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Human gut microbiota produce a variety of molecules, some of which enter the bloodstream and impact health. Conversely, dietary or pharmacological compounds may affect the microbiota before entering the circulation. Characterization of these interactions is an important step towards understanding the effects of the gut microbiota on health. In this cross-sectional study, we used deep metagenomic sequencing and ultra-high-performance liquid chromatography linked to mass spectrometry for a detailed characterization of the gut microbiota and plasma metabolome, respectively, of 8583 participants invited at age 50 to 64 from the population-based Swedish CArdioPulmonary bioImage Study. Here, we find that the gut microbiota explain up to 46% of the variance of individual plasma metabolites and we present 997 associations between alpha diversity and plasma metabolites and 546,819 associations between specific gut metagenomic species and plasma metabolites in an online atlas ( https://gutsyatlas.serve.scilifelab.se/ ). We exemplify the potential of this resource by presenting novel associations between dietary factors and oral medication with the gut microbiome, and microbial species strongly associated with the uremic toxin p -cresol sulfate. This resource can be used as the basis for targeted studies of perturbation of specific metabolites and for identification of candidate plasma biomarkers of gut microbiota composition. Here, Dekkers et al. characterize associations of 1528 gut metagenomic species with the plasma metabolome in 8583 participants of the SCAPIS Study, and find that gut microbiota explain up to 58% of the variance of individual plasma metabolites.

Harbour porpoises Phocoena phocoena are common in continental shelf areas of the North Atlantic, but little information is available on their occurrence outside coastal areas. In this study, 30 harbour porpoises were actively caught in West Greenland and instrumented with satellite transmitters to document their seasonal movements and diving behaviour. The porpoises displayed long-range oceanic movements within the North Atlantic, especially during winter/spring where they moved over areas with water depths >2500 m. While offshore, 2 females demonstrated an average maximum dive depth of 248 m, with the deepest dive reaching 410 m. This behaviour is in contrast to 71 porpoises tagged in Danish waters of the North Sea which did not leave the continental shelf but showed a preference for areas with shallow waters year round, even when at the edge of the continental shelf where greater depths were available. Six tags from Greenland transmitted long enough (up to 3 yr) to demonstrate extensive movements and strong site fidelity to the tagging site in West Greenland the following summer. This study documents that harbour porpoises use oceanic habitats and can dive to depths that enable mesopelagic foraging, while repeatedly demonstrating summer site fidelity to coastal areas.

The narwhal (Monodon monoceros) is a high‐Arctic species inhabiting areas that are experiencing increases in sea temperatures, which together with reduction in sea ice are expected to modify the niches of several Arctic marine apex predators. The Scoresby Sound fjord complex in East Greenland is the summer residence for an isolated population of narwhals. The movements of 12 whales instrumented with Fastloc‐GPS transmitters were studied during summer in Scoresby Sound and at their offshore winter ground in 2017–2019. An additional four narwhals provided detailed hydrographic profiles on both summer and winter grounds. Data on diving of the whales were obtained from 20 satellite‐linked time‐depth recorders and 16 Acousonde™ recorders that also provided information on the temperature and depth of buzzes. In summer, the foraging whales targeted depths between 300 and 850 m where the preferred areas visited by the whales had temperatures ranging between 0.6 and 1.5°C (mean = 1.1°C, SD = 0.22). The highest probability of buzzing activity during summer was at a temperature of 0.7°C and at depths > 300 m. The whales targeted similar depths at their offshore winter ground where the temperature was slightly higher (range: 0.7–1.7°C, mean = 1.3°C, SD = 0.29). Both the probability of buzzing events and the spatial distribution of the whales in both seasons demonstrated a preferential selection of cold water. This was particularly pronounced in winter where cold coastal water was selected and warm Atlantic water farther offshore was avoided. It is unknown if the small temperature niche of whales while feeding is because prey is concentrated at these temperature gradients and is easier to capture at low temperatures, or because there are limitations in the thermoregulation of the whales. In any case, the small niche requirements together with their strong site fidelity emphasize the sensitivity of narwhals to changes in the thermal characteristics of their habitats. Narwhals avoid areas with warm temperatures. Both their prey capturing and diving behavior show their clear preference for cold habitats. They preferentially select habitats where the temperature ranges between 0 and 1°C. Photo: Carsten Egevang

The mesopelagic layer is represented in all oceans and is of crucial importance to the pelagic communities, and in this paper it is hypothesised that the Greenlandic harbour porpoise (Phocoena phocoena) is seasonally dependent on mesopelagic prey when abandoning the ice-covered continental shelf areas and remains in offshore areas. Data from 15 harbour porpoises instrumented with satellite-linked transmitters in West Greenland were analysed with regard to foraging that may target mesopelagic prey. Contact with the porpoises was maintained for an average of 404 days where they conducted extensive offshore movements and spent an average of 90% of their time over deep waters (> 1000 m) in the North Atlantic. When entering deep water, they increased their daily travel rate significantly from 22.5 to 36.7 km d−1. Five of the 15 porpoises provided information on dive depth which suggested that dive depths > 100 m are important for these porpoises both day and night; however, the porpoises dove significantly more at nighttime compared to daytime. Harbour porpoises from West Greenland probably target vertically migrating species from the mesopelagic layer that are accessible at shallower depths at night and at lower energetic cost than during the day.

A decreasing trend in narwhal (Monodon monoceros Linnaeus, 1758) abundance has been identified in a small population in Scoresby Sound, Southeast Greenland. We hypothesize that excessive hunting has affected life history and population dynamics of this population. Biological information and samples collected from the Inuit hunt, from satellite-tagged narwhals and from official hunters’ reports, were used to estimate age, growth, and reproduction. During 2007 through 2019, a decreasing proportion of young and increasing proportion of older whales were harvested. Male and female body length and male tusk length increased significantly, while body mass of both sexes showed a nonsignificant increase. The probability of catching a female decreased significantly, while a nonsignificant decline of catching a pregnant female was observed in both biological samples and hunters’ reports. Narwhal swimming speeds correlated with fluke widths indicated that larger whales attain greater speeds. The decline in juveniles and females is probably due to an opportunistic hunting practice targeting the easiest-to-catch whales, where bigger whales are faster and more difficult to catch. The cumulative effect of overharvest with a declining proportion of females, an overrepresentation of large males, and a lack of calves and juveniles has detrimental implications for this small narwhal population.

Deep diving air-breathing species by necessity must balance submergence time and level of exercise during breath-holding: a low activity level preserves oxygen stores and allows longer duration submergence whereas high activity levels consume oxygen quickly and shorten submergence time. In this study, we combined high-resolution multi sensor animal-borne tag data to investigate diving behavior and locomotion styles of the narwhal (Monodon monoceros) ( n = 13, mean record length 91 h)–a deep diving Arctic species. Narwhals in this study dove down to >800 m but despite the deep diving abilities, one-third of the dives (33%) were shallow (>100 m) and short in duration (<5 min). Narwhals utilized energy saving measures such as prolonged gliding during descent with increasing target depth but stroked actively throughout the ascent indicating excess oxygen storages. Foraging behavior, as detected by the presence of buzzes, was a key factor influencing dive depth and spinning behavior—the rolling movement of the animal along its longitudinal axes. Narwhals in East Greenland utilized two foraging strategies, while transiting and while stationary, with different target depths and buzzing rates. The first targeted deep-dwelling, possibly solitary prey items and the latter, more schooling prey closer to the surface. The buzzing rate during stationary foraging was on average twice as high as during transiting foraging. Spinning was an integrated part of narwhal swimming behavior but the amount of spinning was correlated with foraging behavior. The odds for spinning during all dive phases were 2–3 times higher during foraging than non-foraging. Due to the spinning behavior, stroking rate might be better suited for estimating energy consumption in narwhals than ODBA (overall dynamic body acceleration). The narwhal is considered as one of the most sensitive species to climate change–the results from this study can act as a baseline essential for evaluating changes in the behavior and energy usage of narwhals caused by stressors evolving in the Arctic.

Background There is mounting evidence supporting the role of the microbiota in hypertension from experimental studies and population-based studies. We aimed to investigate the relationship between specific characteristics of the gut microbiome and 24-h ambulatory blood pressure measurements. Methods The association of gut microbial species and microbial functions, determined by shotgun metagenomic sequencing of fecal samples, with 24-h ambulatory blood pressure measurements in 3695 participants and office blood pressure was assessed in multivariable-adjusted models in 2770 participants without antihypertensive medication from the Swedish CArdioPulmonary bioImage Study. Results Gut microbiome alpha diversity was negatively associated with diastolic blood pressure variability. Additionally, four microbial species were associated with at least one of the 24-h blood pressure traits. Streptococcus sp001556435 was associated with higher systolic blood pressure, Intestinimonas massiliensis and Dysosmobacter sp001916835 with lower systolic blood pressure, Dysosmobacter sp001916835 with lower diastolic blood pressure, and ER4 sp900317525 with lower systolic blood pressure variability. Moreover, office blood pressure data from a subsample without ambulatory blood pressure measurements replicated the association of Intestinimonas massiliensis with systolic blood pressure and Dysosmobacter sp001916835 with diastolic blood pressure. Species associated with 24-h blood pressure were linked to a similar pattern of metabolites. Conclusions In this large cross-sectional analysis, gut microbiome alpha diversity negatively associates with diastolic blood pressure variability, and four gut microbial species associate with 24-h blood pressure traits. Plain language summary High blood pressure is a major risk factor for heart disease and stroke. Recent research suggests that bacteria in the gut may influence blood pressure, but more studies are needed. In this study, we analyzed data from 3695 people in Sweden who wore a 24-h blood pressure monitor and provided stool samples for gut microbiome analysis—a method that identifies the types and abundance of microorganisms in the sample. We found that people with greater gut bacteria diversity had more stable blood pressure. Additionally, four specific bacterial species were linked to blood pressure levels; three were associated with lower blood pressure, while one was linked to higher levels. These findings suggest that gut bacteria may play a role in regulating blood pressure. Future research could explore whether changing the gut microbiome might help prevent or treat high blood pressure. Lin et al. investigate the relationship between specific characteristics of the gut microbiome and 24-h ambulatory blood pressure measurements. Four gut microbial species and microbial diversity associate with 24-h blood pressure traits, supporting a potential role for the gut microbiome in blood pressure regulation and variability.

This benchmark paper highlights the true level of variability in microbiome data across the world and across sectors, underscoring the critical need for the use of WHO International DNA Gut Reference Reagents (RRs) to elevate the quality of data in microbiome research. This global study is the first of its kind, revealing the reality of the bias in the field, comprehensively testing methodologies used by leading laboratories across the world, but also providing avenues for workflow optimization, to accelerate innovation and translational research and move the field forward.

Fifty of 58 walruses (Odobenus rosmarus rosmarus) instrumented with satellite-linked transmitters in four areas in eastern Smith Sound, Northwest Greenland, during May and June of 2010–13 and 2015 provided data for this study. These animals departed from the feeding banks along the Greenland coast in June–July (average 14th June), simultaneously with the disappearance of sea ice from these areas. Most of them moved to Canadian waters in western Smith Sound. The most frequently used summering grounds were along the coasts of Ellesmere Island: on the eastern coast, the area around Alexandra Fiord, Buchanan Bay, and Flagler Bay (west of Kane Basin) and Talbot Inlet farther south, and on the southern coast, Craig Harbour. This distribution of tagged walruses is consistent with prior understanding of walrus movements in summer. In addition, however, nine tracks of these tagged animals entered western Jones Sound and four entered the Penny Strait-Lancaster Sound area, crossing two putative stock boundaries. Since these 13 tracks were made by 12 animals, one walrus entered both areas. It is possible that some of the tracked walruses used terrestrial haul-out sites in the largely ice-free areas of Jones Sound and Lancaster Sound for short periods during the summer, though this cannot be confirmed with certainty. The return migration from western Smith Sound to the wintering area in eastern Smith Sound takes place in October. The tracked walrus showed high affinity to coastal areas, while walruses moving between Greenland and Canada also used offshore areas in Smith Sound. This study demonstrates that the walrus population that winters along the northwestern coast of Greenland is shared more widely in Canada than previously thought and should be managed accordingly. En mai et juin 2010 à 2013 et 2015, 50 des 58 morses (Odobenus rosmarus rosmarus) munis d'émetteurs liés à des satellites dans quatre régions à l'est du détroit de Smith, au nord-ouest du Groenland, ont permis de recueillir des données pour cette étude. Ces animaux ont quitté les aires d'alimentation le long de la côte du Groenland aux mois de juin et juillet (en moyenne le 14 juin), au même moment que la disparition de la glace marine de ces régions. La plupart des animaux se sont déplacés vers les eaux canadiennes dans l'ouest du détroit de Smith. Les aires d'été les plus souvent utilisées étaient celles situées le long des côtes de l'île d'Ellesmere : sur la côte est, la région autour du fjord Alexandra, la baie Buchanan et la baie Flagler (à l'ouest du bassin Kane) et le passage Talbot plus au sud, et sur le littoral sud du village Craig Harbour. Cette distribution des morses munis d'émetteurs correspond aux déplacements de morses déjà constatés en été. Toutefois, neuf signaux provenant d'animaux munis d'émetteurs sont entrés dans la partie ouest du détroit de Jones et quatre sont entrés par les détroits de Penny et de Lancaster, traversant les limites de deux aires de stocks présumés. Puisque ces 13 signaux ont été émis par 12 animaux, un morse est entré dans les deux régions. Il se peut que certains des morses suivis aient emprunté la portion terrestre qui entoure les échoueries dans les régions en grande partie dépourvues de glace des détroits de Jones et de Lancaster pendant de courtes périodes durant l'été, mais il est impossible de le confirmer avec certitude. La migration de retour de l'ouest du détroit de Smith vers l'aire d'hivernage dans l'est du détroit de Smith a lieu en octobre. Les morses suivis ont montré une grande affinité pour les zones côtières, tandis que les morses qui se déplaçaient entre le Groenland et le Canada empruntaient également les zones extracôtières du détroit de Smith. Cette étude démontre que la population de morses qui hiverne le long de la côte nord-ouest du Groenland est plus importante au Canada qu'on ne le pensait auparavant et devrait être gérée en conséquence.