The document summarizes several marine ecosystems. It describes how oceans cover 70% of the Earth's surface and include shorelines like tidal flats and mangrove forests. Specific ecosystems are found around the world, depending on climate and geography. These include coral reefs, estuaries, salt marshes, mangrove forests, and the deep sea. Salt marshes are coastal wetlands flooded by tides that are dominated by salt-tolerant grasses. The intertidal zone is the shore area above and below the water line during tides, containing habitats for starfish and coral. Mangroves are salt-tolerant trees adapted to harsh coastal conditions.