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We still do not understand how planets form or why extrasolar planetary systems are so different from our own Solar System. However, the past few years have dramatically changed our view of the disks of gas and dust around young stars. Observations with the Atacama Large Millimeter/submillimeter Array and extreme adaptive-optics systems have revealed that most—if not all—disks contain substructure, including rings and gaps1–3, spirals4–6, azimuthal dust concentrations7 and shadows cast by misaligned inner disks5,8. These features have been interpreted as signatures of newborn protoplanets, but the exact origin is unknown. Here we report the kinematic detection of a few-Jupiter-mass planet located in a gas and dust gap at 130 au in the disk surrounding the young star HD 97048. An embedded planet can explain both the disturbed Keplerian flow of the gas, detected in CO lines, and the gap detected in the dust disk at the same radius. While gaps appear to be a common feature in protoplanetary disks2,3, we present a direct correspondence between a planet and a dust gap, indicating that at least some gaps are the result of planet–disk interactions.Pinte et al. report the kinematic detection of a few-Jupiter-mass planet orbiting at 130 au from the young star HD 97048. The radial position of the planet coincides with a gap in both the gas and dust components of the protoplanetary disk, showing that at least some gaps can be linked to the presence of planets.

Endogenous and environmental variables are fundamental in explaining variations in fish condition. Based on more than 20 yr of fish weight and length data, relative condition indices were computed for anchovy and sardine caught in the Gulf of Lions. Classification and regression trees (CART) were used to identify endogenous factors affecting fish condition, and to group years of similar condition. Both species showed a similar annual cycle with condition being minimal in February and maximal in July. CART identified 3 groups of years where the fish populations generally showed poor, average and good condition and within which condition differed between age classes but not according to sex. In particular, during the period of poor condition (mostly recent years), sardines older than 1 yr appeared to be more strongly affected than younger individuals. Time-series were analyzed using generalized linear models (GLMs) to examine the effects of oceanographic abiotic (temperature, Western Mediterranean Oscillation [WeMO] and Rhône outflow) and biotic (chlorophyll a and 6 plankton classes) factors on fish condition. The selected models explained 48 and 35% of the variance of anchovy and sardine condition, respectively. Sardine condition was negatively related to temperature but positively related to the WeMO and mesozooplankton and diatom concentrations. A positive effect of mesozooplankton and Rhône runoff on anchovy condition was detected. The importance of increasing temperatures and reduced water mixing in the NW Mediterranean Sea, affecting planktonic productivity and thus fish condition by bottom-up control processes, was highlighted by these results. Changes in plankton quality, quantity and phenology could lead to insufficient or inadequate food supply for both species.

We determined the δ15N and δ13C values of individual amino acids (AAs) isolated from chick blood of 4 penguin species that forage in different oceanic regions (from the subtropics of the Indian Ocean to Antarctica) to test if: (1) the δ15N values of phenylalanine (δ15Nphe) revealed different foraging areas among the species; (2) the difference between glutamic acid and phenylalanine δ15N values (Δδ15Nglu-phe) accurately predicted trophic levels; and (3) the δ13C value of AAs could resolve species foraging locations, similar to bulk δ13C values. The δ13C values of all AAs decreased with latitude, were positively correlated with bulk δ13C data, and, therefore, tracked the isotopic baseline. However, we were not able to discern additional ecological information from these δ13C values. In contrast, the δ15N values of AAs distinguished the isotopic value of the nitrogen at the base of the food web from the trophic level of the consumer, providing new insight for the study of the trophic ecology of seabirds. The difference in the bulk δ15N values of northern and southern rockhopper penguinsEudyptes chrysocomessp. was due to both a difference in their foraging location (different δ15Nphe) and their trophic levels (different Δδ15Nglu-phe). The δ15Nphevalues of kingAptenodytes patagonicusand Adélie penguinsPygoscelis adeliaewere higher than those of rockhoppers, which could reflect a foraging on mesopelagic prey for king penguins and, in the highly productive Antarctic shelf waters, for Adelie penguins. The Δδ15Nglu-pheaccurately reflected the relative trophic level of penguins, but further work is required to determine the trophic enrichment factors for compound-specific isotope analysis.

The radial velocities of a young star are measured, revealing the presence of a planet of mass about three-quarters that of Jupiter, orbiting its host star very closely, and thus demonstrating that ‘hot Jupiters’ can migrate inwards in less than two million years. An inwardly migrating hot Jupiter Jean-François Donati et al . present evidence for a close-in giant planet (hot Jupiter) orbiting the 2-million-year-old Sun-like star V830 Tau. It is thought that hot Jupiters form in the outer part of the primordial disk from which both the central star and surrounding planets are born, and then migrate inwards. This new finding supports that theory by demonstrating the formation and rapid inward migration of a hot Jupiter around a young star. Hot Jupiters are giant Jupiter-like exoplanets that orbit their host stars 100 times more closely than Jupiter orbits the Sun. These planets presumably form in the outer part of the primordial disk from which both the central star and surrounding planets are born, then migrate inwards and yet avoid falling into their host star 1 . It is, however, unclear whether this occurs early in the lives of hot Jupiters, when they are still embedded within protoplanetary disks 2 , or later, once multiple planets are formed and interact 3 . Although numerous hot Jupiters have been detected around mature Sun-like stars, their existence has not yet been firmly demonstrated for young stars 4 , 5 , 6 , whose magnetic activity is so intense that it overshadows the radial velocity signal that close-in giant planets can induce. Here we report that the radial velocities of the young star V830 Tau exhibit a sine wave of period 4.93 days and semi-amplitude 75 metres per second, detected with a false-alarm probability of less than 0.03 per cent, after filtering out the magnetic activity plaguing the spectra. We find that this signal is unrelated to the 2.741-day rotation period of V830 Tau and we attribute it to the presence of a planet of mass 0.77 times that of Jupiter, orbiting at a distance of 0.057 astronomical units from the host star. Our result demonstrates that hot Jupiters can migrate inwards in less than two million years, probably as a result of planet–disk interactions 2 .

Theoretical works that use a dynamical approach to study the ability of ecological communities to resist perturbations are largely based on randomly generated ecosystem structures. In contrast, we propose here to asses the robustness of food webs drawn from ecological and evolutionary processes with the use of community evolution models. In a first part, with the use of Adaptive Dynamics theoretical framework, we generate a variety of diversified food webs by solely sampling different richness levels of the environment as a control parameter, and obtain networks that satisfactory compare with empirical data. This allows us to highlight the complex, structuring role of the environmental richness during the evolutionary emergence of food webs. In a second part, we study the short-term ecological responses of food webs to swift changes in their customary environmental richness condition. We reveal a strong link between the environmental conditions that attended food webs evolutionary constructions and their robustness to environmental perturbations. When focusing on emergent properties of our evolved food webs, especially con-nectance, we highlight results that seem to contradict the current paradigm. Among these food webs, the most connected appear to be the less robust to sudden depletion of the environmental richness that constituted their evolutionary environment. Otherwise, we appraise the \"adapta-tion\" of food webs, by examining how they perform after being suddently immersed in an environment of modified richness level, in comparison with a trophic network that experienced this latter environmental condition all along its evolution.

Characteristics of the tropical oceanic environment (low productivity, little seasonality) and poor diversity of tropical seabird foraging methods and prey relative to temperate and polar species suggest that tropical seabirds overall encompass a narrow range of isotopic niches, with large overlaps among species. To test this hypothesis, we examined the stable carbon (δ13C) and nitrogen (δ15N) isotopic composition of blood and feathers of 5 seabird species from Europa Island, Mozambique Channel. While differences were small, blood δ13C and δ15N values characterized 5 distinct and non-overlapping trophic niches during the breeding period. Seabirds used 2 distinct foraging areas (δ13C), one used by sooty ternSterna fuscataand white-tailed tropicbirdPhaethon lepturusand one used by red-footed boobySula sulaand greatFregata minorand lesserF. arielfrigatebirds. Seabird species overall encompassed less than 1 trophic level (δ15N), which is in agreement with a diet mainly based on flying fish and squid. Feather δ13C and δ15N values showed that the trophic structure of the community was different during the breeding and non-breeding (moulting) periods, suggesting a shift in the feeding ecology when adult birds were no longer central-place foragers. The stable isotope method underlined sex-related (red-footed booby) and age-related (great frigatebird immatures and adults) feeding strategies. It also suggested that breeding adults could feed themselves on different prey than those given to their chicks (sooty tern). Within the tropical pelagic ecosystem, seabirds overall shared the same trophic level as large predatory fishes (albacore, yellowfin and skipjack tunas), but they had lower δ15N values than the deeper-dwelling bigeye tuna and swordfish. We conclude that analyzing stable isotope values in blood and feathers appears to be a promising alternative method for investigating food and feeding ecology of tropical seabirds year round, and for determining sex- and age-related differences in their foraging strategies. A limitation of the method is the lack of information on marine isoscapes; future studies aimed at isotopically characterizing the tropical marine environment could help to associate consumer signatures to geographic origins.

The European FP7 project DIANA has performed a coherent analysis of a large set of observational data of protoplanetary disks by means of thermo-chemical disk models. The collected data include extinction-corrected stellar UV and X-ray input spectra (as seen by the disk), photometric fluxes, low and high resolution spectra, interferometric data, emission line fluxes, line velocity profiles and line maps, which probe the dust, polycyclic aromatic hydrocarbons (PAHs) and the gas in these objects. We define and apply a standardized modeling procedure to fit these data by state-of-the-art modeling codes ( ProDiMo , MCFOST , MCMax ), solving continuum and line radiative transfer (RT), disk chemistry, and the heating and cooling balance for both the gas and the dust. 3D diagnostic RT tools (e.g., FLiTs) are eventually used to predict all available observations from the same disk model, the DIANA-standard model. Our aim is to determine the physical parameters of the disks, such as total gas and dust masses, the dust properties, the disk shape, and the chemical structure in these disks. We allow for up to two radial disk zones to obtain our best-fitting models that have about 20 free parameters. This approach is novel and unique in its completeness and level of consistency. It allows us to break some of the degeneracies arising from pure Spectral Energy Distribution (SED) modeling. In this paper, we present the results from pure SED fitting for 27 objects and from the all inclusive DIANA-standard models for 14 objects. Our analysis shows a number of Herbig Ae and T Tauri stars with very cold and massive outer disks which are situated at least partly in the shadow of a tall and gas-rich inner disk. The disk masses derived are often in excess to previously published values, since these disks are partially optically thick even at millimeter wavelength and so cold that they emit less than in the Rayleigh–Jeans limit. We fit most infrared to millimeter emission line fluxes within a factor better than 3, simultaneously with SED, PAH features and radial brightness profiles extracted from images at various wavelengths. However, some line fluxes may deviate by a larger factor, and sometimes we find puzzling data which the models cannot reproduce. Some of these issues are probably caused by foreground cloud absorption or object variability. Our data collection, the fitted physical disk parameters as well as the full model output are available to the community through an online database ( http://www.univie.ac.at/diana ).

To test whether predation is an opportunistic size-based process within a tuna community, analyses were carried out on the size composition of stomach contents of bigeye tunaThunnus obesus(Lowe, 1839) and yellowfin tunaT. albacares(Bonnaterre, 1788) caught in 1995 to 1997 during longline scientific surveys in the French Polynesian Exclusive Economic Zone (EEZ). Prey size distributions were compared with the size distribution of organisms collected by pelagic trawls carried out during the same programme. Relationships between prey size and predator size were studied using quantile regressions, and were related to tuna mouth-gape measurements. The results showed that mean and maximum sizes of prey increased with increasing predator size, and that maximum prey sizes (versus tuna size) were below those predicted by tuna mouth-gape size. Minimum prey size varied little with tuna size, and the size distributions of prey in tuna stomachs were very asymmetrical (lognormal type), confirming that during growth, tunas continue to feed on small prey. Comparison with previous studies on other piscivorous species from different ecosystems underlined that tunas feed on very small prey in relation to their own size. However, comparison of size distributions of prey in stomach contents and prey in pelagic trawls revealed that bigeye tuna select larger prey than yellowfin tuna when such prey are available.

The patterns of variations in fisheries time series are known to result from a complex combination of species and fisheries dynamics all coupled with environmental forcing (including climate, trophic interactions, etc.). Disentangling the relative effects of these factors has been a major goal of fisheries science for both conceptual and management reasons. By examining the variability of 169 tuna and billfish time series of catch and catch per unit effort (CPUE) throughout the Atlantic as well as their linkage to the North Atlantic Oscillation (NAO), we find that the importance of these factors differed according to the spatial scale. At the scale of the entire Atlantic the patterns of variations are primarily spatially structured, whereas at a more regional scale the patterns of variations were primarily related to the fishing gear. Furthermore, the NAO appeared to also structure the patterns of variations of tuna time series, especially over the North Atlantic. We conclude that the patterns of variations in fisheries time series of tuna and billfish only poorly reflect the underlying dynamics of these fish populations; they appear to be shaped by several successive embedded processes, each interacting with each other. Our results emphasize the necessity for scientific data when investigating the population dynamics of large pelagic fishes, because CPUE fluctuations are not directly attributable to change in species' abundance.