The Great Barrier Reef isn’t just one reef, it’s actually a string of nearly 3,000 individual reefs and 900 islands stretching for over 1,600 miles. The reef system is millions of years old with new coral growing on top of dead coral. Parts of the dead coral are up to 20 million years old.
Coral reefs are built by and made up of thousands of tiny animals called polyps. The polyps are related to anemones and jellyfish. A polyp has a sac-like body and an opening, or mouth, encircled by stinging tentacles called nematocysts or cnidae. The polyp uses calcium and carbonate ions from seawater to build itself a hard, cup-shaped skeleton made of calcium carbonate (limestone). This limestone skeleton protects the soft, delicate body of the polyp. Polyps have clear bodies with white skeletons. The bright colors come from zooxanthellae (tiny algae) that live inside their tissue. One square inch of a polyp has several million zooxanthellae living inside of it producing the pigment that gives it its bright color.
An incredible ten percent of the world’s species of fish call the reef home with over 1,500 species living amongst the coral. It is also home to 30 species of whale, dolphin, and porpoise; 6 species of turtles, and 17 species of sea snakes. Some of the fish species trace their ancestry back as far as 500 million years.
Between climate change, rising sea temperatures, and pollution the reef is unfortunately seeing a lot of bleaching and death of the reef. Bleaching is a term that refers to when negative changes in conditions cause the polyps to expel the algae in which they depend on to survive. Since the algae is what gives it its bright color the coral then looks like it’s been bleached (hence the name). If conditions don’t get better after a coral is bleached it will die as it has lost its primary source of food. On average about 15 percent of The Great Barrier Reef is bleached.
You can help save the reef by visiting The Great Barrier Reef Foundation