HOW DO CORAL REEFS FORM?
After fertilization, coral larvae float around in the water column until they're ready to descend down to the reef. The larvae find a suitable spot, attach themselves to the substrate, and begin to build their skeletons. Stony corals, the backbone of most reefs, grow when polyps secrete skeletons made from calcium carbonate. Some species secrete their skeletons in the shape of a cup called a corallite, and some are more integrated with less separation between polyps. In both cases, as the skeletal deposits build up, the coral colony grows in height and width.
Close-up shots of staghorn coral (left) and boulder coral (right) defining individual corallites. © Alex Neufeld/Coral Restoration Foundation™
There are three formations of coral reefs: fringing, barrier and atoll. Fringing reefs form close to islands or continents, and grow outward towards the open ocean until the seafloor becomes too deep. Barrier reefs are similar to fringing reefs, but are found farther from land and serve as a barrier to wave energy and storm surges. Atolls are fringing reefs that form on the edges of sunken or eroded volcanoes, encircling lagoons that formed over the original craters.
The 360 mile-long Florida Reef Tract stretches the length of the Florida Keys from Miami to the Dry Tortugas. It is classified as a barrier reef, but it sits slightly closer to land than most barrier reefs. Fun fact: the Florida Reef Tract is the only barrier reef in the continental United States!
Satellite image of the Florida Reef Tract. ©NOAA
Reef growth is an incredibly slow process, which is one reason why they're the one of the oldest ecosystems on Earth. Branching corals grow at an average rate of 10cm per year, and it can take up to 10,000 years for an entire coral reef to form from larvae. The Florida Reef Tract is thought to have formed about 10,000 years ago, after the last Ice Age. That may seem like a long time, but corals in general have been on Earth for over 500 million years!
The Florida Reef Tract is made up of both stony corals and soft octocorals. The most common varieties of stony corals are staghorn, elkhorn, star, and brain corals. The unique brain coral is easily recognized by its deep ridges and grooves, similar to its namesake, the brain!
Clockwise from top left: staghorn outplants, natural elkhorn, boulder corals in Tavernier Nursery, and brain coral in the Dry Tortugas. © Alex Neufeld/Coral Restoration Foundation™ and NOAA
At Coral Restoration Foundation™, we predominately work to restore populations of staghorn, elkhorn, and boulder corals. We support the reefs’ natural recovery processes through the large-scale cultivation, outplanting, and monitoring of genetically diverse, reef-building corals. We primarily focus on restoring populations of staghorn (Acropora cervicornis), elkhorn (Acropora palmata), and two species of boulder coral (Orbicella faveolata and Obricella annularis). To learn more about our work, visit coralrestoration.org.
Stop back next week to read the third edition of “Roadmap to Coral Reefs” where we'll explain why coral reefs are so important to humans!
REEFocus Editorial Intern
Indira Khera is a third year at the University of Chicago from Simsbury, Connecticut. She is majoring in Biology with a minor in Environmental Studies. Indira has always been passionate about marine ecology, an interest that started with her childhood summers in coastal Maine. On campus, she works in a Cognitive Neuroscience laboratory, sits on the board of UChicago Women in Science, and writes for the University's Research Magazine, The Triple Helix. Indira is so excited to be a part of the CRF™ team as our Research and Writing Intern.