Environmental temperature, salinity, oxygen, and pH/carbonate chemistry can profoundly affect the energy budget of marine organisms, thus negatively affecting their fitness and competitive ability in the ecosystem. It is often claimed that environmental stress increases the costs of homeostatic processes at the expense of reproduction and growth, yet little experimental data exists to support this idea. It is also unclear whether biomineral precursors are formed intra- or extracellularly and how important extra- and intracellular acid-base regulation is for biomineralization processes. Further, energetic costs of biomineralization, as well as potential species-specific differences are poorly understood. This session will bring together researchers working on whole organism and cellular energy budgets of marine organisms, with a focus on mechanistic aspects of cellular homeostasis, energy metabolism and biomineralization, and the effects of environmental stress. We hope to facilitate discussions leading to improved energy budget models, with the ultimate goal of better forecasting potential impacts of natural and ongoing anthropogenic environmental change on marine organisms.