The past years have seen a rapid development of model applications for monitoring the ocean biogeochemical state, the management of marine living resources and ocean ecosystems for research as well as operational applications. These model systems draw on the increasing availability of in situ and satellite-based observations, as well as on advances in coupled physical-biogeochemical and ecosystem ocean modeling. This session aims at providing an overview of the status of the field, identifying blocking points and charting avenues for future progress. It will highlight recent advances in model development and operational systems. We invite submissions of studies exploring innovative approaches to model-data fusion (e.g. novel methods in data assimilation, assimilation of data from novel in situ or remote platforms, assimilation of up- or downstream products of ocean color remote sensing), model skill assessment, downscaling from large to regional domains, and case studies of research and operational applications (e.g. HAB prediction, episodic hypoxia, ocean acidification, management of living marine resources).