Abstract: Accelerometry has been widely used to estimate energy expenditure in a broad array of terrestrial and aquatic species. However, a recent reappraisal of the method showed that relationships between dynamic body acceleration (DBA) and energy expenditure weaken as the proportion of non-mechanical costs increases. Aquatic air breathing species often exemplify this pattern, as buoyancy, thermoregulation and other physiological mechanisms disproportionately affect oxygen consumption during dives. Combining biologging with the doubly labelled water method, we simultaneously recorded daily energy expenditure (DEE) and triaxial acceleration in one of the world's smallest wing-propelled breath-hold divers, the dovekie (Alle alle). These data were used to estimate the activity-specific costs of flying and diving and to test whether overall dynamic body acceleration (ODBA) is a reliable predictor of DEE in this abundant seabird. Average DEE for chick-rearing dovekies was 604±119 kJ day−1 across both sampling years. Despite recording lower stroke frequencies for diving than for flying (in line with allometric predictions for auks), dive costs were estimated to surpass flight costs in our sample of birds (flying: 7.24× basal metabolic rate, BMR; diving: 9.37× BMR). As expected, ODBA was not an effective predictor of DEE in this species. However, accelerometer-derived time budgets did accurately estimate DEE in dovekies. This work represents an empirical example of how the apparent energetic costs of buoyancy and thermoregulation limit the effectiveness of ODBA as the sole predictor of overall energy expenditure in small shallow-diving endotherms.

Abstract: Mercury (Hg) is highly toxic in its methylated form (MeHg), and global change is likely to modify its bioavailability in the environment. However, it is unclear how top predators will be impacted. We studied blood Hg concentrations of chick-rearing black-legged kittiwakes Rissa tridactyla (2000–2019) in Svalbard (Norway). From 2000 to 2019, Hg concentrations followed a U-shaped trend. The trophic level, inferred from nitrogen stable isotopes, and chlorophyll a (Chl a) concentrations better predicted Hg concentrations, with positive and U-shaped associations, respectively. As strong indicators of primary productivity, Chl a concentrations can influence production of upper trophic levels and, thus, fish community assemblage. In the early 2000s, the high Hg concentrations were likely related to a higher proportion of Arctic prey in kittiwake’s diet. The gradual input of Atlantic prey in kittiwake diet could have resulted in a decrease in Hg concentrations until 2013. Then, a new shift in the prey community, added to the shrinking sea ice-associated release of MeHg in the ocean, could explain the increasing trend of Hg observed since 2014. The present monitoring provides critical insights about the exposure of a toxic contaminant in Arctic wildlife, and the reported increase since 2014 raises concern for Arctic seabirds.

Abstract: Aim In the context of intensifying threats of climate change on marine communities, ecological models are widely applied for conservation strategies, though polar studies remain scarce given the limited number of datasets available. Correlative (e.g. species distribution models, SDM) and mechanistic (e.g. dynamic energy budget models, DEB) modelling approaches are usually used independently in studies. Using both approaches in integrative, hybrid models could help to better estimate the species potential ecological niche, as mechanistic and correlative models complement each other very well, giving more insights into species potential response to fast-changing environmental conditions. Location The study focusses on the Baie du Morbihan, a silled basin located in the east of the Kerguelen Islands (sub-Antarctic). Methods A hybrid, correlative-mechanistic model was implemented to predict the response of the endemic sea urchin Abatus cordatus (Verrill, 1876). We compared the performances of classic and integrated approaches to predict A. cordatus distribution according to two dates representing seasonal contrasts. Two integrated approaches were studied and performed by either (1) including the spatial projection of the DEB model as an input layer inside the SDM (‘integrated SDM-DEB’) or (2) using a Bayesian procedure to use DEB model outputs as priors of the SDM (‘integrated Bayesian’ approach). Results Results show higher performances of ‘integrated Bayesian’ approaches to evaluate A. cordatus potential ecological niche compared with ‘classic’ and ‘integrated SDM-DEB’ methods. The influence of environmental conditions on model predictions is further captured with these Bayesian procedures and better highlights the environmental influence on the species-predicted distribution. Model performance is good for the different simulations, and uncertainty in predictions is well-highlighted. Main conclusions The good performances of ‘integrated Bayesian’ approaches to estimate species potential ecological niche opens perspectives for future applications to a broad panel of natural examples, noteworthy for decision-making and conservation management purposes.

Abstract: In the follow-up of the Australian ”Black Summer” event that persisted from August 2019 to March 2020, we present the optical properties of the stratospheric aerosols injected into the atmosphere by these wildfires. The outbreak of pyrocumulonimbus (PyroCb) activity triggered between 2019/12/29 and 2020/01/04 has raised the stratospheric aerosol load of the Southern Hemisphere to unprecedented levels. Long-range transport brought some of the plumes down to the Antarctic region, where general circulation patterns kept them circling around the continent. The 532 nm Rayleigh/Mie/Raman ground-based lidar of the French Antarctic station Dumont d’Urville (66.6°S–140°E) acquired unprecedented time series of these carbonaceous aerosols starting approximately 20 days after the injection and up to the most recent measurements in October 2019 where local radiosonde reported anomalous ozone depletion as compared to the decadal average. The lidar provides a first and unique time series at high vertical and temporal resolution, complemented by satellite measurements from Ozone Monitoring Instrument, Ozone Mapping and Profiler Suite, and Microwave Limb Sounder. Aerosol backscatter ratio decreases from 1.9 to 1.2 between January and June 2020. Aerosol origin and persistence are characterized, as well as their optical properties and vertical distribution over several months.

Abstract: Mature super-Earths and sub-Neptunes are predicted to be ≃ Jovian radius when younger than 10 Myr. Thus, we expect to find 5–15 R ⊕ planets around young stars even if their older counterparts harbor none. We report the discovery and validation of TOI 1227b, a 0.85 ± 0.05 R J (9.5 R ⊕) planet transiting a very-low-mass star (0.170 ± 0.015 M ⊙) every 27.4 days. TOI 1227's kinematics and strong lithium absorption confirm that it is a member of a previously discovered subgroup in the Lower Centaurus Crux OB association, which we designate the Musca group. We derive an age of 11 ± 2 Myr for Musca, based on lithium, rotation, and the color–magnitude diagram of Musca members. The TESS data and ground-based follow-up show a deep (2.5%) transit. We use multiwavelength transit observations and radial velocities from the IGRINS spectrograph to validate the signal as planetary in nature, and we obtain an upper limit on the planet mass of ≃0.5 M J. Because such large planets are exceptionally rare around mature low-mass stars, we suggest that TOI 1227b is still contracting and will eventually turn into one of the more common <5 R ⊕ planets.