Zooplankton play a pivotal role in aquatic ecosystems and global biogeochemical cycles. They function as prey for economically important fish, grazers of primary production, and drivers of carbon and nutrient cycles. Their population and community dynamics, including their growth, mortality, distribution, and diversity, structure the ecosystem. At the same time, a changing environment influences their dynamics. Climate change is profoundly impacting marine ecosystems through changes in zooplankton. A combination of new technologies and techniques, together with classical in situ and laboratory studies, is required to understand the changing ecosystems. In response to the need to understand zooplankton dynamics, their sensitivity to change, and the resultant effects on ecosystems, ICES and PICES are holding the 5th International Zooplankton Production Symposium as a forum to discuss zooplankton and their role in the global ecosystem.