BackgroundThe electronic nose (e-nose) detects volatile organic compounds (VOCs) in exhaled air. We hypothesized that the exhaled VOCs print is different in stable vs. exacerbated patients with chronic obstructive pulmonary disease (COPD), particularly if the latter is associated with airway bacterial infection, and that the e-nose can distinguish them.MethodsSmell-prints of the bacteria most commonly involved in exacerbations of COPD (ECOPD) were identified in vitro. Subsequently, we tested our hypothesis in 93 patients with ECOPD, 19 of them with pneumonia, 50 with stable COPD and 30 healthy controls in a cross-sectional case-controlled study. Secondly, ECOPD patients were re-studied after 2 months if clinically stable. Exhaled air was collected within a Tedlar bag and processed by a Cynarose 320 e-nose. Breath-prints were analyzed by Linear Discriminant Analysis (LDA) with “One Out” technique and Sensor logic Relations (SLR). Sputum samples were collected for culture.ResultsECOPD with evidence of infection were significantly distinguishable from non-infected ECOPD (p = 0.018), with better accuracy when ECOPD was associated to pneumonia. The same patients with ECOPD were significantly distinguishable from stable COPD during follow-up (p = 0.018), unless the patient was colonized. Additionally, breath-prints from COPD patients were significantly distinguished from healthy controls. Various bacteria species were identified in culture but the e-nose was unable to identify accurately the bacteria smell-print in infected patients.ConclusionE-nose can identify ECOPD, especially if associated with airway bacterial infection or pneumonia.

Non‐native freshwater fish species can have adverse ecological impacts on native populations. However, the mechanisms determining the success or otherwise of their invasion and their role in invaded communities remain largely unknown. This is particularly true for the Mediterranean region, where endemic species characterised by restricted natural ranges may be at high risk of extinction. The largemouth bass (Micropterus salmoides) is native to North America but is invasive in the Italian Peninsula. The aim of this study was to explore the trophic position of M. salmoides, its diet and niche overlap with native fish species in the littoral areas of a Mediterranean lake. Our study was supported by analysis of stable C and N isotopes in the tissues of fish and their potential food sources, twenty years after the introduction of the largemouth bass to Lake Bracciano (Italy). Samples were collected in locations varying in terms of physical structure and resource availability at lower trophic levels in the food web, which was greater in the southern (hereafter: South) than in the northern (hereafter: North) area of the lake. These differences made it possible to explore the mechanisms linking environmental conditions and the role of alien predators in the invaded food web. The abundance of M. salmoides was higher, and the diversity of native fish species was lower, in North than South. In North, M. salmoides had a piscivorous diet and occupied a higher trophic position in the food web than in South, where invertebrates constituted an important part of its diet. As a consequence, trophic niche interference with other fish species at intermediate trophic levels was higher in South. In contrast, in North, M. salmoides showed stronger trophic interference with the percid Perca fluviatilis, a native top predator in the food web, but weaker interference with remaining fish species. Our results help to understand the role of alien species in the food webs of Lake Bracciano, which primarily depends on the habitat and the availability of prey across trophic levels. Physical and ecological variations in the habitat were associated with differences in predatory interactions among native and alien fish species. This suggests that a reduction in productivity and biodiversity at lower trophic levels in lake food webs may favour the success of opportunistic invasive fish species, given the ability of the invaders to maintain some of their characteristics silent, and to fully express their genotype under favourable environmental conditions.

In the original article, we neglected to include three students in the Acknowledgments section.The correct text of the Acknowledgments section should state:We thank Mr. George Metcalf for revising the English text and two Reviewers for their comments, which improved the manuscript. We also thank Simone D'Alessandro, Lorenzo Maria Iozia, and Flaminia Tito for the help with the preliminary processing of the samples.The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.

Determining food web architecture and its seasonal cycles is a precondition for making predictions about Antarctic marine biodiversity under varying climate change scenarios. However, few scientific data concerning Antarctic food web structure, the species playing key roles in web stability and the community responses to changes in sea-ice dynamics are available. Based on C and N stable isotope analysis, we describe Antarctic benthic food webs and the diet of species occurring in shallow waters (Tethys Bay, Ross Sea) before and after seasonal sea-ice break-up. We hypothesized that the increased availability of primary producers (sympagic algae) following sea-ice break-up affects the diet of species and thus food web architecture. Basal resources had distinct isotopic signatures that did not change after sea-ice break-up, enabling a robust description of consumer diets based on Bayesian mixing models. Sympagic algae had the highest δ13C (∼−14‰) and red macroalgae the lowest (∼−37‰). Consumer isotopic niches and signatures changed after sea-ice break-up, reflecting the values of sympagic algae. Differences in food web topology were also observed. The number of taxa and the number of links per taxon were higher before the thaw than after it. After sea-ice break-up, sympagic inputs allowed consumers to specialize on abundant resources at lower trophic levels. Foraging optimization by consumers led to a simpler food web, with lower potential competition and shorter food chains. However, basal resources and Antarctic species such as the bivalve Adamussium colbecki and the sea-urchin Sterechinus neumayeri were central and highly connected both before and after the sea-ice break-up, thus playing key roles in interconnecting species and compartments in the web. Any disturbance affecting these species is expected to have cascading effects on the entire food web. The seasonal break-up of sea ice in Antarctica ensures the availability of resources that are limiting for coastal communities for the rest of the year. Identification of species playing a key role in regulating food web structure in relation to seasonal sea-ice dynamics, which are expected to change with global warming, is central to understanding how these communities will respond to climate change.

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