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Photo : Dave Gilliam

Coral Facts

Coral reefs are an amazing expression of nature. These living reef structures provide shelter, food and breeding grounds for numerous marine plants and animals. Coral reefs are the basis for a dynamic ecosystem with tremendous biodiversity. Most of Florida’s sport fish species, including spiny lobster, snapper, and grouper, spend significant parts of their lives around coral reefs.

Florida is the only state in the continental United States with extensive shallow coral reef formations near its coasts. Florida’s Coral Reef stretches over 350 linear miles from Dry Tortugas National Park west of the Florida Keys to the St. Lucie Inlet in Martin County. Roughly two-thirds of Florida’s Coral Reef lies within Biscayne National Park and the Florida Keys National Marine Sanctuary. The reefs stretching north of Biscayne National Park and the marine sanctuary are managed by the Florida Department of Environmental Protection’s Coral Reef Conservation Program with insight from the Southeast Florida Coral Reef Initiative (SEFCRI).

What is coral?

Although corals may look like rocks or plants, they are in fact animals, closely related to jellyfish and anemones. Corals are sessile, meaning they attach themselves to the ocean floor. They are classified under the phylum Cnidaria and the class Anthozoa

A single coral is a colonial organism, meaning it is made up of hundreds to thousands of individual animals called polyps. Corals are often referred to as colonies. Each soft-bodied polyp has a stomach with only one opening that is surrounded by tentacles. A polyp both takes in food and expels waste through its opening. The tentacles are used in defense, to pull food into the mouth and to clear away debris.

All polyps on one coral colony are connected to one another by a thin band of living tissue, called the coenosarc. 

Where are corals found?

Coral communities can be found in shallow or deep waters. However, coral reef development occurs only in areas with specific environmental characteristics: a solid structure for attachment; tropical or subtropical temperatures; clear waters low in phosphate and nitrogen nutrients; and moderate wave action to disperse waste and bring oxygen and plankton to the reef.

Other factors that influence where corals can live include the salinity of the water (the amount of salt), the amount of sunlight that penetrates the water, and the presence of species that help control macroalgae, like urchins and herbivorous fish.  

Florida’s offshore waters have these characteristics and support shallow water reefs. 

How do corals eat?

Close-up of the polyps of a Montastraea cavernosa coral with tentacles extended. Photo: David Gilliam

Corals get their nutrients from multiple sources. They feed on tiny particles in the water column by extending their tentacles, which are armed with stinging cells called nematocysts, into the surrounding water to catch prey, and they obtain nutrients from microscopic algae, colloquially called zooxanthellae, that live inside their tissues in a unique partnership called symbiosis.

Symbiosis means that each partner benefits from the partnership. Corals obtain energy, nutrients and oxygen from these algae, and the symbionts receive nutrients and protection. The symbionts also give the corals their beautiful spectrum of colors.

What is coral bleaching?

A bleaching coral is healthy (left), pale (middle) then bleached (right). 
Photo: Mote Marine Lab

Bleaching is a stress response that results when the coral-algae symbiosis breaks down. The corals lose their algae, causing them to turn pale or completely white, which is referred to as bleaching.

Coral bleaching can be caused by a wide range of environmental stressors such as pollution, oil spills, increased sedimentation, extreme increases or decreases in ocean temperatures, fluctuations in salinity, low oxygen, disease and predation.

Bleached corals are still living, and if the environmental conditions return to normal soon enough, the corals can regain or regrow their symbionts and survive the bleaching event. If the stressors are severe, repeated or prolonged, however, bleaching can lead to the death of corals. Bleached corals are more susceptible to disease, predation and death because they are without their primary energy source.

Localized or colony-specific bleaching events have been recorded for over 100 years. Localized bleaching is often caused by direct human-caused stressors, such as spikes in pollution or freshwater runoff, which can be addressed by land-based management that reduces those stressors. However, since the 1980s, scientists have seen mass bleaching events in which a wide range of coral species bleach over a large area of a reef.

Along Florida’s Coral Reef, there is an indication that these mass coral bleaching events have increased in frequency and severity since the 1980s. While the influence of local stressors can explain small-scale bleaching events, the widespread mass bleaching events are mostly attributed to climate change.

Paling Grooved Brain Coral (Diploria Labyrinthiformis) in Rock Key.

Paling Grooved Brain Coral (Diploria Labyrinthiformis)  in Rock Key. Photo: Emily Hower 

Because most corals live close to their upper temperature limits, a temperature increase of only 2° Celsius (4° Fahrenheit) above the long-term average can trigger mass bleaching, particularly when prolonged. This was demonstrated in 1997-1998, when anomalously high ocean temperatures worldwide – linked to the El Nino climate phenomenon – coincided with bleached reefs in over 50 countries.

In situations where bleaching causes extensive coral death, recovery is dependent on new coral recruits settling and growing on the reef. This is a time-consuming process, even on relatively healthy reefs. Unassisted regrowth of reefs that have been severely impacted by bleaching may take decades or centuries, and the new reef may be significantly different from that which existed before bleaching.

In locations suffering from pollution, decreased herbivore biomass, repeated stressors or other chronic pressures, reef recovery can be particularly slow or inhibited altogether.

How are reefs formed?

Reef growth is extremely slow; an individual coral colony may grow only a half-inch to 7 inches (1-18 cm) a year, depending on the species. Stony corals are the major reef architects. Individual polyps in stony coral colonies extract calcium from seawater and combine it with carbon dioxide to construct the elaborate calcium carbonate (limestone) skeletons that form a reef’s backbone.

Caption: A diver surveys a massive reef structure in Biscayne National Park, at the heart of Florida’s Coral Reef.

Caption: A diver surveys a massive reef structure in Biscayne National Park, at the heart of Florida’s Coral Reef.  Photo: Shaun Wolfe, National Park Service 

By repeating this process over many years, stony corals can create massive reef structures that provide habitat for many important species, including most of Florida’s sport fish species, particularly during their younger development stages.

How do corals reproduce?

A mountainous star coral spawns on Florida’s Coral Reef.
Attribution: Mote Marine Laboratory. (Coral Reef Restoration | Research Programs | Mote Marine Laboratory & Aquarium) 

Corals can reproduce asexually through budding or fragmentation and sexually via broadcast spawning or brooding.

Budding occurs when new polyps form from a dividing parent polyp, causing a coral colony to grow outward. This process produces polyps that are genetically identical to the parent polyp.

Fragmentation occurs when a portion of a larger colony is broken off from the main colony, creating a new colony that is genetically identical to the original colony. This can result from storm activity and disturbances from large marine animals like turtles. The new fragment will settle and grow, however, only if it is exposed to favorable growth conditions.

Broadcast spawning occurs as a synchronized event, when corals release large quantities of eggs and sperm at about the same time in response to cues from the environment that include temperature and lunar cues. Because corals are sessile and cannot move, timing is very important. The egg and sperm join to form free-floating larvae called planulae that are transported by water currents until they land on suitable substrate to settle and grow.

This type of sexual reproduction contributes to offspring that are spread over a wide geographical area.

What types of reefs are found in Florida?

The three major types of coral reefs around the world are:

  1. Atolls.
  2. Fringing reefs.
  3. Barrier reefs.

Fringing reefs form borders along shorelines and grow toward the sea from the shore. Barrier reefs form parallel to shore but are separated from it by a lagoon.

Atolls are reefs that continue to grow upward after the island they surround has sunk. Other types of reefs are bank reefs, which have no obvious link to a coastline, and patch reefs, which are small, isolated reefs that grow between the reef tract and land.

Florida’s Coral Reef is composed of many different types of reefs and most closely resembles a barrier reef; however, the reefs are closer to shore, and they lack the shallow inshore lagoons found on most barrier reefs. For this reason, Florida’s Coral Reef is more aptly referred to as a bank-barrier reef. Florida also has patch reefs, which grow in shallower water in between the reef and land. Patch reefs are typically small (the size of a backyard or a small home).

Additionally, there is one atoll on Florida’s Coral Reef, the Marquesas Islands, that was initially formed as the result of a prehistoric meteor strike.

General cross section of Florida’s Coral Reef at Miami-Dade County. 
Attribution: Dawn Witherington 

Generally, the reefs in the Coral ECA occur in three parallel lines extending north from Miami-Dade County and changing to more isolated patch reefs in Martin County.

Different reef organisms characterize the type of habitats found along Southeast Florida’s reefs, typically transitioning from a cover of algae and small octocorals nearshore to numerous octocorals and varied stony coral populations on the outer reefs.

In the Florida Keys, the reef can be found several miles offshore. These reefs tend to be a spur and groove structure, or a series of successive ridges separated by channels. Additionally, small patch reefs can be found in between the islands and the outer reef. Farthest south, the coral reefs in the Dry Tortugas are found in the shallow waters surrounding the seven islands of the national park.

The coral reefs live on platforms created by calcified corals that have accumulated over thousands of years up to 15 meters above the seafloor. In the wide channels between these platforms are soft corals and sponges.

The various reef architectural and compositional components create an environment that is ecologically diverse and productive, and one that supports all the plants and animals that inhabit Florida’s Coral Reef.

What types of corals can be found in Florida?

Corals take on many shapes and are generally classified in two main classes: hexacorals and octocorals.

Hexacorals have polyps with six tentacles (or six-fold symmetry), and octocorals have polyps with eight feather-like tentacles (or eight-fold symmetry). Hexacorals include stony corals, also known as scleractinian corals, and corallimorphs, which look similar to stony corals but lack a stony skeleton. Octocorals include sea fans, gorgonians and sea whips.

More than 45 species of stony corals and 35 species of octocorals are found along Florida’s Coral Reef. Marine sponges are also very important within the coral reef community, and more than 70 species can be found along Florida’s Coral Reef.

Historically, Florida’s reef-building corals were brain, star and branching, all of which are not as common now as they once were.

  • Brain coral is dome-shaped and has the waves, folds and ridges that resemble those of a human brain.
  • Star coral is also dome-shaped with a distinctive star pattern on its surface that is caused by the accordion-like folds within its polyp cups.
  • Branching corals are so named because of their branchlike projections, resembling animal antlers.



Octocorals tend to have eight tentacles on their polyps, often feather-like in appearance.

Branching coral

Branching coral, staghorn coral (Acropora cervicornis), was historically an important reef-building coral. The tips are white because growth has recently occurred.

mountainous star coral

A mountainous star coral (Orbicella faveolata), so called for the star-like shape of the polyps.

What is the current state of our estuarine, coastal and ocean habitats?

Located within a mile of a densely populated, urban shoreline, Southeast Florida’s estuarine, coastal and ocean habitats face an ever-increasing list of threats. For example, recreational and commercial activities taking place on, in and above the water, as well land-based activities such as coastal development and pollution, are negatively affecting the coral reef ecosystem. 

In 1950, it was estimated that Florida had over 5 million acres of seagrass. Currently, seagrasses cover nearly 2.5 million acres of shallow waters near Florida’s coastlines, estuaries and bays. Southeast Florida’s estuaries have recently had multiple seagrass die offs, primarily due to declining water quality by human-induced eutrophication. Mangrove communities in South Florida have steadily disappeared since the early 1900s as a result of coastal development and wetland infilling. Florida’s estimated 469,000 acres of mangrove forests contribute to the overall health of the state’s southern coastal zone. 

Over time, the loss of nearshore hardbottom habitats may lead to a reduction in the populations of marine invertebrates, such as sponges, coral, lobster and crabs, and may cause significant changes to the food web close to shore. In the interconnected ocean and coastal environment, damage and habitat loss result in fewer natural resources for providing food, income and recreation.  

Coral reef restoration

As Florida’s Coral Reef is impacted heavily by local and global threats, coral populations are being restored by marine scientists, natural resource managers, environmental nonprofits and local stakeholders. 

Restoration of Florida’s Coral Reef is important to keep population levels stable when there are disease outbreaks or other large-scale die offs, but it is also a key step in reacting to unplanned impacts from vessel groundings, anchors or cable drags.  

There are many different approaches to coral reef restoration that are generally categorized under biological or physical restoration.  

Biological restoration generally involves increasing the amount of living corals on the reef and includes methods such as collecting and rehabilitating broken or threatened coral fragments, propagating coral colonies, and outplanting or transplanting coral colonies. The SCTLD response showcases the power of biological restoration and effectiveness of combining multiple approaches.  

At the beginning of the STCLD outbreak, partners across South Florida helped retrieve healthy corals from St. Lucie inlet to the Dry Tortugas to be stored in land-based nurseries. At the nurseries, scientists can use a technique called micro-fragmentation.  

Micro-fragmentation separates one original healthy coral colony into multiple smaller fragments. When these fragments are placed near each other, they grow even faster and eventually can fuse back together. This process allows the reef to be reseeded quicker, which leads to more coral offspring being pushed out onto the reef and overall higher densities of corals. Corals that are taken into land-based nurseries are still sexually producing, and through the collection of gametes, a genetically diverse population of corals can also be put out onto the reef once the larvae are large enough to have settled.  

Mission: Iconic Reefs is a project led by NOAA in the Florida Keys that is restoring coral reef habitat at several iconic sites to help change the trajectory of the ecosystem and protect one of the country’s unique areas for future generations.  

Another notable restoration project is 100 Yards of Hope from FORCE BLUE. The yearlong project honoring the NFL’s 100th season and America’s military veterans restored a football field-length stretch of coral reef offshore of Key Biscayne.  

Physical or structural restoration generally involves increasing the amount of reef structure and habitat available for corals and other reef organisms. The Florida Department of Environmental Protection’s Coral Reef Conservation Program executed its first management-led restoration project to repair direct impacts to coral reef at two vessel grounding locations offshore Fort Lauderdale. 

A diver outplanting corals on Florida’s Coral Reef.  Attribution: Sarah Hamlyn, Mote Marine Laboratory
A diver outplanting corals on Florida’s Coral Reef. 
Attribution: Sarah Hamlyn, Mote Marine Laboratory 

For this project, there were two stages of restoration, physical and biological. For physical restoration, contractors dived construction equipment to reduce loose rubble at the site and reconstruct the reef framework that had been fractured, creating the critical 3D structure that marine organisms need in their environment. The next phase of biological restoration will include transplanting stony and soft coral colonies from land-based nurseries.  

Long-term monitoring of the restoration sites is still occurring, and it is important to monitor because it is the key to understanding ecological changes and highlights ways to keep improving for the future. Restoration plans for anchoring and vessel impacts are managed on a case-by-case basis and are tailored to best account for the specific damages of the site.  

Government regulation and services

Coral Reef Protection Act Brochure Cover

In 1990, the State of Florida banned the collection of hard corals, octocorals and other associated organisms in an effort to increase protection of these critical components of the reef. Then in 2009, the State of Florida enacted the Florida Coral Reef Protection Act (CRPA) to increase protection of coral reef resources off the coasts of Martin, Palm Beach, Broward, Miami-Dade, and Monroe counties. The CRPA provides Florida with the ability to recover monetary damages to provide additional disincentive for damaging coral reefs. In addition, size and catch limits of fish and lobster are managed by law to reduce over fishing.

Industry standards of best practice

Increasingly, mooring buoys are being installed as a way of protecting bottom resources from anchor damage. Commercial and recreational divers and fishers should use mooring buoys whenever possible. When moorings are not available, boaters should anchor in sandy bottom areas, not on coral reef habitats. Increased presence of pump-out facilities for marine toilets provides for improved water quality. Recycling promotes environmentally sound ways of disposing of motor oils, as well as consumer waste products like plastic bags, cans and aluminum. The State of Florida and the state’s counties have also offered many different benefits to citizens who use environmentally-friendly household appliances, such as toilets and shower heads. Be sure to check with your local county to see what benefits they may offer you for replacing your older models with new, environmentally-friendly models.

Improved science and management

As we gain greater understanding of our coral reef systems through increased science and application of information, we are better able to manage our resources for better use by all. New information on the benefits of herbivorous fishes and invertebrates on reefs has led to re-stocking efforts of key species like the long-spined sea urchin. Coral spawning studies are helping us better understand coral recruitment and restoration of damaged areas. Many citizen groups and educational institutions are engaged in active research targeted to learn more about current reef conditions and increase our understanding of impacts to reefs. Some of the most beneficial research involves coral mapping, which allows scientists to better understand and monitor the distribution of this invaluable resource.

Changes in user actions and awareness

Without an understanding of the existence and vulnerability of the reef and its unique, irreplaceable value to the natural world and humans alike, it is difficult for people to act on minimizing local and global threats. Fortunately, education and engagement are tools for connecting the public with coral reefs.  

By creating this connection, users can form a mutually beneficial relationship with the reef, gaining value from all it has to offer while doing their part to protect it.  

Engaging the public through outreach at local events can be incredibly helpful for developing awareness. Some residents who have spent their entire life in South Florida are unaware that nearshore lies the only barrier coral reef in the continental U.S. 

These events give the public the opportunity to learn about a resource they may never have encountered otherwise. Engagement and education efforts can be broad such as community shoreline cleanups to more targeted activities, such as working with fishing and scuba diving communities, so they understand how their activities affect the reef.  

When Floridians and visitors are engaged with their surroundings and learn about the value and fragility of Florida’s Coral Reef, more people will be dedicated to protecting this incredible ecosystem. The more that awareness increases, the more people can take action to ensure the reef will be healthier for future generations to treasure.  

Community Involvement
Community Involvement

Photo: Taylor Tucker

Many opportunities are available for members of the public to become actively involved in helping to better understand and protect coral reef systems. Beach and underwater clean-ups, volunteer fish and coral surveys, sea turtle nesting watches, and other opportunities provide great ways to learn more about the marine environment as well as provide valuable services and information to help protect it. Taking part in scoping meetings and even expressing your opinion to your representatives is important in shaping the direction and funding allocated to protecting coral reefs. SEFCRI is an important part of improving the condition of local reefs. By bringing together a diverse group of stakeholders to guide activities, everyone gets to become a partner in coral reef conservation and help advance actions that have positive impacts for reefs.