Development of a metabolite-driven daphnia ecophysiological model

Abstract

One of the founding principles of modern aquatic ecology is that human-induced perturbations in the autotroph-herbivore interface have the potential to affect ecological processes at higher trophic levels. Thus, zooplankton’s physiological state can be an early warning sign of broader impairments of aquatic ecosystems. Based on this reasoning, the micro-crustacean Daphnia is often identified as a keystone freshwater species, but its bioenergetic motivations and physiological priorities remain only partially understood. Using a bioenergetically explicit ecophysiological approach, we model how trade-offs in resource allocation can shape a daphnid's growth. Our multi-faceted hierarchical approach to metabolite utilization challenges the popular paradigm of elemental stoichiometry being the primary regulatory factor of algal food quality. We examine the post-gut bioenergetic ramifications of an unbalanced diet, showing that animal growth can be significantly compromised by the elevated energetic requirements of homeostasis. Our modeling framework offers an excellent stepping-stone to connect zooplankton physiological processes with the signals of external stressors, and subsequently evaluate the patterns of mass and energy flow at an ecosystem scale. The proposed microscopic-to-macroscopic strategy will likely offer a new prospect towards the development of early warning systems for the management of freshwater resources.