A Photo Essay on Coral Reef Restoration Efforts in Florida » Yale Climate Connections

Over the past 40 years, nearly 90% of the living coral on the reefs of the Florida Keys has been lost. Worldwide, the cover of tropical coral reefs has declined by 30% to 50% since the 1980s, as climate change increases temperatures, sea levels and ocean acidity. The authors of a recent study predict catastrophic effects on coral reefs worldwide from a 1.5°C rise above pre-industrial levels.

We will miss these corals. These ecosystems cover less than 1% of the Earth’s surface, but they feed and support more than a quarter of all marine fish species, as well as many other marine animals.

According to the International Union for Conservation of Nature (IUCN), coral reefs directly support more than 500 million people, providing food, coastal protection and livelihoods from fishing and tourism. Mote Marine Laboratory in Sarasota, Fla., reports that the reefs that stretch approximately 350 miles between Dry Tortugas and St. Lucie Inlet contribute $8 billion to the state’s economy through tourism, fishing and protection against violent storms. Mote scientists join experts around the world to try and restore these ecosystems. One such project, the Florida Keys National Marine Sanctuary’s “Mission: Iconic Reefs,” aims to restore seven reefs, one of the largest such efforts in the world. Organizations doing in-water restoration work for the first phase of the project include Coral Restoration Foundation (CRF), Mote and Reef Renewal.

Photo documentary

Bleached Brain Coral (Pseudodiploria strigosa). This symmetrical coral grows in the shallow parts of the Caribbean Sea and off the coasts of the Bahamas, Bermuda, Florida and Texas. One of the ways climate change affects coral reefs is that it causes a process called bleaching. Coral reefs are colonies of thousands of individual polyps, tiny animals that depend on symbiotic algae for 80% of their nutritional needs. At temperatures above their preferred range, corals become stressed and expel their algae. The coral skeleton then appears white, or bleached, as seen here. If temperatures return to normal soon enough, algae can grow back. Otherwise, the coral will eventually starve.
The dazzling whiteness of this coral is a clear sign of bleaching. The first documented global bleaching event – defined as bleaching affecting reefs in the Atlantic, Pacific and Indian Oceans in the same year – occurred from 1997 to 1998, killing at least 15% of reefs worldwide. Another event, from June 2014 to May 2017, affected more than 70% of the world’s reefs, and the IUCN reports that bleaching occurred every year from 2019 to 2021. In 2021, the world’s oceans were the warmest on record and the latest research shows an increasing frequency, magnitude and persistence of extreme marine heat events.

Florida’s reefs also face a number of other threats, including disease outbreaks and storms, compounded by climate change. Indeed, coral reefs globally are one of the most threatened ecosystems on Earth.

NOAA’s “Mission: Iconic Reefs” restoration program raises corals in nurseries and plants them on damaged reefs. Here, divers with CRF attach fragments of staghorn coral (Acropora cervicornis) to coral trees, simple PVC structures that CRF has developed to grow large numbers of fragments in offshore nurseries. Fragmentation is a form of asexual reproduction (corals also reproduce sexually through spawning): a branch of coral that breaks off can attach itself to a reef and begin to develop a new colony if the conditions are right. CRF currently cares for seven offshore coral tree nurseries along the South Florida coast, where it grows more than 20 different species.
Once the coral tree fragments have grown to a sufficient size, divers mark them and attach them directly to existing reefs using a non-toxic marine epoxy, a process called transplanting. Coral restoration efforts are not without criticism. “We have received criticism for launching this mission from highly respected scientists,” said Sarah Fangman, Superintendent of the Sanctuary. “Yes, we are doing this work in the midst of continuously rising temperatures and intense thunderstorms. But I don’t think we have the luxury of waiting. We need to address heat stress and water quality issues and, to give this system a chance, support it while we fix these issues.
Since 2012, CRF has planted over 170,000 corals on Florida reefs, including this kite. Scientists are also studying coral genetics to better inform restoration work. “We believe in selling some hope,” says Mike Echevarria, founder of Reef Renewal. “We have people saying all the time, why bother, it won’t work. But there is a lot of research on genetics, heat tolerance, and selective breeding. For example, the authors of a study recently found that corals exposed to stressful heat treatment in the laboratory for 90 days were more tolerant of increased water temperature.
Staghorn and elkhorn coral (Acropora palmata), pictured here, are listed on the IUCN Red List of Endangered Species as “Critically Endangered”. Mote researchers are among those working to identify native genetic coral varieties that are resistant to stressors such as increased water temperature. The lab has planted over 100,000 corals, including genetic varieties of staghorn and elk that are strategically bred from native parent corals. This approach maintains genetic diversity, which increases the resilience of reefs.

Melissa Gaskill is an Austin-based science writer who frequently covers climate change and ocean issues. Photos: Courtesy of Brandon Cole Marine Photography.

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