The study of organism-scale dynamics allows for more accurate estimates of key ecological processes. For instance, predator-prey interactions drive energy and material transfer through intermediate levels of food webs. Predators such as cnidarian jellyfishes act as trophic links between primary productivity and large marine animals, and contribute to vertical carbon flux from surface waters to the seafloor. In this presentation, I will show how behavioral studies on jellyfish allow to determine their prey capture efficiency, and consequently, provide means to measure their impact on prey population dynamics and carbon ingestion rates.