Coral reefs are marine structures made up of tiny animals called polyps. These marine structures are made of limestone which is deposited by coral polyps on layer upon layer, eventually forming reefs. Upon completing their life cycle, coral polyps leave out their limestone shell skeletons, which serve as new foundations for new polyps to grow. Successive layer of living polyps form, over time, enormous reef structures. These limestone structures provides the habitat for a great variety of marine animal and plant species.
Plants or animals
Corals are neither plants nor rocks. They're living organisms that feed on other microorganisms to survive. Corals are marine animals made up of thousands of tiny polyps. Polyps are invertebrates that are usually only some millimeters across by a few centimeters long. Corals don't produce their own food as plants do, so they're not plants. They posses a set of tentacles that they use to catch their food from water and put it into a central opening or mouth. The polyp secretes calcium carbonate to build a crust skeleton that is used for protection.
What are coral reefs made of
Coral reefs are made of hundreds of thousands of tiny coral polyps. Each polyp secretes calcium carbonate (CaCO3) which forms an outer skeleton around the coral polyp. The skeleton attaches to the skeletons of other polyps. Coral polyps live, reproduce and die in repeated life cycles. their calcium carbonate skeletons grow on top of the skeletons of death polyps, forming layers of limestone skeletons. Over time, giving shape to the coral reef structure. The rate at which calcium carbonate is deposited on the reef structure varies from 0.3 to 2 centimeters every year.
Corals live in a close partnership with microalgea called zooxanthellae. The coral provides the microalgae with a protective shell from the ocean environment and also the necessary compounds, such as carbon dioxide and nutrients for photosynthesis. In return, the algae supplies the coral with the products of photosynthesis, such as oxygen and compounds, including amino acids, glucose and glycerol which the coral uses to build fats, proteins and carbohydrates. The symbiotic relation between the algae and coral are crucial for the production of limestone in coral reefs.
The symbiotic zooxanthellae provide the coral with its color. Sometimes, environmental stressors, such as increased or reduced water temperatures, water chemistry changes, bacterial infection, sedimentation, variations in salinity and overfishing, may force the coral polyp to expel the algae. When this occurs, the coral takes a lighter or totally white color, which is a condition known as coral bleaching. Coral bleaching occurs when the conditions to maintain the symbiotic algae cannot be sustained, leading to the expulsion of the algae. Corals may regain zooxanthellae back if the stressor is supressed within short periods of time.
Where do coral reefs form
Coral reefs support a great diversity of animal and plant species. Coral reefs are the habitat of 25% of all marine species, including more than 4,000 species of fish, 800 species of coral and a number of other plants and animals. Most coral reefs are found in the tropical latitudes of the world 30 ° north or south of the equator.; however, coral reefs have been found in bermuda, 32 ° north of the equator, due that it is in the path of the Gulf Stream's warming water currents. Corals can also form on colder, deeper, darker waters, although, their capacity to produce calcium carbonate is greatly reduced.
Corals are ancient animals that have evolved into reef-building organisms over the past 25 million years. Coral reefs are sometimes referred to as the rainforests of the sea for the great diversity of marine animal and plant species that thrive in their ecosystem. Coral reefs are the largest and most complex structures of biological origin in the world. According to floridakeys.noaa.go, corals are the principle architects of the reef. They are primitive life forms, on an evolutionary scale, sitting one step beyond sponges and being less advanced than the flat worms.