Hermatypic or reef-building corals can have the most diverse growth forms. Most stony coral species excrete calcium carbonate at their base and a calcareous skeleton is formed through a symbiosis with zooxanthellae, unicellular microalgae. They reproduce by forming new coral calyxes on top of old ones or when coral polyps become independent. If undisturbed they will continue doing so as long as the seawater remains clean and there is enough sunlight.
Some species of stony coral can live for several hundred years, which may explain why at certain points in the history of Earth, stony coral formed entire islands and archipelagos over thousands of years, such as the Bahamas, Bermuda and the Maldives. Moreover, about 600,000 years ago, corals began to build the Great Barrier Reef off the coast of Australia. Today, with its 359 species of stony coral, the reef is the largest structure created by living creatures on earth and provides habitat for a multitude of other species.
That said, worldwide coral mortality has been linked to increased surface water temperatures caused by global heating. Severe ‘coral bleaching’ occurred in 1998 after an occurrence of the El Niño phenomenon in the western Pacific and Indian Oceans when temperatures were 1 to 3°C above the long-term average for months. To ensure that the ocean habitat remains as diverse and colourful as on the Luminous Marine Life coins, it is thus imperative that we protect it, not least from ourselves.
Coin Motif
All 12 of the magical sea creatures in the Luminous Marine Life series are shown in silhouette on the coin’s obverse. Air bubbles up between them and a tail fin disappears beneath the waves to the right. On the coin’s reverse, a wide band, reminiscent of an old-fashioned porthole frames an aquatic scene that features a coral reef. Stony corals are depicted in the top left of the scene, sea fans to the right, brain coral in the centre and sea anemones in the bottom left, while clownfish are dotted around the reef. When the coin is illuminated with UV light, the coral and sea anemones glow and change colour.
