Zooplankton in the Celtic Sea play a crucial role in transferring energy from tiny plants to the rest of the ecosystem. By studying their size and diet changes throughout the seasons, scientists found that in spring, smaller plankton were eaten by larger ones, leading to more predators. In summer, the plankton community was linked to recycling organic matter. The Celtic Sea ecosystem is mainly limited by energy. Different regions of the sea showed varying patterns of zooplankton growth and structure. The researchers used size and stable isotope analyses to track these changes, showing how different species interact and evolve over time.