Picture this: A kaleidoscope of colourful corals, from gargantuan brain corals to gently swaying fan corals, haloed by schools of dancing anthias and preened by peckish parrotfish. A green olive riley turtle might even glide past. Rivalling the Amazon rainforest, coral reefs are some of the most biodiverse ecosystems on the planet; from the corals themselves, which are actually colonies of tiny animals called polyps that form reefs, to the marine life they support. Home to 25% of all marine life they are a source of food, shelter and a nursery for a plethora of juvenile marine animals which later make their way to the big blue world beyond. These are the cities of the ocean.
A Colourful Community
While there are a huge (understatement) number of different corals, most are classified as hard or soft corals. Hard corals are the building blocks of coral reefs as these secrete calcium carbonate that form reef structures. Soft corals do not have a hard skeleton and are often bendy, with a leathery feel. These corals often have wood-like cores made of calcium for support and fleshy rinds for protection. While polyps are actually translucent, they have a symbiotic partnership with zooxanthellae algae, which gives them their vibrant colours - soft corals in particular display truly psychedelic colours under torch or flash light.
Coral Reef Types
There are three main types of coral reef: fringing reefs, which are the most common and exist along a coastline; barrier reefs that grow parallel to shorelines but are farther from shore and are usually separated from the land by a deep lagoon; and finally coral atolls, which are rings of coral reef growing on top of old sunken volcanoes in the ocean. They begin as fringing reefs surrounding a volcanic island then, as the volcano sinks, the reef continues to grow, and eventually only the reef remains.
Adapting To Survive
Climate change is a major threat to corals, as rising sea temperatures (as well as ocean acidification and pollution) increases thermal stress causing coral bleaching, whereby corals expel the zooxanthellae algae living in their tissues causing them to turn a ghostly white. If the algae does not return in a few months, the coral will die. However, the coral in Raja Ampat in Indonesia is thought to have developed a greater resilience to temperature change, protecting itself from the bleaching we so sadly see in other areas of the world. A wealth of resorts are also taking action to protect these fragile ecosystems, from developing coral nurseries to education programmes, which guests can also get involved with.
Where To Find Them
While coral can be found across the world, the most biodiverse marine region on earth is The Coral Triangle. Spanning 2.3 million square miles from The Philippines to Timor to Papua New Guinea and the Solomon Islands (with Raja Ampat in Indonesia right in the centre), it is home to 76% of all known coral species, over 1,200 species of reef fish, two species of manta ray and six of the seven species of turtle (among other accolades). Elsewhere, Fiji's kaleidoscopic reefs have crowned it the 'soft coral capital of the world' while the Red Sea in Egypt has the best-preserved reefs close to Europe.
Inch
Rate at which corals grow per year
Miles
Length of the Great Barrier Reef
Inches
Diameter of largest coral polyps