Zooplankton in lakes play a crucial role in the ecosystem by eating algae, recycling nutrients, and being food for other animals. Scientists studied how changes in fish populations affect zooplankton biomass and body size. They found that zooplankton can be both influenced by the animals that eat them and can impact the growth of algae and recycling of nutrients in the lake. This research helps us understand how different parts of the ecosystem interact and depend on each other.