Australia‘s Great Barrier Reef

Hardy Reef in the Great Barrier Reef it a heart-shaped mini atoll located about 100 km (60 mi) off the coast of Queensland and the Whitsunday Islands in northeastern Australia. The Great Barrier Reef stretches along the Australian continental shelf in the Coral Sea and is the largest living structure on earth with a length of 2000 km (1600 mi), and can even be seen from space. It comprises more than 2500 individual reefs and 540 islands forming an offshore barrier.
The combination of fringing reefs that form along the coast and around offshore islands and shelf reefs that grow offshore creates beautiful turquoise-colored lagoons. The lagoons are filled with soft sediment that consists mainly out of the remains of living organisms. The reef tops are close to sea-level and their bases can be at 40 to 100 m (130-330 ft) depth. Seaward of the lagoon the reef flat and the windward edge marks the transition zone where the continental shelf ends and the water depth increases. Visually, the ocean color changes from turquoise in the lagoons and brownish colors on the reef flat to the deep blue of the open ocean. Often, the windward edge of the reef is additionally marked by the white water of braking waves.
Corals grow most prolific in shallow, warm and light-flooded saltwater, without turbidity from coastal sediments or freshwater rivers discharge. Throughout the year the Great Barrier Reef sea surface temperature varies between 24°C (75°F) and 30°C (86°F), which is ideal for coral growth. The growth rate of the reef is a dynamic balance between the coral organisms that form and cement the hard substrate and the erosive forces of the organisms that feed on the reef and the destructive wave action at high wind speeds. Cyclones are a particular threat to reefs. Their hurricane winds cause destructive waves that bury the corals under sand and debris. Over the last thousands of years the balance was positive and the Great Barrier Reef has been growing at an average speed of 5-8 mm (0.2 to 0.3 in) per year.
Flying over Hardy Reef is a truly unique experience. The varying water colors and shapes of the coral reefs have fascinated me deeply and helped me to better understand and appreciate this unique environment and the fragility of this ecosystem.