Links Between Fluctuations in Sockeye Salmon Abundance and Riparian Forest Productivity Identified by Remote Sensing

Pacific salmon (Oncorhynchus spp.) carcasses can fertilize riparian forests with marine-derived nutrients when populations make their annual return to natal streams to spawn; however, the strength of this cross-system linkage likely varies substantially among years due to the interannual fluctuations in abundance that characterize most salmon populations. Here, we used a 36-yr time series (1984–2019) of satellite imagery and salmon abundance estimates to assess spatiotemporal associations between forest greenness (a measure of plant productivity) and adult sockeye salmon (Oncorhynchus nerka) abundance in the lower Adams River, British Columbia, Canada. The Adams River sockeye population displays a quadrennial pattern of abundance, with a dominant cohort that spawns every four years in numbers that are typically two to three orders of magnitude larger than non-dominant cohorts. We found that variation in forest greenness was consistently explained best by models including dominant cohort year, whereas models lacking an index of salmon abundance were the lowest-ranked. Greenness of riparian vegetation increased by an average of 0.015 NDVI units (approximately 1%) in the summer after a dominant cohort return, and this effect on greenness persisted into the subsequent fall (11–13 months after spawning). The positive association between quadrennial pulses of salmon and riparian greenness occurred in plots both within 30 m of the stream and 95–125 m away from the stream, indicating that the spatial extent of fertilization may occur well beyond areas directly adjacent to the riverbank. These results suggest that forests respond to cyclical variation in salmon abundance and that overwinter storage of marine-derived nutrients within catchments allows plants to capitalize on these nutrients in the following growing season. Continued advances in remote sensing technology will enhance our understanding of cross-system resource linkages and can inform the ecosystem-based management of Pacific salmon

Equivalent roles of marine subsidies and island characteristics in shaping island bird communities

AimSpecies distributions across islands are shaped by dispersal limitations, environmental filters and biotic interactions but the relative influence of each of these processes has rarely been assessed. Here, we examine the relative contributions of island characteristics, marine subsidies, species traits, and species interactions on avian community composition.LocationCentral Coast region of British Columbia, Canada.TaxonTerrestrial breeding birds.MethodsWe observed 3610 individuals of 32 bird species on 89 islands that spanned multiple orders of magnitude in area (0.0002–3 km$^{2}$). We fit a spatially explicit joint species distribution model to estimate the relative contributions of island physical characteristics, island‐specific inputs of marine subsidies, species' traits, and biotic interactions on species distributions. Biogeographic characteristics included island area, isolation, and habitat heterogeneity, while marine influence was represented by forest‐edge soil δ$^{15}$N, wrack biomass, shoreline substrate, and distance to shore. This approach also allowed us to estimate how much variation in distributions resulted from species' biological traits (i.e. body mass, feeding guild, feeding height, and nesting height).ResultsBird species distributions were determined almost equivalently by island biogeographic characteristics (23.5% of variation explained) and marine influence (24.8%). We detected variation in species‐specific responses to both island biogeographic characteristics and marine influence, but no significant effect of any biological trait examined. Additionally, we found evidence that habitat preferences were a more important driver than competitive interactions.Main ConclusionsAlthough most island biogeographic studies focus only on islands' physical characteristics, we found evidence for an equivalent role of marine subsidy in structuring island bird communities. Our study suggests that for small islands, disentangling the effects of island biogeographic characteristics, marine inputs, and biotic interactions is a useful next step in understanding species distributions

Sleep disturbances among medical students: A global perspective

Medical students carry a large academic load which could potentially contribute to poor sleep quality above and beyond that already experienced by modern society. In this global literature review of the medical students' sleep experience, we find that poor sleep is not only common among medical students, but its prevalence is also higher than in non-medical students and the general population. Several factors including medical students' attitudes, knowledge of sleep, and academic demands have been identified as causative factors, but other potential mechanisms are incompletely understood. A better understanding about the etiology of sleep problems in medical trainees is essential if we hope to improve the overall quality of medical students' lives, including their academic performance. Sleep selfawareness and general knowledge appear insufficient in many studied cohorts, so increasing education for students might be one beneficial intervention. We conclude that there is ample evidence for a high prevalence of the problem, and research in this area should now expand towards initiatives to improve general sleep education for medical students, identify students at risk, and target them with programs to improve sleep. © 2015 Clinical Sleep Medicine

Equivalent roles of marine subsidies and island characteristics in shaping island bird communities

Aim: Species distributions across islands are shaped by dispersal limitations, environmental filters and biotic interactions but the relative influence of each of these processes has rarely been assessed. Here, we examine the relative contributions of island characteristics, marine subsidies, species traits, and species interactions on avian community composition. Location: Central Coast region of British Columbia, Canada. Taxon: Terrestrial breeding birds. Methods: We observed 3610 individuals of 32 bird species on 89 islands that spanned multiple orders of magnitude in area (0.0002–3 km2). We fit a spatially explicit joint species distribution model to estimate the relative contributions of island physical characteristics, island-specific inputs of marine subsidies, species' traits, and biotic interactions on species distributions. Biogeographic characteristics included island area, isolation, and habitat heterogeneity, while marine influence was represented by forest-edge soil δ15N, wrack biomass, shoreline substrate, and distance to shore. This approach also allowed us to estimate how much variation in distributions resulted from species' biological traits (i.e. body mass, feeding guild, feeding height, and nesting height). Results: Bird species distributions were determined almost equivalently by island biogeographic characteristics (23.5% of variation explained) and marine influence (24.8%). We detected variation in species-specific responses to both island biogeographic characteristics and marine influence, but no significant effect of any biological trait examined. Additionally, we found evidence that habitat preferences were a more important driver than competitive interactions. Main Conclusions: Although most island biogeographic studies focus only on islands' physical characteristics, we found evidence for an equivalent role of marine subsidy in structuring island bird communities. Our study suggests that for small islands, disentangling the effects of island biogeographic characteristics, marine inputs, and biotic interactions is a useful next step in understanding species distributions

Nocturnal Hypoxia and Loss of Kidney Function

Background: Although obstructive sleep apnea (OSA) is more common in patients with kidney disease, whether nocturnal hypoxia affects kidney function is unknown. Methods: We studied all adult subjects referred for diagnostic testing of sleep apnea between July 2005 and December 31 2007 who had serial measurement of their kidney function. Nocturnal hypoxia was defined as oxygen saturation (SaO2) below 90 % for $12$4 ml/min/1.73 m2 per year. Results: 858 participants were included and followed for a mean study period of 2.1 years. Overall 374 (44%) had nocturnal hypoxia, and 49 (5.7%) had accelerated loss of kidney function. Compared to controls without hypoxia, patients with nocturnal hypoxia had a significant increase in the adjusted risk of accelerated kidney function loss (odds ratio (OR) 2.89, 95 % confidence interval [CI] 1.25, 6.67). Conclusion: Nocturnal hypoxia was independently associated with an increased risk of accelerated kidney function loss. Further studies are required to determine whether treatment and correction of nocturnal hypoxia reduces loss of kidney function

Scale-dependent effects of marine subsidies on the island biogeographic patterns of plants

Although species richness can be determined by different mechanisms at different spatial scales, the role of scale in the effects of marine inputs on island biogeography has not been studied explicitly. Here, we evaluated the potential influence of island characteristics and marine inputs (seaweed wrack biomass and marine-derived nitrogen in the soil) on plant species richness at both a local (plot) and regional (island) scale on 92 islands in British Columbia, Canada. We found that the effects of subsidies on species richness depend strongly on spatial scale. Despite detecting no effects of marine subsidies at the island scale, we found that as plot level subsidies increased, species richness decreased; plots with more marine-derived nitrogen in the soil hosted fewer plant species. We found no effect of seaweed wrack at either scale. To identify potential mechanisms underlying the decrease in diversity, we fit a spatially explicit joint species distribution model to evaluate species level responses to marine subsidies and effects of biotic interactions among species. We found mixed evidence for competition for both light and nutrients, and cannot rule out an alternative mechanism; the observed decrease in species richness may be due to disturbances associated with animal-mediated nutrient deposits, particularly those from North American river otters (Lontra canadensis). By evaluating the scale-dependent effects of marine subsidies on island biogeographic patterns of plants and revealing likely mechanisms that act on community composition, we provide novel insights on the scale dependence of a fundamental ecological theory, and on the rarely examined links between marine and terrestrial ecosystems often bridged by animal vectors

Biogeographic features mediate marine subsidies to island food webs

Although marine subsidies often enrich terrestrial ecosystems, their influence is known to be context-dependent. Additionally, the multitrophic impact of marine subsidies has not been traced through food webs across physically diverse islands. Here, we test predictions about how island characteristics can affect marine enrichment of food web constituents and how nutrients flow through island food webs. To evaluate enrichment and trace marine nutrients across food webs, we used stable isotopes of soil, flora, and fauna (n = 4752 samples) collected from 97 islands in British Columbia, Canada. Island area was the strongest predictor of enrichment across taxa; we found that samples were more 15N-rich on smaller islands. Enrichment declined with distance from shore but less so on small islands, implying a higher per-unit-area subsidy effect. These area and distance-to-shore effects were taxon-specific, and nearly twice as strong in basal food web groups. We also found that increases in δ15N correlated with increases in %N in basal trophic groups, as well as in songbirds, implying biologically relevant uptake of a potentially limiting nutrient. Path analysis demonstrated that subsidies in soil flow through plants and detritivores, and into upper-level consumers. Our results reveal an interplay between island biogeography and marine subsidies in shaping island food webs through bottom-up processes

Sleep Apnea and Aortic Dissection

A 62-year-old man presented with obstructive sleep apnea, congestive heart failure and Cheyne-Stokes respiration. Further evaluation revealed a chronic dissecting aneurysm of the aorta causing vena caval obstruction. Surgical correction or the aneurysm dramatically improved ventricular function with resolution of Cheyne-Stokes respiration. Nasal continuous positive airway pressure corrected the obstructive sleep apnea and associated clinical features. The cardiopulmonary interactions between sleep apnea and aortic dissection are discussed