浮游动物化学计量学稳态性特征研究进展

稳态性是有机体的基本属性,也是生态化学计量学理论成立的前提和基础。一般来讲,浮游植物的元素组成变化较大,而浮游动物具有明显的稳态性特征。浮游动物稳态性特征的研究不仅有助于了解水生生态系统的能量流动和物质循环,同时也对研究营养元素如何调节生物生长、繁殖和代谢起到促进作用。在综述生态化学计量学研究的基础上,主要介绍了稳态性的概念和浮游动物稳态性特征的基本框架及变化规律,以期为促进国内相关研究工作的开展提供参考。     

Elemental composition and degree of homeostasis of fungi: are aquatic hyphomycetes more like metazoans,bacteria or plants?

Ecological stoichiometry generally assumes that heterotrophs have a higher degree of elemental homeostasis than autotrophs. Differences between fixed consumer nutrient requirements and nutrients available in resources allow prediction of the intensity of nutrient recycling ensured by heterotrophs. Despite their fundamental role in detritus decomposition, extremely few data are currently available on fungal elemental composition. In this study, we quantified the degree of elemental homeostasis of aquatic hyphomycetes used as model organisms. Contrary to metazoans, but similar to plants, aquatic hyphomycetes exhibited highly plastic elemental compositions. Mycelium also reached far higher C/nutrient ratios than reported for bacteria. Our results suggest that non-homeostasis of fungi should be explicitly included in stoichiometric models dealing with nutrient recycling, and that the discrepancy in homeostasis between some bacterial strains and fungi should certainly be considered when investigating interactions between both groups of decomposers.     

Are you what you eat? Physiological constraints on organismal stoichiometry in an elementally imbalanced world

The relative supply of energy and elements available to organisms in the environment has strong effects on their physiology, which, in turn, can alter important ecological processes. Here we consider how resource imbalances affect three basic physiological processes common to all organisms: elemental uptake, incorporation, and release. We review recent research that addresses these core issues (uptake, incorporation, and release) as they relate to elemental homeostasis in autotrophs and heterotrophs. Our review shows the importance that organism elemental homeostasis plays in determining the types of physiological processes used to acquire, assemble, store, and release biogenic elements, which are found in widely varying ratios in the environment. Future research should examine the degree to which organisms assess their internal nutritional composition and that of their food sources within a multiple elemental and biochemical context. Also, scientists should explore if and how the stoichiometry of cellular and molecular responses underlying nutrient (elemental and biochemical) acquisition, incorporation, and release depends on the nutritional composition of food resources. These types of queries will further improve our understanding of the physiological processing of primary elements involved in growth, reproduction, and maintenance of organisms.     

Stoichiometric flexibility in response to fertilization along gradients of environmental and organismal nutrient richness

Ecosystems globally are undergoing rapid changes in elemental inputs. Because nutrient inputs differently impact high‐ and low‐fertility systems, building a predictive framework for the impacts of anthropogenic and natural changes on ecological stoichiometry requires examining the flexibility in stoichiometric responses across a range of basal nutrient richness. Whether organisms or communities respond to changing conditions with stoichiometric homeostasis or flexibility is strongly regulated by their species‐specific capacity for nutrient storage, relative growth rate, physiological plasticity, and the degree of environmental resource availability relative to organismal demand. Using a meta‐analysis approach, we tested whether stoichiometric flexibility following nutrient enrichment correlates with the relative fertility of terrestrial and aquatic systems or with the initial stoichiometries of the organism or community. We found that regardless of limitation status, N‐fertilization tended to significantly reduce biota C:N and increase N:P, and P fertilization reduced C:P and N:P in both terrestrial and aquatic systems. Further, stoichiometric flexibility in response to fertilization tended to decrease as environmental nutrient richness increased in both terrestrial and aquatic systems. Positive correlations were also detected between the initial biota C:nutrient ratio and stoichiometric flexibility in response to fertilization. Elucidating these relationships between stoichiometric flexibility, basal environmental and biota fertility, and fertilization will increase our understanding of the ecological consequences of ongoing nutrient enrichment across the world.     

Phosphorus limitation and excess carbon in zooplankton

Organisms rely on a series of chemical reactions, which are constrained by the availability of key chemical elements, such as carbon (C), nitrogen (N), and phosphorus (P). Ecological stoichiometry provides a tool for analyzing how the balance of elements required by organisms affects food-web dynamics. Ecological stoichiometric theory suggests that the balance between supply and demand of elements is determined by the conversion efficiency from resources to organisms.Autotrophs and heterotrophs commonly face unequal access to and uptake of elements. The stoichiometric variability of autotrophs is based on their ability to maintain the balance of elements required for growth. This creates a challenge for their grazers. Phytoplankton can adjust their P content to ambient nutrient concentrations, while zooplankton cannot store excess nutrients. Ecological stoichiometric theory thus suggests that zooplankton have relatively fixed stoichiometry compared with phytoplankton.Nutrient limitation is common in aquatic systems. Stoichiometric imbalances between phytoplankton and zooplankton mean that zooplankton rarely find optimal food sources, and phytoplankton production is in excess. P availability potentially limits zooplankton growth, because of the high C:P ratio in phytoplankton relative to zooplankton demand. Based on the Liebig minimum principle, organisms are normally limited by a single nutrient, while everything else is in excess. Under P deficiency, excess C cannot be allocated to zooplankton somatic growth, and the net intake of C must balance the C:P ratio of zooplankton. Thus, when zooplankton encounter nutritionally imbalanced foods the elements in excess are released in order to maintain homeostasis. Excess C, released by zooplankton results in two biochemical challenges: (1) to sequester the limiting element and (2) to either store or dispose of the element in surplus.Zooplankton must resort to various physiological solutions to cope with these challenges. As a first option, zooplankton can reduce their C assimilation efficiency but maintain their P assimilation efficiency. Alternatively, after assimilation, excess C may be stored in C-rich compounds. Finally, assimilated excess C could also be disposed of through respiration or extracellular release. Excess C released by zooplankton reduces C transfer efficiency and sequestration in aquatic ecosystems.In aquatic ecosystems, C sequestration largely depends on the balance between uptake and demand for key nutrient elements. These feedback mechanisms have arisen only because organisms must obey stoichiometric rules at the cell and body levels, which greatly constrain the range of element values in ecosystems. Thus, the fate of C in ecosystems is determined by the absolute and relative demands for N and P of each organism. Limiting elements are utilized for growth and transferred in food chains with high efficiency, while non-limiting elements must be disposed of. Therefore, low C:P phytoplankton communities subject to high turnover rates and high productivity are selectively channeled into zooplankton. When zooplankton face high C:P foods, excess C is returned to the environment. Hence, nutrient-deficient phytoplankton constitute poor food, influencing the entire food web and adversely affecting secondary production at all levels.Excess C processed by zooplankton has far-reaching implications for ecosystem food-web functioning and C sequestration. Studies of the fate of excess C in zooplankton would increase the understanding of energy flow and material cycling in aquatic ecosystems. This paper reviews the reasons for P limitation and excess C in zooplankton, principal routes for the disposal of excess C, and the ecological effects of this. In addition, the paper aims to provide insight and a theoretical foundation for related studies in China.     

Ecological stoichiometry of Eurasian perch – intraspecific variation due to size,habitat and diet

The turnover and distribution of energy and nutrients in food webs is influenced by consumer stoichiometry. Although the stoichiometry of heterotrophs is generally considered to vary only little, there may be intraspecific variation due to factors such as habitat, resources, ontogeny and size. We examined intraspecific variation in Eurasian perch Perca fluviatilis stoichiometry, a common species that exhibits habitat and resource specialization, ontogenetic niche shifts and a large size range. This study investigated the elemental stoichiometry of a wide size range of perch from littoral and pelagic habitats. The mean C:N:P stoichiometry of whole perch was 37:9:1 (molar ratios). However, %C, %P, C:N, C:P and N:P varied with size, morphology, habitat and diet category. These factors together explained 24–40% of the variation in C:N:P stoichiometry. In contrast, perch stoichiometry was not related to diet stoichiometry, suggesting that the former is homeostatically regulated. The results suggest that the high P content of perch may result in stoichiometric constraints on the growth of non‐piscivorous perch, and that piscivory is an efficient strategy for acquiring P. Resource polymorphism, individual diet specialization and intraspecific size variation are widespread among animals. Thus changes in stoichiometry with size, habitat, morphology and resource use, and therefore also stoichiometric demands, are probably common.     

Resource quality and stoichiometric constraints on stream ecosystem functioning

1. Resource quality and stoichiometric imbalances in carbon : nutrient ratios between consumers and resources can influence key ecosystem processes. In many streams, this has important implications for food webs that are based largely upon the utilization of terrestrial leaf‐litter, which varies widely among litter types in its value as a food source for detritivores and as a substrate for microbial decomposers. 2. We measured breakdown rates and macroinvertebrate colonization of leaf‐litter from a range of native and exotic plants of differing resource quality and palatability to consumers [e.g. carbon : nitrogen : phosphorus (C : N : P) ratios, lignin and cellulose content], in a field experiment. We also measured C : N : P ratios of the principal leaf‐shredding invertebrates, which revealed strong stoichiometric imbalances across trophic levels: C : N and C : P ratios typically differed by at least one order of magnitude between consumers and resources, whereas N : P imbalances were less marked. Application of the threshold elemental ratio approach, which integrates animal bioenergetics and body elemental composition in examining nutrient deficiency between consumers and resources, revealed less marked C : P imbalances than those based on the simpler arithmetic differences described above. 3. Litter breakdown rates declined as nutrient imbalances widened and resource quality fell, but they were independent of whether resources were exotic or native. The principal drivers of total, microbial and invertebrate‐mediated breakdown rates were lignin : N, lignin : P and fungal biomass, respectively. However, multiple regression using orthogonal predictors yielded even more efficient models of litter breakdown, as consumers responded to more than one aspect of resource quality. For example, fungal biomass and litter C : N both influenced invertebrate‐mediated breakdown. 4. Large stoichiometric imbalances and changes in resource quality are likely to have serious consequences for stream ecosystem functioning, especially when riparian zones have been invaded by exotic plant species whose chemical composition differs markedly from that of the native flora. Consequently, the magnitude and direction of change in breakdown rates and, thus, resource depletion, will be driven to a large extent by the biochemical traits (rather than taxonomic identity per se) of the resident and invading flora.     

Aridity Decouples C:N:P Stoichiometry Across Multiple Trophic Levels in Terrestrial Ecosystems

Increases in aridity forecasted by the end of this century will decouple the cycles of soil carbon (C), nitrogen (N) and phosphorus (P) in drylands—the largest terrestrial biome on Earth. Little is known, however, about how changes in aridity simultaneously affect the C:N:P stoichiometry of organisms across multiple trophic levels. It is imperative that we understand how aridity affects ecological stoichiometry so that we can develop strategies to mitigate any effects of changing climates. We characterized the C, N, P concentration and stoichiometry of soils, autotrophs (trees, N-fixing shrubs, grasses and mosses) and heterotrophs (microbes and ants) across a wide aridity gradient in Australia. Our results suggest that increases in aridity by the end of this century may alter the C:N:P stoichiometry of heterotrophs (ants and microbes), non-woody plants and in soil, but will not affect that one from woody plants. In particular, increases in aridity were positively related to C:P and N:P ratios in microbes and ants, negatively related to concentration of C, and the C:N and C:P ratios in mosses and/or short grasses, and not related to the C:N:P stoichiometry of either shrubs or trees. Because of the predominant role of C:N:P stoichiometry in driving nutrient cycling, our findings provide useful contextual information to determine ecological responses in a drier world.     

Consumer-resource stoichiometry in detritus-based streams

Stoichiometric relationships between consumers and resources in detritus‐based ecosystems have received little attention, despite the importance of detritus in most food webs. We analysed carbon (C), nitrogen (N), and phosphorus (P) content of invertebrate consumers, and basal food resources in two forested headwater streams (one reference and the other nutrient‐enriched). We found large elemental imbalances between consumers and food resources compared with living plant‐based systems, particularly in regard to P content, which were reduced with enrichment. Enrichment significantly increased nutrient content of food resources (consistent with uptake of N and P by detritus‐associated microbes). P content of some invertebrates also increased in the enriched vs. reference stream, suggesting deviation from strict homeostasis. Nutrient content varied significantly among invertebrate functional feeding groups, orders and, to some extent, size classes. Future application of stoichiometric theory to detritus‐based systems should consider the potential for relatively large consumer‐resource elemental imbalances and P storage by insect consumers.     

Litter elemental stoichiometry and biomass densities of forest soil invertebrates

To maintain constant chemical composition, i.e. elemental homeostasis, organisms have to consume resources of sufficient quality to meet their own specific stoichiometric demand. Therefore, concentrations of elements indicate resource quality, and rare elements in the environment may act as limiting factors for individual organisms scaling up to constrain population densities. We investigated how the biomass densities of invertebrate populations of temperate forest soil communities depend on 1) the stoichiometry of the basal litter according to ecological stoichiometry concepts and 2) the population average body mass as predicted by metabolic theory. We used a large data set on biomass densities of 4959 populations across 48 forests in three regions of Germany. Following various ecological stoichiometry hypotheses, we tested for effects of the carbon‐to‐element ratios of 10 elements. Additionally, we included the abiotic litter characteristics habitat size (represented by litter depth), litter diversity and pH, as well as forest type as an indicator for human management. Across 12 species groups, we found that the biomass densities scaled significantly with population‐averaged body masses thus supporting metabolic theory. Additionally, 10 of these allometric scaling relationships exhibited interactions with stoichiometric and abiotic co‐variables. The four most frequent co‐variables were 1) forest type, 2) the carbon‐to‐phosphorus ratio (C:P), 3) the carbon‐to‐sodium ratio (C:Na), and the carbon‐to‐nitrogen ratio (C:N). Hence, our analyses support the sodium shortage hypothesis for microbi‐detritivores, the structural elements hypothesis for some predator groups (concerning N), and the secondary productivity hypothesis (concerning P) across all trophic groups in our data. In contrast, the ecosystem size hypothesis was only supported for some meso‐ and macrofauna detritivores. Our study is thus providing a comprehensive analysis how the elemental stoichiometry of the litter as the basal resource constrain population densities across multiple trophic levels of soil communities.     

植物生态化学计量内稳性特征

化学计量内稳性是生态化学计量学研究的核心概念之一,是指生物在面对外界变化的时候保持自身化学组成相对稳定的能力,其反映了生物对周围环境变化作出的生理和生化响应与适应。通过研究植物生态化学计量内稳性,有助于深入了解植物对环境的适应策略和生态适应性,以及植物化学计量内稳性与生态系统功能的关系,但目前关于植物生态化学计量内稳性的研究较少。已有的研究结果表明:不同物种或功能群由于其生长策略不同而具有不同的生态化学计量内稳性特征;同一物种的不同器官、不同生长阶段以及不同元素的内稳性存在较大的差异。该文对植物生态化学计量内稳性概念、内稳性指数的测算方法,不同植物物种或功能群、不同器官、不同生长阶段内稳性特征,以及植物内稳性与生态系统结构、功能和稳定性的关系等方面进行了综述,并结合现已开展的工作,对有待进一步拓展的相关植物生态化学计量内稳性研究领域进行了展望,以期为促进国内相关研究工作的开展提供参考。     

Caught in the web: Spider web architecture affects prey specialization and spider–prey stoichiometric relationships

Quantitative approaches to predator–prey interactions are central to understanding the structure of food webs and their dynamics. Different predatory strategies may influence the occurrence and strength of trophic interactions likely affecting the rates and magnitudes of energy and nutrient transfer between trophic levels and stoichiometry of predator–prey interactions. Here, we used spider–prey interactions as a model system to investigate whether different spider web architectures—orb, tangle, and sheet‐tangle—affect the composition and diet breadth of spiders and whether these, in turn, influence stoichiometric relationships between spiders and their prey. Our results showed that web architecture partially affects the richness and composition of the prey captured by spiders. Tangle‐web spiders were specialists, capturing a restricted subset of the prey community (primarily Diptera), whereas orb and sheet‐tangle web spiders were generalists, capturing a broader range of prey types. We also observed elemental imbalances between spiders and their prey. In general, spiders had higher requirements for both nitrogen (N) and phosphorus (P) than those provided by their prey even after accounting for prey biomass. Larger P imbalances for tangle‐web spiders than for orb and sheet‐tangle web spiders suggest that trophic specialization may impose strong elemental constraints for these predators unless they display behavioral or physiological mechanisms to cope with nutrient limitation. Our findings suggest that integrating quantitative analysis of species interactions with elemental stoichiometry can help to better understand the occurrence of stoichiometric imbalances in predator–prey interactions.     

The C : N : P stoichiometry of autotrophs – theory and observations

Evolution has set biochemical constraints on the chemical composition of living organisms. These constraints seem to lead to increases in N : C and P : C ratios with increasing relative growth rate for all types of organisms. The N : P ratio also seems to decrease with relative growth rate for heterotrophs whereas autotrophs may show a more complex behaviour. Here I will show that, from biochemical considerations, N : C should increase linearly and P : C quadratically with relative growth rate in autotrophs with the consequence that N : P increases at low relative growth rates, passes a maximum and then decreases at high relative growth rates. These predictions are verified against observations for a freshwater alga (Selenastrum minutum) and a tree seedling (Betula pendula). Changes in temperature, light or other factors that affect the growth rate of autotrophs interact with nutrient supply in such a way that there are no simple rules for as to how N : P will change.     

Elemental stoichiometry of basal resources and benthic macroinvertebrates along a land use gradient in a Great Basin watershed

The effects of land use on the elemental stoichiometry of aquatic organisms have rarely been studied in semi-arid watersheds. In eight semi-arid sub-watersheds differing in land use, we determined which predictor variable(s) best explains the elemental variability in two basal food resources and benthic macroinvertebrates (BMI). The elemental composition of periphyton and seston was best explained by percentage of urban and agricultural areas, forested land and associated differences in SRP, DOC, and stream water N:P ratios. In contrast, consumer elemental stoichiometry was related to taxonomic identity and feeding mode. Elemental imbalances were higher for collector-gatherer than for scraper and collector-filterer. However, high spatial and temporal variability in the elemental composition of basal food resources obscured clear spatial patterns of imbalances between nutrient-poor upstream and nutrient-rich downstream sites. Results from this study suggest that land use can affect BMI due to alteration in stoichiometry of their food resources. However, taxonomy and allometry must be taken into account to better understand spatial and temporal changes in the elemental composition of BMI. Our results indicate the importance of considering multiple effects to accurately assess land use effects on producer and consumer stoichiometry, particularly the in highly variable Great Basin watersheds.     

Correlates of elemental‐isotopic composition of stream fishes: the importance of land‐use,species identity and body size

The isotopic (δ¹³C and δ¹⁵N) and stoichiometric (C:N:P) compositions of four fish species (Family Centrarchidae: Lepomis auritus, Lepomis cyanellus; Family Cyprinidae: Nocomis leptocephalus, Semotilus atromaculatus) were examined across four North Carolina Piedmont streams arrayed along an urbanization gradient. Both isotopic and stoichiometric composition of fishes appeared to track changes occurring in basal resource availability. Values of δ¹³C of basal resources and consumers were more enriched at the most urbanized streams. Similarly, basal resources and consumers were δ¹⁵N–enriched at more urbanized streams. Basal resource stoichiometry varied across streams, with periphyton being the most variable. Primary consumers stoichiometry also differed across streams. Intraspecific variation in fish stoichiometry correlated with the degree of urbanization, as the two cyprinids had higher N content and L. cyanellus had higher P content in more urbanized streams, probably due to enrichment of basal resources. Intrinsic factors, specifically species identity and body size also affected stoichiometric variation. Phosphorus (P) content increased significantly with body size in centrarchids, but not in cyprinids. These results suggest that although species identity and body size are important predictors of elemental stoichiometry, the complex nature of altered urban streams may yield imbalances in the elemental composition of consumers via their food resources.     

Stoichiometric imbalances between detritus and detritivores are related to shifts in ecosystem functioning

How are resource consumption and growth rates of litter‐consuming detritivores affected by imbalances between consumer and litter C:N:P ratios? To address this question, we offered leaf litter as food to three aquatic detritivore species, which represent a gradient of increasing body N:P ratios: a crustacean, a caddisfly and a stonefly. The detritivores were placed in microcosms and submerged in a natural stream. Four contrasting leaf species were offered, both singly and in two‐species mixtures, to obtain different levels of stoichiometric imbalance between the resources and their consumers. The results suggest that detritivore growth was constrained by N rather than C or P, even though 1) the N:P ratios of the consumers’ body tissue was relatively low and 2) microbial leaf conditioning during the experiment reduced the N:P imbalance between detritivores and leaf litter. This surprisingly consistent N limitation may be a consequence of cumulative N‐demand arising from the production of N‐rich chitin in the exoskeletons of all three consumer species, which is lost during regular moults, in addition to N‐demand for silk production by the caddisfly. These N requirements are not commonly quantified in stoichiometric analyses of arthropod consumers. There was no evidence for compensatory feeding, but when offered mixed‐species litter varying in C:N:P ratios, detritivores consumed more of the litter species showing the highest N:P and lowest C:N ratio, accelerating the mass loss of the preferred leaf species in the litter mixture. These results show that imbalances in consumer–resource stoichiometry can have contrasting effects on coupled processes, highlighting a challenge in developing a mechanistic understanding of the role of stoichiometry in regulating ecosystem processes such as leaf litter decomposition.     

Interactive effects of light and nutrients on phytoplankton stoichiometry

The stoichiometric composition of autotrophs can vary greatly in response to variation in light and nutrient availability, and can mediate ecological processes such as C sequestration, growth of herbivores, and nutrient cycling. We investigated light and nutrient effects on phytoplankton stoichiometry, employing five experiments on intact phytoplankton assemblages from three lakes varying in productivity and species composition. Each experiment employed two nutrient and eight irradiance levels in a fully factorial design. Light and nutrients interactively affected phytoplankton stoichiometry. Thus, phytoplankton C:N, C:P, and N:P ratios increased with irradiance, and slopes of the stoichiometric ratio versus irradiance relationships were steeper with ambient nutrients than with nutrients added. Our results support the light–nutrient hypothesis, which predicts that phytoplankton C:nutrient ratios are functions of the ratio of available light and nutrients; however, we observed considerable variation among lakes in the expression of this relationship. Phytoplankton species diversity was positively correlated with the slopes of the C:N and C:P versus irradiance relationships, suggesting that diverse assemblages may exhibit greater flexibility in the response of phytoplankton nutrient stoichiometry to light and nutrients. The interactive nature of light and nutrient effects may render it difficult to generate predictive models of stoichiometric responses to these two factors. Our results point to the need for future studies that examine stoichiometric responses across a wide range of phytoplankton communities.     

Extending the growth rate hypothesis to species development: Can stoichiometric traits help to explain the composition of macroinvertebrate communities?

Ecological stoichiometry seeks to understand the ecological consequences of elemental imbalances between consumers and their resources. Therein, the well-accepted growth rate hypothesis (GRH) states that organisms exhibiting rapid growth have higher phosphorus (P) demand – and thus lower C:P and N:P ratios – than slow growing ones, due to a higher allocation to P-rich rRNA. However, GRH has rarely been extended to other biological traits than growth, especially at the community level. In this study, we investigated whether macroinvertebrate stoichiometric traits (e.g. C:P and N:P ratios) can be linked to their development traits, and whether these stoichiometric traits are related to macroinvertebrate community assemblage under different nutrient conditions. We allocated more than 400 European taxa to different groups, defined using available information about three development-related traits: ‘life span', ‘voltinism' and ‘number of reproductive cycles per individual'. We sampled 18 invertebrate taxa in six streams exhibiting different levels of nutrient concentration and measured their stoichiometric traits. Further, we quantified invertebrate taxon abundances in these streams during an annual survey. Based on these data, we tested whether community composition regarding the developmental groups differs, depending on nutrient concentration. We found significant differences in the proportions of the developmental groups along a gradient of water N:P, in relation to their stoichiometric traits. Taxa with low C:P and N:P ratios were generally associated with faster development groups, and these taxa tended to occur at higher proportions in streams exhibiting low dissolved N:P ratios. In contrast, communities from P-poor, high dissolved N:P streams, were dominated by slowly developing taxa with high N:P ratios. Our results highlight that extending the GRH to species development rate might give some insights about the mechanisms by which nutrient concentrations in ecosystems influence consumers' community composition.     

Ecological Stoichiometry and Multi-element Transfer in a Coastal Ecosystem

Energy (carbon) flows and element cycling are fundamental, interlinked principles explaining ecosystem processes. The element balance in components, interactions and processes in ecosystems (ecological stoichiometry; ES) has been used to study trophic dynamics and element cycling. This study extends ES beyond its usual limits of C, N, and P and examines the distribution and transfer of 48 elements in 16 components of a coastal ecosystem, using empirical and modeling approaches. Major differences in elemental composition were demonstrated between abiotic and biotic compartments and trophic levels due to differences in taxonomy and ecological function. Mass balance modeling for each element, based on carbon fluxes and element:C ratios, was satisfactory for 92.5% of all element–compartment combinations despite the complexity of the ecosystem model. Model imbalances could mostly be explained by ecological processes, such as increased element uptake during the spring algal bloom. Energy flows in ecosystems can thus realistically estimate element transfer in the environment, as modeled uptake is constrained by metabolic rates and elements available. The dataset also allowed us to examine one of the key concepts of ES, homeostasis, for more elements than is normally possible. The relative concentrations of elements in organisms compared to their resources did not provide support for the theory that autotrophs show weak homeostasis and showed that the strength of homeostasis by consumers depends on the type of element (for example, macroelement, trace element). Large-scale, multi-element ecosystem studies are essential to evaluate and advance the framework of ES and the importance of ecological processes.