Bridging Ecological Stoichiometry and Nutritional Geometry with homeostasis concepts and integrative models of organism nutrition

Riparian plant-soil-microbial C:N:P stoichiometry: are they conserved at plant functional group level?

As a consequence of the tight linkages between plants, soil, and microorganisms, we hypothesized the variations in plant species would change soil and microbial stoichiometry. Here, we examined the plant leaf carbon (C):nitrogen (N):phosphorus (P) ratios of nine species coming from three plant functional groups (PFGs) in the riparian zones of Hulunbuir steppe during near-peak biomass. The soil C:N:P, microbial biomass carbon (MBC):microbial biomass nitrogen (MBN), and extracellular enzyme's C:N:P were also assessed using the soils from each species. We found that plant tissue, soil nutrient, microbial, and enzyme activity stoichiometry significantly differed among different PFGs. Plant leaf and soil nutrient ratios tended to be similar (p > 0.05) between different species within the same PFGs. The variations in leaf C:N:P significantly correlated with the changes in soil C:N:P and MBC:MBN ratios. The homeostatic coefficients (H) < 1 suggested the relationships between plants and their resources C:N:P ratios might be non-homeostatic in the examined riparian zone. By assessing plant tissue and its soil nutrient stoichiometry, this study provided a perspective to understand the linkages of plant community, soil nutrient, and microbial characteristics.

Reverse diversity-biomass patterns in grasslands are constrained by climates and stoichiometry along an elevational gradient

Diversity and biomass play an important role in grassland ecosystem functions. However, diversity and biomass are variable because of their high sensitivity to environmental change in natural ecosystems. How plant diversity, biomass, and driving factors (climates, soils, and plants) in grasslands vary with environmental change remains unclear. We conducted intensive fieldwork (≈1000 km transect) on plant diversity, biomass, and associated drivers (i.e., climates, soils, and plants) to identify the patterns of diversity and biomass along an elevational gradient (50-4000 m) in grasslands of southwest China. Grassland biomass decreased significantly, but grassland diversity increased with increasing elevation. Consequently, a significant reverse pattern between biomass and diversity was detected along an elevational gradient. We also observed that the reverse pattern was primarily driven by the shifts in climates (i.e., temperature and precipitation), leaf stoichiometric traits (i.e., leaf N:P ratio), and soil properties (i.e., soil N content) along the elevational gradient. Our results contradicted previous studies on the positive diversity-biomass relationships, suggesting that previous studies might weaken the effects of climatic factors and plant stoichiometry under environmental change. These findings revealed that the reverse pattern between diversity and biomass in grasslands was shaped by the combined effects (climates, plants, soils) in grasslands, thus providing new insights into the debates and predictions on the diversity and biomass in grasslands under climate change.

Geochemical landscapes as drivers of wildlife reproductive success: Insights from a high-Arctic ecosystem

The bioavailability of essential and non-essential elements in vegetation is expected to influence the performance of free-ranging terrestrial herbivores. However, attempts to relate the use of geochemical landscapes by animal populations directly to reproductive output are currently lacking. Here we measured concentrations of 14 essential and non-essential elements in soil and vegetation samples collected in the Zackenberg valley, northeast Greenland, and linked these to environmental conditions to spatially predict and map geochemical landscapes. We then used long-term (1996-2021) survey data of muskoxen (Ovibos moschatus) to quantify annual variation in the relative use of essential and non-essential elements in vegetated sites and their relationship to calf recruitment the following year. Results showed that the relative use of the geochemical landscape by muskoxen varied substantially between years and differed among elements. Selection for vegetated sites with higher levels of the essential elements N, Cu, Se, and Mo was positively linked to annual calf recruitment. In contrast, selection for vegetated sites with higher concentrations of the non-essential elements As and Pb was negatively correlated to annual calf recruitment. Based on the concentrations measured in our study, we found no apparent associations between annual calf recruitment and levels of C, Mn, Co, Zn, Cd, Ba, Hg, and C:N ratio in the vegetation. We conclude that the spatial distribution and access to essential and non-essential elements are important drivers of reproductive output in muskoxen, which may also apply to other wildlife populations. The value of geochemical landscapes to assess habitat-performance relationships is likely to increase under future environmental change.

Environmental safety of second and third generation bioplastics in the context of the circular economy

Bioplastics derived from organic materials other than crude oil are often suggested as sustainable solutions for tackling end-of-life plastic waste, but little is known of their ecotoxicity to aquatic species. Here, we investigated the ecotoxicity of second and third generation bioplastics toward the freshwater zooplankton Daphnia magna. In acute toxicity tests (48 h), survival was impacted at high concentrations (g.L^-1 range), within the range of salinity-induced toxicity. Macroalgae-derived bioplastic induced hormetic responses under chronic exposure (21 d). Most biological traits were enhanced from 0.06 to 0.25 g.L^-1 (reproduction rate, body length, width, apical spine, protein concentration), while most of these traits returned to controls level at 0.5 g.L^-1. Phenol-oxidase activity, indicative of immune function, was enhanced only at the lowest concentration (0.06 g.L^-1). We hypothesise these suggested health benefits were due to assimilation of carbon derived from the macroalgae-based bioplastic as food. Polymer identity was confirmed by infra-red spectroscopy. Chemical analysis of each bioplastic revealed low metal abundance whilst non target exploration of organic compounds revealed trace amounts of phthalates and flame retardants. The macroalgae-bioplastic disintegrated completely in compost and biodegraded up to 86 % in aqueous medium. All bioplastics acidified the test medium. In conclusion, the tested bioplastics were classified as environmentally safe. Nonetheless, a reasonable end-of-life management of these safer-by-design materials is advised to ensure the absence of harmful effects at high concentrations, depending on the receiving environment.

Biosynthetic constraints on amino acid synthesis at the base of the food chain may determine their use in higher-order consumer genomes

Dietary nutrient composition is essential for shaping important fitness traits and behaviours. Many organisms are protein limited, and for Drosophila melanogaster this limitation manifests at the level of the single most limiting essential Amino Acid (AA) in the diet. The identity of this AA and its effects on female fecundity is readily predictable by a procedure called exome matching in which the sum of AAs encoded by a consumer's exome is used to predict the relative proportion of AAs required in its diet. However, the exome matching calculation does not weight AA contributions to the overall profile by protein size or expression. Here, we update the exome matching calculation to include these weightings. Surprisingly, although nearly half of the transcriptome is differentially expressed when comparing male and female flies, we found that creating transcriptome-weighted exome matched diets for each sex did not enhance their fecundity over that supported by exome matching alone. These data indicate that while organisms may require different amounts of dietary protein across conditions, the relative proportion of the constituent AAs remains constant. Interestingly, we also found that exome matched AA profiles are generally conserved across taxa and that the composition of these profiles might be explained by energetic and elemental limitations on microbial AA synthesis. Thus, it appears that ecological constraints amongst autotrophs shape the relative proportion of AAs that are available across trophic levels and that this constrains biomass composition.

In defense of elemental currencies: can ecological stoichiometry stand as a framework for terrestrial herbivore nutritional ecology?

Nutritional ecologists aim to predict population or landscape-level effects of food availability, but the tools to extrapolate nutrition from small to large extents are often lacking. The appropriate nutritional ecology currencies should be able to represent consumer responses to food while simultaneously be simple enough to expand such responses to large spatial extents and link them to ecosystem functioning. Ecological stoichiometry (ES), a framework of nutritional ecology, can meet these demands, but it is typically associated with ecosystem ecology and nutrient cycling, and less often used to study wildlife nutrition. Despite the emerging zoogeochemical evidence that animals, and thus their diets, play critical roles in nutrient movement, wildlife nutritional ecology has not fully embraced ES, and ES has not incorporated nutrition in many wildlife studies. Here, we discuss how elemental currencies are "nutritionally, organismally, and ecologically explicit" in the context of terrestrial herbivore nutritional ecology. We add that ES and elemental currencies offer a means to measure resource quality across landscapes and compare nutrient availability among regions. Further, we discuss ES shortcomings and solutions, and list future directions to advance the field. As ecological studies increasingly grow in spatial extent, and attempt to link multiple levels of biological organization, integrating more simple and unifying currencies into nutritional studies, like elements, is necessary for nutritional ecology to predict herbivore occurrences and abundances across regions.

Effect of queen number on colony-level nutrient regulation, food collection and performance in two polygynous ant species

There is growing appreciation for how social interactions influence animal foraging behavior, especially with respect to key nutrients. Ants, given their eusocial nature and ability to be reared and manipulated in the laboratory, offer unique opportunities to explore how social interactions influence nutrient regulation and related processes. At the colony-level, ants simultaneously regulate their protein and carbohydrate intake; a regulation tied to the presence of larvae. However, even though 45% of the approximately 10,000 ant species are polygynous, we know little about the influence of queen number on colony-level foraging behavior and performance. Here we explored the direct effects of queen number on colony-level protein-carbohydrate regulation, food collection, survival, and brood production in two polygynous ant species (Nylanderia fulva and Solenopsis invicta). For both species we conducted choice and no-choice experiments using small experimental colonoids (20 workers) with 0, 1, or 2 queens. Both species regulated their relative intake of protein and carbohydrate around a P1:C2 mark. However, only N. fulva responded to the addition of queens, increasing overall food collection, biasing intake towards carbohydrates, and over-collecting imbalanced foods. N. fulva also exhibited reduced survival and reproduction on protein-biased foods. In contrast, S. invicta showed no response to queen number and reduced food collection on the protein-biased diet while maintaining high survival and reproduction. Our results demonstrate the potential for queens of some ant species to impact colony-level foraging and performance, with interspecific variation likely being shaped by differences in life history traits.

Deforestation for Agriculture Temporarily Improved Soil Quality and Soil Organic Carbon Stocks

Deforestation for agricultural development or extension is a common land-use problem that may cause a series of changes in the ecological environment and soil carbon stock in planting systems. However, the response of soil physical, chemical properties and carbon stocks in agricultural systems in the initial period after deforestation have not been thoroughly examined, especially in the subsoil. We investigated the variations in the soil physicochemical properties and organic carbon stocks to a depth of 100 cm in a poplar (Populus deltoides cv. 35) plantation, a summer maize (Zea mays L.) followed by winter wheat (Triticum aestivum L.) field after 1 year of deforestation of a poplar plantation, and a wheat–maize rotation field used for decades. The soil bulk density and pH decreased, and the soil total nitrogen (TN), total phosphorus, and total potassium contents increased considerably. The soil organic carbon (SOC) content and stocks (to 100 cm) increased by 32.8% and 20.1%, respectively. The soil TN content was significantly (p < 0.001) positively correlated with the SOC content, and the C:N ratio increased for the field following deforestation. Furthermore, the nitrogen in the poplar plantation and the field following deforestation was limited. We recommend increasing the amount of nitrogen fertilizer following deforestation to improve fertility and this will be beneficial to SOC storage.

Critical links between biodiversity and health in wild bee conservation

Wild bee populations are declining due to human activities, such as land use change, which strongly affect the composition and diversity of available plants and food sources. The chemical composition of food (i.e., nutrition) in turn determines the health, resilience, and fitness of bees. For pollinators, however, the term 'health' is recent and is subject to debate, as is the interaction between nutrition and wild bee health. We define bee health as a multidimensional concept in a novel integrative framework linking bee biological traits (physiology, stoichiometry, and disease) and environmental factors (floral diversity and nutritional landscapes). Linking information on tolerated nutritional niches and health in different bee species will allow us to better predict their distribution and responses to environmental change, and thus support wild pollinator conservation.

Distinguishing Stoichiometric Homeostasis of Soil Microbial Biomass in Alpine Grassland Ecosystems: Evidence From 5,000 km Belt Transect Across Qinghai-Tibet Plateau

The biogeographic characteristics of soil microbial biomass stoichiometry homeostasis and also its mechanisms are commonly thought to be key factors for the survival strategies and resource utilization of soil microbes under extreme habitat. In this work, we conducted a 5,000-km transect filed survey in alpine grassland across Qinghai-Tibet Plateau in 2015 to measure soil microbial biomass carbon (MBC) and nitrogen (MBN) across alpine steppe and meadow. Based on the differences of climate and soil conditions between alpine steppe and meadow, the variation coefficient was calculated to investigate the homeostatic degree of MBC to MBN. Furthermore, the "trade-off" model was utilized to deeply distinguish the homeostasis degree of MBC/MBN between alpine steppe and meadow, and the regression analysis was used to explore the variability of trade-off in response to environmental factors in the alpine grassland. The results showed that the coefficient of variation (CV) of MBC/MBN in alpine meadow (CV = 0.4) was lower than alpine steppe (CV = 0.7). According to the trade-off model, microbial turnover activity of soil N relative to soil C increased rapidly and then decreased slightly with soil organic carbon (SOC), soil total nitrogen (STN), and soil water content across alpine meadow. Nevertheless, in alpine steppe, SOC/STN had a positive effect on microbial turnover of soil N. These results suggested that water, heat, and soil nutrients availability were the key factors affecting the C:N stoichiometry homeostasis of soil microbial biomass in Qinghai-Tibet Plateau (QTP)'s alpine grassland. Since the difference of survival strategy of the trade-off demands between soil C and N resulting in different patterns and mechanism, the stoichiometry homeostasis of soil microbial biomass was more stable in alpine meadow than in alpine steppe.

Integrating plant stoichiometry and feeding experiments: state-dependent forage choice and its implications on body mass

Intraspecific feeding choices comprise a large portion of herbivore foraging decisions. Plant resource quality is heterogeneously distributed, affected by nutrient availability and growing conditions. Herbivores navigate landscapes, foraging not only according to food qualities, but also energetic and nutritional demands. We test three non-exclusive foraging hypotheses using the snowshoe hare (Lepus americanus): (1) herbivore feeding choices and body conditions respond to intraspecific plant quality variation; (2) high energetic demands mitigate feeding responses; and (3) feeding responses are inflated when nutritional demands are high. We measured black spruce (Picea mariana) nitrogen, phosphorus and terpene compositions, as indicators of quality, within a snowshoe hare trapping grid and found plant growing conditions to explain spruce quality variation (R² < 0.36). We then offered two qualities of spruce (H1) from the trapping grid to hares in cafeteria-style experiments and measured their feeding and body condition responses (n = 75). We proxied energetic demands (H2) with ambient temperature and coat insulation (% white coat) and nutritional demands (H3) with the spruce quality (nitrogen and phosphorus content) in home ranges. Hares with the strongest preference for high-quality spruce lost on average 2.2% less weight than hares who ate the least high-quality spruce relative to low-quality spruce. The results supported our energetic predictions as follows: hares in colder temperatures and with less-insulative coats (lower % white) consumed more spruce and were less selective towards high-quality spruce. Collectively, we found variation in plant growing conditions within herbivore home ranges substantial enough to affect herbivore body conditions, but energetic stats mediate plant-herbivore interactions.

Responses of Ecological Stoichiometric Characteristics of Carbon, Nitrogen, and Phosphorus to Periodic Submergence in Mega-Reservoir: Growth of Taxodium distichum and Taxodium ascendens

Ecological stoichiometric studies can be useful for managing the deteriorated riparian zones of mega-reservoirs in which nutrients significantly impact the balanced vegetation cover. The present study aims to explore the effects of periodic submergence on the stoichiometric ecological characteristics of carbon (C), nitrogen (N), and phosphorus (P), as well as the growth conditions of two leading conifer species (Taxodium distichum and Taxodium ascendens) in the hydro-fluctuation zone of the Three Gorges Reservoir (TGR) region, China. The stoichiometrical contents of C, N, and P in fine roots, leaves, and branches, and the growth conditions of T. distichum and T. ascendens were measured in July 2019. The results showed that periodic submergence affected the stoichiometric characteristics and growth conditions of these two woody species, and the impact was restrained, but both grew well. The effects of inundation on the C, N, and P ecological stoichiometric characteristics differed in different parts of trees. In general, the C contents showed the following pattern: leaves > branches > fine roots. The N and P content showed the following pattern: leaves > fine roots > branches, while the C/N and C/P ratios showed an opposite trend to that of N and P. The N and P content in all parts of T. distichum (with means of 17.18 and 1.70 g/kg for leaves, 4.80 and 0.57 g/kg for branches, and 6.88 and 1.10 g/kg for fine roots, respectively) and T. ascendens (with means of 14.56 and 1.87 g/kg for leaves, 5.03 and 0.63 g/kg for branches, and 8.17 and 1.66 g/kg for fine roots, respectively) were higher than the national average level (with means of 14.14 and 1.11 g/kg for leaves, 3.04 and 0.31 g/kg for branches, and 4.85 and 0.47 g/kg for fine roots, respectively). Except for N and P contents in the leaves of T. distichum, there was a significant correlation between N and P elements in other parts (p < 0.05). Nevertheless, the N/P ratio (10.15, 8.52, 6.44, and 7.93, 8.12, 5.20 in leaves, branches, and fine roots of T. distichum and T. ascendens, respectively) was lower than the critical ratio of 14. The growth conditions of T. distichum and T. ascendens were significantly negatively correlated with their leaf C contents and significantly positively correlated with their fine root N and P contents. This study showed that T. distichum and T. ascendens could maintain their normal growth needs by properly allocating nutrients between different organs to adapt to the long periodic submergence in the hydro-fluctuation zone of the TGR region.

Quantifying the energetic cost of food quality constraints on resting metabolism to integrate nutritional and metabolic ecology

Consumer metabolism controls the energy uptake from the environment and its allocation to biomass production. In natural ecosystems, available energy in food often fails to predict biomass production which is also (co)limited by the relative availability of various dietary compounds. To date, the link between energy metabolism and the effects of food chemical composition on biomass production remains elusive. Here, we measured the resting metabolic rate (RMR) of Daphnia magna along ontogeny when undergoing various (non-energetic) nutritional constraints. All types of dietary (co)limitations (Fatty acids, Sterols, Phosphorus) induced an increase in mass-specific RMR up to 128% between highest and lowest quality diets. We highlight a strong negative correlation between RMR and growth rate indicating RMR as a promising predictor of consumer growth rate. We argue that quantifying the energetic cost imposed by food quality on individual RMR may constitute a common currency enabling the integration of nutritional and metabolic ecology.

Transcriptomic response of Daphnia magna to nitrogen- or phosphorus-limited diet

Effects of nutrient-imbalanced diet on the growth and fitness of zooplankton were widely reported as key issues to aquatic ecology. However, little is known about the molecular mechanisms driving the physiological changes of zooplankton under nutrient stress.In this study, we investigated the physiological fitness and transcriptomic response of Daphnia magna when exposed to nitrogen (N)-limited or phosphorus (P)-limited algal diet (Chlamydomonas reinhardtii) compared to regular algae (N and P saturated).D. magna showed higher ingestion rates and overexpression of genes encoding digestive enzymes when fed with either N-limited or P-limited algae, reflecting the compensatory feeding. Under P-limitation, both growth rate and reproduction rate of D. magna were greatly reduced, which could be attributed to the downregulated genes within the pathways of cell cycle and DNA replication. Growth rate of D. magna under N-limitation was similar to normal group, which could be explained by the high methylation level (by degradation of methionine) supporting the body development.Phenotypic changes of D. magna under nutrient stress were explained by gene and pathway regulations from transcriptome data. Generally, D. magna invested more on growth under N-limitation but kept maintenance (e.g., cell structure and defense to external stress) in priority under P-limitation. Post-translational modifications (e.g., methylation and protein folding) were important for D. magna to deal with nutrient constrains.This study reveals the fundamental mechanisms of zooplankton in dealing with elemental imbalanced diet and sheds light on the transfer of energy and nutrient in aquatic ecosystems.

Understanding the evolution of nutritive taste in animals: Insights from biological stoichiometry and nutritional geometry

A major conceptual gap in taste biology is the lack of a general framework for understanding the evolution of different taste modalities among animal species. We turn to two complementary nutritional frameworks, biological stoichiometry theory and nutritional geometry, to develop hypotheses for the evolution of different taste modalities in animals. We describe how the attractive tastes of Na-, Ca-, P-, N-, and C-containing compounds are consistent with principles of both frameworks based on their shared focus on nutritional imbalances and consumer homeostasis. Specifically, we suggest that the evolution of multiple nutritive taste modalities can be predicted by identifying individual elements that are typically more concentrated in the tissues of animals than plants. Additionally, we discuss how consumer homeostasis can inform our understanding of why some taste compounds (i.e., Na, Ca, and P salts) can be either attractive or aversive depending on concentration. We also discuss how these complementary frameworks can help to explain the evolutionary history of different taste modalities and improve our understanding of the mechanisms that lead to loss of taste capabilities in some animal lineages. The ideas presented here will stimulate research that bridges the fields of evolutionary biology, sensory biology, and ecology.

Local flexibility in feeding behaviour and contrasting microhabitat use of an omnivore across latitudes

As the environment is getting warmer and species are redistributed, consumers can be forced to adjust their interactions with available prey, and this could have cascading effects within food webs. To better understand the capacity for foraging flexibility, our study aimed to determine the diet variability of an ectotherm omnivore inhabiting kelp forests, the sea urchin Echinus esculentus, along its entire latitudinal distribution in the northeast Atlantic. Using a combination of gut content and stable isotope analyses, we determined the diet and trophic position of sea urchins at sites in Portugal (42° N), France (49° N), southern Norway (63° N), and northern Norway (70° N), and related these results to the local abundance and distribution of putative food items. With mean estimated trophic levels ranging from 2.4 to 4.6, omnivory and diet varied substantially within and between sites but not across latitudes. Diet composition generally reflected prey availability within epiphyte or understorey assemblages, with local affinities demonstrating that the sea urchin adjusts its foraging to match the small-scale distribution of food items. A net "preference" for epiphytic food sources was found in northern Norway, where understorey food was limited compared to other regions. We conclude that diet change may occur in response to food source redistribution at multiple spatial scales (microhabitats, sites, regions). Across these scales, the way that key consumers alter their foraging in response to food availability can have important implication for food web dynamics and ecosystem functions along current and future environmental gradients.

Dietary-based developmental plasticity affects juvenile survival in an aquatic detritivore

Developmental plasticity is ubiquitous in natural populations, but the underlying causes and fitness consequences are poorly understood. For consumers, nutritional variation of juvenile diets is probably associated with plasticity in developmental rates, but little is known about how diet quality can affect phenotypic trajectories in ways that might influence survival to maturity and lifetime reproductive output. Here, we tested how the diet quality of a freshwater detritivorous isopod (Asellus aquaticus), in terms of elemental ratios of diet (i.e. carbon : nitrogen : phosphorus; C : N : P), can affect (i) developmental rates of body size and pigmentation and (ii) variation in juvenile survival. We reared 1047 individuals, in a full-sib split-family design (29 families), on either a high- (low C : P, C : N) or low-quality (high C : P, C : N) diet, and quantified developmental trajectories of body size and pigmentation for every individual over 12 weeks. Our diet contrast caused strong divergence in the developmental rates of pigmentation but not growth, culminating in a distribution of adult pigmentation spanning the broad range of phenotypes observed both within and among natural populations. Under low-quality diet, we found highest survival at intermediate growth and pigmentation rates. By contrast, survival under high-quality diet survival increased continuously with pigmentation rate, with longest lifespans at intermediate growth rates and high pigmentation rates. Building on previous work which suggests that visual predation mediates the evolution of cryptic pigmentation in A. aquaticus, our study shows how diet quality and composition can generate substantial phenotypic variation by affecting rates of growth and pigmentation during development in the absence of predation.

Effects of grazing on C:N:P stoichiometry attenuate from soils to plants and insect herbivores in a semi-arid grassland

Understanding the processing of limiting nutrients among organisms is an important goal of community ecology. Less known is how human disturbances may alter the stoichiometric patterns among organisms from different trophic levels within communities. Here, we investigated how livestock grazing affects the C:N:P ecological stoichiometry of soils, plants (Leymus chinensis), and grasshoppers (Euchorthippus spp.) in a semi-arid grassland in northeastern China. We found that grazing significantly enhanced soil available N and leaf N content of the dominant L. chinensis grass by 15% and 20%, respectively. Grazing also reduced (soluble) C:N of L. chinensis leaves by 22%. However, grazing did not affect total C, N, or P contents nor their ratios in Euchorthippus grasshoppers. Our results reveal that the effects of grazing disturbances on elemental composition attenuated from lower to higher trophic levels. These findings support the theory that organisms from higher trophic levels have relatively stronger stoichiometric homeostasis compared to those from lower trophic levels. Moreover, grasshopper abundance dropped by 66% in the grazed areas, and they reduced the feeding time on their host L. chinensis grass by 43%, presumably to limit the intake of excess nitrogen from host plants. The energetic costs associated with the maintenance of elemental homeostasis likely reduced grasshopper individual performance and population abundance in the grazed areas. A comprehensive investigation of stoichiometric properties of organisms across trophic levels may enable a better understanding of the nature of species interactions, and facilitate predictions of the consequences of future environmental changes for a community organization.

Stoichiometric Ecotoxicology for a Multisubstance World

Nutritional and contaminant stressors influence organismal physiology, trophic interactions, community structure, and ecosystem-level processes; however, the interactions between toxicity and elemental imbalance in food resources have been examined in only a few ecotoxicity studies. Integrating well-developed ecological theories that cross all levels of biological organization can enhance our understanding of ecotoxicology. In the present article, we underline the opportunity to couple concepts and approaches used in the theory of ecological stoichiometry (ES) to ask ecotoxicological questions and introduce stoichiometric ecotoxicology, a subfield in ecology that examines how contaminant stress, nutrient supply, and elemental constraints interact throughout all levels of biological organization. This conceptual framework unifying ecotoxicology with ES offers potential for both empirical and theoretical studies to deepen our mechanistic understanding of the adverse outcomes of chemicals across ecological scales and improve the predictive powers of ecotoxicology.

Stoichiometric niche, nutrient partitioning and resource allocation in a solitary bee are sex-specific and phosphorous is allocated mainly to the cocoon

Life histories of species may be shaped by nutritional limitations posed on populations. Yet, populations contain individuals that differ according to sex and life stage, each of which having different nutritional demands and experiencing specific limitations. We studied patterns of resource assimilation, allocation and excretion during the growth of the solitary bee Osmia bicornis (two sexes) under natural conditions. Adopting an ecological perspective, we assert that organisms ingest mutable organic molecules that are transformed during physiological processes and that the immutable atoms of the chemical elements composing these molecules may be allocated to specific functions, thereby influencing organismal fitness and life history. Therefore, using the framework of ecological stoichiometry, we investigated the multielemental (C, N, S, P, K, Na, Ca, Mg, Fe, Zn, Mn, Cu) compositions of six components of the bee elemental budget: food (pollen), eggs, pupae, adults, cocoons and excreta. The sexes differed fundamentally in the assimilation and allocation of acquired atoms, elemental phenotypes, and stoichiometric niches for all six components. Phosphorus, which supports larval growth, was allocated mainly (55-75%) to the cocoon after larval development was complete. Additionally, the majority (60-99%) of the Mn, Ca, Mg and Zn acquired during larval development was allocated to the cocoon, probably influencing bee fitness by conferring protection. We conclude that for holometabolous insects, considering only the chemical composition of the adult body within the context of nutritional ecology does not provide a complete picture. Low ratios of C to other nutrients, low N:P and high Na concentrations in excreta and cocoons may be important for local-scale nutrient cycling. Limited access to specific nutritional elements may hinder bee development in a sex-dependent manner, and N and P limitations, commonly considered elsewhere, may not play important roles in O. bicornis. Sexual dimorphism in nutritional limitations due to nutrient scarcity during the larval stage may influence bee population function and should be considered in bee conservation efforts.

What is the status of metabolic theory one century after Pütter invented the von Bertalanffy growth curve?

Metabolic theory aims to tackle ecological and evolutionary problems by explicitly including physical principles of energy and mass exchange, thereby increasing generality and deductive power. Individual growth models (IGMs) are the fundamental basis of metabolic theory because they represent the organisational level at which energy and mass exchange processes are most tightly integrated and from which scaling patterns emerge. Unfortunately, IGMs remain a topic of great confusion and controversy about the origins of the ideas, their domain and breadth of application, their logical consistency and whether they can sufficiently capture reality. It is now 100 years since the first theoretical model of individual growth was put forward by Pütter. His insights were deep, but his model ended up being attributed to von Bertalanffy and his ideas largely forgotten. Here I review Pütter's ideas and trace their influence on existing theoretical models for growth and other aspects of metabolism, including those of von Bertalanffy, the Dynamic Energy Budget (DEB) theory, the Gill-Oxygen Limitation Theory (GOLT) and the Ontogenetic Growth Model (OGM). I show that the von Bertalanffy and GOLT models are minor modifications of Pütter's original model. I then synthesise, compare and critique the ideas of the two most-developed theories, DEB theory and the OGM, in relation to Pütter's original ideas. I formulate the Pütter, DEB and OGM models in the same structure and with the same notation to illustrate the major similarities and differences among them. I trace the confusion and controversy regarding these theories to the notions of anabolism, catabolism, assimilation and maintenance, the connections to respiration rate, and the number of parameters and state variables their models require. The OGM model has significant inconsistencies that stem from the interpretation of growth as the difference between anabolism and maintenance, and these issues seriously challenge its ability to incorporate development, reproduction and assimilation. The DEB theory is a direct extension of Pütter's ideas but with growth being the difference between assimilation and maintenance rather than anabolism and catabolism. The DEB theory makes the dynamics of Pütter's 'nutritive material' explicit as well as extending the scheme to include reproduction and development. I discuss how these three major theories for individual growth have been used to explain 'macrometabolic' patterns including the scaling of respiration, the temperature-size rule (first modelled by Pütter), and the connection to life history. Future research on the connections between theory and data in these macrometabolic topics have the greatest potential to advance the status of metabolic theory and its value for pure and applied problems in ecology and evolution.

Nutritional niches reveal fundamental domestication trade-offs in fungus-farming ants

During crop domestication, human farmers traded greater productivity for higher crop vulnerability outside specialized cultivation conditions. We found a similar domestication tradeoff across the major co-evolutionary transitions in farming systems of attine ants. First, the fundamental nutritional niches (FNNs) of cultivars narrowed during ~ 60 million years of naturally selected domestication, and laboratory experiments showed that ant farmers representing subsequent domestication stages strictly regulate protein harvest relative to cultivar FNNs. Second, ants with different farming systems differed in their abilities to harvest the resources that best matched the nutritional needs of their fungal cultivars. This was assessed by quantifying realized nutritional niches (RNNs) from analyses of items collected from the mandibles of laden ant foragers in the field. Third, extensive field collections suggest that among-colony genetic diversity of cultivars in small-scale farms may offer population-wide resilience benefits that species with large-scale farming colonies achieve by more elaborate and demanding cultivation practices of less diverse crops. Our results underscore that naturally selected farming systems have potential to shed light on nutritional tradeoffs that shaped the course of culturally evolved human farming.

Ecological stoichiometric characteristics of Carbon (C), Nitrogen (N) and Phosphorus (P) in leaf, root, stem, and soil in four wetland plants communities in Shengjin Lake, China

Ecological stoichiometric should be incorporated into management and nutrient impacted ecosystems dynamic to understand the status of ecosystems and ecological interaction. The present study focused on ecological stoichiometric characteristics of soil, and leaves, stems, and roots of different macrophytes after the banning of seine fishing in Shengjin Lake. For C, N, and P analysis from leaves, stems, roots, and soil to explore their stoichiometric ratio and deriving environmental forces, four dominant plant communities (Vallisneria natans, Zizania latifolia, Trapa natans and Carex schmidtii) were collected. The concentration of C, N, P and C: N: P ratio in leaves, stems, roots, and soil among the plant communities varied significantly. Along the depth gradient high C: N was measured in C.schmidtii soil (7.08±1.504) but not vary significantly (P >0.05). High C: P result was found in T.natans (81.14±43.88) and in V.natans soil (81.40±42.57) respectively with no significant difference (p>0.05). Besides, N: P ratio measured high in V. natans (13.7±4.05) and showed significant variation (P<0.05). High leaf C: N and N: P ratio was measured in C. schmidtii and V. natans respectively. Nevertheless, high leaf C: P ratio was measured in Z. latifolia. From the three studied organs, leaf C: N and N: P ratio showed high values compared to root and stems. The correlation analysis result showed that at 0-10cm depth soil organic carbon (SOC) correlated negatively with stem total phosphorus (STP), and root total nitrogen (RTN) (P<0.05) but positively strongly with leaf total phosphorus (LTP) and leaf total nitrogen (LTN) (P<0.01) respectively. Soil total nitrogen (STN) at 0-10cm strongly positively correlated with leaf total phosphorus (LTP) (P<0.01) and positively with RN: P and leaf total carbon (LTC) (P<0.05). Soil basic properties such as soil moisture content (SMC), bulky density (BD) and pH positively correlated with soil ecological stoichiometric characteristics. Redundancy analysis (RDA) result showed available nitrogen (AN), soil total nitrogen (STN), and available phosphorus (AP) were the potential determinants variables on plants stoichiometric characteristics.

Multielemental Stoichiometry in Plant Organs: A Case Study With the Alpine Herb Gentiana rigescens Across Southwest China

Multiple elements are required to be allocated to different organs to meet the demands for plant growth, reproduction, and maintenance. However, our knowledge remains limited on the stoichiometry in all plant organs in response to heterogeneous environments. Here, we present the systematic investigation of multielemental stoichiometry in organs of the alpine plant Gentiana rigescens across different environmental conditions. The slopes of N-P stoichiometric relationships among organs in G. rigescens did not differ significantly between environments even in flowers, the most active organ with the highest N and P level. C:P ratios had strong positive relationships with N:P ratios within and between organs. Zn had strong positive correlations with Fe, S, or Cu in each organ, indicating the potential interactions among the homeostases of these elements. The contents of macroelements, such as C, N, P, Ca, Mg, and S, were higher in plant organs than those in soil and exhibited a relatively narrow range in plant organs. However, G. rigescens reduced Fe uptake from soil and showed the strictest homeostasis in its root, implying its resistance to excess Fe. Furthermore, precipitation and temperature associated with geography, followed by soil P, were the main divers for the multielemental stoichiometry in this species. Plant stoichiometry responded differently to abiotic environmental factors, depending on organ type and element. N:P ratio, no matter in which organ, showed little flexibility to climate factors. The results have implications for understanding the regulation of multielemental stoichiometry in plant individuals to environmental changes. Further studies are needed on the interactions of multielement homeostasis in plants.

Diet composition and social environment determine food consumption, phenotype and fecundity in an omnivorous insect

Nutrition is the single most important factor for individual's growth and reproduction. Consequently, the inability to reach the nutritional optimum imposes severe consequences for animal fitness. Yet, under natural conditions, organisms may face a mixture of stressors that can modulate the effects of nutritional asymmetry. For instance, stressful environments caused by intense interaction with conspecifics. Here, we subjected the house cricket Acheta domesticus to (i) either of two types of diet that have proved to affect cricket performance and (ii) simultaneously manipulated their social environment throughout their complete life cycle. We aimed to track sex-specific consequences for multiple traits during insect development throughout all life stages. Both factors affected critical life-history traits with potential population-level consequences: diet composition induced strong effects on insect development time, lifespan and fitness, while the social environment affected the number of nymphs that completed development, food consumption and whole-body lipid content. Additionally, both factors interactively determined female body mass. Our results highlight that insects may acquire and invest resources in a different manner when subjected to an intense interaction with conspecifics or when isolated. Furthermore, while only diet composition affected individual reproductive output, the social environment would determine the number of reproductive females, thus indirectly influencing population performance.

Dynamics of soil microbial C:N:P stoichiometry and its driving mechanisms following natural vegetation restoration after farmland abandonment

Vegetation restoration after farmland abandonment has increased greatly and is commonly used to improve soil fertility and ecosystem service. Knowledge of soil community-level elemental homeostasis following natural vegetation restoration is specially limited for the abandoned farmlands. This study examined the changes in soil microbial biomass stoichiometry and homeostasis with a chronosequence of 3, 8, 13, 18, 23 and 30 years following natural vegetation restoration since farmland abandonment on the Loess Plateau, China. Vegetation communities, soil properties, microbial communities, and enzyme activities were analyzed to study the drivers on soil microbial C:N:P stoichiometry. The results showed that soil microbial biomass C: N ratios had little change following natural vegetation restoration since farmland abandonment, natural vegetation >23 years had significantly enhanced the microbial biomass C:P and N:P ratios by 26.1%-133.9% and 31.7%-67.4%, respectively. However, microbial biomass C:N, C:P and N:P ratios were constrained following natural vegetation restoration. Vegetation restoration for 30 years enhanced urease and alkaline phosphatase activities by 125.4% and 42.9%, respectively, which showed synchronous changes with N and P contents in microbial biomass. Soil fungi, urease and alkaline phosphatase were the drivers to the changes in microbial C:N:P stoichiometry. The results suggest that long-term vegetation restoration (>23 years) will aggravate microbial P limitation, however, soil microorganism maintained the homeostatic regulation of stoichiometric ratios to mitigate P limitation. Fungi played a strong role in shaping microbial community-level elemental homeostasis and nutrient cycling through releasing N-converting and P-converting enzymes into soil following natural vegetation restoration.

Predicting population responses to environmental change from individual-level mechanisms: towards a standardized mechanistic approach

Animal populations will mediate the response of global biodiversity to environmental changes. Population models are thus important tools for both understanding and predicting animal responses to uncertain future conditions. Most approaches, however, are correlative and ignore the individual-level mechanisms that give rise to population dynamics. Here, we assess several existing population modelling approaches and find limitations to both 'correlative' and 'mechanistic' models. We advocate the need for a standardized mechanistic approach for linking individual mechanisms (physiology, behaviour, and evolution) to population dynamics in spatially explicit landscapes. Such an approach is potentially more flexible and informative than current population models. Key to realizing this goal, however, is overcoming current data limitations, the development and testing of eco-evolutionary theory to represent interactions between individual mechanisms, and standardized multi-dimensional environmental change scenarios which incorporate multiple stressors. Such progress is essential in supporting environmental decisions in uncertain future conditions.

Using nutritional geometry to define the fundamental macronutrient niche of the widespread invasive ant Monomorium pharaonis

The emerging field of nutritional geometry (NG) provides powerful new approaches to test whether and how organisms prioritize specific nutritional blends when consuming chemically complex foods. NG approaches can thus help move beyond food-level estimates of diet breadth to predict invasive success, for instance by revealing narrow nutritional niches if broad diets are actually composed of nutritionally similar foods. We used two NG paradigms to provide different, but complementary insights into nutrient regulation strategies and test a hypothesis of extreme nutritional generalism in colony propagules of the globally distributed invasive ant Monomorium pharaonis. First, in two dimensions (protein:carbohydrates; P:C), M. pharaonis colonies consistently defended a slightly carbohydrate-biased intake target, while using a generalist equal-distance strategy of collectively overharvesting both protein and carbohydrates to reach this target when confined to imbalanced P:C diets. Second, a recently developed right-angled mixture triangle method enabled us to define the fundamental niche breadth in three dimensions (protein:carbohydrates:lipid, P:C:L). We found that colonies navigated the P:C:L landscape, in part, to mediate a tradeoff between worker survival (maximized on high-carbohydrate diets) and brood production (maximized on high-protein diets). Colonies further appeared unable to avoid this tradeoff by consuming extra lipids when the other nutrients were limiting. Colonies also did not rely on nutrient regulation inside their nests, as they did not hoard or scatter fractions of harvested diets to adjust the nutritional blends they consumed. These complementary NG approaches highlight that even the most successful invasive species with broad fundamental macronutrient niches must navigate complex multidimensional nutritional landscapes to acquire limiting macronutrients and overcome developmental constraints as small propagules.

Interspecific homeostatic regulation and growth across aquatic invertebrate detritivores: a test of ecological stoichiometry theory

Across resource quality gradients, primary consumers must regulate homeostasis and release of nutrients to optimize growth and fitness. Based primarily on internal body composition, the ecological stoichiometry theory (EST) offers a framework to generalize interspecific patterns of these responses, yet the predictions and underlying assumptions of EST remain poorly tested across many species. We used controlled laboratory feeding experiments to measure homeostasis, nutrient release, and growth across seven field-collected aquatic invertebrate detritivore taxa fed wide resource carbon:nitrogen (C:N) and carbon:phosphorus (C:P) gradients. We found that most invertebrates exhibited strict stoichiometric homeostasis (average 1/H = - 0.018 and 0.026 for C:N and C:P, respectively), supporting assumptions of EST. However, the stoichiometry of new tissue production during growth intervals (growth stoichiometry) deviated - 30 to + 54% and - 145 to + 74% from initial body C:N and C:P, respectively, and across species, growth stoichiometry was not correlated with initial body stoichiometry. Notably, smaller non- and hemimetabolous invertebrates exhibited low, decreasing growth C:N and C:P, whereas larger holometabolous invertebrates exhibited high, often increasing growth C:N and C:P. Despite predictions of EST, interspecific sensitivity of egestion stoichiometry and growth rates to the resource gradient were weakly related to internal body composition across species. While the sensitivity of these patterns differed across taxa, such differences carried a weak phylogenetic signal and were not well predicted by EST. Our findings suggest that traits beyond internal body composition, such as feeding behavior, selective assimilation, and ontogeny, are needed to generalize interspecific patterns in consumer growth and nutrient release across resource quality gradients.

Ecological Stoichiometry: A Link Between Developmental Speed and Physiological Stress in an Omnivorous Insect

The elemental composition of organisms belongs to a suite of functional traits that may adaptively respond to fluctuating selection pressures. Life history theory predicts that predation risk and resource limitations impose selection pressures on organisms’ developmental time and are further associated with variability in energetic and behavioral traits. Individual differences in developmental speed, behaviors and physiology have been explained using the pace-of-life syndrome (POLS) hypothesis. However, how an organism’s developmental speed is linked with elemental body composition, metabolism and behavior is not well understood. We compared elemental body composition, latency to resume activity and resting metabolic rate (RMR) of western stutter-trilling crickets (Gryllus integer) in three selection lines that differ in developmental speed. We found that slowly developing crickets had significantly higher body carbon, lower body nitrogen and higher carbon-to-nitrogen ratio than rapidly developing crickets. Slowly developing crickets had significantly higher RMR than rapidly developing crickets. Male crickets had higher RMR than females. Slowly developing crickets resumed activity faster in an unfamiliar relative to a familiar environment. The rapidly developing crickets did the opposite. The results highlight the tight association between life history, physiology and behavior. This study indicates that traditional methods used in POLS research should be complemented by those used in ecological stoichiometry, resulting in a synthetic approach that potentially advances the whole field of behavioral and physiological ecology.

Consumption explains intraspecific variation in nutrient recycling stoichiometry in a desert fish

Consumer-driven nutrient recycling can have substantial effects on primary production and patterns of nutrient limitation in aquatic ecosystems by altering the rates as well as the relative supplies of the key nutrients nitrogen (N) and phosphorus (P). While variation in nutrient recycling stoichiometry has been well-studied among species, the mechanisms that explain intraspecific variation in recycling N:P are not well-understood. We examined the relative importance of potential drivers of variation in nutrient recycling by the fish Gambusia marshi among aquatic habitats in the Cuatro Ciénegas basin of Coahuila, Mexico. There, G. marshi inhabits warm thermal springs with high predation pressure as well as cooler, surface runoff-fed systems with low predation pressure. We hypothesized that variation in food consumption among these habitats would drive intraspecific differences in excretion rates and N:P ratios. Stoichiometric models predicted that temperature alone should not cause substantial variation in excretion N:P, but that further reducing consumption rates should substantially increase excretion N:P. We performed temperature and diet ration manipulation experiments in the laboratory and found strong support for model predictions. We then tested these predictions in the field by measuring nutrient recycling rates and ratios as well as body stoichiometry of fish from nine sites that vary in temperature and predation pressure. Fish from warm, high-predation sites excreted nutrients at a lower N:P ratio than fish from cool, low-predation sites, consistent with the hypothesis that reduced consumption under reduced predation pressure had stronger consequences for P retention and excretion among populations than did variation in body stoichiometry. These results highlight the utility of stoichiometric models for predicting variation in consumer-driven nutrient recycling within a phenotypically variable species.

When is an herbivore not an herbivore? Detritivory facilitates herbivory in a freshwater system

Herbivory is thought to be an inefficient diet, but it independently evolved from carnivorous ancestors in many metazoan groups, suggesting that plant-eating is adaptive in some circumstances. In this study, we tested two hypotheses to explain the adaptive evolution of herbivory: (i) the Heterotroph Facilitation hypothesis (herbivory is adaptive because herbivores supplement their diets with heterotrophic microbes); and (ii) the Lipid Allocation hypothesis (herbivory is adaptive because algae, which have high lipid concentrations, are nutritionally similar to carnivory). We tested these hypotheses using enclosure cages placed in the Everglades and stocked with Sailfin Mollies (Poecilia latipinna), a native herbivore. Using shading and phosphorus addition (P), we manipulated the heterotrophic microbe and lipid composition of colonizing epiphyton and examined the effects of varying food quality on Sailfin Molly life history. Epiphyton grown in "shade only" conditions had a 55% increase in bacterial fatty acids and 34% lower ratios of saturated + monounsaturated to polyunsaturated fatty acids relative to the other treatments. Ratio of autotroph to heterotroph biovolume varied throughout the experiment, with a 697% increase at 3 weeks and 98% decrease at 6 weeks compared to the other treatments. Gut contents revealed that fish fed selectively on epiphyton to compensate for apparent deficiencies in the available food. Fish raised in "shade only" cages experienced the highest survival, which was best explained by autotrophic biovolume and algal- and bacterial-derived fatty acids at 3 weeks (2-6× more likely than alternative models with ∆AICc > 2.00), and by percentage of bacterial fatty acids in the diet at 6 weeks (3-8× more likely than alternative models with ∆AICc > 2.00). There were no differences in fish growth among treatments. Autotrophic lipids play a role in early fish life history, but we did not find these to be the best predictors of life history later in the juvenile period. Instead, heterotrophic lipids facilitated the herbivorous diet and enhanced survival of juvenile fish in our experiment. Bacterial fatty acid content of the diet promoted herbivore survival, consistent with the Heterotroph Facilitation hypothesis. This is the first study to explicitly contrast Heterotrophic Facilitation and Lipid Allocation hypotheses for the adaptive evolution of herbivory in an aquatic system.

The AmP project: Comparing species on the basis of dynamic energy budget parameters

We developed new methods for parameter estimation-in-context and, with the help of 125 authors, built the AmP (Add-my-Pet) database of Dynamic Energy Budget (DEB) models, parameters and referenced underlying data for animals, where each species constitutes one database entry. The combination of DEB parameters covers all aspects of energetics throughout the full organism’s life cycle, from the start of embryo development to death by aging. The species-specific parameter values capture biodiversity and can now, for the first time, be compared between animals species. An important insight brought by the AmP project is the classification of animal energetics according to a family of related DEB models that is structured on the basis of the mode of metabolic acceleration, which links up with the development of larval stages. We discuss the evolution of metabolism in this context, among animals in general, and ray-finned fish, mollusks and crustaceans in particular. New DEBtool code for estimating DEB parameters from data has been written. AmPtool code for analyzing patterns in parameter values has also been created. A new web-interface supports multiple ways to visualize data, parameters, and implied properties from the entire collection as well as on an entry by entry basis. The DEB models proved to fit data well, the median relative error is only 0.07, for the 1035 animal species at 2018/03/12, including some extinct ones, from all large phyla and all chordate orders, spanning a range of body masses of 16 orders of magnitude. This study is a first step to include evolutionary aspects into parameter estimation, allowing to infer properties of species for which very little is known.

We discovered that parameters of Dynamic Energy Budget (DEB) models can be estimated from a set of simple data on animal life history aspects, growth and reproduction, if treated in combination. Apart from goodness-of-fit as an estimation criterion, relations with parameter values of other species are important, since DEB parameters have a clear physiological interpretation and a good fit for the wrong reasons is always a risk to consider. We developed and optimized methods for this type of parameter estimation-in-context and organized the results of over 1000 animal species in the open-access Add-my-Pet (AmP) database, to which 125 authors contributed so far. We also developed software package AmPtool to compare parameter values in the collection, that builds on DEBtool to assist applications of DEB theory. A family of related DEB models, structured with respect to the modes of metabolic acceleration, captures biodiversity, including various life stages. We discuss some features of the family structure of DEB models in an evolutionary context. The AmP collection has a great potential for research on the role of biodiversity in ecosystem structure and functioning, which will grow with the size of the database.

Comparing the Ecological Stoichiometry in Green and Brown Food Webs - A Review and Meta-analysis of Freshwater Food Webs

The framework of ecological stoichiometry was developed primarily within the context of "green" autotroph-based food webs. While stoichiometric principles also apply in "brown" detritus-based systems, these systems have been historically understudied and differ from green ones in several important aspects including carbon (C) quality and the nutrient [nitrogen (N) and phosphorus (P)] contents of food resources for consumers. In this paper, we review work over the last decade that has advanced the application of ecological stoichiometry from green to brown food webs, focusing on freshwater ecosystems. We first review three focal areas where green and brown food webs differ: (1) bottom-up controls by light and nutrient availability, (2) stoichiometric constraints on consumer growth and nutritional regulation, and (3) patterns in consumer-driven nutrient dynamics. Our review highlights the need for further study of how light and nutrient availability affect autotroph-heterotroph interactions on detritus and the subsequent effects on consumer feeding and growth. To complement this conceptual review, we formally quantified differences in stoichiometric principles between green and brown food webs using a meta-analysis across feeding studies of freshwater benthic invertebrates. From 257 datasets collated across 46 publications and several unpublished studies, we compared effect sizes (Pearson's r) of resource N:C and P:C on growth, consumption, excretion, and egestion between herbivorous and detritivorous consumers. The meta-analysis revealed that both herbivore and detritivore growth are limited by resource N:C and P:C contents, but effect sizes only among detritivores were significantly above zero. Consumption effect sizes were negative among herbivores but positive for detritivores in the case of both N:C and P:C, indicating distinct compensatory feeding responses across resource stoichiometry gradients. Herbivore P excretion rates responded significantly positively to resource P:C, whereas detritivore N and P excretion did not respond; detritivore N and P egestion responded positively to resource N:C and P:C, respectively. Our meta-analysis highlights resource N and P contents as broadly limiting in brown and green benthic food webs, but indicates contrasting mechanisms of limitation owing to differing consumer regulation. We suggest that green and brown food webs share fundamental stoichiometric principles, while identifying specific differences toward applying ecological stoichiometry across ecosystems.