Zooplankton are small, drifting organisms found in aquatic environments, including oceans, seas, and freshwater bodies. They play a crucial role in the food web, serving as primary consumers that feed on phytoplankton and in turn are preyed upon by larger organisms. Zooplankton are significant in marine biology and paleontology for understanding ocean ecosystems, carbon cycling, and the fossil record in marine sediments.
Reference: Brierley, A. S. (2007). “Biological Oceanography of Zooplankton.” Science, 316(5827), 213-216.