Shifts in Allocation of Metabolic Energy Highlight Biochemical Bases of Resilience to Environmental Change

Maintaining homeostasis in response to environmental change in the ocean requires the continuous re-allocation of metabolic energy to support essential cellular processes. Yet information on the regulation of ATP allocation in response to environmental variation remains scant in marine organisms. To assess the consequence of ocean change for tradeoffs in ATP use, we developed a cellular energy budget for larvae of a mollusc (Crassostrea gigas), in which five biochemical processes (protein synthesis & degradation, ion transport, calcification, nucleic acid synthesis) account for ~90% of the whole-organism ATP consumption. In response to change in environmental temperature, protein synthesis (the major ATP-consuming process) has higher sensitivity, in contrast to respiration (the ATP-producing process). This uncoupling of thermal responses for these two major biological processes results in an increase in the allocation of ATP for protein synthesis with increasing temperature, leaving a smaller proportion of ATP available to support other essential functions. Defining the biochemical bases of tipping points – where ATP demand exceeds supply – will provide new insights into predicting the capacity of marine organisms to adapt to various scenarios of global environmental change.