Restoring TCI reefs.

By Kort Alexander and Kara Rumage, The School for Field Studies Center for Marine Resource Studies, South Caicos

A large colony of elkhorn coral grows on the reef near South Caicos.

We sit on the siderails of the boat in anticipation, hands holding our masks and regulators in place. The captain counts down from three and we lean back until our tanks hit the water. We are instantly transported to another world. Schools of yellow and blue grunts congregate warily under a nearby ledge while silvery barracuda with gaping mouths full of sharp teeth glide by on their morning prowl. An endless array of colors flash by as numerous fishes—angelfish, butterflyfish, wrasses, jacks, parrotfish, tangs, snappers, just to name a few—go about their daily lives.

At the center of all this activity are corals and the reefs they create. A thick trunk of deep orange elkhorn coral extends from the hard bottom towards the surface, gathering sunlight with branches that resemble open hands (hence elkhorn’s scientific name, Acropora palmata). Other species, including brain corals and boulder star corals, dot the reef with a dazzling variety of textures and patterns.

The power of polyps

Although they are immobile and might seem more like plants, corals are actually animals, most closely related to jellyfish and anemones. They are made of thousands of tiny individuals called polyps, mere millimeters in size, that form giant colonies and build hard skeletons of calcium carbonate which form the foundations of reefs in tropical seas worldwide.

This close-up details a colony of rose coral being grown in the coral lab at the School for Field Studies in South Caicos.

Corals not only provide shelter for fish and structure for habitat, but also serve as the basis of energy for the entire ecosystem. Using tiny tentacles, coral                    polyps ensnare and feed on plankton floating through the water, but they get most of their energy from microscopic algae called zooxanthellae that live inside their cells. The zooxanthellae use sunlight to make food through photosynthesis and share the energy that they produce with the coral polyp in exchange for shelter. This energy then gets passed up the food web through animals that feed on coral, forming the basis of one of the most biodiverse ecosystems on the planet. 

Coral reefs, including those in the Turks & Caicos, provide economic value through coastal protection, fisheries, and tourism. Reefs absorb some of the impact of ocean waves, protecting the coastline from being damaged and eroded, especially during intense storms and hurricanes. Coral reefs form protective barriers that enclose lagoons, providing nursery habitats and feeding grounds for fish and other organisms that serve as a primary source of protein in many tropical countries. Many of these countries also have tourism-based economies, which rely on coral reefs to draw visitors. Estimates of the total economic value of coral reefs worldwide vary but are in the range of tens of billions of dollars every year.

Corals in crisis

Sadly, coral reefs are now facing several threats to their existence. As global temperatures rise, marine heat waves have become more frequent and severe. In the summer of 2023, the Caribbean experienced record ocean temperatures, with a buoy off the Florida coast reading a stunning temperature of 101.1°F (38.39°C) in July. As a result, reefs across the region, including here in the Turks & Caicos, experienced a mass bleaching event. Bleaching occurs when corals become heat-stressed and expel the zooxanthellae that live inside their tissues. Without their zooxanthellae, corals lose their vibrant coloring and main source of energy. Bleached corals are likely to die unless water temperatures drop immediately. 

The threat of bleaching is coinciding with existing coral stressors like overfishing, disease, and pollution. In 2008, elkhorn and staghorn corals around South Caicos were ravaged by white band disease, and in 2019 stony corals in TCI were devastated by stony coral tissue loss disease (SCLTD), resulting in a 62% loss of coral coverage on reefs around South Caicos. While these diseases are no longer prevalent in TCI, they have exacerbated the threat now posed by bleaching. Unless these challenges are addressed, many corals could soon be driven to extinction, spelling disaster for the communities that depend on them.

Reef revival

School for Field Studies students maintain coral nursery structures and promote coral growth by removing algae.

Luckily, there are steps we can take to help the corals. To restore and build more resilient reefs, coral nurseries have been established in recent years on reefs around the world. Small pieces of coral colonies are taken from a healthy reef and attached to underwater nursery structures, which provide more ideal conditions for corals to grow. Once these coral fragments reach a certain size, they can be returned to the reef in a process called outplanting. Outplanted fragments then grow into full-size colonies themselves, providing more habitat for fish and improving the overall health of the reef.

In 2023, the South Caicos Coral Reef Consortium (SCCRC) was established as a collaboration among stakeholders—the School for Field Studies (SFS), Salterra Resort and Spa, the Turks & Caicos Reef Fund, and The Reef Institute—with the common goal of supporting South Caicos reef recovery. To accomplish this goal, SFS has led the construction and implementation of several coral nurseries. In the spring of 2023, coral nursery structures were installed at four sites (at two different depth categories) around South Caicos, which were selected based on accessibility and location, bottom type, and available data. Five different structure types were tested to determine which was the most cost-effective. A total of 300 fragments of two coral species—elkhorn and staghorn—were attached to the structures. The five types of nursery structures include a rope and fishing longline, a PVC tree, a PVC rope square, a PVC line square, and cement blocks with PVC pipes.

Beginning in the fall of 2023, SFS students and staff have regularly conducted maintenance dives to remove algae from the nursery structures and monitor coral health. Each coral fragment is photographed to determine its growth rate and health. SFS students have found that nursery structure type doesn’t seem to impact growth rate, but that corals grow faster at the shallow nursery sites (<10 m) than the deep sites (>10 m), possibly because shallower corals have greater access to sunlight for photosynthesis.

A partially bleached fragment of staghorn coral hangs from a nursery structure.

Once the coral fragments have grown to a viable size, they will be outplanted onto a nearby reef. During the fall, SFS students investigated five potential outplanting sites, each of which was assessed to determine the size and number of resident fish and the diversity of substrate for coral to grow on. Shark Alley, one of the five sites, has the most herbivores such as parrotfish. These fish play a crucial role on coral reefs by eating algae, which compete with coral for space on the reef. However, relative to other sites, Shark Alley also had more sand and rubble, which are unstable and hard for coral to grow on, making it less suitable for outplanting. This example demonstrates the many often-contradictory factors that go into selecting sites for outplanting.

In addition to the coral nurseries, other initiatives are also underway. With the support of The Reef Institute, SFS has designed and constructed a land-based coral laboratory, which was finished in late fall 2023. During the spring of 2024, the lab was populated with 54 colonies representing 13 species of coral, including mustard hill, finger, rose, and flower corals collected from local dive and snorkel sites. The collected colonies were chosen because they were damaged or already detached from the reef. The lab environment helps mitigate external stressors and gives the corals better conditions in which to grow. Lab corals are also being fragmented into smaller pieces, which has been shown to dramatically increase growth rates. Once healthy, these lab-grown corals will be moved to the underwater nurseries and eventually outplanted, bolstering local reefs for years to come.

School for Field Studies student Kara Rumage maintains coral fragments on a PVC tree structure.

Back on the reef, we swim through the blue water towards one of our nurseries. There, coral fragments hang from trees of PVC and lengths of fishing line strung between thicker ropes. Many are partially or fully bleached after suffering a brutally hot summer, but against all odds some still have a vibrant apricot color. In these tiny fragments, swinging gently with the ocean swell, lies the hope of a reef restored to its full potential, bursting with life and able to support a robust economy centered around fisheries and tourism. All it takes to make this vision a reality is some PVC pipe, a scrub pad, and a little elbow grease.

The School for Field Studies (SFS) is a US-based, academic institution that provides multidisciplinary, field-based environmental study abroad opportunities to undergraduate university students. Long term data collection by staff and students is a crucial element of observing and understanding climate impacts, beneficial to stakeholders and essential to policy makers.

To learn more about the SFS TCI program, visit www.fieldstudies.org/tci. For detailed article references, contact Director Heidi Hertler on South Caicos at hhertler@fieldstudies.org.