They teem with life, with perhaps one quarter of all ocean species depending on reefs for food and shelter. Reefs cover just a tiny fraction (less than one percent) of earth's surface and less than two percent of the ocean bottom. Corals have multiple reproduction strategies-they can both be male or female or both, and can reproduce either asexually or sexually. The fastest corals expand at six inches per year, but most grow less than one inch per year. Corals are found across the word's ocean, in both shallow and deep water, but reef building corals are only found in shallow tropical and subtropical water. There are deep-sea corals that thrive in the cold, dark water at depths up to 20,000 feet. The coral reefs have many dangers.
Corals are small, marine animals that remain in one place throughout their adult lives and produce a hard skeleton made of calcium carbonate, or limestone. Many species of corals grow in colonies that continue to enlarge year after year. Other species are solitary; that means that they live alone. The largest coral reef in the world, the Great Barrier Reef, off the coast of Australia. It is more than 1,250 miles long. The particular shapes and patterns of corals are characteristic for each species and are the result of the growth pattern of the millions of tiny individual animals that make up a colony. Corals can be very colorful underwater but most species fade when they die or are removed from the water. Vast coral colonies are built by the animals being connected by their extensive skeletal work. Nutrients are passed from individuals on the outside of their colony to those on the inside. There are three kinds of reefs-Barrier, Fringing, and Atolls.
About one-third of all marine fish species live part of their lives on coral reefs. Coral reefs protect coastlines from storms. Corals are a type of invertebrate. Corals live in tropical waters throughout the world, generally close to the surface where the sun rays can reach the algae. A corals diet is carnivore. Coral reefs cover less the zero and two tenths percent of our ocean floor, but they contain twenty five percent of the world's marine fish. Coral reefs are second only to rain forests in biodiversity of species.
An individual coral is called a polyp. A polyps average life span in the wild is two years to hundreds of years. A colony's average life span in the wild is five years to several centuries. A polyps size is usually zero and twenty five tenths inches to twelve inches. Thousands of identical polyps live together and form a coral colony. The polyps extend their tentacles at night to sting and ingest tiny organisms called plankton and other organisms.
Coral reefs are one of the world's most colorful and diverse ecosystems. Corals are related to anemones and jellyfish. Corals rely on photosynthesis to survive, but the coral polyps are not doing any actual photosynthesizeing. Reefs are an important location for finding food, shelter, mates, and places to reproduce. Reefs also act as nurseries for large fish species keeping them safe until they are large enough to strike out into the deeper ocean. Coral reefs are important to the development of new medicines. Nearly sixty percent of the world's coral reefs are threatened by human activity. Many programs work to protect coral reefs through research, education, and preservation programs.
The Great Barrier Reef is a popular tourist destination with over two million visitors each year. The Great Barrier Reef is the world's largest coral reef system, composed of over 2,900 individual reef. There are multiple species living on the Great Barrier Reef. The Great Barrier Reef has over 900 islands stretching for over 2600 kilometers. The Great Barrier Reef is so large it can be seen from outer space. The Great Barrier Reef is roughly half the size of Texas. The Great Barrier Reef is extremely ancient maybe even twenty million years old.
The most common type of reef is a fringing reef. The Fringing Reef grows seaward directly from the shore. Fringing reefs form borders along the shore line and surrounding islands. Islands subside to become a guyot, its a ring shaped Fringing Reef turns into a barrier reef. Barrier reefs border the shoreline and are separated from land by an expense of water.
An Atoll is a ring shaped Coral Reef, island, or series of islets. An Atoll surrounds a body of water called a Lagoon. Atolls develop underwater volcanoes, called sea mounts. Atolls are often uninhabited "desert" islands. Desert doe not refer to the islands climate "deserted" uninhabited status. The thin, shallow strip of water between the Fringing Reef and the island is the Lagoon. Atolls are usually circular or oval in shape with an open Lagoon in the center.
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