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Identifying factors determining the performance of individuals is an essential part of resolving what drives population dynamics. For species undergoing ontogenetic shifts in resource and habitat use, this entails assessing individual performance in all habitats used. Whereas survival and growth of anadromous Atlantic salmon, Salmo salar L., in its juvenile, river habitat are known to depend on size‐dependent foraging and food availability, individual performance of salmon in the growth habitat out at sea is commonly explained only by abiotic factors. Still, individuals undergo this habitat shift to grow large, suggesting performance should be food‐dependent also in the growth habitat. Because fish communities are highly size‐structured, the link between predators and their prey may depend on their respective body sizes. Here, we study whether the performance of Baltic Sea salmon in its growth habitat is food‐ and size‐dependent, by combining extensive diet and body size data of Baltic salmon with spatially resolved monitoring data on abundance and size distribution of their main prey, herring, Clupea harengus L., and sprat, Sprattus sprattus L. We found that both the species and size composition of prey in the diet varied with salmon body size. By accounting for this size‐dependent predation and the spatially varying size distribution of prey species, we could explain the variation in salmon diet composition among salmon individuals in different Baltic Sea basins and of different length. The proportion of sprat in diet of salmon was better explained by size‐specific prey availability (SSP) than total prey biomass, especially for small salmon. Further, salmon body condition increased with SSP, whereas total prey biomass could not explain variation in the condition of salmon. These findings demonstrate that food‐ and size‐dependent processes indeed can influence the performance of anadromous fish also in large marine systems. Thus, we argue that consideration of these processes, stretching across habitats, is important for understanding performance and dynamics of predatory fish in open aquatic systems, as well as for successful management of species such as Atlantic salmon.

Size‐dependent interactions and habitat complexity have been identified as important factors affecting the persistence of intraguild predation (IGP) systems. Habitat complexity has been suggested to promote intraguild (IG) prey and intraguild predator coexistence through weakening trophic interactions particularly the predation link. Here, we experimentally investigate the effects of habitat complexity on coexistence and invasion success of differently sized IG‐predators in a size‐structured IGP system consisting of the IG‐predator Poecilia reticulata and a resident Heterandria formosa IG‐prey population. The experiments included medium‐long and long‐term invasion experiments, predator–prey experiments and competition experiments to elucidate the mechanisms underlying the effect of prey refuges. Habitat complexity did not promote the coexistence of IG‐predator and IG‐prey, although the predation link was substantially weakened. However, the presence of habitat structure affected the invasion success of large IG‐predators negatively and the invasion success of small IG‐predators positively. The effect of refuges on size‐dependent invasion success could be related to a major decrease in the IG‐predator's capture rate and a shift in the size distribution of IG‐predator juveniles. In summary, habitat complexity had two main effects: (i) the predation link was diminished, resulting in a more competition driven system and (ii) the overall competitive abilities of the two species were equalized, but coexistence was not promoted. Our results suggest that in a size‐structured IGP system, individual level mechanisms may gain in importance over species level mechanisms in the presence of habitat complexity.

Humans are intentionally exposed to gold nanoparticles (AuNPs) where they are used in variety of biomedical applications as imaging and drug delivery agents as well as diagnostic and therapeutic agents currently in clinic and in a variety of upcoming clinical trials. Consequently, it is critical that we gain a better understanding of how physiochemical properties such as size, shape, and surface chemistry drive cellular uptake and AuNP toxicity in vivo. Understanding and being able to manipulate these physiochemical properties will allow for the production of safer and more efficacious use of AuNPs in biomedical applications. Here, AuNPs of three sizes, 5 nm, 10 nm, and 20 nm, were coated with a lipid bilayer composed of sodium oleate, hydrogenated phosphatidylcholine, and hexanethiol. To understand how the physical features of AuNPs influence uptake through cellular membranes, sum frequency generation (SFG) was utilized to assess the interactions of the AuNPs with a biomimetic lipid monolayer composed of a deuterated phospholipid 1.2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (dDPPC). SFG measurements showed that 5 nm and 10 nm AuNPs are able to phase into the lipid monolayer with very little energetic cost, whereas, the 20 nm AuNPs warped the membrane conforming it to the curvature of hybrid lipid-coated AuNPs. Toxicity of the AuNPs were assessed in vivo to determine how AuNP curvature and uptake influence cell health. In contrast, in vivo toxicity tested in embryonic zebrafish showed rapid toxicity of the 5 nm AuNPs, with significant 24 hpf mortality occurring at concentrations ≥20 mg/L, whereas the 10 nm and 20 nm AuNPs showed no significant mortality throughout the five-day experiment. By combining information from membrane models using SFG spectroscopy with in vivo toxicity studies, a better mechanistic understanding of how nanoparticles (NPs) interact with membranes is developed to understand how the physiochemical features of AuNPs drive nanoparticle-membrane interactions, cellular uptake, and toxicity.

Ecologists have long wondered how plants and algae persist under constant herbivory, and studies have shown that factors like chemical defense and morphology can protect these species from consumption. However, grazers are also highly diverse and exert varying top-down control over primary producers depending on traits such as body size. Moreover, susceptibility of plants and algae to herbivory may vary across life stages and size classes, with juveniles potentially the most vulnerable. Here, we focus on diverse grazing communities within giant kelp forests and compared consumption on two size classes of juvenile giant kelp (Macrocystis pyrifera) across four herbivore species ranging in size. We also integrated field and literature densities to estimate impacts on populations of juvenile kelp. We found that purple sea urchins, a species known for exerting strong control over adult M. pyrifera, had weak per capita impact on microscopic kelp, on par with a much smaller crustacean species. While urchin consumption increased with macroscopic juvenile kelp, it never surpassed the smaller brown turban snail, suggesting that feeding morphology, in addition to herbivore body size, is a predictor of consumption at these small size classes. The smaller herbivores also occurred in high densities in the field, increasing their predicted population-level impacts on juvenile kelp compared to urchins and perhaps other larger, but less abundant, herbivores. This study highlights the variation in species’roles within an herbivore guild and the importance of age-related changes in grazing vulnerability to better understand herbivore control on plant and algae population dynamics.

1. Tree mortality has important influences on forest structure and composition, but the mechanisms that cause tree mortality are not well understood. Asymmetric competition is known to be a dominant cause of plant mortality, but this idea has not received much attention in studies of long‐lived trees. 2. We hypothesised that while tree mortality is dependent on size relative to neighbours as a result of asymmetric competition, tree mortality of shade‐tolerant species varies little with size because of their physiological and morphological adaptations to shaded environments. Furthermore, we hypothesised that tree mortality is higher in more crowded stands because of higher average resource competition, in conspecific stands because of potential negative intra‐specific interactions, and in older stands because of the physiological limitations and susceptibility to minor disturbances of large trees. 3. Using data from repeatedly measured permanent sampling plots that covered a wide range of tree sizes, stand developmental stages and stand compositions in boreal forests, we simultaneously tested, by boosted regression tree models, the effects of an individual’s relative size, stand crowding, species interaction and ageing on mortality of Pinus banksiana, Populus tremuloides, Betula papyrifera and Picea mariana. 4. Mortality increased strongly with decreasing relative size for all study species, and the size‐dependent mortality was stronger for shade‐intolerant than for shade‐tolerant species. With increasing stand basal area, mortality increased for Pinus banksiana, Populus tremuloides and Picea mariana but decreased for Betula papyrifera. Mortality was higher in stands with more conspecific neighbours for Populus tremuloides, Betula papyrifera and Picea mariana, but was slightly lower for Pinus banksiana. Mortality also increased with stand age for all species. Furthermore, the size‐dependent mortality was generally stronger in more crowded stands. 5. Synthesis. Our findings show that tree mortality over a wide range of tree sizes, stand developmental stages and stand compositions in non‐equilibrium boreal forests was strongly controlled by competition, but species interactions and ageing were also important mechanisms. Furthermore, the relative importance of these mechanisms to tree mortality differed with the shade tolerance of species.

The outcome of competition between individuals often depends on body size. These competitive asymmetries can drive variation in demographic rates, influencing the ecology and evolution of life histories. The magnitude and direction of such asymmetries differ among taxa, yet little is known empirically about how adaptation to resource limitation alters competitive asymmetries. Here, we investigate the relationship between size‐dependent competitive ability and adaptation to resource limitation. We examined size‐dependent competition in two ecotypes of Trinidadian guppy, adapted to high or low levels of resource competition. Using aquaria‐based competition experiments, we describe how the size and ecotype of competitors influence somatic growth rate, whilst controlling for the confounding effect of niche differentiation. We replicated our study across two independent evolutionary origins of the “competitive” ecotype. The two “competitive” ecotypes differed markedly in size‐dependent asymmetry, indicating that adaptation to resource limitation alone is insufficient to explain changes in size‐dependent competitive asymmetry. For one origin, the ecotype adapted to resource limitation was a superior competitor over a wide range of size pairings. The equivalence of competitors varied over fivefold, dependent on size and ecotype; in three of four populations, larger individuals had a competitive advantage. Our results demonstrate that competitive asymmetry has strong effects on somatic growth. Because somatic growth contributes to demographic parameters, intraspecific trait variation is likely to play a key role in regulating demographic rates. Our findings imply that the evolution of size‐dependent asymmetries under conditions of intense competition is likely to be constrained by niche availability, although further research is needed to verify this. Competition is often modelled as a function of population density: competitors are considered equal. The authors show that competitive equivalence between individuals can vary fivefold dependent on size and population in Trinidadian guppies. The traits of competitors have a significant effect on a key driver of demographic rates and somatic growth.

Summary Quantifying predator–prey body size relationships is key to understanding food webs. Food web models often assume that all individuals of predator species prefer the same relative body size of prey, using a single constant called preferred predator–prey mass ratio (preferred PPMR). In contrast, empirical studies have shown that relative prey body size in diet varies with individual predator size, challenging the food web models based on size‐invariant preferred PPMR and their predictions. We point out that this apparent inconsistency arises because empirical PPMR in those previous studies has been measured only through dietary data (i.e. realized PPMR rather than preferred PPMR) without considering the effects of environmental prey availability, suggesting the possibility that preferred PPMR may be in fact independent of individual predator size. Here, we present a new approach to revisit the assumption of size‐invariant preferred PPMR in food web models. The approach compares two measures of PPMR calculated from prey compositions in predator diet and environmental prey composition, respectively (i.e. realized PPMR vs. environmental PPMR). The deviations between realized and environmental PPMRs are considered as a proxy of individual variations in relative prey size preference (i.e. preferred PPMR). We apply this idea to long‐term dietary data of an omnivorous predatory fish species collected from a lake ecosystem over four decades. Our results showed that the preferred PPMR is independent of individual predator size when the foraging mode (i.e. the major prey type) of the predator is considered while the realized PPMR is size‐dependent regardless of the foraging mode, especially when analysed analogously to previous empirical studies. We suggest that the apparent inconsistency between theoretical assumption and empirical observation of PPMR is due to the conceptual and methodological confusion and could be resolved by distinguishing between preferred and realized PPMRs. Further, in contrast to the previous arguments based on realized PPMR, we provide the first empirical support for size‐invariant preferred PPMR. Future studies are encouraged to apply our ideas to other species/systems to test the robustness of size‐invariant preferred PPMR and to better describe food web models. A lay summary is available for this article. Lay Summary

Nanozymes (NZs), or nanostructures exhibiting enzyme mimicking exertion, have drawn a lot of attention recently owing to their ability to substitute enzymes that are naturally occurring in an array of bio-medical applications, notably biological detection, therapeutics, pharmaceutical administration, as well as biological imaging. In comparison to single enzymatic NZs, multi-enzymatic NZs have additional benefits, especially improved selectivity, a more favorable ecological impact, and synergistic effects. In contrast, the catalytic mechanism and rational design of multi-enzymatic NZs are more complex than those of single enzymatic NZs, which have simple catalytic mechanisms. NZs that can regulate cellular redox equilibrium by emulating the antioxidant enzymes in cells are particularly crucial towards alleviating ailments induced on by cellular oxidative stress. Carbonaceous materials i.e. graphene, fullerenes, quantum dots, carbon nano-sheets, nano-rods, MOFs etc. demonstrated peroxidase (POD), oxidase (OXD), superoxide dismutase (SOD), and catalase (CAT)-like functioning in a range of domains on the basis of oxidation mitigation mechanisms employing electron transport channels. Furthermore, integrating a couple of hetero-atoms to carbon-based materials enhanced their efficacy in various industries. NZs derived from bioactive materials demonstrate catalytic properties similar to those of enzymes. Bioactive material-based NZs are essential because of their unique catalytic properties, which surpass the efficiency, selectivity, and flexibility of traditional catalysts moreover, offering a cost-effective and environmentally friendly alternative to conventional precursors in catalysis. Their surfaces can be precisely modified, opening up new possibilities for selective and green synthetic techniques. Bioactive materials-based NZs have exceptional biological activity and compatibility in the field of medicine, thus rendering them useful instruments for both diagnosis and therapy. Due to their innate capacity to imitate the catalytic functions of natural enzymes, they can be utilized to develop intricate bio-sensors, precise drug delivery systems, and extremely sensitive diagnostic platforms. Moreover, low cytotoxicity of these materials facilitates the easier integration of chemicals into biological systems. This review provided an overview of the multi-enzymatic activities of rationally designed carbon-based NMs, both the internal and external variables that regulate the multi-enzymatic enzymes endeavours, and current advancements in application areas which benefit from multi-enzymatic distinctive characteristics. Prospective uses and development of multi-enzymatic carbon-based NZs might confront multiple challenges. This review aims to stimulate and improve our understanding of multi-enzymatic carbon-based processes to a greater extent. Graphical Abstract

Background and aims Belowground interspecific plant facilitation is supposed to play a key role in enabling species co-existence in hyperdiverse ecosystems in extremely nutrient-poor, semi-arid habitats, such as Banksia woodlands in southwestern-Australia. Manganese (Mn) is readily mobilised by Banksia cluster root activity in most soils and accumulates in mature leaves of native Australian plant species without significant remobilisation during leaf senescence. We hypothesised that neighbouring shrubs are facilitated in terms of Mn uptake depending on distance to surrounding cluster root-forming Banksia trees. Methods We mapped all Banksia trees and selected neighbouring shrubs within a study site in Western Australia. Soil samples were collected and analysed for physical properties and nutrient concentrations. To assesses the effect of Banksia tree proximity on leaf Mn concentrations [Mn] of non-cluster-rooted woody shrubs, samples of similarly aged leaves were taken. We used multiple linear models to test for factors affecting shrub leaf [Mn]. Results None of the assessed soil parameters showed a significant correlation with shrub leaf Mn concentrations. However, we observed a significant positive effect of very close Banksia trees (2 m) on leaf [Mn] in one of the understorey shrubs. We found additional effects of elevation and shrub size. Conclusions Leaf micronutrient concentrations of understorey shrubs were enhanced when growing within 2 m of tall Banksia trees. Our model predictions also indicate that belowground facilitation of Mn uptake was shrub size-dependent. We discuss this result in the light of plant water relations and shrub root system architecture.

Great efforts have been made to separate micro/nanoparticles in small-volume specimens, but it is a challenge to achieve the simple, maneuverable and low-cost separation of sub-microliter suspension with large separation distances. By simply adding trace amounts of cations (Mg2+/Ca2+/Na+), we experimentally achieved the size-dependent spontaneous separation of colloidal particles in an evaporating droplet with a volume down to 0.2 μL. The separation distance was at a millimeter level, benefiting the subsequent processing of the specimen. Within only three separating cycles, the mass ratio between particles with diameters of 1.0 μm and 0.1 μm can be effectively increased to 13 times of its initial value. A theoretical analysis indicates that this spontaneous separation is attributed to the size-dependent adsorption between the colloidal particles and the aromatic substrate due to the strong hydrated cation-π interactions.