Exploring a first-principles-based model for zooplankton respiration

Abstract

Oxygen consumption (R) is caused by the respiratory electron transfer system (ETS), not biomass. ETS is ubiquitous in zooplankton, determines the level of potential respiration (Φ), and is the enzyme system that ultimately oxidizes the products of food digestion, makes ATP, and consumes O2. Current respiration hypotheses are based on allometric relationships between R and biomass. The most accepted version at constant temperature (T) is R = i0M0.75, where i0 is a constant. We argue that, for zooplankton, a Φ-based, O2-consuming algorithm is more consistent with the cause of respiration. Our point: although biomass is related to respiration, the first-principles cause of respiration is ETS, because it controls O2 consumption. Biomass itself is indirectly related to respiration, because it packages the ETS. Consequently, we propose bypassing the packaging and modelling respiration from ETS and hence Φ. This Φ is regulated by T, according to Arrhenius theory, and by specific reactants (S) that sustain the redox reactions of O2 consumption, according to Michaelis–Menten kinetics. Our model not only describes respiration over a large range of body sizes but also explains and accurately predicts respiration on short time-scales. At constant temperature, our model takes the form: forumla where Ea is the Arrhenius activation energy, Rg, the gas constant, and Km, the Michaelis–Menten constant.