Geometric Stoichiometry: Unifying Concepts of Animal Nutrition to Understand How Protein-Rich Diets Can Be “Too Much of a Good Thing”

Abstract

Understanding the factors that control the growth of heterotrophic organisms is central to predicting food web interactions and biogeochemical cycling within ecosystems. We present a new framework, Geometric Stoichiometry (GS), that unifies the disciplines of Nutritional Geometry (NG) and Ecological Stoichiometry (ES) by extending the equations of ES to incorporate core NG concepts, including macromolecules as currencies and the ability of animals to select foods that balance deficits and excesses of nutrients. The resulting model is used to investigate regulation of consumer growth by dietary protein:carbohydrate ratio. Growth on protein-poor diets is limited by nitrogen. Likewise, we show that growth is also diminished on protein-rich diets and that this can be mechanistically explained by means of a metabolic penalty that arises when animals use protein for energy generation. These penalties, which are incurred when dealing with the costs of producing and excreting toxic nitrogenous waste, have not hitherto been represented in standard ES theory. In order to incorporate GS within ecosystem and biogeochemical models, a new generation of integrated theoretical and experimental studies based on unified concepts of NG and ES is needed, including measurements of food selection, biomass, growth and associated physiology, and involving metabolic penalties.

Is the growth of marine copepods limited by food quantity or quality?

“…This result was, however, inconclusive because the modeled gross growth efficiencies (GGEs) for N were considerably higher than values measured in laboratory experiments (Checkley Jr 1980;Kiørboe 1989). State-of-the-art ecological stoichiometry models now represent metabolism, and hence growth efficiencies, with explicit metabolic terms for biomass turnover, basal metabolism, and specific dynamic action (SDA) (Anderson et al 2017(Anderson et al , 2020. Here, we use one such model (Anderson et al 2020) to investigate the role of food quantity vs. quality in limiting the growth of marine copepods.…”

Understanding the Evolution of Nutritive Taste in Animals: Insights from Biological Stoichiometry and Nutritional Geometry

“…There are large bodies of literature devoted to the development and application of these frameworks, including several recent papers highlighting their connections and encouraging their synthesis (14,15,16). As such, we provide only brief summaries of their basic principles to establish their usefulness in describing the ecological contexts under which different taste (which was not certified by peer review) is the author/funder.…”

“…Ecologists have long recognized that the quantity and nutritional quality of foods affect the growth and performance of animals (1). Given that nutritional requirements vary among animal species, shifts in the nutrient composition of available foods can scale beyond individual and population effects to alter community and ecosystem dynamics, including fluxes of energy and nutrients to and from the environment and among trophic levels (14, 15). Increasing recognition of the role of animal nutrition in driving ecological dynamics, from foraging behavior to consumer driven nutrient recycling, has led to the development of multiple conceptual frameworks that seek to characterize the nature and consequences of nutritional imbalances in trophic interactions (1).…”

“…Increasing recognition of the role of animal nutrition in driving ecological dynamics, from foraging behavior to consumer driven nutrient recycling, has led to the development of multiple conceptual frameworks that seek to characterize the nature and consequences of nutritional imbalances in trophic interactions (1). Biological stoichiometry theory and nutritional geometry are perhaps the most prominent of these frameworks and have been developed in parallel over the last several decades (14, 15). Though these frameworks focus on different nutritional currencies (i.e., elements versus macro- and micronutrients) there is substantial conceptual overlap, including an emphasis on homeostasis, that suggest promise in their ability to inform our understanding of how nutritional imbalances have shaped the evolutionary history of gustation in animals (14).…”

“…Though these frameworks focus on different nutritional currencies (i.e., elements versus macro- and micronutrients) there is substantial conceptual overlap, including an emphasis on homeostasis, that suggest promise in their ability to inform our understanding of how nutritional imbalances have shaped the evolutionary history of gustation in animals (14). There are large bodies of literature devoted to the development and application of these frameworks, including several recent papers highlighting their connections and encouraging their synthesis (14, 15, 16). As such, we provide only brief summaries of their basic principles to establish their usefulness in describing the ecological contexts under which different taste modalities have evolved.…”