CO32− concentration, make oceans warmer and alter ocean circulation patterns. This will also affect the production and biogeographic distribution of marine calcifying organisms including coccolithophores. The lowering of oceanic CO32− is expected to interfere with the coccolithophore calcification process and cause malformation of coccoliths, whereas changes in the oceanic temperature and circulation patterns may shift their biogeographic boundaries. In this study, we have investigated Emiliania huxleyi coccolith and coccosphere size response to the wide-ranging physico-chemical conditions of the Indian sector of the Southern Ocean between latitudes 38oS and 58oS during the austral summer of 2010 (January–February). This study helps to understand the response of E. huxleyi coccolith/coccosphere morphometry and mass changes to the fluctuating temperature, salinity, CO32−, pCO2, and nutrient values. Our results show that in the Indian sector of the Southern Ocean, E. huxleyi coccoliths are larger and coccospheres are smaller in the Subtropical Zone (STZ). In contrast, coccoliths size is smaller and coccospheres size is larger in the Subantarctic Zone (SAZ), which is due to the decrease in Sea Surface Temperature, Sea Surface Salinity and increase in nutrient concentrations. In the Indian sector of the Southern Ocean, E. huxleyi shows a north-to-south morphotype shift from the heavily calcified ‘Group A’ (E. huxleyi morphotype A) to the weakly calcified ‘Group B’ (E. huxleyi morphotypes B/C, C) forms. We demonstrate that although weakly calcified E. huxleyi morphotypes (morphotypes B/C and C) comprise less mass than that of the E. huxleyi morphotype A, due to the large-sized coccospheres and numerous coccoliths per coccosphere, ‘Group B’ coccospheres precipitate large amount of CaCO3 in the SAZ compared to ‘Group A’ coccospheres located in the STZ. We have documented the presence of large E. huxleyi overcalcified coccospheres with large-sized coccoliths in the southernmost cold, high pCO2, and nutrient-rich waters which show extracellular calcite precipitation. The energy dispersive spectrometry analysis indicates the presence of a large amount of Mg in the overcalcified E. huxleyi specimens. We suspect that E. huxleyi in the colder nutrient-rich waters, with future projected changes in the carbonate chemistry, may adapt to low pH, high pCO2 conditions through extracellular Ca and Mg mineralization.