Elevated pCO2 enhances bacterioplankton removal of organic carbon.

Factors that affect the removal of organic carbon by heterotrophic bacterioplankton can impact the rate and magnitude of organic carbon loss in the ocean through the conversion of a portion of consumed organic carbon to CO2. Through enhanced rates of consumption, surface bacterioplankton communities can also reduce the amount of dissolved organic carbon (DOC) available for export from the surface ocean. The present study investigated the direct effects of elevated pCO2 on bacterioplankton removal of several forms of DOC ranging from glucose to complex phytoplankton exudate and lysate, and naturally occurring DOC. Elevated pCO2 (1000-1500 ppm) enhanced both the rate and magnitude of organic carbon removal by bacterioplankton communities compared to low (pre-industrial and ambient) pCO2 (250 -~400 ppm). The increased removal was largely due to enhanced respiration, rather than enhanced production of bacterioplankton biomass. The results suggest that elevated pCO2 can increase DOC consumption and decrease bacterioplankton growth efficiency, ultimately decreasing the amount of DOC available for vertical export and increasing the production of CO2 in the surface ocean

Removal of organic carbon by natural bacterioplankton communities as a function of pCO2 from laboratory experiments between 2012 and 2016

Data Set 3A: Utilization of dissolved organic carbon by a natural bacterial community as a function of pCO2Factors that affect the removal of organic carbon by heterotrophic bacterioplankton can impact the rate and magnitude of organic carbon loss in the ocean through the conversion of a portion of consumed organic carbon to CO2. Through enhanced rates of consumption, surface bacterioplankton communities can also reduce the amount of dissolved organic carbon (DOC) available for export from the surface ocean. The present study investigated the direct effects of elevated pCO2 on bacterioplankton removal of several forms of DOC ranging from glucose to complex phytoplankton exudate and lysate, and naturally occurring DOC. Elevated pCO2 (1000 – 1500 ppm) enhanced both the rate and magnitude of organic carbon removal by bacterioplankton communities compared to low (pre-industrial and ambient) pCO2 (250 – ~400 ppm). The increased removal was largely due to enhanced respiration, rather than enhanced production of bacterioplankton biomass. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/472032NSF Division of Ocean Sciences (NSF OCE) OCE-104103

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Mean TOC concentration and mean bacterioplankton abundance for Sargasso Sea and Santa Barbara Channel CNP- and natural-DOC experiments.

<p>Mean TOC concentration (± SD) and mean bacterioplankton abundance (BA; ± SD) averaged across duplicate incubations through time and as a function of <i>p</i>CO₂ for natural bacterioplankton assemblages incubated with: A: Natural DOC, Sargasso Sea Exp. #1A; B: Natural DOC, South Pacific Subtropical Gyre Exp. #7; C: Natural DOC, Santa Barbara Channel Exp. #2A; D. CNP, Sargasso Sea Exp. #1B; E. CNP, Santa Barbara Channel Exp. #2B. For treatments at all sites, red denotes elevated <i>p</i>CO_2, while blue denotes ambient <i>p</i>CO₂ in the Sargasso Sea experiment and pre-industrial <i>p</i>CO₂ in the Santa Barbara Channel and South Pacific Subtropical Gyre experiments. Squares represent TOC (μmol C L^-1) while triangles denote BA (10⁶ cells mL^-1) over the course of the incubation.</p

Mean TOC concentration and mean bacterioplankton abundance for Santa Barbara Channel phytoplankton-DOC experiments.

<p>Mean TOC concentration (± SD) and mean bacterioplankton abundance (BA; ± SD) averaged across duplicate incubations through time and as a function of <i>p</i>CO₂ for natural bacterioplankton assemblages in the Santa Barbara Channel experiments incubated with: A: <i>D</i>. <i>fragilissimus</i>-derived DOC, Exp. #3; B: <i>T</i>. <i>weissflogii</i>-derived DOC, Exp. #4; C: <i>T</i>. <i>weissflogii</i>-derived DOC, Exp. #5A; D: <i>C</i>. <i>socialis-</i>derived DOC, Exp. #5B; E: <i>A</i>. <i>glacialis</i>-derived DOC, Exp. #5C; F: <i>E</i>. <i>huxleyi</i>-derived DOC, Exp. #6. Red denotes elevated <i>p</i>CO_2, while blue denotes low (250 ppm) <i>p</i>CO₂. Squares represent TOC (μmol C L^-1) while triangles denote bacterioplankton abundance (10⁶ cells mL^-1) over the course of the incubation.</p

Cell-specific TOC removal.

<p>Mean (± SD) cell-specific TOC removal averaged across duplicate incubations and calculated as the change in TOC divided by the concurrent change in bacterioplankton abundance (BA) from the start of the incubations to stationary phase. Numbers on X-axis label refer to the experiment number (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0173145#pone.0173145.t001" target="_blank">Table 1</a>). Colors denote cell-specific TOC removal at elevated <i>p</i>CO₂ (red) and low (ambient or pre-industrial) <i>p</i>CO₂ (blue). Only experiments where a change in TOC was resolvable are shown.</p

Mean TOC concentration and mean bacterioplankton abundance for phytoplankton-DOC South Pacific Subtropical Gyre experiments.

<p>Mean TOC concentration (± SD) and mean bacterial abundance (BA; ± SD) averaged across duplicate incubations through time and as a function of <i>p</i>CO₂ for natural bacterioplankton assemblages in the South Pacific Subtropical Gyre experiments incubated with <i>E</i>. <i>huxleyi</i>-derived DOC: A: Exp. #7B; B: Exp. #8B; C: Exp. #9B. The same experimental design was used for these experiments (note that only the amended treatments are shown). Red denotes elevated <i>p</i>CO_2, while blue denotes low (250 ppm) <i>p</i>CO₂. Squares represent TOC (μmol C L^-1) while triangles denote BA (10⁶ cells mL^-1) over the course of the incubation.</p

Summary of experimental conditions and results.

<p>Summary of experimental conditions and results.</p

Bacterioplankton Carbon Demand.

<p>Mean (± SD) bacterioplankton carbon demand (BCD) averaged across duplicate incubations and calculated as the change in DOC from T₀ to stationary phase. Change in DOC was calculated as TOC less the carbon content of bacterioplankton biomass (using a carbon conversion factor of 30 fg C cell^-1 for bacterioplankton in the Santa Barbara Channel and 10 fg C cell^-1 for bacterioplankton in the Sargasso Sea and South Pacific Subtropical Gyre). Colors denote BCD at elevated <i>p</i>CO₂ (red) and low (ambient or pre-industrial) <i>p</i>CO₂ (blue). Numbers refer to the experiment number (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0173145#pone.0173145.t001" target="_blank">Table 1</a>). Only experiments where a change in TOC was resolvable are shown.</p

Bacterioplankton growth efficiency.

<p>Mean (± SD) Bacterioplankton growth efficiency averaged across duplicate incubations and calculated as the change in bacterioplankton biomass carbon (using a carbon conversion factor of 30 fg C cell^-1 for bacterioplankton in the Santa Barbara Channel and 10 fg C cell^-1 for bacterioplankton in the Sargasso Sea and South Pacific Subtropical Gyre) divided by the concurrent change in DOC from T₀ to stationary phase. Colors denote bacterioplankton growth efficiency at elevated <i>p</i>CO₂ (red) and low (ambient or pre-industrial) <i>p</i>CO₂ (blue). Numbers refer to the experiment number (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0173145#pone.0173145.t001" target="_blank">Table 1</a>). Only experiments where a change in TOC was resolvable are shown.</p