Scuba Diving, Heron Island, Queensland
For 18 million years the Great Barrier Reef has been built, destroyed and rebuilt in one of nature’s most remarkable acts of renewal.
The Great Barrier Reef is a spectacular monument to the power of nature. It is constantly evolving as coral grows, spawns, dies and becomes rock hard. On the dead coral new coral forms and algae, anemones, sponges, fish, worms, starfish, turtles, molluscs, snakes and crustaceans breed and prosper – and slowly the reef continues its never-ending cycle of growing and retreating.
In the beginning
When you dive into the waters and marvel at the beauty of the Great Barrier Reef you are experiencing the miracle of the biggest single structure made by living organisms on the planet – a reef that is estimated to have started 18 million years ago when, due to continental drift, the coast of North Queensland moved into warm waters which were ideal for reef development. The coral is comprised of billions of microscopic living creatures and those living creatures sustain the plants and animals that, in turn, die and form a rock-hard layer upon which a newer reef grows. The reef expands and retreats in response to changing water temperatures – retreating during ice ages, advancing as the ice melts.
Vlassoff Cay, Great Barrier Reef, Queensland
Cycles of change
The base of the reef is probably around 400,000- 600,000 years old. During that time the sea warmed (by up to 4°C) and the sea level rose, creating ideal conditions for the reef. Since then, with the rising and falling of the sea level, the reef has evolved and expanded as myriad creatures, attracted to the warm waters and plentiful food supplies, have populated its gardens of brightly coloured soft and hard corals. As the sea rises new reefs form on the skeletal remains of previous reefs.
The reef we see today
It is believed the current reef dates from a time when the sea level was 120 metres lower than it is today. The reef you see today is probably around 6,000-8,000 years old. It started to form on the remnants of previous reefs at the end of the last ice age. When the sea warms and rises, the coral takes full advantage of the changing conditions and grows towards the surface until it is exposed at low tide. Remarkably, although it is vulnerable to storms and the heat of summer, it is sufficiently resilient that very few species of coral have become extinct over the past 100,000 years.
Hardy Reef, Great Barrier Reef, Queensland
The reef is visible from the moon
Today the reef stretches for 2,300 km up the coast of Queensland from Bundaberg to Cape York and covers an area of almost 350,000 square kilometres. It is recognised as the world’s largest coral reef with over 3,000 different reefs, 600 coral islands, 300 coral cays and 150 mangrove islands on the edge of the mainland. Every year, for thousands of years, in October and November millions of tiny coral polyps release tiny egg and sperm bundles into the water as the coral spawns and reproduces. It survives because it is endlessly adapting to the new oceanic circumstances. The result, World Heritage-listed, can be seen from the moon, and is considered one of the seven natural wonders of the world. It is resilient, adaptable and capable of resisting most of the challenges that degrade it.
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