Coral reefs grow in three of the earth's oceans (Pacific, Atlantic and Indian), in areas that are near the equator. Coral reefs require warm water to grow and thrive. They grow in areas where the sunlight reaches due to their need for the light during photosynthesis. Their tolerance for salt content in the water is very specific, and a drastic change in the salinity in the water can destroy the growth of coral. Coral reefs are necessary for the existence of the many creatures that call them home.
The area wherein a body of freshwater flow into a body of saltwater is an estuary, which is sometimes called a lagoon, an inlet or a harbor. Estuaries are protected from the full crash of waves by strips of land separating them from the ocean, and protect their many inhabitants by filtering out pollution. Estuaries are often places where people gather to fish and go boating and swimming.
Mangroves are evergreen trees that grow in wetland areas. Madagascar is home to the largest mangrove forest on the Indian Ocean. Mangrove forests grow in coastal areas and estuaries along Madagascar's edges. Their roots rise from the mud to extract oxygen from the air and water instead. The roots of the mangroves collect sand and mud and stop water flow, protecting coastlines from erosion. A great number of species call these forests their home, from wild cats to fish to monkeys.
Seagrass beds grow in close proximity to coral reefs, bivalve reefs, mangrove forests, and other aquatic habitats. These beds are home to many species of marine life, and also serve as a nursery for many fish and shellfish species. Seagrasses are the primary food source of dugongs and sea turtles. There are only six bioregions of seagrass on the planet, containing perhaps more than 24 species of grasses.