The Great Barrier Reef

Located off the northeastern coast of Australia is the most complex and diverse eco-system in the world. The Great Barrier Reef is comprised of more than 3,000 individual coral reefs and is home to a plethora of species of plants and animals.

Geology of Great Barrier Reef

Formation of the Great Barrier Reef began millions of years ago. Volcanic activity created what is known as the Coral Sea Basin and a series of raised islands surrounding the basin. As the sea level changed over time so did life living in the basin and on the islands. Over time coral reefs grew, died and were buried under sediment from volcanic eruptions. This layer of rich sediment built up over time forming shelves. The earliest individual coral located on in the raised area now known as the Great Barrier Reef is thought to have formed a half-million years ago. Around 600,000 years ago complete corals began forming in the area and the origin of oldest of those still living today dates back 20,000 years. Sea levels in the area continued to rise until approximately 6,000 years ago. At that point, the water level evened out creating the ideal conditions for the formation of a fusion of coral and other plant and animal life. The shallow grounds created by years of volcanic activity and sedimentary build up combined with the warm waters and high levels of sunlight provide the perfect environment for the Great Barrier Reef to form and thrive

Life in the Great Barrier Reef

Within the Great Barrier Reef, there are several habitats. Consistent throughout the entire 1,616 mile formation are coral reefs. What we consider a piece of coral is actually a collection of a several individual coral polyps. Each coral is actually a number of polyps. Coral polyps are living creatures that encase themselves in hard, protective shells made of calcium carbonate. These shells band together forming colonies. The colonies together are known as reefs. Within the Great Barrier Reef, there are millions of coral featuring a multitude of colors and textures. There are more than 400 species of hard and soft corals living in the Reef.

Housed within the reefs is a vastly diverse collection of animal life, many of which are endangered. Within its waters, the Great Barrier Reef provides homes to 5,000 species of mollusks and 125 species of sharks, stingrays, and skates. In addition, there are more than 1,500 species of fish including the colorful clown fish. Thirty species of whales, dolphins, and porpoises live in the Great Barrier Reef including humpback whales which use its warm, shallow waters as breeding grounds before journeying to Hawaii to give birth. Six endangered species of marine turtles also use the area to reproduce. The loggerhead turtle, one of the most highly protected endangered species, lives and breeds in the Great Barrier Reef. Over the last 40 years, the number of these turtles has decreased so rapidly that there are only 3% the number of creatures alive today. Housed around this extremely diverse collection of animal life are 2,195 species of plants. Above water 215 species of birds live on the Great Barrier Reef.

Environmental Threats

Because of the diversity, complexity, and uniqueness of the eco-system, the Great Barrier Reef was placed under the protection of the Australian federal parks system, was named a World Heritage Site in 1981 and has been called one of the Seven Natural Wonders of the World. Still, life in the Reef is at risk.

Coral Bleaching

One of the greatest threats to the Great Barrier Reef is climate change, also known as global warming. Three times over the last ten years, the water in the seas surrounding the Great Barrier Reef has risen 1 or more degrees Celsius. While this may not seem that significant, any temperature increase threatens the coral reefs. When the water becomes warmer, coral become stressed. This stress causes them to force Zooxanthellae, an algae living in coral shells essential to the sustenance of the coral polyp, out of their shells. Without this algae, the coral is unable to use photosynthesis to form its color which is why the phenomenon is known as “coral bleaching”. Once the algae are absent, the coral’s white skeleton shows and the coral begins dying, stops reproducing and becomes vulnerable to disease. The Great Barrier Reef experienced episodes of coral bleaching in 1998, 2002 and 2006. Scientists estimate that the 2002 temperature increase caused 60 to 95% of the Reef’s coral to become bleached. Because water temperatures are likely to continue to rise, researchers predict that episodes of coral bleaching will continue to occur. Therefore, the Great Barrier Reef Marine Park Authority has formed a response plan aimed at detecting and responding to future occurrences.

Crown of Thorns Starfish

Another natural threat to the Great Barrier Reef is the Crown of Thorns Starfish. This creature which is a naturally occurring species, feeds on coral. While a small number of starfish pose no major threat to the vast collection of coral reefs, when they rapidly multiply, they place the Reef at risk. Eradicating these creatures (by forcing them to migrate out of the area) takes anywhere between 1 and 15 years.

Over the last 40 years, there have been three major outbreaks of Crown of Thorn Starfish. During those periods large portions of the coral reefs were damaged. These outbreaks combined with episodes of coral bleaching have had dramatic impacts on the coral forming the foundation of the Great Barrier Reef as well as threatening marine and bird species living in the Reef.

Human Impact

Not all of the destruction of the Great Barrier Reef has come from natural sources. Human actions have also negatively impacted the area. Water pollution has threatened life in the Reef. A series of rivers feed the sea where the Reef is located. These rivers have flooded farm lands upstream siphoning large amounts of pesticides used on cattle and sugar cane farms surrounding the rivers. These waters then empty into the seas polluting the waters that the ecosystem.

In addition, land development poses risks to the Great Barrier Reef. Because of its beauty and diversity, the area attracts a huge number of visitors. Though the Reef is protected by the Australian Parks Authority, the tourism industry has built up commercial areas on the lands surrounding the area. This coastal development threatens the delicate ecosystem adjacent to it.

Beyond this, boats have damaged the Reef. Fishing boats have stripped the area of a number of key species of fish including the Giant Triton. While fishing of certain types of fish has been limited, the boats legitimately fishing in the area pose a potential threat to the entire collection of life located in the Great Barrier Reef. Because the boats carry large amounts of oil necessary for their operation, they always hold the possibility of creating a hazardous situation by spilling the oil into the area’s waters.

How is this selection organized?