The concept of metabolism in ocean biogeochemistry: departures, consistencies, and implications

‘Metabolism’ is a term commonly defined as the sum total of chemical processes happening within some living entity which sustains that entity. Biogeochemists use this concept somewhat differently. A stark example comes from marine contexts, where biogeochemists sometimes refer to ‘ocean metabolism’. From the standard biomedical perspective, the ocean does not seem to be the kind of thing which can possess metabolism; it does not seem to be a single living entity that is sustained by chemical processes. In the light of this puzzle, this paper does three things: first, we flesh out a distinct biogeochemical sense of metabolism, exploring how this differs from, but retains connections to, biomedical definitions of metabolism. Second, we use this to explain how the ocean can be considered metabolic without needing to be considered an organism. Finally, we explore the consequences and implications of this sense of metabolism–in scientific, epistemic and social dimensions – and of recognising biogeochemical systems, such as oceans or parts of them, as metabolic.