Tropical coral reefs are deep-sea habitat made of calcium carbonate. Corals secrete the calcium carbonate making most of the coral reefs. They occur in warm tropical waters with bountiful sunlight necessary for their survival. Coral reefs are made up of tiny marine creatures made up of few nutrients. Stony corals consisting of polyps make the basis for most of the coral reefs. Polyps belong to group cnidarians in the animal kingdom. This group of animals also consist the jellyfish and anemones. Different from the sea anemones, coral polyps secrete a hard exoskeleton made up of carbonate offering mechanical support to their bodies. Reefs grow best in shallow, clear, and warm waters. For maximum growth, sunny and agitated waters provide the perfect conditions in addition to the warmth and shallowness.
Coral reefs are one of the most diverse ecosystems in the world. The name rain forest of the sea I sometimes used for describing coral reefs. Coral reef occupies less than 0.1% of the world’s total ocean surface. Despite this coverage, coral reefs provide home to more than 25% of sea animals (Muhall M 321-351). There is also the existence of deep-sea corals as well as some corals thriving in cold waters.
Live corals are colonies of small animals embedded in calcium carbonate shell. Accumulations of small animals called polyps make up the heads of coral reefs. The individual polyps are tiny but accumulate to form a head of approximately 12 inches in size. Reef building coral also known as, hermtypic corals live within 50 m from the surface in areas with sufficient penetration by sunlight hence allowing formation of nutrients by photosynthesis. Coral polyps, on the other hand, do not photosynthesize but rather live in a symbiotic relationship with zooxanthellae. These organisms live within the tissues of coral polyps providing them with the required nutrients for survival. Corals get more than 90% of nutrients from this relationship. As reefs grow, other organisms deposit their calcium carbonate exoskeletons therefore forming the basis of coral reefs. Coralline algae form an important part of stabilizing the reefs in areas where the reefs are affected by mechanical waves. The algae offer mechanical strength to the coral reefs by depositing limestone in sheets over the reefs hence preventing them from collapsing. The shape of the coral reefs vary depending on various factors including the history of the reefs, the duration of exposure to sunlight (Chappell 249-252)and mechanical events such as breakages and collapse.
The mode of reproduction of corals varies between sexual and asexual depending on the type. Reproductive cells found on the mesentery membrane radiate inside from the stomach cavity. Some of the species of corals change sex as they grow but still reproduce sexually. The eggs are internally fertilized within the polyp and develop to a tiny larva also called a Panola. Some polyps have their eggs externally fertilized but still grow to form a larva before fully becoming an adult. Reproduction requires calm water with less wave movements especially tor polyps that have external fertilization (Polovina, Jeffrey J 1-11). The ideal timing for reproduction occurs during spring while the period between release and settlement of the eggs taking only a few days.
Coral reefs play a major role in the tropical waters. They prevent the movements of sharks to the beaches. Coral reefs also play an important role in tourism and economy. Since they form a habitat for fish, areas around the reefs form productive fishing grounds. They also provide a habitat for the survival of other marine animals apart from fish hence contributing to the larger marine ecosystem.
Cárdenas, Anny, et al. "Shifts in bacterial communities of two caribbean reef-building coral species affected by white plague disease." The ISME journal 6.3 (2012): 502-512.
Glynn, P. W. "Coral reef bleaching: ecological perspectives." Coral reefs 12.1 (1993): 1-17.
Polovina, Jeffrey J. "Model of a coral reef ecosystem." Coral reefs 3.1 (1984): 1-11.