Microbial Dynamics Associated with Decomposing \u3ci\u3eTypha angustifolia\u3c/i\u3e Litter in two Contrasting Lake Erie Coastal Wetlands

We compared the decomposition of sediment-associated litter of Typha angustifolia in 2 Lake Erie coastal wetlands, examining the effects of sedimentation on microbial biomass, production and litter decay dynamics. Experimental manipulations of sediment had no statistically significant effect (p \u3e 0.05) on microbial biomass or metabolism. However, unforeseen differences between wetland sites (i.e. permanently inundated vs. exposed) had a major influence on microbial colonization and growth, litter mass loss, and nutrient dynamics. Litter-associated bacterial biomass and production were greater at the inundated site vs. the exposed wetland site (e.g. 487 vs. 158 µg C g–1 detrital C after 146 d, respectively). In contrast, fungal biomass and production were greater at the exposed site (e.g. 125 vs. 56 mg C g–1 detrital C after 146 d, respectively). Microbial degradative enzymes involved in the acquisition of phosphorus, nitrogen and carbon followed similar patterns as observed for fungal biomass and production, with higher activities associated with decaying litter at the exposed site. Microbial respiration rates were initially similar at both sites, but increased at the inundated site towards the end of the study period. Despite greater litter-associated microbial biomass, production and enzyme activities at the exposed wetland site, rates of litter mass loss were similar, suggesting that the greater metabolic potential of microbiota at the exposed site may have been offset by environmental conditions (e.g. fluctuations in water availability). Although mass loss rates were similar, significant differences in nutrient dynamics were observed, with higher N and P associated with higher litter-associated microbial biomass. These results illustrate how microbial decay dynamics can potentially interact with environmental variables (e.g. water availability) to modulate the carbon and nutrient dynamics of a litter resource that dominates many wetlands

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42·4% vs 44·2%; absolute difference -1·69 [-9·58 to 6·11] p=0·67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H2O; p=0·0011). ICU mortality was higher in MICs than in HICs (30·5% vs 19·9%; p=0·0004; adjusted effect 16·41% [95% CI 9·52-23·52]; p<0·0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0·80 [95% CI 0·75-0·86]; p<0·0001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status