Extreme climate events can slow down litter breakdown in streams

Extreme temperatures have increased in intensity, duration and frequency in the last century, with potential consequences on key ecological processes such as organic matter breakdown. Many stream ecosystems are fueled by the breakdown of terrestrial leaf litter, which is exposed to atmospheric conditions for certain periods of time before entering the stream. Thus, extreme warming or freezing events may affect the litter physicochemical structure, which could translate into altered breakdown within the stream. The above prediction was tested by exposing litter of common riparian tree species in southern Chile to freezing (-20 oC; dry or wet litter) or heating (40 oC) and comparing breakdown with control litter exposed to room temperature (20 oC), separating the effects of different breakdown agents (i.e., leaching, microorganisms and detritivores). The greatest effects were found in wet litter subjected to freezing; this treatment significantly increased leaching in the short term (48 h) and slowed down breakdown in the long term (30 days), mostly due to the inhibition of microbial breakdown. Heating also retarded microbial breakdown, but the effect was smaller. Our results suggest that short-term extreme temperatures-particularly cold ones-have the potential to slow down litter breakdown in streams, which will most likely impact global biogeochemical cycles where streams play a key role

Impacts of diffuse urban stressors on stream benthic communities and ecosystem functioning: A review

Catchment urbanisation results in urban streams being exposed to a multitude of stressors. Notably, stressors originating from diffuse sources have received less attention than stressors originating from point sources. Here, advances related to diffuse urban stressors and their consequences for stream benthic communities are summarised by reviewing 92 articles. Based on the search criteria, the number of articles dealing with diffuse urban stressors in streams has been increasing, and most of them focused on North America, Europe, and China. Land use was the most common measure used to characterize diffuse stressor sources in urban streams (70.7 % of the articles characterised land use), and chemical stressors (inorganic nutrients, xenobiotics, metals, and water properties, including pH and conductivity) were more frequently reported than physical or biological stressors. A total of 53.3 % of the articles addressed the impact of urban stressors on macroinvertebrates, while 35.9 % focused on bacteria, 9.8 % on fungi, and 8.7 % on algae. Regarding ecosystem functions, almost half of the articles (43.5 %) addressed changes in community dynamics, 40.3 % addressed organic matter decomposition, and 33.9 % addressed nutrient cycling. When comparing urban and non-urban streams, the reviewed studies suggest that urbanisation negatively impacts the diversity of benthic organisms, leading to shifts in community composition. These changes imply functional degradation of streams. The results of the present review summarise the knowledge gained to date and identify its main gaps to help improve our understanding of urban streams.This study has received funding from the Iberian Association of Limnology (AIL) through the project URBIFUN (Urbanization effects on the relationship between microbial biodiversity and ecosystem functioning), awarded to Míriam Colls and Ferran Romero. Authors thank as well the Basque Government (Consolidated Research Group IT951-16) and the MERLIN project 101036337 – H2020-LC-GD-2020/H2020-LC-GD-2020-3.info:eu-repo/semantics/publishedVersio

Latitude dictates plant diversity effects on instream decomposition

Abstract Running waters contribute substantially to global carbon fluxes through decomposition of terrestrial plant litter by aquatic microorganisms and detritivores. Diversity of this litter may influence instream decomposition globally in ways that are not yet understood. We investigated latitudinal differences in decomposition of litter mixtures of low and high functional diversity in 40 streams on 6 continents and spanning 113° of latitude. Despite important variability in our dataset, we found latitudinal differences in the effect of litter functional diversity on decomposition, which we explained as evolutionary adaptations of litter-consuming detritivores to resource availability. Specifically, a balanced diet effect appears to operate at lower latitudes versus a resource concentration effect at higher latitudes. The latitudinal pattern indicates that loss of plant functional diversity will have different consequences on carbon fluxes across the globe, with greater repercussions likely at low latitudes

Whole-genome sequencing reveals host factors underlying critical COVID-19

Altres ajuts: Department of Health and Social Care (DHSC); Illumina; LifeArc; Medical Research Council (MRC); UKRI; Sepsis Research (the Fiona Elizabeth Agnew Trust); the Intensive Care Society, Wellcome Trust Senior Research Fellowship (223164/Z/21/Z); BBSRC Institute Program Support Grant to the Roslin Institute (BBS/E/D/20002172, BBS/E/D/10002070, BBS/E/D/30002275); UKRI grants (MC_PC_20004, MC_PC_19025, MC_PC_1905, MRNO2995X/1); UK Research and Innovation (MC_PC_20029); the Wellcome PhD training fellowship for clinicians (204979/Z/16/Z); the Edinburgh Clinical Academic Track (ECAT) programme; the National Institute for Health Research, the Wellcome Trust; the MRC; Cancer Research UK; the DHSC; NHS England; the Smilow family; the National Center for Advancing Translational Sciences of the National Institutes of Health (CTSA award number UL1TR001878); the Perelman School of Medicine at the University of Pennsylvania; National Institute on Aging (NIA U01AG009740); the National Institute on Aging (RC2 AG036495, RC4 AG039029); the Common Fund of the Office of the Director of the National Institutes of Health; NCI; NHGRI; NHLBI; NIDA; NIMH; NINDS.Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care or hospitalization after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes-including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)-in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease