Ocean ecosystems make up the largest living space on the planet. Understanding the behavior, physiology, and evolution of marine organisms in the context of their chemical and physical environments and species interactions is key to advancing our understanding of biodiversity and ecosystem functioning across systems. Multiple general concepts in ecology have originated from pelagic systems, including ecological stoichiometry, trophic cascades, and the match/mismatch hypothesis. However, a fundamental hurdle in advancing our understanding of ecological processes in the ocean remains the traditional boundary between ecology and oceanography. In this session, we seek to ing together oceanographers and ecologists posing questions about ocean ecosystems, bridging empirical investigations with ecological theory and process models. We welcome both theoretical and empirical research addressing ecological interactions and biodiversity across a range of scales and trophic levels, with particular emphasis on the integration of field sampling, ecological theory, and/or modeling aimed to reveal processes structuring ocean ecosystems. Presentations may include innovative observational or experimental approaches, ranging from microscopy, imaging, flow cytometry and remote sensing, to molecular (e.g. -omics), trait-based, or isotopic tools, with the aim to characterize variability in diet, diversity (taxonomy, barcoding, metabarcoding), abundance, and/or the physiological status of the organisms in response to perturbations and interactions. We especially look to highlight recent advances since 2018.