Coral Reef Restoration in the Florida Keys

Earlier this month we sat down the the Nature Conservancy’s Coral Recovery Coordinator Caitlin Lustic to discuss how climate change affects coral reefs in the Florida Keys. Coral reefs play an important role in protecting ocean front property from damage during storm surges by reducing the height of incoming waves. Residents of coastal Southeast Florida need these reefs more than ever as the sea level rises and storms worsen, but reefs are suffering their own climate change impacts.

Threats

My first impression of Caitlin’s work left me in awe of the complex task she and other marine biologists studying coral have at hand. Scientific understanding of corals is limited relative to other fields due to their complexity and slow growth rate. It takes years to answer questions about coral because they take so long to show measurable growth and because studying them means diving down to an underwater field site which is much more time consuming and expensive than driving to one on land.

Even with these barriers to understanding, it is clear that corals in the Keys face a slew of threats. Coral reefs began to decline noticeably in the 1980’s when a pathogen killed off a sea urchin species that kept a coral-competing algae at bay. That algae caused immense harm in the following decades and scientists have worked with mixed results to reintroduce the urchins. At first urchins were raised in tanks and then released back to the reef, but their ignorance of predators left them comically vulnerable and they were quickly snapped up by bigger fish. Now they are raised in tanks with an octopus to scare them straight, hopefully increasing their odds of survival.

Climate change poses an even bigger threat than algae to coral reefs. Ocean temperatures are rising and so is the level of carbon dioxide in sea water, making the water more acidic. These two factors seem to exacerbate both coral bleaching and disease, although due to the aforementioned complexity of coral reefs implicating a single threat is difficult. Coral bleaching, for example, occurs when ocean water is too warm and too still. The colorful algae living within the corals die off in these conditions, leaving the white “bleached” coral structure exposed and the coral without an important source of food. The algae usually return when the water cools off in the winter, but the coral can be left weaker and more susceptible to disease. Corals are prone to a variety of diseases which are thought to spread between the corals via predators (think a mosquito spreading malaria), corals that are touching, or the water itself.

Restoration

Caitlin’s job involves overseeing and completing coral restoration in the remaining coral reefs in the Florida Keys. The Nature Conservancy coordinates with multiple coral reef nurseries in the Keys to grow a fast growing species called staghorn coral in underwater nurseries. Clippings can be taken from it’s branches and “replanted” onto struggling reefs. This is done using two-part epoxy to affix the clipping to the reef where it continues to grow.

Other nurseries grow a species called boulder coral and reintroduce clippings to reefs through a technique called resheeting. A boulder coral start is cut into multiple small pieces in a lab with a band saw and then the pieces are epoxied to the reef in a group. The pieces are near to each other but are not touching at first. As the clippings grow they eventually join together to form a much larger boulder coral than can be grown in the same amount of time from a single clipping.

Staghorn coral fragments in a nursery. © Ken Nedimyer

Staghorn coral fragments in a nursery. © Ken Nedimyer

Next Steps

We asked Caitlin if restoration was working and she reminded us that improvement in reefs takes place very slowly over a number of years and is hard to measure. Many small-scale studies are underway studying the benefits of coral restoration, but to study these efforts over the long term is incredibly challenging. These types of studies are hard to fund unless they examine a factor that directly affects the economy, such as supporting commercially fished species, and that connection is difficult to establish in a reasonable timeframe.

 She mentioned two other factors that are benefitting coral including the protection of 2,800 square nautical miles called the Florida Keys National Marine Sanctuary. This area allows marine life to thrive by restricting boating and commercial fishing and protects the largest known sea grass bed in the world, greatly benefiting the coral reef ecosystem. In addition, the Florida Keys is near to completing the process of shifting from septic tanks to a piped sewage system. This change will keep nutrient-rich human waste from clogging the crystal clear waters of the Keys with algae while benefiting coral reefs.

Caitlin’s response to our questions about climate change and coral reefs had a similar theme to those of our other interviews throughout Climate Odyssey. When trying to protect a specific place or system from damage by people, climate change is just one of many threats competing for attention.

To see more pictures of coral restoration click here