The Ocean’s Heart: The Tiny Creatures Essential to Life

Gr 4-7–In this informational picture book for older readers, Hoffmann introduces zooplankton as tiny, restless creatures that are the “ocean’s heart.” Zooplankton are drifting animals, mostly microscopic, that live hidden in the deepest zone of the ocean (up to 3,300 feet below the surface) to avoid predators during daylight. The core of the narrative is zooplankton’s massive nightly vertical migration—a dangerous “marathon” to the ocean’s surface–to feast on phytoplankton. (Phytoplankton are described as the ocean’s “lungs”; these plantlike organisms produce most of Earth’s oxygen through photosynthesis, making them the foundation of the entire marine food web.) Hoffmann emphasizes the vital role of zooplankton migration in regulating the Earth’s climate through nutrient circulation and creating a carbon sink to slow global warming. The writing uses imaginative and compelling descriptions, referring to escaping zooplankton as an “underwater meteor shower” and “glowing pinwheels.” The book also directly addresses urgent threats like industrial trawling, plastic pollution, and the severe decline of phytoplankton populations. The information is rich, clearly presented, and supported by Le’s vivid illustrations.