Growth rate–stoichiometry couplings in diverse biota

TLDR

Biological stoichiometry links cellular and biochemical traits of organisms to ecosystem energy and nutrient constraints, and variation in C:N:P ratios is a key integrative biology priority, with differences in C:P and N:P thought to reflect organismal P content via ribosomal RNA allocation at varying growth rates (the growth‑rate hypothesis). The study aims to understand variation in biomass C:N:P stoichiometry across diverse biota. We tested the GRH using data from microbes, insects, and crustaceans, showing that growth, RNA content, and biomass P content are tightly coupled across species, ontogeny, and under physiological P limitation. The coupling is relaxed when P is not limiting for growth, and the close relationship between P and RNA contents indicates that ribosomes serve as a biogeochemically significant P reservoir, making ribosome generation a central process in biological production.

Abstract

Abstract Biological stoichiometry provides a mechanistic theory linking cellular and biochemical features of co‐evolving biota with constraints imposed by ecosystem energy and nutrient inputs. Thus, understanding variation in biomass carbon : nitrogen : phosphorus (C : N : P) stoichiometry is a major priority for integrative biology. Among various factors affecting organism stoichiometry, differences in C : P and N : P stoichiometry have been hypothesized to reflect organismal P‐content because of altered allocation to P‐rich ribosomal RNA at different growth rates (the growth rate hypothesis, GRH). We tested the GRH using data for microbes, insects, and crustaceans and we show here that growth, RNA content, and biomass P content are tightly coupled across species, during ontogeny, and under physiological P limitation. We also show, however, that this coupling is relaxed when P is not limiting for growth. The close relationship between P and RNA contents indicates that ribosomes themselves represent a biogeochemically significant repository of P in ecosystems and that allocation of P to ribosome generation is a central process in biological production in ecological systems.