Coral atolls, according to Darwin, are built upon the remnants of a subsiding volcano and coral growth has kept pace with this subsidence over millions of years to produce the structure which we see today. An atoll reef goes through stages of fringing reef, barrier reef, and finally, a truly atoll reef as the volcano submerges. There is shelter and cover provided by dense blades of plants. Seagrass beds provide a food source for many marine animals in the region. The mangrove forest is another ecosystem that exists in the marine areas of S.E.A. Mangroves are an intermediate area between land and sea.
Mangroves are tropical forests that occur within tidal zones along coastlines and river deltas.
They predominate during times of high tide and are home to many varieties of plants and animals. Different Invertebrate Species that Makes up the Coral Reefs in Indonesia and the Philippines A. Sponges Sponges are the oldest group of multicellular organisms, first appearing 500 million years ago. Many varieties can be found throughout the Philippines and Indonesia. In Indonesia, the number of different species is over 1,000. They are very interesting and colorful creatures.