Photos courtesy of Noelle Knowlton

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Suspended in the still serenity of the tank, gnarled thickets of pink and orange Staghorn corals branch upward—the knobby stubs are inches tall, but the stoic structures bear the weight of the survival of Florida’s coral reefs (and by extension, the life that inhabits entire coral reef ecosystems, and even our own lives, as we are beneficiaries of the fishing, ecotourism, and medical industries that rely on coral reefs). From this desperation emerged an empowering sense of exigence championed by The Reef Institute, a local coral conservation organization of oceanic stewards committed to revitalizing our coral reefs through the pillars of education, advocacy, and research. The Reef Institute’s founders posit that “environmental sensitivity plus scientific skills equals oceanic stewards.” As Leneita Fix, Executive Director of The Reef Institute, guided me through the organization’s coral biobanking facility in a tour, she emphasized the critical nature of her organization’s work by invoking a harrowing statistic, “Florida has lost nearly 98% of its coral cover,” which means that as little as 2% of living coral cover remains. Through the convergence of “environmental sensitivity” and “scientific skills,” Leneita underscores that humans are largely to blame for the degradation of our world’s oceans and it is up to us to save it. In their efforts to mitigate the loss of coral reefs by coral bleaching, Stony Coral Tissue Loss Disease, and human activities like dredging, coastal development, pollution, and climate change, The Reef Institute has intervened on local and global scales. Their impacts are wide-reaching, from Palm Beach County to the Caribbean, but it is here where the promise of salvation lies—Peanut Island. 

From the localized lens of oceanic stewardship, The Reef Institute has spearheaded research projects, coral recruitment missions, and educational campaigns on Peanut Island to inspire locals and everyday visitors to adopt Leneita’s resolute plea for environmental responsibility. Over the past few years, emergent research published by the University of Miami has uncovered a promising phenomenon—bleached corals are surviving. In concurrent research projects by The Reef Institute, the phenomenon was observed in Peanut Island’s coral reefs. How are the coral reefs on Peanut Island not only surviving, but thriving? The Reef Institute has the answer, and it may just be the key to saving our coral reefs. 

In order to understand the solution to coral bleaching, we must first break down the science behind coral reefs. Which prompts layman marine enthusiasts like myself to consider, “What exactly is coral?” In an exclusive interview with coral biologist Kaleigh Fix, I learned a very important tidbit: corals poop. This is definitely weird, but it makes sense considering the first surprising piece of information Leneita imparted to me upon entering the facility, “Coral is an animal.” As explained in an article by the National Park Service, coral is considered an animal by definition because it is multicellular, feeds on organic matter, possesses an internal digestive system, reproduces via embryonic development, and can move independently and react to stimuli. Specifically, corals are invertebrates categorized under the phylum Cnidaria, which also includes marine species like sea anemones, jellyfish, Portuguese man o’ war, and sea fans. According to the International Coral Reef Initiative, all Cnidarians are alike in that “they all share the same distinguishing characteristics; a simple stomach with a single mouth opening surrounded by stinging tentacles.” An individual coral is called a polyp, and a group of polyps is called a colony. In the process known as budding, coral polyps propagate to form hundreds to thousands of genetic copies of themselves in the creation of coral colonies. There are two types of coral: hard coral and soft coral. The International Coral Reef Initiative explains that hard coral, also known as reef-building coral, is differentiated from soft coral with its “rock-like calcareous skeleton,” hence the name “hard” coral. Soft corals like sea fans, sea whips, and sea feathers lack this hardy exterior and instead are composed of “wood-like cores for support and fleshy rinds for protection.” 

The artificial reefs on Peanut Island fall under the category of hard, reef-building coral because they are constructed from limestone, a carbonate sedimentary rock composed of calcite and aragonite, which are crystal forms of calcium carbonate. It’s for this reason that Leneita has adopted a nuanced definition of “artificial” reefs when it comes to Peanut Island, because compared to other man-made structures that are submerged as artificial reefs, like the sunken ships and shopping carts of Phil Foster’s artificial reef snorkeling trail, Peanut Island’s reefs are more organic than artificial, as its calcium carbonate structure is used as a natural extension of the reef itself. According to the National Oceanic and Atmospheric Administration (NOAA), “Stony corals (or scleractinians) are the corals primarily responsible for laying the foundations of, and building up, reef structures. Massive reef structures are formed when each individual stony coral organism—or polyp—secretes a skeleton of calcium carbonate.” In relation to Peanut Island’s artificial reefs, NOAA clarifies, “These colonies consist of millions of polyps that grow on top of the limestone remains of former colonies, eventually forming massive reefs.” Thus, the artificial reefs on Peanut Island were developed by these submerged limestone surfaces, upon which coral larvae landed and propagated to grow into the colonies they are today. 

The process by which coral larvae develop into adult corals is called coral recruitment. In recent years, it was speculated that corals weren’t landing at Peanut Island anymore due to rising ocean temperatures and consequential mass bleaching events. Yet, Peanut Island’s reefs defied the odds. Reflecting on her involvement in The Reef Institute’s coral recruitment research project at Peanut Island, Kaleigh shared, “The question really was, ‘Are babies surviving here and growing?’ We found in our recruitment study that the answer was basically yes. We found corals that were zero to six months old, one year old, two years old, and even three, four, and five years old, and we found that they were not only present but abundantly present.” 

Peanut Island’s success story in coral recruitment prompts further research into the anomaly. The results are surprising, considering the nearly inhospitable conditions that coral polyps are up against at Peanut Island. Kaleigh confessed, “It’s really strange, there are all these conditions that are not good for coral. It’s really shallow, there are a lot of people going through, and you wouldn’t think that coral would want to survive there. And yet there are these corals that are thriving.” Thus, Kaleigh and her fellow coral biologists have been researching the factors that contribute towards successful coral recruitment. What do coral larvae like, and what causes them to land in certain areas over others? Kaleigh answers, “We found that they tend to like areas with more water flow, like more current, and we found most of the babies in those areas.” This finding has enhanced the efficacy of The Reef Institute’s outplanting missions. Through the Marine Living Structures Initiative with Michael Singer Studios, The Reef Institute “seeks to create intentionally designed and material driven structures that can grow living coral and attract animals living in a coral reef.” The Reef Institute has designed wave tiles with textured surfaces and holes to encourage coral larvae to land on them, take advantage of the enhanced water flow through, and facilitate successful coral recruitment. As for the why, Kaleigh stated, “We are still trying to figure out, ‘Is it because there are more nutrients going through? Is it because they’re getting more flow so they’re not going to get buried by sand or sediment? Is it because that’s just the first spot they hit?’” While these questions remain unanswered for now, one thing is reassuringly certain: coral babies are out there and thriving at Peanut Island.

In another research project conducted at Peanut Island, The Reef Institute has identified what might just be the key to saving our coral reefs from the devastation of mass coral bleaching events. As reported by the Florida Fish and Wildlife Conservation Commission, Florida experienced the worst coral bleaching event on record during the summer of 2023. The coral bleaching in the Florida Keys was so extreme that the Coral Restoration Foundation removed corals from coral trees (their innovative PVC pipe design to farm corals in large, offshore nurseries) and relocated them to tanks at The Reef Institute. This coral bleaching was also observed last summer on the reefs of Peanut Island, but instead of bleaching beyond repair like those in the Florida Keys, Peanut Island’s reefs remarkably survived and recovered. The research team at Peanut Island deduced that the secret to Peanut Island’s resilient coral reefs lies in its algal symbiont. In order to gain energy, coral polyps participate in cellular respiration by producing carbon dioxide and H2O, which are then used in a symbiotic relationship with a type of algae called zooxanthellae to facilitate photosynthesis. Kaleigh broke down the process, explaining how corals get their color as a byproduct of the symbiotic relationship between coral and photosynthetic algae. 

However, this symbiotic relationship also results in coral bleaching. According to Kaleigh, the coral reefs on Peanut Island undergo an annual cycle of coral bleaching. “When we get to the hotter, warmer months of July and August, [the corals] bleach completely and will basically turn white, but as we get to the cooler months of December and January, they’ll gain all of their zooxanthellae back and regain all of their color,” Kaleigh stated. Zooxanthellae is the name for this photosynthetic algae, or algal symbiont. Kaleigh continued, “And then, as waters get warmer, or either extreme of getting too hot or too cold, the zooxanthellae starts choking the coral. So the coral just expels it because it’s producing too much oxygen, and then the coral is just left eating by their polyps, just manually feeding, and that doesn’t give them nearly as much energy as they need.” This is what causes mass coral bleaching events, and it should be the end of the story for Peanut Island’s reefs, but it isn’t. Kaleigh observed, “We’ve seen on Peanut Island that corals go through that cycle of coral bleaching, and then in the cooler months, they get their zooxanthellae back completely and they get their color back, and they’re healthy again.” In a coral sampling partnership with the University of Miami, The Reef Institute ascertained that the corals on Peanut Island are surviving through this bleaching cycle and thriving because they possess a special type of zooxanthellae called Durusdinium. Kaleigh defined Durusdinium as “a more resilient, stronger algae.” Kaleigh explained, “They’ve recently found that there are different species of this algae, of this algal symbiont, there are some that are more resilient to the temperature changes and some that aren’t as resilient. So some coral have algae that is more resilient, so they’re more likely to come back.”As described in the article titled “The Algae That Might Save Earth’s Coral Reefs” by Juli Berwald, “Durusdinium was left unnamed because it was historically rare, at the time probably making up less than 10 percent of coral symbionts.” Yet after further research, it was found that “Durusdinium dominated where waters were warmest. The conclusion: Durusdinium were thermally tolerant.” As Durusdinium dominates the coral reefs of Peanut Island, the algal symbiont ensures the survival of our local coral reefs.

Peanut Island’s artificial reefs are instrumental in maintaining the health of the ecosystem, and we must preserve them as a critical environmental resource. The reefs provide critical habitat for the propagation of coral colonies, which in-turn stimulates biodiversity and attracts a rich variety of marine species to the island. Yet, reefs also provide another vital eco-service as natural breakwaters. Citing a statistic published in a Stanford study, The Reef Institute asserts, “Coral reefs absorb 97% of the energy from waves headed toward shores, protecting millions from natural disasters and rising sea levels.” Thus, the survival of our coral reefs also ensures our survival. As we are part of the problem, so we must also be part of the solution. I asked Kaleigh how everyday visitors of Peanut Island can become oceanic stewards and make a difference. She shared, “The biggest thing that needs to change is our behavior and how we live our lives . . . there are bigger things like eliminating single-use plastics and trying to be a good steward by sustainably sourcing whatever you’re eating, but a real simple thing that people can change is the type of sunscreen that they’re using. We talk about how, if you’re looking in the active ingredients, look for Zinc Oxide or Titanium Dioxide. Look to see if it has the Z or the T: if it has one or both of those, fine, if it has anything else, especially a vowel, it’s not good. It’s not good for you, it’s not good for the ocean, and it’s just something simple that people can change—it’s sunscreen.” The next time you visit Peanut Island’s reefs, wear reef-safe sunscreen and be part of the solution to save our coral reefs.