The Environmental Microfluidics Group of Prof. Roman Stocker in the Institute of Environmental Engineering at ETH Zurich is seeking a dynamic and motivated doctoral student for a project on the scaling of metabolic rates with organism size, with a focus on microorganisms from the ocean. The position is funded by a recently awarded SNSF Sinergia Grant, for a collaboration between the groups of Prof. Roman Stocker (ETHZ), Prof. Andrea Rinaldo (EPFL), and Prof. Arti Ahluwalia (Uni Pisa). Review of applications will begin on August 1, 2019, with the position to start as early as September 1, 2019, or as soon as filled. PhD Position on “The ocean’s carbon pump through the lens of metabolic rate–biomass relations” The ocean’s carbon (or, biological) pump, the large flux of carbon from the surface to the depths of the oceans caused by the sinking of particles, plays a crucial role in the Earth’s carbon cycle. Marine particles host diverse microbial communities, which, collectively, are responsible for the consumption of the sinking carbon, and thus effectively attenuate the amount of carbon that is exported, with direct consequences on the global carbon cycle and climate change. Yet, despite their importance, we currently lack a proper characterization of the metabolisms of the diverse species assemblages that colonize marine particles. Physiological studies have shown that metabolic rates scale with body mass according to a universal power-law, known as Kleiber’s law. However, metabolic rates have typically been measured at the level of individual species, and how they are modified when species are part of a community remains poorly understood. This project aims at generalizing Kleiber’s law into the realm of communities of microorganisms by quantifying the total metabolism of the marine communities which colonize marine particles and comparing these to the metabolisms of species in isolation. The student will have the unique opportunity to learn, develop and apply a range of cutting-edge experimental techniques, including microfluidic technology, state-of-the-art microscopy, Raman microspectroscopy, and PAM fluorometry. Measurements will be guided and compared with theory developed within the collaboration. Findings will help advance one of the most important paradigms in ecology and will carry fundamental implications for our ability to predict the response of marine microorganisms to environmental perturbations.