Explore the vast range of titles available.

1. Coasts and estuaries contain among the most productive and ecologically important habitats in the world and face intense pressure from current and projected human activities, including coastal development. Seagrasses are a key habitat feature in many estuaries perceived to be in widespread decline owing to human actions. 2. We use spatio-temporal models and a 41-year time series from 100s of km of shoreline which includes over 160 000 observations from Puget Sound, Washington, USA, to examine multiscale trends and drivers of eelgrass (Zostera spp.) change in an urbanizing estuary. 3. At whole estuary scale (100s of km), we find a stable and resilient eelgrass population despite a more than doubling of human population density and multiple major climactic stressors (e.g. ENSO events) over the period. However, the aggregate trend is not reflected at the site scale (10s of km), where some sites persistently increase while others decline. 4. Site trends were spatially asynchronous; adjacent sites sometimes exhibited opposite trends over the same period. Substantial change in eelgrass occurred at the subsite (0-1 km) scale, including both complete local loss and dramatic increase of eelgrass. 5. Metrics of local human development including shoreline armouring, upland development (imperviousness) and human density provide no explanatory power for eelgrass population change at any spatial scale. 6. Our results suggest that the appropriate scale for understanding eelgrass change is smaller than typically assumed (approximately 1- to 3-km scale) and contrasts strongly with previous work. 7. Synthesis. Despite ongoing conservation concern over seagrasses world-wide, eelgrass in Puget Sound has been highly resilient to both anthropogenic and environmental change over four decades. Our work provides general methods that can be applied to understand spatial and temporal scales of change and can be used to assess hypothesized drivers of change.

Unanticipated declines among exploited species have commonly occurred despite harvests that appeared sustainable prior to collapse. This is particularly true in the oceans where spatial scales of management are often mismatched with spatially complex metapopulations. We explore causes, consequences, and potential solutions for spatial mismatches in harvested metapopulations in three ways. First, we generate novel theory illustrating when and how harvesting metapopulations increases spatial variability and in turn masks local-scale volatility. Second, we illustrate why spatial variability in harvested metapopulations leads to negative consequences using an empirical example of a Pacific herring metapopulation. Finally, we construct a numerical management strategy evaluation model to identify and highlight potential solutions for mismatches in spatial scale and spatial variability. Our results highlight that spatial complexity can promote stability at large scales, however, ignoring spatial complexity produces cryptic and negative consequences for people and animals that interact with resources at small scales. Harvesting metapopulations magnifies spatial variability, which creates discrepancies between regional and local trends while increasing risk of local population collapses. Such effects asymmetrically impact locally constrained fishers and predators, which are more exposed to risks of localized collapses. Importantly, we show that dynamically optimizing harvest can minimize local risk without sacrificing yield. Thus, multiple nested scales of management may be necessary to avoid cryptic collapses in metapopulations and the ensuing ecological, social, and economic consequences.

Twenty-first century conservation is centered on negotiating trade-offs between the diverse needs of people and the needs of the other species constituting coupled human-natural ecosystems. Marine forage fishes, such as sardines, anchovies and herring, are a nexus for such trade-offs because they are both central nodes in marine food webs and targeted by fisheries. An important example is Pacific herring, Clupea pallisii in the Northeast Pacific. Herring populations are subject to two distinct fisheries: one that harvests adults and one that harvests spawned eggs. We develop stochastic, age-structured models to assess the interaction between fisheries, herring populations and the persistence of predators reliant on herring populations. We show that egg- and adult-fishing have asymmetric effects on herring population dynamics - herring stocks can withstand higher levels of egg harvest before becoming depleted. Second, ecosystem thresholds proposed to ensure the persistence of herring predators do not necessarily pose more stringent constraints on fisheries than conventional, fishery driven harvest guidelines. Our approach provides a general template to evaluate ecosystem trade-offs between stage-specific harvest practices in relation to environmental variability, the risk of fishery closures and the risk of exceeding ecosystem thresholds intended to ensure conservation goals are met.

Unanticipated declines among exploited species have commonly occurred despite harvests that appeared sustainable prior to collapse. This is particularly true in the oceans where spatial scales of management are often mismatched with spatially complex metapopulations. We explore causes, consequences and potential solutions for spatial mismatches in harvested metapopulations in three ways. First, we generate novel theory illustrating when and how harvesting metapopulations increases spatial variability and in turn masks local scale volatility. Second, we illustrate why spatial variability in harvested metapopulations leads to negative consequences using an empirical example of a Pacific herring metapopulation. Finally, we construct a numerical management strategy evaluation model to identify and highlight potential solutions for mismatches in spatial scale and spatial variability. Our results highlight that spatial complexity can promote stability at large scales, however ignoring spatial complexity produces cryptic and negative consequences for people and animals that interact with resources at small scales. Harvesting metapopulations magnifies spatial variability, which creates discrepancies between regional and local trends while increasing risk of local population collapses. Such effects asymmetrically impact locally constrained fishers and predators, which are more exposed to risks of localized collapses. Importantly, we show that dynamically optimizing harvest can minimize local risk without sacrificing yield. Thus, multiple nested scales of management may be necessary to avoid cryptic collapses in metapopulations and the ensuing ecological, social and economic consequences.

After the current spasm of extinction ends, the number of species on Earth may well return to past levels, but here will surely be fewer higher-level taxonomic groups than today. Such a wholesale shift in Earth's biota will impoverish the planet for many millions of years to come. This a the real threat to biodiversity--not a decline in species per se, but a long-term erosion in the variety of biological characteristics and functions that grace the natural world.

Aridification is often considered a major driver of long-term ecological change and hominin evolution in eastern Africa during the Plio-Pleistocene; however, this hypothesis remains inadequately tested owing to difficulties in reconstructing terrestrial paleoclimate. We present a revised aridity index for quantifying water deficit (WD) in terrestrial environments using tooth enamel δ18O values, and use this approach to address paleoaridity over the past 4.4 million years in eastern Africa. We find no long-term trend in WD, consistent with other terrestrial climate indicators in the Omo-Turkana Basin, and no relationship between paleoaridity and herbivore paleodiet structure among fossil collections meeting the criteria for WD estimation. Thus, we suggest that changes in the abundance of C₄ grass and grazing herbivores in eastern Africa during the Pliocene and Pleistocene may have been decoupled from aridity. As in modern African ecosystems, other factors, such as rainfall seasonality or ecological interactions among plants and mammals, may be important for understanding the evolution of C₄ grass- and grazer-dominated biomes.

This randomized, controlled trial evaluated AZD7442 (a combination of tixagevimab and cilgavimab, monoclonal antibodies targeting the SARS-CoV-2 spike protein) for the prevention of Covid-19 in adults at high risk for SARS-CoV-2 infection. AZD7442 was found to have approximately 77% efficacy in preventing symptomatic infection.

High-density lipoproteins (HDL) have many biological functions, including reducing endothelial activation and adhesion molecule expression. We recently reported that HDL transport and deliver functional microRNAs (miRNA). Here we show that HDL suppresses expression of intercellular adhesion molecule 1 (ICAM-1) through the transfer of miR-223 to endothelial cells. After incubation of endothelial cells with HDL, mature miR-223 levels are significantly increased in endothelial cells and decreased on HDL. However, miR-223 is not transcribed in endothelial cells and is not increased in cells treated with HDL from miR-223 −/− mice. HDL inhibit ICAM-1 protein levels, but not in cells pretreated with miR-223 inhibitors. ICAM-1 is a direct target of HDL-transferred miR-223 and this is the first example of an extracellular miRNA regulating gene expression in cells where it is not transcribed. Collectively, we demonstrate that HDL’s anti-inflammatory properties are conferred, in part, through HDL-miR-223 delivery and translational repression of ICAM-1 in endothelial cells. Lipoproteins such as HDL can bind and transport microRNAs throughout the body. Here the authors provide a new mechanism contributing to the anti-inflammatory effects of HDL by which HDL-associated miR-223 is transferred to endothelial cells, where it inhibits expression of the adhesion molecule ICAM-1.

A stool test that measures mutant KRAS, abnormal gene methylation, and hemoglobin detected significantly more colorectal cancers than a commercial fecal immunochemical test (FIT) but had more false positive results. Colorectal cancer is a major cause of death and disease among men and women in the United States. 1 The underlying neoplastic processes of colorectal carcinogenesis lend themselves to screening. 2 Evidence supports and guidelines endorse several tests and strategies, 3 – 5 and screening for colorectal cancer has been found to be cost-effective. 5 – 7 Despite the supporting evidence, recommendations, and availability of several screening tests, a substantial proportion of the U.S. population is not up to date with screening. 8 A simple, noninvasive test with high sensitivity for both colorectal cancer and advanced precancerous lesions might increase uptake and adherence rates, which could improve . . .