Earth's seas play a tremendous role in the planet's systems: Ocean currents transfer water and heat around the globe, and ocean ecosystems are among the most biologically productive anywhere. But the oceans are being abused. Wild fisheries are harvested to the point of collapse, and some aquaculture damages life and the environment. People intentionally or inadvertently dump wastes - sewage, oil, toxic chemicals, detergents, fertilizers, and invasive species - and all have an impact on ocean ecosystems. Offering full-color photographs and illustrations and captivating text, Oceans introduces young science students to these urgent issues. This important new work shows how protecting the oceans requires protecting the entire planet, and describes the importance of setting aside marine reserves to save vital ecosystems.