Coral Biology

We know that over 70% of this planet is made up of water, from lakes, rivers seas and oceans.  Reef systems actually only cover around 2% of this vast water expanse and are still visible from space.  For such a small footing they play a very important role to life on earth.  They play a very important role in the fixation of Carbon and Carbon Dioxide and produce Oxygen as a byproduct.  In fact Corals within the reef system produce more oxygen than the tropical rain forests.

Corals are in fact ancient animals whose fossil records date back as far as 520 million years, these Cambrian period fossils are rare records; more are recorded from the Ordovician period dating back some 100 million years.  Corals are made up of colonies of genetically identical polyps.  A polyp is a simple sac like animal related to Jelly fish and Anemones.  They are part of the Phylum Cnidaria.  These polyps and corals come in 2 main categories Soft and Hard Corals.  Each individual Polyp is a few millimeter in diameter and a few centimeters in length.  They are made up of a simple stomach, mouth and have a set of tentacles that surround the mouth which contain stinging cells called Nematocysts.

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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 toughened by the presence of tiny skeletal elements known as sclerites; this too is made from calcium carbonate.  Most soft coral species are connected 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 composed of either fibrous protein called Gorgonin 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 structure that hard corals come in from encrusting, plate like, bushy, columnar or massive solid structure.  Each of the various forms can be found on the reef system in various zones, this is linked to the variation of light and water movement.

Both soft and hard corals are connected by a well developed gastro vascular canal system.  This allows for significant sharing of nutrients and symbionts.  Polyps feed on a variety of different small organisms from small fish to microscopic zooplankton found in the water column.  Each polyp uses its stinging tentacles to capture prey, the tentacles release the nematocysts which carry venom, they rapidly release this venom in response to contact with another organism.  The tentacles will then move the immobilized prey to the mouth which contracts pushing the prey into the stomach, where it is digested and later released what is not used as waste.

Ecology of coral reefs

With it numerous crevices and crannies, a coral reef is a home and feeding ground for countless numbers of fascinating marine life-forms. No ecosystem on Earth plays host to the diversity of inhabitants as found in and around a coral reef. Except for mammals and insects, almost every major group of animals is represented.

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, an international environmental monitoring organization, 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 this is believed to be over 35%.  Some of those reefs can never be recovered, while some could possibly come back.  The report pointed out that global warming was the biggest threat facing coral reefs, followed by water pollution, sediment from coastal development, and destructive fishing techniques (such as using dynamite and cyanide). If nothing is done to stop the destruction caused by humans, 60 percent of the world’s coral reefs will disappear by 2030.

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Coral reefs also benefit humans by protecting shorelines from the full onslaught of storm-driven waves. Humans, however, are responsible for causing severe damage to coral reefs. Reefs are often destroyed by collectors, who use coral to create jewelry, and fisherman, who use poison or dynamite to catch fish. Because corals need sunlight and sediment-free water to survive, water pollution poses a grave danger. Oil spills, the dumping of sewage wastes, and the runoff of soil and agricultural chemicals such as pesticides all threaten the delicately balanced ecosystem of coral reefs.

The Importance of Coral Reefs

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

Reefs play an important role in protecting the shoreline from storms and surge water.  Barrier reefs help stabilize mangroves and sea grass beds, which can easily be uprooted by large waves and strong currents.  Coral reefs also help with Erosion prevention.
As the foundation for complex food webs, coral reefs support an incredible diversity of fish. Algae, soft coral, sponges and invertebrates create the base of this web. From small herbivorous fish to large predatory fish, all find food and protection on the reef.

Along side reef fish is an equally diverse array of marine crustaceans, reptiles and mammals. Everything from lobsters and octopus to sea turtles and dolphins depend on the reef for food, habitat and protection. Each animal plays an important role in the reef ecosystem, be it filtering water, consuming prolific algae or keeping a particular species under control. By supporting such a wide range of plants and animals, reefs are able to maintain balanced relationships between predators and prey and organisms in competition f

Fish and other marine life have been a primary source of protein for as long as people have lived along the coast. From small scale artisanal fisheries to major commercial fleets, harvesting of marine life is a major economic force in all of the world’s oceans. Local fisheries, such as lobster, stone crab, snapper and grouper, all directly rely on the reef for spawning and habitat. Other fisheries, such as tuna, dolphin and other pelagic species, rely on the reef indirectly, though the bait fish that they consume.
Most corals and sponges are filter feeders, which means that they consume particulate matter suspended in the water column. This contributes to enhanced quality and clarity of our near shore water
Coral reefs often form the backbone of local economies. Tourists coming to dive need not only dive boats and guides, but also restaurants, hotels and commercial and entertainment facilities. In many cases, tourism associated with reefs has expanded to transform the entire economy of a region. This of course has both positive and negative consequences for both the marine environment and the communities involved. For example, someone who harvests sea turtle eggs may choose to sell turtle tours as an alternative livelihood. On the other hand, an unmonitored number of tourists may result in environmental problems such as coral damage, pollution and inadequate waste treatment.