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Abstract Energy subsidies from the sea typically underpin ocean-exposed sandy beach ecosystems. Strandings of detached macroalgae – ‘wrack’ – can be a spectacular form of such cross-ecosystem transfers of organic matter that sustain consumers in the recipient shore system; this has given rise to a model of wrack promoting the diversity and abundance of invertebrates, with scaling effects on upper trophic levels. However, most wrack is often wave-cast to the upper beach, whereas a distinct part of the shore fauna is limited to the ocean fringe of beaches – the ‘swash zone’. This has the potential to create a spatial asymmetry between the location of subsidies (concentrated at the landwards fringe) and the location of some of the putative recipients distributed at the ocean fringe. Here, we tested whether the fauna of the swash zone can benefit from wrack subsidies, by sampling fauna and algal deposits on a range of beaches in NW Spain. We also measured the potential functional link between algal wrack and nutrients released from wrack during decay. Wrack decay increased nutrient concentrations, and it is the combination of wrack cover, nutrient levels, and sediment coarseness that jointly drove variation in the assemblage structure of the swash fauna among beaches. Similarly, the density of the swash fauna and species richness increased markedly at higher nutrient levels and wrack cover. Filter feeders were an important compartment in the food web of the swash macrofauna; we hypothesize that wrack deposits in the upper beach enhance food availability for this trophic guild via increasing nutrients in the water column, stimulating primary production and providing particulate organic matter derived from algal decay. Besides, several polychaetes and peracarid species function as secondary consumers and detritus feeders that plausibly benefit, directly or indirectly, on the particulate organic matter that accumulates on the sediment surface or percolates into the interstitial environment. These findings expand the ‘wrack enhancement’ model to include the promotion of consumers at the ocean edge of sandy shores; it also contains a cross-shore linkage via decomposition processes that favourably change the nutrient regime across all the beach face and thereby couple the swash zone with the upper strandline. 

The extent and distribution of tropical peatlands, and their importance as a vulnerable carbon (C) store, remain poorly quantified. Although large peatland complexes in Peru, the Congo basin, and Southeast Asia have been mapped in detail, information on many other tropical areas is uncertain. In the Eastern Colombian lowlands, peatland area estimates range from 700 km2 to nearly 60,000 km2, leading to highly uncertain C stocks. Using new field data, high‐resolution Earth observation (EO), and a random forest approach, we mapped peatlands across Colombian territory East of the Andes below 400 m elevation. We estimated peatland extent using two approaches: a conservative method focused on medium‐to‐high peat probability areas and a more inclusive one accounting for large low‐probability areas. Multiplying these extents by below‐ground carbon density yields a conservative estimate of 0.95 (0.6–1.39 Pg C, 95% confidence interval) over 9,391 km2(7,369–11,549 km2) and up to 2.86 Pg C (1.76–4.22 Pg C) across 29,069 km2 (22,429–36,238 km2). Among four potentially peat‐forming ecosystems identified, palm swamps and floodplain forests contributed most to the peat extent and C stock. We found that most peatland patches were relatively small, covering less than 100 ha. We compared our map to previously published global and pan‐tropical peat maps and found low spatial overlap among them, suggesting that peat maps uninformed by local field information may not precisely specify which landscape areas within a peatland‐rich region are actually peatlands. We further assessed the suitability of different EO and climate variables, highlighting the need for high‐resolution data to capture local heterogeneities in the landscape. 

Abstract The thermally dynamic nearshore Beaufort Sea, Alaska, is experiencing climate change-driven temperature increases. Measuring thermal tolerance of broad whitefish (Coregonus nasus) and saffron cod (Eleginus gracilis), both important species in the Arctic ecosystem, will enhance understanding of species-specific thermal tolerances. The objectives of this study were to determine the extent that acclimating broad whitefish and saffron cod to 5°C and 15°C changed their critical thermal maximum (CTmax) and HSP70 protein and mRNA expression in brain, muscle and liver tissues. After acclimation to 5°C and 15°C, the species were exposed to a thermal ramping rate of 3.4°C · h−1 before quantifying the CTmax and HSP70 protein and transcript concentrations. Broad whitefish and saffron cod acclimated to 15°C had a significantly higher mean CTmax (27.3°C and 25.9°C, respectively) than 5°C-acclimated fish (23.7°C and 23.2°C, respectively), which is consistent with trends in CTmax between higher and lower acclimation temperatures. There were species-specific differences in thermal tolerance with 15°C-acclimated broad whitefish having higher CTmax and HSP70 protein concentrations in liver and muscle tissues than saffron cod at both acclimation temperatures. Tissue-specific differences were quantified, with brain and muscle tissues having the highest and lowest HSP70 protein concentrations, respectively, for both species and acclimation temperatures. The differences in broad whitefish CTmax between the two acclimation temperatures could be explained with brain and liver tissues from 15°C acclimation having higher HSP70a-201 and HSP70b-201 transcript concentrations than control fish that remained in lab-acclimation conditions of 8°C. The shift in CTmax and HSP70 protein and paralogous transcripts demonstrate the physiological plasticity that both species possess in responding to two different acclimation temperatures. This response is imperative to understand as aquatic temperatures continue to elevate. 

Seascape genomics provides a powerful framework to evaluate the presence and strength of environmental pressures on marine organisms, as well as to forecast long term species stability under various perturbations. In the highly productive North Pacific, forage fishes, key trophic links across ecosystems, are also contending with a rapidly warming climate and a litany of associated oceanographic changes (e.g., changes in salinity, dissolved oxygen, pH, primary production, etc.). These changes can place substantial selective pressures on populations over space and time. While several population genomics studies have targeted forage fishes in the North Pacific, none have formally analyzed the interactions between genotype and environment. However, when population genomics studies provide collection location information and other critical data, it is possible to supplement a published genomic dataset with environmental data from existing public databases and perform “post hocseascape genomics” analyses. In reviewing the literature, we find pertinent metadata (dates and locations of sample collection) are rarely provided. We identify specific factors that may impede the application of seascape genomics methods in the North Pacific. Finally, we present an approach for supplementing data in a reproducible way to allow forpost hocseascape genomics analysis, in instances when metadata are reported. Overall, our goal is to demonstrate – via literature review – the utility and importance of seascape genomics to understanding the long term health of forage fish species in the North Pacific. 

We present the first threefold differential measurement for neutral-pion multiplicity ratios produced in semi-inclusive deep-inelastic electron scattering on carbon, iron, and lead nuclei normalized to deuterium from CLAS at Jefferson Lab. We found that the neutral-pion multiplicity ratio is maximally suppressed for the leading hadrons (energy fraction $z\to$1), suppression varying from 25% in carbon up to 75% in lead. An enhancement of the multiplicity ratio at low $z$and high $p_T^2$is observed, suggesting an interconnection between these two variables. This behavior is qualitatively similar to the previous twofold differential measurement of charged pions by the HERMES Collaboration and, recently, by CLAS Collaboration. The largest enhancement was observed at high $p_T^2$for heavier nuclei, namely, iron and lead, while the smallest enhancement was observed for the lightest nucleus, carbon. This behavior suggests a competition between partonic multiple scattering, which causes enhancement, and hadronic inelastic scattering, which causes suppression. 

Context.Blazars are beamed active galactic nuclei (AGNs) known for their strong multi-wavelength variability on timescales ranging from years down to minutes. Many different models have been proposed to explain this variability. Aims.We aim to investigate the suitability of the twisting jet model presented in previous works to explain the multi-wavelength behaviour of BL Lacertae, the prototype of one of the blazar classes. According to this model, the jet is inhomogeneous, curved, and twisting, and the long-term variability is due to changes in the Doppler factor due to variations in the orientation of the jet-emitting regions. Methods.We analysed optical data of the source obtained during monitoring campaigns organised by the Whole Earth Blazar Telescope (WEBT) in 2019–2022, together with radio data from the WEBT and other teams, andγ-ray data from theFermisatellite. In this period, BL Lacertae underwent an extraordinary activity phase, reaching its historical optical andγ-ray brightness maxima. Results.The application of the twisting jet model to the source light curves allows us to infer the wiggling motion of the optical, radio, andγ-ray jet-emitting regions. The optical-radio correlation shows that the changes in the radio viewing angle follow those in the optical viewing angle by about 120 days, and it suggests that the jet is composed of plasma filaments, which is in agreement with some radio high-resolution observations of other sources. Theγ-ray emitting region is found to be co-spatial with the optical one, and the analysis of theγ-optical correlation is consistent with both the geometric interpretation and a synchrotron self-Compton (SSC) origin of the high-energy photons. Conclusions.We propose a geometric scenario where the jet is made up of a pair of emitting plasma filaments in a sort of double-helix curved rotating structure, whose wiggling motion produces changes in the Doppler beaming and can thus explain the observed multi-wavelength long-term variability. 

A classical interatomic potential for iron/iron-fluoride systems is developed in the framework of the charge optimized many-body (COMB) potential. This interatomic potential takes into consideration the effects of charge transfer and many-body interactions depending on the chemical environment. The potential is fitted to a training set composed of both experimental and ab initio results of the cohesive energies of several Fe and FeF 2 crystal phases, the two fluorine molecules F 2 and the F 2 −1 dissociation energy curve, the Fe and FeF 2 lattice parameters of the ground state crystalline phase, and the elastic constants of the body centered cubic Fe structure. The potential is tested in an NVT ensemble for different initial structural configurations as the crystal ground state phases, F 2 molecules, iron clusters, and iron nanospheres. In particular, we model the FeF 2 /Fe bilayer and multilayer interfaces, as well as a system of square FeF 2 nanowires immersed in an iron solid. It has been shown that there exists a reordering of the atomic positions for F and Fe atoms at the interface zone; this rearrangement leads to an increase in the charge transfer among the atoms that make the interface and put forward a possible mechanism of the exchange bias origin based on asymmetric electric charge transfer in the different spin channels. 

Context.3C 84 is a nearby radio source with a complex total intensity structure, showing linear polarisation and spectral patterns. A detailed investigation of the central engine region necessitates the use of very-long-baseline interferometry (VLBI) above the hitherto available maximum frequency of 86 GHz. Aims.Using ultrahigh resolution VLBI observations at the currently highest available frequency of 228 GHz, we aim to perform a direct detection of compact structures and understand the physical conditions in the compact region of 3C 84. Methods.We used Event Horizon Telescope (EHT) 228 GHz observations and, given the limited (u, v)-coverage, applied geometric model fitting to the data. Furthermore, we employed quasi-simultaneously observed, ancillary multi-frequency VLBI data for the source in order to carry out a comprehensive analysis of the core structure. Results.We report the detection of a highly ordered, strong magnetic field around the central, supermassive black hole of 3C 84. The brightness temperature analysis suggests that the system is in equipartition. We also determined a turnover frequency ofν_m = (113 ± 4) GHz, a corresponding synchrotron self-absorbed magnetic field ofB_SSA = (2.9 ± 1.6) G, and an equipartition magnetic field ofB_eq = (5.2 ± 0.6) G. Three components are resolved with the highest fractional polarisation detected for this object (m_net = (17.0 ± 3.9)%). The positions of the components are compatible with those seen in low-frequency VLBI observations since 2017–2018. We report a steeply negative slope of the spectrum at 228 GHz. We used these findings to test existing models of jet formation, propagation, and Faraday rotation in 3C 84. Conclusions.The findings of our investigation into different flow geometries and black hole spins support an advection-dominated accretion flow in a magnetically arrested state around a rapidly rotating supermassive black hole as a model of the jet-launching system in the core of 3C 84. However, systematic uncertainties due to the limited (u, v)-coverage, however, cannot be ignored. Our upcoming work using new EHT data, which offer full imaging capabilities, will shed more light on the compact region of 3C 84.