LIFE IN THE WILD: STRESSORS ON THE REEF
Outplanted corals face many stressors that impact their survivorship and growth. A lot of the impacts to coral reefs are anthropogenic, or human-caused. However, there are natural stressors which take a toll on corals as well. At Coral Restoration Foundation™, we use a supplementary monitoring protocol at one month and one year post outplanting to help us understand the stressors that affect our corals.
There are two coral predators that we monitor and mitigate. Yellow-footed snails and fire worms, both of which eat coral polyps. In a healthy population of coral, these small invertebrates are part of life. Unfortunately, Florida’s reef has lost 98% of its staghorn and elkhorn corals. This means that any predation on outplanted colonies is a risk to the future stabilization of the reef system.
Fireworms and yellow footed snails are natural coralivores, coral eaters. ©Coral Restoration Foundation™
Yellow-footed snails are often covered in algae and look like a ball attached to the underside of the branches of staghorn and elkhorn corals. They usually start eating the colony from the base up, leaving behind wondering pathways of exposed coral skeleton. At CRF™, we're authorized by permit to remove them from our outplants during our monitoring trips. After removal, we take them to a nearby research facility where they're studied for their ecological impact.
After removing snails from restored corals they are shipped to a collaborating facility for an ongoing research project. ©Coral Restoration Foundation™
Fire worms are another predator of corals, known for their voracious feeding habits. A single worm can eat the tips off an entire section of fresh outplants. These segmented worms can regrow if cut in half, doubling the trouble for the corals in the area. Instead, in order to control their populations artificially and protect newly restored corals, CRF™ has permits to remove fireworms from restoration sites. It is important to note that recreational divers should never take it upon themselves to remove animals from their natural environment. Our divers are trained and can ONLY act during work hours when our permitting is in effect. This oversight and regulation ensures that divers are not misidentifying pest animals, resulting in the death of innocent inverts, and ensures divers are humanely and appropriately removing the threats to the endangered corals without damaging the corals themselves.
As animals, corals can get sick! One of the most common symptoms we see in corals is Rapid Tissue Loss (RTL). This symptom is recognizable by its distinct pattern of tissue loss in which bits of the coral flake off into the water creating a speckled appearance in the coral that remains attached to its skeleton. The cause of RTL is currently unknown, and research is ongoing to determine if the symptom is caused by a true disease linked to a bacteria or virus or if it is simply a reaction to stressful conditions like when humans lose hair from extended periods of stress.
A disease that emerged in 2014 is Stony Coral Tissue Loss Disease (SCTLD). First reported in Miami, it has spread around the Caribbean, affecting 20 of the 45 species of coral found on Florida's Coral Reef. It is waterborne and a bacterial vector is suspected but not confirmed. It can be treated using an antibiotic paste and its spread can be reduced with awareness of how to properly clean dive gear! For helpful information about Stony Coral Tissue Loss Disease visit https://floridakeys.noaa.gov/coral-disease/citizen-participation.html and https://floridadep.gov/rcp/coral/content/stony-coral-tissue-loss-disease-response
Stony Coral Tissue Loss Disease affects 20 of the 45 known species of coral present on Florida's Coral Reef, however elkhorn and staghorn coral are not affected by this disease.
Space on the reef is limited, meaning there is a fierce competition to grow once corals are outplanted. Algae is one of the plants that is constantly fighting for the same space as corals. A bloom of algae can smother corals, blocking the sunlight they both need to survive!
Climate change is one of the biggest threats to coral reefs. Too warm water temperatures cause coral bleaching, which is the loss of the zooxanthellae, a symbiotic photosynthetic organism, that lives in coral tissue. That zooxanthellae provides the coral with over 90% of its nutrients and without it the coral turns white and slowly starves. In the last 20 years, Florida has experienced several hot water bleaching events. Acidification of the ocean is another problem caused by climate change, specifically caused by the increase in carbon dioxide in our atmosphere. The CO2 mixes with ocean water, creating a chemical reaction which makes the water more acidic. This also makes it harder for corals to produce successful offspring and make their skeletons, leaving them vulnerable to damage.
Coral bleaching is a stress response that occurs when the coral-zooxanthellae relationship breaks down resulting in the pigmented zooxanthellae leaving the coral tissue, exposing the white limestone skeleton beneath. ©Coral Restoration Foundation™
The many stressors that affect coral growth and survivorship are complex, and made even more so by the addition of stressors caused by humans, including climate change. Corals are resilient and have been resilient for millions of years. Like any group of organisms, however, their resiliency comes from evolution's ability to naturally select from a diverse wild population. Without a genetically diverse wild population, evolution's selective power in the face of environmental change is limited, and the population's resiliency is lessened. By ensuring that CRF™ is working to support the reefs’ natural diversity in our restoration practices, we are giving coral reefs a better chance of adapting to changing environmental conditions.
Our restoration sites are essentially stepping stones, refugia of biodiversity scattered along the reef that will be able to "seed" the rest of the reef with life. Restoration is about hitting an ecological tipping point after which reefs natural processes of recovery can take over. This means returning a critical mass of corals to the wild. We saturate the reefs with corals knowing that not all will survive but many will, and these survivors will grow larger, fuse and push us closer to that tipping point. Since 2012 we have returned over 230,000 corals to the wild, restoring over 34,000 square meters of reef habitat, and in 2021 and 2022 we saw over 50% increase in coral tissue cover across all species and all restoration sites, meaning there is more living coral on our restoration sites one year after outplanting.
Despite the many stressors corals face in the wild, we know that our methods do work – outplanting year after year means that even with mortality – for whatever reasons – we end up with large numbers of corals in places where they were previously absent. And we’re not talking about small numbers of corals, but tens of thousands of square meters, and even more in the future.
CRF™ elkhorn coral outplants thrive in the wild, 2 years after their original outplanting date. ©Alexander Neufeld/Coral Restoration Foundation™
"Talking Science" Editorial Intern
Sage grew up landlocked in Colorado but was fortunate to travel to the ocean growing up. Her interest in the unique creatures she found inspired her to start her marine science journey by volunteering at the Denver Aquarium. She attended the University of Hawaii at Manoa, earning a bachelor's of science degree in marine biology in 2019. After graduating and moving an island over to Kauai, she earned her PADI open water SCUBA instructor certification in order to spend as much time as possible underwater while searching for her next career step. After spending months searching, Sage found the internship at CRF and realized this opportunity was too good to pass up and moved to the Florida Keys. She is ready to make a difference at the forefront of active reef restoration made possible through CRF internship.
Coral Chronicles Editor
Madalen Howard is CRF's Communications and Outreach Coordinator. Madalen comes to CRF™ via a winding road from the Tennessee hills, to the South Carolina low country, ending here in Florida’s Coral Reef. She earned her Bachelor's degree in Marine Biology and a Minor in Environmental Studies from the College of Charleston in 2016. Her experience ranges from field research to education, marketing and digital communications.
With CRF™ Madalen creates inclusive pathways to scientific discovery through content creation and by building and fostering relationships with press, digital media creators, and local community members. Throughout her life Madalen has had a skill connecting people with nature, and is excited to bring people into the world of coral restoration.