Ernst Maier-Reimer was one of the pioneers in global modelling of ocean biogeochemical cycles and especially the carbon cycle. He published – together with Klaus Hasselmann – the first comprehensive paper on anthropogenic carbon uptake by the ocean. He provided extensive models on both the inorganic as well as the organic carbon cycle in the ocean. His models were elegant in their mathematical formulation, efficient, and computationally economic. He was very influential in this field through the sharing of his knowledge. A number of state-of-the-art biogeochemical ocean model components in Earth system models can be traced back to him and his modelling philosophy. His ability to separate important processes from unimportant provided a role model for geoscientific modellers. Ernst implemented numerous different tracers into his ocean models and took advantage of considering all in a synoptic view of constraining the overall biogeochemical action of the world ocean. This special issue had been open for submissions from everyone who knew Ernst, learned from him, or collaborate with him. It should be a celebration of classical and new topics in quantitative biogeochemistry with key papers aimed at understanding the ocean as a chemical plant.