Body Size Dependence Research Articles

External dose measurements to investigate the body-size dependence of personal dosemeter responses in areas affected by the Fukushima Daiichi nuclear accident.

To formulate necessary protective measures after a large-scale nuclear accident, it is crucial to understand the levels of radiation to which persons living in radionuclide-contaminated areas are exposed. Individual monitoring using personal dosemeters (PDs) plays a role in this, although PDs were not originally intended to be used by members of the public. The present study investigated PD responses in areas highly affected by the Fukushima Daiichi nuclear accident, as well as the dependence of those measurements on body size. Three types of commercially available electronic PDs, including D-shuttle, which has often been used in Fukushima, were placed on the front surfaces of three age-specific anthropometric phantoms imitating a 5-y-old, a 10-y-old and an adult male, and these phantoms were then exposed to radiation in an open field in the affected area. In the case of D-shuttle, the ratios of PD readings to the ambient dose rate for the 5-y-old phantom and the adult male phantom were 0.79 and 0.72, respectively. The ratios were somewhat higher for the other PDs; any PDs showed higher readings than the effective doses estimated by simulations based on the assumed ground deposition of 134Cs and/or 137Cs over the affected areas.

Differences in functional trait responses to elevation among feeding guilds of Aculeata community.

The response of communities to environmental change is expected to vary among feeding guilds. To evaluate the response of guilds to environmental factors without considering the taxonomic specificities, it is useful to examine Aculeata bees and wasps, which consist of closely related taxa including different guilds, pollinators, predators, and parasitoids. In this study, we evaluated changes in species diversity (SD) and functional traits of each feeding guild along an elevational gradient in a boreal forest in northern Japan. We used yellow pan traps to collect Aculeata bees and wasps at 200–1600 m above sea level. We investigated six functional traits (trophic level, seasonal duration, body size, elevational range, nesting position, and soil dependency) and the horizontal distribution of the species. The SD of all Aculeata, predators, and parasitoids decreased with an increase in elevation; however, the SD of pollinators did not show any specific trend. Although the functional trait composition of all Aculeata species did not show any trend, that of each feeding guild responded to elevation in different ways. Pollinators increased in body size and showed a decrease in seasonal duration with increasing elevation, suggesting that tolerance and seasonal escape from physical stress at high elevations are important for shaping pollinator communities. Predators increased their elevational range and the proportion of above‐ground nesting species increased with increasing elevation, suggesting that the ability to live in a wider range of environments and avoid unsuitable soil environments at high elevations might be important. Parasitoids changed their hosts and displayed variable traits with increasing elevation, suggesting that brood parasitoids have difficulty in surviving at high elevation. The traits for each guild responded in different ways, even if they were dominated by the same environmental factors. Our findings imply that differences in the responses of functional traits would produce different community assembly patterns in different guilds during further climate change.

Postnatal remodeling of the laryngeal airway removes body size dependency of spectral features for ultrasonic whistling in laboratory mice

AbstractIn many mammals, spectral properties of acoustic signals scale with body size within and among species. In rodents, however, despite drastic changes in body size, fundamental frequency (F0) range of ultrasonic whistles produced for social communication remain relatively uniform from birth to adulthood. Such divergent patterns may be due to a novel sound production mechanism unique to rodents involving an intralaryngeal midline pocket termed the ventral pouch. In this study, we analyzed the postnatal shape and size of the laryngeal airway in CD1 mice over ontogeny to better understand the association between ventral pouch geometry and F0 of ultrasonic whistles. Ventral pouch volume (0.06 ± 0.01 mm3) did not differ between pups and 1‐year‐old adults despite extensive shape‐inducing remodeling of the intralaryngeal musculature and connective tissue. In contrast, ventral pouch volume was 50% less in 2‐year‐old compared to 1‐year‐old mice. Thus, allometry of the laryngeal airway appears to explain spectral overlap between ultrasonic whistles of young, small mice and older, larger mice. The causal association between the reduction in vocal behavior and a seemingly shrinking ventral pouch in geriatric mice remains unclear. Together, these data inform our understanding of the postnatal development and remodeling of the intralaryngeal airway in Mus musculus.

Ontogeny, phylogeny and mechanisms of adaptive changes in evaporative water loss in geckos.

Body size dependence of metabolic rate, body surface and scale morphology complicate disentangling the contribution of these characteristics to adaptive changes in total evaporative water loss (TEWL) of reptiles. To separate adaptive changes from size-related dependence, we compared intra- and interspecific scaling of several candidate traits in eyelid geckos (Eublepharidae), a group exhibiting large variation in body size and TEWL. The intraspecific allometry of TEWL of a eublepharid species fits the geometric surface-mass relationship. However, evolutionary shifts to both higher and lower evaporation were strongly correlated with habitat aridity and cannot be explained by shifts in body size alone. The intraspecific allometry of standard metabolic rate is nearly the same as the interspecific allometry. Unlike for mammals and birds, this pattern rules out respiratory water loss as a driver of the adaptive changes in TEWL among eublepharids. Scale morphology was independent of TEWL variation as well, but the correlation between cutaneous water loss and TEWL suggests a crucial role of skin permeability in adaptation to habitat aridity. Our analyses demonstrate how powerful a comparison between intra- and interspecific allometries can be for detecting body size-dependent mechanisms of adaptive changes in ecophysiological traits correlated with body size.

A macroecological perspective on the fluctuations of exploited fish populations

The natural variability of fish populations is increased by exploitation, but the specific mechanisms driving this variability are still debated. We propose a macroscopic approach combining the size-density relationship and Taylor’s law to predict the temporal variance of exploited and unexploited fish populations. Using information from 11 years of fishery-independent abundance surveys, we showed that the body-size dependence of the variance of exploited (targeted) and unexploited (non-targeted or bycatch) fish populations can be accurately predicted. Targeted fish populations showed a variability that was 2 orders of magnitude greater than that of non-targeted fish populations. Such variability was explained solely by the higher relative abundance of the former, regardless of their specific trophic position, while aggregated community fluctuation was lower in a high trophic position group. This study showed the usefulness of the macroscopic approach to predict fish variability and fishing effect in the whole community. This approach is complementary to other modeling strategies and seems to be useful in tackling the problem of variability in population fluctuations of exploited fish, particularly in cases where specific details of the interacting species are lacking.

The body size and temperature dependence of organismal locomotion.

The speed and maneuverability of organisms are central to their fitness, determining the strength and outcome of many species interactions that drive population and community-level processes. While locomotion is influenced by many internal and external factors, body size and temperature are two key factors governing organismal locomotion. Biologists have been measuring locomotor performance, particularly maximum speed, for over a century. Studies have tended to focus on single species or groups of species that are either phylogenetically related, functionally similar, or use the same habitat. Few studies compare locomotor performance across a diverse range of taxa or locomotor modes, very few have incorporated locomotor traits other than maximum speed, and the data are not accessible in a single database with standardized units. Here, we present a data set we compiled from the literature that contains 2,951 measurements of locomotor performance for five traits (exploratory speed, maximum speed, maximum acceleration, minimum powered turn radius, and maximum angular speed) that are important in the daily lives of many organisms. This represents the most diverse and comprehensive database on animal locomotion yet published and includes 884 species spanning 23 orders of magnitude of body size. Together with body size (mass and length) and temperature (body and ambient), we also provide data on trophic group and habitat (aerial, terrestrial, aquatic). In publishing our data set, we hope to encourage others to contribute to a continued effort to build this locomotion database and to analyze these data for underlying patterns. Interspecific analyses can help elucidate how organismal locomotion varies with important morphological and physiological traits and environmental conditions, revealing generalities and deviations in organismal locomotion. Additionally, intraspecific analyses, which are possible for a number of species in our data set, can help corroborate these patterns and deviations and explore potential mechanisms that could underlie these patterns. Insights from these analyses should uncover drivers of locomotor performance and contribute to an understanding about how locomotion shapes ecological processes across scales. There are no copyright or proprietary restrictions, except this data paper should be cited when data are used for publication. In addition, we would appreciate hearing for which research projects or teaching exercises these data are used.

Over all variability of mitral annular plane peak systolic velocity and peak global longitudinal strain rate in relation to age, body size, and sex: The HUNT Study.

Left ventricular (LV) systolic global function can be assessed by peak annular systolic velocity S'. Global longitudinal strain rate (GLSR) is relative LV shortening rate, equivalent to normalizing S' for LV length (S'n ). It has previously been shown that mitral annular plane systolic excursion (MAPSE) and global longitudinal strain (GLS) have similar biological variability, but GLS normalizes for one dimension only, inducing a systematic error, increasing body size dependence. The objective of this study was to compare S' with GLSR in the same way, comparing biological variability and body size dependence. A total of 1266 subjects from the third wave of Nord-Trøndelag Health Study (HUNT), without evidence of heart disease, were examined. Strain rate, S' and wall lengths were measured in the four walls of the two- and four-chamber views. Mean S' was 8.4 (1.4)cm/s, (S'n ) was 0.7 (0.14)s-1 and GLSR 1.02 (0.14)s-1 . All measures declined with age. Normalization of mitral annular velocities for LV length, or the use of GLSR, did not reduce overall biological variability compared with S'. S' did show a weak, positive correlation to BSA, while S'n and GLSR a slightly stronger, negative correlation to BSA. S', S'n , and GLSR have similar biological variability, which is mainly due to age, not body size variation. Normalizing S' for LV length (as in Sn or GLSR) reverses correlation with BSA inducing a systematic error, due to the one-dimensional normalization for one dimension only.

Body Size, Light Intensity, and Nutrient Supply Determine Plankton Stoichiometry in Mixotrophic Plankton Food Webs.

Trophic strategy determines stoichiometry of plankton. In general, heterotrophic zooplankton have lower and more stable C∶N and C∶P ratios than photoautotrophic phytoplankton, whereas mixotrophic protists, which consume prey and photosynthesize, have stoichiometry between zooplankton and phytoplankton. As trophic strategies change with cell size, body size may be a key trait influencing eukaryotic plankton stoichiometry. However, the relationship between body size and stoichiometry remains unclear. Here we measured plankton size-fractionated C∶N ratios under different intensities of light and nutrient supply in subtropical freshwater and marine systems. We found a unimodal body size-C∶N ratio pattern, with a maximum C∶N ratio at ∼50 μm diameter in marine and freshwater systems. Moreover, the variation in C∶N ratios is explained mainly by body size, followed by light intensity and nutrient concentration. To investigate the mechanisms behind this unimodal pattern, we constructed a size-based plankton food web model in which the trophic strategy and C∶N ratio are an emerging result. Our model simulations reproduce the unimodal pattern with a C∶N ratio of photoautotrophs ≤50 μm increasing with body size due to increase of photosynthetic carbon, whereas C∶N ratios of organisms >50 μm decrease with size due to decreasing photoautotrophic but increasing heterotrophic uptake. Based on our field observations and simulation, we extend the classic "light-nutrient" theory that determines plankton C∶N ratio to include body size and trophic strategy dependency. We conclude that body size and size-dependent uptake of resources (light, nutrients, and prey) determine plankton stoichiometry at various light and nutrient supplies.

Determination of contrast medium dose for hepatic CT enhancement with improved body size dependency using a non-linear analysis based on pharmacokinetic principles

To propose a pharmacokinetic non-linear analysis method to determine contrast medium (CM) dose for computed tomography (CT) hepatic enhancement to improve body size dependency and validate the proposed CM dose determination method through a clinical study. Enhancement data of 105 patients who underwent hepatic dynamic CT with a fixed CM dose were analysed. From the analysis results, CM doses as a function of each of four body size indices (body weight [BW], lean body weight [LBW], blood volume [BV], and body surface area [BSA]) for achieving improved body size dependency were determined (proposed method), and the body size dependencies were simulated using the enhancement data from 105 patients. The proposed method was validated with a two-arm clinical study on BW. Body size dependency was evaluated using p-value of correlation coefficient between Body size indices and enhancements (p<0.05: significant dependency) and mean absolute error (MAE). The simulation showed that significant body size dependencies not considered by the conventional method can be improved by the proposed method. MAEs of BW, LBW, and BV were also significantly reduced (p<0.05). The clinical study with BW demonstrated a similar improvement to that in the simulation result. MAE was also significantly reduced (p<0.001). The proposed method demonstrated more improved BW, LBW, and BV dependence compared to the conventional method. Through the two-arm clinical study, the proposed method using BW only, without height information, is a suitable index for improving body size dependency.

Determination of contrast medium dose for aortic CT enhancement with improved body size dependency using a non-linear analysis based on pharmacokinetic principles

Determination of contrast medium dose for aortic CT enhancement with improved body size dependency using a non-linear analysis based on pharmacokinetic principles

Global drivers of reef fish growth

AbstractFew studies have attempted to understand how fish growth scales at community and macroecological levels. This study evaluated the drivers of reef fish growth across a large gradient of environmental variables and a range of morphological and behavioural traits. We compiled Von Bertalanffy Growth parameters for reef fishes and standardized K relative to species maximum sizes, obtaining Kmax. We then modelled the response of Kmax to body size, diet, body shape, position relative to the reef, schooling behaviour, sea surface temperature, pelagic net primary productivity and ageing method, while accounting for phylogenetic structure in the data. The final model explained 61.5% of the variation in Kmax and contained size, temperature, diet, method and position. Body size explained 64% of the modelled Kmax variability, while the other variables explained between 6% (temperature) and 2.5% (position). Kmax steadily decreased with body size and increased with temperature. All else being equal, herbivores/macroalgivores and pelagic reef fishes had higher growth rates than the other groups. Moreover, length–frequency ageing tended to overestimate Kmax compared to other methods (e.g. otolith's rings). Our results are consistent with (a) metabolic theory that predicts body size and temperature dependence of physiological rates; and (b) ecological theory that implies influence of resource availability and acquisition on growth. At last, we use machine learning to accurately predict growth coefficients for combinations of traits and environmental settings. Our study helps to bridge the gap between individual and community growth patterns, providing insights into the role of fish growth in the ecosystem process of biomass accumulation.

Predator Persistence through Variability of Resource Productivity in Tritrophic Systems.

The trophic structure of species communities depends on the energy transfer between trophic levels. Primary productivity varies strongly through time, challenging the persistence of species at higher trophic levels. Yet resource variability has mostly been studied in systems with only one or two trophic levels. We test the effect of variability in resource productivity in a tritrophic model system including a resource, a size-structured consumer, and a size-specific predator. The model complies with fundamental principles of mass conservation and the body-size dependence of individual-level energetics and predator-prey interactions. Surprisingly, we find that resource variability may promote predator persistence. The positive effect of variability on the predator arises through periods with starvation mortality of juvenile prey, which reduces the intraspecific competition in the prey population. With increasing variability in productivity and starvation mortality in the juvenile prey, the prey availability increases in the size range preferred by the predator. The positive effect of prey mortality on the trophic transfer efficiency depends on the biologically realistic consideration of body size-dependent and food-dependent functions for growth and reproduction in our model. Our findings show that variability may promote the trophic transfer efficiency, indicating that environmental variability may sustain species at higher trophic levels in natural ecosystems.

Dual-energy x-ray absorptiometry metabolic maps to resting energy expenditure estimation, and body size dependence in Brazilian young men.

The model most suitable for estimating resting energy expenditure (REE) using dual-energy X-ray absorptiometry (DXA) metabolic maps is not known; moreover, the applicability in individuals with different body sizes also is uncertain. The aim of this study was to test the accuracy of REE estimation from models of DXA metabolic maps with four, five, and six tissue-organ components in young men, stratified by body size. We studied 52 young men between the ages of 18 and 29y. Participants were clustered to small (SW; n=32) and large (LW; n=20) weight, and small (SWH; n=25) and large (LWH; n=27) weight-height. REE was measured by indirect calorimetry (REEm), and predicted from DXA metabolic maps with four (REEc1), five (REEc2) and six (REEc3) tissue-organ components. REEc1, REEc2, and REEc3 explained 54% (P<0.001), 56% (P<0.001), and 58% (P<0.001) of REEm variance in all participants, respectively. However, REEc2 showed mean difference between REEm (P<0.001), and REEc3 showed trends in estimating the REE (P<0.05). In contrast, REEc1 showed limits of agreement (95%) of -248.3 to 285.8kcal/d, 18.7±136.3kcal/d of bias, and no trends in the Bland-Altman analysis. The relationship between all predicted models and measured REE decreased in LW and LWH. REEc1 can be considered the best accurate model of REE estimation in Brazilian young men, providing the REE and metabolically active tissue-organ of four components. Caution should be exercised with the use of DXA metabolic maps in populations with greater weight and greater weight-height.

First experience of using a new database on net zooplankton in the Far-Eastern Seas and adjacent Pacific waters

Unique database on zooplankton collected by 0.1 m 2 Juday planktonic net (mesh size 0.168 mm) in the Chukchi, Bering, Okhotsk, and Japan Seas and the North Pacific in 1984-2013 is presented. History of its creation, sources and volume of the data are described and the first operating experience and prospects of its using for applied and fundamental researches of marine biological resources are explained. Some new results based on this database are discussed. In particular, 5 tabular reference-books of species composition, occurrence and abundance of zooplankton for the main fishing grounds in the Russian part of this region were prepared and published in 2014-2015, where the information is summarized by species, stages of development, size fractions, biostatistical areas, water layers, light and dark time of day, four seasons, and quasi-decadal periods. Charts of spatio-temporal distribution of certain taxonomic and dimensional groups are drawn. Assumption is offered on negative dependence of zooplankton body size on water temperature, that needs additional verification. Vertical zooplankton migrations are considered and there is concluded that its biomass in the upper layer increases usually in the nighttime in the Okhotsk and Japan Seas but in the daytime in the Bering Sea and North Pacific, therefore attempts to recalculate the daytime biomass to the nighttime one using constant coefficients give opposite results for these pairs of regions. Prospects for developing of GIS and atlases of zooplankton for the North Pacific are discussed with examples of charts for the data generalized by abovementioned criteria, but this application is postponed until the best times because of funding reduction.

Ocean warming and the demography of declines in coral body size

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 560:147-158 (2016) - DOI: https://doi.org/10.3354/meps11931 Ocean warming and the demography of declines in coral body size Robin Elahi1,*, Kenneth P. Sebens2, Giulio A. De Leo1 1Hopkins Marine Station, Stanford University, Pacific Grove, CA 93940, USA 2Department of Biology and Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA *Corresponding author: elahi@stanford.edu ABSTRACT: Reductions in body size are hypothesized to be a universal response to climate warming, yet the proximate causes of change remain unresolved. In this study, we combined field evidence and demographic models to explore mechanisms relevant to temperature-related declines in the body size of an ectotherm exhibiting indeterminate growth. Our field data demonstrate that the body size of cup corals Balanophyllia elegans has decreased by ~35% over nearly 4 decades (1969-2007), during which seawater temperatures have increased by 0.6°C in the San Juan Islands, Washington State, USA. We developed a modeling framework, based on the Arrhenius equation and temperature-size theory, to explore the thermal dependence of maximum body size. Our models identified the growth rate of corals as a key demographic leverage point for changes in maximum body size, but temperature alone was likely insufficient to cause the observed magnitude of change. Our case study provides a simple template for integrating detailed demographic data with predictions derived from the temperature-size theory, in order to evaluate empirically the magnitude of body size decline in the context of climate warming. KEY WORDS: Balanophyllia elegans · Climate change · Temperature-size rule Full text in pdf format Supplementary material PreviousNextCite this article as: Elahi R, Sebens KP, De Leo GA (2016) Ocean warming and the demography of declines in coral body size. Mar Ecol Prog Ser 560:147-158. https://doi.org/10.3354/meps11931 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 560. Online publication date: November 24, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

The thermal environment of the nest affects body and cell size in the solitary red mason bee (Osmia bicornis L.)

Many ectotherms grow larger at lower temperatures than at higher temperatures. This pattern, known as the temperature-size rule, is often accompanied by plastic changes in cell size, which can mechanistically explain the thermal dependence of body size. However, the theory predicts that thermal plasticity in cell size has adaptive value for ectotherms because there are different optimal cell-membrane-to-cell-volume ratios at different temperatures. At high temperatures, the demand for oxygen is high; therefore, a large membrane surface of small cells is beneficial because it allows high rates of oxygen transport into the cell. The metabolic costs of maintaining membranes become more important at low temperatures than at high temperatures, which favours large cells. In a field experiment, we manipulated the thermal conditions inside nests of the red mason bee, a solitary bee that does not regulate the temperature in its nests and whose larvae develop under ambient conditions. We assessed the effect of temperature on body mass and ommatidia size (our proxy of cell size). The body and cell sizes decreased in response to a higher mean temperature and greater temperature fluctuations. This finding is in accordance with predictions of the temperature-size rule and optimal cell size theory and suggests that both the mean temperature and the magnitude of temperature fluctuations are important for determining body and cell sizes. Additionally, we observed that males of the red mason bee tend to have larger ommatidia in relation to their body mass than females, which might play an important role during mating flight.

Modelling the dynamics of growth, development and lipid storage in the marine copepod Calanus finmarchicus

Mechanistic models are essential tools for interpreting and predicting the consequences of a changing environment and stressors such as pollution on the life histories of marine organisms. Here, we apply the simple and generic energy-budget model DEBkiss to the life history of the marine copepod Calanus finmarchicus. Model modifications were needed to accommodate the copepod life cycle, which deviates in several respects from most other animals (e.g., a sudden stop of growth after the final moult). We identified an acceleration of growth in the early copepodite stages, which could be linked to an increase in the specific feeding rate of the animals. Lipid storage, an essential element of C. finmarchicus biology, was successfully captured with the reproduction buffer of the DEBkiss model. The resulting model was fitted to a detailed data set from the literature and was able to explain growth, development and lipid storage from egg to adult, at different temperatures and food availabilities, within a single consistent framework. The parameterised model could subsequently be used to elucidate the energetic constraints on gonad maturation and reproduction. Interestingly, the overhead costs for egg production seem to be substantially higher than the default value applied in DEB-based studies. The current model provides a solid basis for applications in stress ecology, although our model analysis also identified several knowledge gaps. Specifically, further research is needed to cover the dynamics of diapause and gonad maturation, to explain the dependence of maximum body size on food and temperature, and to verify the predicted high costs for maturity maintenance.

Body size dependency of ovariole number and timing of reproductive maturation in Semanotus japonicus (Coleoptera: Cerambycidae)

ABSTRACTSemanotus japonicus larvae feed on the phloem of living trees of Cryptomeria japonica and Chamaecyparis obtusa, and newly emerged adults stay in xylem from August through the following April when they emerge from the trees. A positive correlation is known between the female body mass and lifetime fecundity in this insect. To determine the timing of maturation in reproductive organs and the relationships of female body size to the total number of ovarioles of a female (ovariole number) and egg production per ovariole, we dissected adults taken from dead trees from October through the following April. Dissecting females showed that well-developed eggs began to appear in the calyx in April, that the ovariole number ranged from 34 to 79, and that the ovariole number per female and egg production per ovariole increased as the female body mass increased, indicating that the body size-dependent lifetime fecundity was attributed to greater ovariole number and greater egg production per ovariole for large females. Dissecting males taken from dead trees and reared on C. obtusa bolts showed that a great deal of sperms were found in testes and seminal vesicles in October and that a long-term exposing to 25°C at a photoperiodic regime of 16-h photophase and 8-h scotophase broke down the testes internally in which sperms disappeared. Body-size dependency of ovariole number was discussed in relation to the adult feeding and phylogeny.

Nonlinear effects of body size and optical attenuation on Diel Vertical Migration by zooplankton

We adopt a trait-based approach to explain Diel Vertical Migration (DVM) across a diverse assemblage of planktonic copepods, utilizing body size as a master trait. We find a reproducible pattern of body size-dependence of day and night depths occupied, and of DVM. Both the smallest surface-dwelling and the largest deeper-dwelling copepods refrain from migrations, while intermediate-sized individuals show pronounced DVM. This pattern apparently arises as a consequence of size-dependent predation risk. In the size classes of migratory copepods the amplitude of DVM is further modulated by optical attenuation in the ocean water column because increased turbidity decreases encounter rates with visually hunting predators. Long-term changes in the ocean optical environment are expected to alter the vertical distributions of many copepods and thus to affect predator-prey encounters as well as oceanic carbon export.

The body size dependence of trophic cascades.

Trophic cascades are indirect positive effects of predators on resources via control of intermediate consumers. Larger-bodied predators appear to induce stronger trophic cascades (a greater rebound of resource density toward carrying capacity), but how this happens is unknown because we lack a clear depiction of how the strength of trophic cascades is determined. Using consumer resource models, we first show that the strength of a trophic cascade has an upper limit set by the interaction strength between the basal trophic group and its consumer and that this limit is approached as the interaction strength between the consumer and its predator increases. We then express the strength of a trophic cascade explicitly in terms of predator body size and use two independent parameter sets to calculate how the strength of a trophic cascade depends on predator size. Both parameter sets predict a positive effect of predator size on the strength of a trophic cascade, driven mostly by the body size dependence of the interaction strength between the first two trophic levels. Our results support previous empirical findings and suggest that the loss of larger predators will have greater consequences on trophic control and biomass structure in food webs than the loss of smaller predators.