Abstract
The ocean hosts an enormous diversity of microorganisms, which are the main drivers of biogeochemical cycles and control major carbon reservoirs. However, their influence on marine biogeochemistry is not yet adequately represented in global ocean models. This shortcoming reduces our ability to project biological feedbacks in future scenarios. In this talk, I will present examples of how we connect field observations, experiments and theory to inform biogeochemical model development with a focus on dissolved organic carbon (DOC) and microbial interactions. Our results so far have highlighted that microbial processes determine the distribution of DOC on basin-scales, and are closely linked to the cycling of macronutrients. Taking these microbial influences into account suggests that the marine DOC pool may be much more variable than previously thought. The close linkages to nutrient cycles also have potential implications for a future, more stratified ocean, in which nutrient concentrations are projected to decline. By using a microbial community model, we show that nutrient concentrations may influence the balance between cooperation and competition in microbial communities, which impacts the partitioning of dissolved and particulate organic carbon.