July 23 – The Great Carrier Reef

Today’s Factismal: The world’s largest artificial reef is an old aircraft carrier sunk off the Florida coast.

Quick! What’s 911 ft long, 150 ft wide, 150 ft tall, and 70 ft under water? It is the USS Oriskany, also known as the Great Carrier Reef and the USS Orisanky. Once an aircraft carrier and the pride of the US Navy, she is now the world’s largest artificial reef and an on-going experiment in how reefs form.

A view through the superstructure of the Great Carrier Reef (Image courtesy MBT Divers)

A view through the superstructure of the Great Carrier Reef
(Image courtesy MBT Divers)

Sinking things to make a reef isn’t a new idea. The Persians did it 3,000 years ago in order to keep pirates out of their port. The Japanese did it 400 years ago in order to grow kelp for sushi. And the Americans did it two centuries ago in order to get more fish. What is new is using massive structures such as aircraft carriers, automobiles, and even bridges, as the base of the reef.

reefOnce sunken, the structure does three things. First, it deflects the bottom currents, sending them and their nutrient-rich water up to the sunny surface where they feed plankton. That then leads to a population explosion of the tiny little krill and other critters who then provide a banquet for small fish which are eaten by bigger fish.

Second, the structure provides hidey holes for the fish. Groupers, eels, and barracuda lurk in the shadows, hoping for a tasty morsel to swim by, while sardines and minnows span in the crevices, seeking safe places to hide their eggs. All told, reefs provide a habitat for about 25% of the world’s species of fish.

The third thing that artificial reefs do is provide a framework for coral, sponges, and other reef-building animals to live on. By giving the baby coral polyps many different places to rest at different depths in the water, the artificial reefs are able to bootstrap the reef building process. Instead of taking centuries for the basal reef builders to provide a substrate that is then taken over by the secondary reef critters, an artificial reef can have it all happening simultaneously.

If you’d like to learn more about coral reefs and how they form oases in the oceans, then head on over to the Coral Reef Monitoring Program!

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