Biology of Coral Reefs

Over 70% of this planet are lakes, rivers, seas, and oceans. Coral reefs actually only cover around 2% of this vast water expanse. Still, they are visible from space. For such a small footing they play a very important role in the fixation of carbon and carbon dioxide. Also, they produce oxygen as a byproduct. In fact, corals within the reef system produce more oxygen than the tropical rain forests.

Corals are ancient animals. Their fossil records date back as far as 520 million years. These Cambrian period fossils are rare records. Many of these are from the Ordovician period dating back some 100 million years. Corals are nothing more than colonies of genetically identical polyps. A polyp is a simple sac-like animal related to jellyfish and anemones. They are part of the Phylum Cnidaria. These polyps and corals come in two main categories – soft and hard corals. Each individual polyp is a few millimeters in diameter and a few centimeters in length. They have a simple stomach, mouth and have a set of tentacles that surround the mouth. These tentacles contain stinging cells called Nematocysts.

Soft and Hard Corals

Soft corals come in many forms, from sea fans, sea whips, and branching tree-like structures. They have no hard skeleton. Instead, they have tissues of tiny skeletal elements known as sclerites. This too comes from calcium carbonate. Most soft coral species connect with each other by a network of cells called Coenosarc. This is a thick network and allows the polyps to be deeply embedded for protection. For tree and whip-like soft corals, they have a central axial skeleton embedded in the tissue matrix. Their composition is of a fibrous protein called Gorgonian or of a calcified material.

Hard corals, also known as stony corals, produce a calcium carbonate skeleton which is deposited by the polyps to strengthen and protect the colony. All the polyps are connected by a network of living tissue called the Coenosarc. There are a wide variety of shapes and structures. Each of the various forms are on the reef system in various zones. This is because of the variation of light and water movement.

Soft and hard corals connect with each other by a gastrovascular canal system. This allows sharing of nutrients and symbionts. Polyps feed on a variety of different small organisms. For example, small fish to microscopic zooplankton. Each polyp uses its stinging tentacles to capture prey. The tentacles release the nematocysts which carry venom. They release this venom in response to contact with another organism. The tentacles then move the prey to the mouth which contracts and pushes the prey into the stomach. There digestion occurs and what is not used as waste gets released later.

Ecology of Coral Reefs

A coral reef has many crevices and crannies. So, it is a home and feeding ground for a lot of fascinating marine life-forms. No ecosystem on earth plays host to the diversity of inhabitants as found in and around a coral reef. There is are almost every major group of animals excluding mammals and insects.

The extent of the damage done to the world’s coral reefs was first made clear by a report issued at the end of the year 2000. The Global Coral Reef Monitoring Network is an international environmental monitoring organization. It issued the report with data gathered from scientists around the globe. According to the report, the world has lost 27 percent of its coral reefs. Today it is a 35-loss percentage. Some of those reefs can never recover, while some could come back. The report pointed out that global warming was the biggest threat facing coral reefs. Further threats are water pollution, sediment from coastal development, and destructive fishing techniques. If nothing will change, 60 percent of the world’s coral reefs will disappear by 2030.

Coral reefs also protect shorelines from the full onslaught of storm-driven waves. Thus, they also benefit humans. Yet humans are responsible for causing severe damage to coral reefs. Reefs are often destroyed by collectors. They use coral to create jewelry. Also, some fishermen use poison or dynamite to catch fish. Furthermore, corals need sunlight and sediment-free water to survive. Because of that water pollution poses a grave danger. Oil spills, the dumping of sewage wastes, and the runoff of chemicals all threaten the balanced ecosystem of coral reefs.

The Importance of Coral Reefs

Coral reefs are beautiful undersea cities. They are full of colorful fish, intricate formations, and wondrous sea creatures. The importance of coral reefs extends far beyond the pleasure it brings to those who explore it. Coral reefs play an essential role in water filtration, fish reproduction, shoreline protection and erosion prevention.